Users frequently need to enter commands while typing (e.g., for formatting or UI control). These commands usually involve either pointing to GUI controls, which is slow because it requires moving the hand to the mouse, or pressing modifier-based hotkeys, which can be awkward because it requires reaching for the modifier key. Previous research has proposed chording as an alternate mechanism, in which commands are expressed by chording letter keys. Letter chords can be reliably recognized and learned, but previous work does not identify which types of chords are best, and does not assess the performance of letter chords in realistic tasks. We carried out two studies to provide this information: the first measured speed, accuracy, and preference for different types of letter chords; the second evaluates letter-chord performance compared to hotkeys. Our studies identify several features that are important for usable letter chords, and show that in two different tasks, letter chords significantly outperform modifier-based hotkeys by 8-15%.

Game features can create access barriers that undermine player experience for all users, and impede some users from playing. While segments of the games industry have made headway in reducing the number of barriers that players face, the extent to which these barriers remain present in contemporary commercial game titles has been largely unmeasured. We address this problem by measuring the implementation of accessibility features, and where games can improve. We conducted a content analysis of 30 top-played Steam games using the “basic accessibility features” from the Game Accessibility Guidelines. Our results show a positive trend: nearly two-thirds of basic accessibility features were fully implemented. However, there remains substantial room for improvement, as basic features are intended as a baseline, not a gold standard. Our work highlights that under-implemented accessibility features could be better supported at low cost and effort—highlighting a clear path to improvement for games industry stakeholders.

Stacked-dimension tables (SDTs) represent multidimensional data with nested tables, where each table shows two of the dataset’s dimensions. SDTs provide a comprehensive overview of all of the data and all of its dimensions – but overviews are just the starting point for exploration, and there is little information available to designers about how to support further interactions with SDTs. We worked with a crop-breeding research group to develop a stacked-dimension system that suited their complex multidimensional datasets, and to identify requirements for their analyses of differential gene expression across multiple genomes. Based on the requirements, we developed a new SDT system and several new interaction techniques that support the researchers’ needs to filter the data, reconfigure the visualization, provide data context, revisit previous configurations, and integrate findings into a broader workflow. To test the generalizability of our designs, we then extended the requirements and techniques in a second SDT system for a new domain (outcomes from a retirement-planning model) and carried out a small usability study with this system. Our evaluations show that the techniques are easily learned and understood by both domain experts and everyday users, and that they provide support for real-world exploration in stacked-dimension visualizations.

Node-link visualizations are commonly used to gain insights into large network data where the entities of the networks (nodes) are represented as points, and relationships (edges) are drawn as straight line segments or links. With growing access to network data and visualization tools, such visualizations are increasingly appearing in infographics and documents intended for non-specialist readers. This necessitates understanding how these visualizations are perceived by end users who are not necessarily domain experts, and determining how visual summaries can be provided to ensure consistent interpretation of the displayed information. In this paper, we investigate the interpretability of node-link visualizations of large graphs: we designed summary representations that could be provided alongside the visualization to improve interpretation, and we evaluated these designs through two user studies. Our results indicate that the information perceived from traditional node-link representations can vary substantially, especially when the nodes are uniformly distributed rather than forming clusters or tangled structures. We observed that visual summaries can enhance the readability of these visualizations – summaries that reduce clutter were preferred by participants and were more accurate for typical interpretation tasks.

Long page-load time for web applications is a common frustration for users – and despite substantial advances in web infrastructure, pages still regularly take more than a second to load. A potential solution to this problem is to show users a “false front” page that looks like the website (and loads quickly), and then switch to the real page once it has arrived. False front pages quickly show users the visual appearance of the page – but because they have not yet loaded the code for interaction, they may cause problems when users try to click on items or manipulate the interface. To provide a better understanding of how users perceive and perform with false-front pages, we developed a framework that specifies potential architectures and designs for several types of false front pages. Our false-front mechanism shows a realistic-looking version of a web application and allows users to “click ahead” before the full page has loaded (feedback shows users their click has been received, and clicks are queued for execution when the application becomes available). We provide details on how the different architectures can be implemented, and discuss two reference implementations that we have constructed. We carried out two crowdsourced studies that compared our false front pages to traditional representations of loading (an animated spinner and a skeleton screen), to see whether users were confused or frustrated by the false fronts, and to see how they perceived the pages’ loading time and responsiveness. Our results showed that false fronts led to better ratings of responsiveness and speed, faster task completion, and higher preference – suggesting that early loading of false fronts is a promising avenue to improve user experience with web applications.

Virtual Reality systems are increasingly proposed as a platform for everyday interactive software. Many applications are dependent on actions such as navigation and selection, but it is not clear how well immersive environments support these basic activities. Previous studies have suggested advantages for spatial learning in VR, so we carried out a study that investigated two aspects of immersion on spatial memory and selection: the degree to which the user is immersed in the data, and whether the system uses immersive input and output. The study showed that more-immersive conditions had substantially worse selection performance, and did not improve spatial learning. However, most participants believed that the immersive conditions were better for learning object locations, and most people preferred the immersive layout and the HMD. Our study suggests that designers should be cautious about assuming that everyday software applications will benefit from being deployed in an immersive VR environment.

Comparison is a well-studied task in visual analytics, but there is still little support for comparison of temporal streams such as video. There are a wide range of tasks that involve video comparison, but there are very few systems or techniques to support this kind of analysis. To help address this problem, we have developed new interaction techniques that explicitly support video comparison. We provide techniques for equalizing the reference frame of videos to be compared, juxtaposition techniques for enhancing side-by-side and small-multiples comparisons, superposition techniques for comparing overlaid videos, explicit-encoding techniques that visualize differences between extracted points, and temporal-to-linear techniques that translate between a temporal sequence of frames and a 1D timeline. We built a demonstration system with five different datasets, and evaluated our interaction techniques in two ways: an analysis of steps to show their efficiency, and a preliminary user study to explore learnability, utility, and usability.

An interactive application’s overall pace of interaction is a combination of the user’s pace and the system’s pace, and if the system’s pace is mismatched to the user’s pace (e.g., timeouts or animations are too fast or slow for the user), usability and user experience can be impaired. Through a series of four studies, we investigated whether users prefer systems where the system’s pace better matches their own pace. All of the studies used common drag-and-drop interactions with hierarchical folder widgets, in which a folder would expand when the cursor hovered over it for a timeout period. If the system pace in these interactions is too fast (i.e., the timeout is too short), then the user’s performance and subjective experience is likely to be impaired because of unintended expansions; and if the system pace is too slow (i.e., the timeout is too long), then performance and experience could be impaired by unnecessary delay before folders expand. The first experiment was designed to validate the premise that fast-paced users prefer a fast system pace to a slow one (and the inverse for slow-paced users), and results confirmed this premise. The second study used the first experiment’s data to look for measures of user pace that could enable automatic adaptation of system pace, and also examined whether participants adjusted their pace towards that of the system. The study found reliable measures of user pace and showed that participants do entrain to the system’s pace. The third and fourth studies examined whether users would prefer a system that adapted its pace to the user over a system that used a static baseline pace. Results indicated that a majority of fast-paced users preferred the adaptive interface, but that slow-paced users generally preferred the static baseline interface. We discuss several design implications, including opportunities for systems to improve user experience for fast users by automatically adapting system pace to user pace.

Prior studies of human communication have demonstrated that prosocial outcomes occur when facets of communication converge between interlocutors – for example, social likeability and perceived competence increase when people adapt their pitch or rate of speech towards one another. Inspired by these findings, we examined whether user preference for fast or slow system speech rate covaries with user speech rate. Experimental participants uploaded samples of their reading speech and spontaneous speech, and then listened to fast and slow system speech before choosing their preferred system speech rate. Results aligned with our hypothesis that fast speakers prefer faster system speech and that slow speakers prefer slow. Design implications are discussed, as well as plans for future studies that explore the potential for systems to automatically measure the user’s speech rate and converge towards it.

The implicit-association test (IAT) is a method for measuring subconscious associations between concepts in memory. It is widely used in social psychology research for assessing associations that people may be unable or unwilling to articulate, including those relating to race, gender, self harm, and risk-taking behaviour. We describe the motivation for adapting the IAT to user interface evaluation, including its potential to support rapid A/B testing that is amenable to online crowd-source dissemination, while also potentially reducing the validity risks caused by biases such as the good subject effect. We present a method (the UI-IAT) for conducting implicit association tests for A/B user interface evaluation, and we present results of two experiments demonstrating that, although the method can successfully discriminate between 'good' and 'bad' interfaces, its sensitivity is low. We discuss implications for practical use of the UI-IAT and for further work.

Partial automation makes digital games simpler by performing game actions for players. It may simplify gameplay for non-gamers who have difficulty controlling and understanding games. However, the automation may make players confused about what they control and what the automation controls. To describe and explain non-gamers’ experiences of automation confusion, we analyzed gameplay, think-aloud, and interview data from ten non-gamer participants who played two partially automated games. Our results demonstrate how incorrect mental models, behaviours resulting from those models, and players’ attitudes towards the games led to different levels and types of confusion.

Chord and Sankey diagrams are two common techniques for visualizing flows. Chord diagrams use a radial layout with a single circular axis, and Sankey diagrams use a left-to-right layout with two vertical axes. Previous work suggests both strengths and weaknesses of the radial approach, but little is known about the usability and interpretability of these two layout styles for showing flow. We carried out a study where participants answered questions using equivalent Chord and Sankey diagrams. We measured completion time, errors, perceived effort, and preference. Our results show that participants took substantially longer to answer questions with Chord diagrams and made more errors; participants also rated Chord as requiring more effort, and strongly preferred Sankey diagrams. Our study identifies and explains limitations of the popular Chord layout, provides new understanding about radial vs. linear layouts that can help guide visualization designers, and identifies possible design improvements for both visualization types.

The ‘Barnum effect’ is a psychological phenomenon under which people assign higher quality ratings to personality descriptions developed ‘specially for you’ than the same descriptions described as ‘generally true of people.’ This effect suggests that recommender interfaces could elevate the perceived quality of recommendations simply by indicating that they are explicitly personalised. We therefore conducted a crowd-sourced experiment (n=492) that examined the perceived quality of personalised versus non-personalised movie recommendations for good and bad movies – importantly, the actual recommendations were identical, and were merely presented as being either personalised or not. Contrary to the Barnum effect, results showed numerically lower mean quality scores for personalised recommendations, but with no significant difference. Our findings suggest that Barnum-like effects of personalisation have at most a small influence on perceived quality, and that designers should not rely on this effect to improve user experience (despite online design guidance suggesting the opposite).

Applications that use multiple devices and surfaces provide new opportunities for innovative interaction -- but despite the wide variety of research that has been carried out on multi-surface systems, building these kinds of applications is still difficult. In particular, multi-surface apps that use interactive visual workspaces are complicated because current tools do not provide low-level access to a connected and interactive graphical canvas that is shown on different devices. This difficulty limits the explorations that designers and developers can carry out within the multi-surface design space. To address this problem, we have developed WAMS -- an open-source web-based toolkit that provides several programming abstractions for building visual-workspace applications across multiple surfaces. WAMS uses three main concepts -- a virtual visual workspace, views onto that workspace, and graphical workspace objects -- and provides support for connecting multiple devices, creating and manipulating objects, managing and laying out views, and handling events from multiple surfaces. WAMS simplifies the development of a wide variety of applications including composite display configurations, shared-workspace groupware, systems that place different UI elements onto different devices, and bring-your-own-device applications. We describe WAMS's main abstractions and concepts, provide several examples that show the breadth of the approach, and assess the toolkit in terms of effectiveness, coverage, extensibility, and integration with existing practices and tools.

Developing skill and overcoming in-game challenges is of great interest to both players and game designers. Players can improve through repetition, but sometimes practice does not lead to improvement and progress stalls. It would be useful if designers could help players make progress without compromising their long-term skill development. We carried out a study to investigate how two techniques—checkpoints and breaks—affect in-game progress and player skill. Checkpoints allow multiple attempts at a challenge without having to repeat earlier sections; this aids progress, but could potentially hinder skill development. Second, breaks in gameplay have been shown to accelerate skill development, but their effectiveness is unknown when the breaks are integrated into the game's design. Our study evaluated the effects of game-integrated breaks and checkpoints on players' in-game progress (when the techniques were present) as well as two test sessions (with all techniques removed). Our results showed that both checkpoints and breaks aid progress (combining both had the largest effect) and that neither technique reduced performance in the transfer task, suggesting that skill development was not hindered. Our work provides evidence that checkpoints and breaks are valuable techniques that can assist both player progress and skill.

The effective use of assistive interfaces (i.e. those that offer suggestions or reform the user’s input to match inferred intentions) depends on users making good decisions about whether and when to engage or ignore assistive features. However, prior work from economics and psychology shows systematic decision-making biases in which people overreact to low probability events and underreact to high probability events – modelled using a probability weighting function. We examine the theoretical implications of this probability weighting for interaction, including its suggestion that users will overuse inaccurate interface assistance and underuse accurate assistance. We then conduct a new analysis of data from a previously published study, quantifying the degree of bias users exhibited, and demonstrating conformance with these predictions. We discuss implications for design, including strategies that could be used to mitigate the deleterious effects of the observed biases.

Many interactive systems are susceptible to misinterpreting the user’s input actions or gestures. Interpretation errors are common when systems gather a series of signals from the user and then attempt to interpret the user’s intention based on those signals – e.g., gesture identification from a touchscreen, camera, or body-worn electrodes – and previous work has shown that interpretation error can cause significant problems for learning new input commands. Error-reduction strategies from telecommunications, such as repeating a command or increasing the length of the input while reducing its expressiveness, could improve these input mechanisms – but little is known about whether longer command sequences will cause problems for users (e.g., increased effort or reduced learning). We tested performance, learning, and perceived effort in a crowd-sourced study where participants learned and used input mechanisms with different error-reduction techniques. We found that error reduction techniques are feasible, can outperform error-prone ordinary input, and do not negatively affect learning or perceived effort.

The overall pace of interaction combines the user’s pace and the system’s pace, and a pace mismatch could impair user preferences (e.g., animations or timeouts that are too fast or slow for the user). Motivated by studies of speech rate convergence, we conducted an experiment to examine whether user preferences for system pace are correlated with user pace. Subjects first completed a series of trials to determine their user pace. They then completed a series of hierarchical drag-and-drop trials in which folders automatically expanded when the cursor hovered for longer than a controlled timeout. Results showed that preferences for timeout values correlated with user pace – slow-paced users preferred long timeouts, and fast-paced users preferred short timeouts. Results indicate potential benefits in moving away from fixed or customisable settings for system pace. Instead, systems could improve preferences by automatically adapting their pace to converge towards that of the user.

Input mechanisms can produce noisy signals that computers must interpret, and this interpretation can misconstrue the user’s intention. Researchers have studied how interpretation errors can affect users’ task performance, but little is known about how these errors affect learning, and whether they help or hinder the transition to expertise. Previous findings suggest that increasing the user’s attention can facilitate learning, so frequent interpretation errors may increase attention and learning; alternatively, however, interpretation errors may negatively interfere with skill development. To explore these potentially important effects, we conducted studies where participants learned commands with various rates of artificially injected interpretation errors. Our results showed that higher rates of interpretation error led to worse memory retention, higher completion times, higher occurrences of user error (beyond those injected by the system), and greater perceived effort. These findings indicate that when input mechanisms must interpret the user’s input, interpretation errors cause problems for user learning.

Graphical User Interfaces present commands at particular locations, arranged in menus, toolbars, and ribbons. One hallmark of expertise with a GUI is that experts know the locations of commonly-used commands, such that they can find them quickly and without searching. Although GUIs have been studied for many years, however, there is still little known about how this spatial location memory develops, or how designers can make interfaces more memorable. One of the main ways that people remember locations in the real world is landmarks – so we carried out a study to investigate how users remember commands and navigate in four common applications (Word, Facebook, Reader, and Photoshop). Our study revealed that people strongly rely on landmarks that are readily available in the interface (e.g., layout, corners, and edges) to orient themselves and remember commands. We provide new evidence that landmarks can aid spatial memory and expertise development with an interface, and guidelines for designers to improve the memorability of future GUIs.

When software and hardware processes cause delay between an input and an output, consequences can be both harmful and annoying. In games, this type of delay can cause actions to lag behind a player's inputs. Studies on delayed game actions show negative impact on both player performance and quality of experience. Further research could expand upon this knowledge with more robust data modeling and analysis, as well as a wider range of actions. This paper describes publicly available datasets from four user studies on the effects of delay on the fundamental game action of selecting a moving target with a pointing device. They include performance data, such as time to selection, and demographic data, such as age and gaming experience. Example analysis illustrating the use of the datasets is shown, including comparison of pointing devices, demographic analysis with performance, and analytic modeling.

While evidence supports that some commercial off-the-shelf video games may promote mental wellbeing, it is an extensive time investment to experimentally identify games that benefit players. The time delay between commercial games research and commercial game development can render such research out-of-date. In this work, we explore player-written game reviews as a way to expeditiously identifying games with potential benefits for mental wellbeing. Through a content analysis of review data, we found that players publicly disclose experiences consistent with self-care. Our analysis generated categories related to coping and recovery, emotional regulation, social connectedness, and obsessive play. Through this process, we identified several games as strong candidates for further research. Our work contributes to an emerging research agenda of commercial video games as therapy (VGTx), by providing a technique for rapidly identifying games with therapeutic potential. Further, we demonstrate that Steam user reviews are a valuable source of affective player experience data-a contribution with broad implications for player experience research.

Studies in psychology have shown that framing effects, where the positive or negative attributes of logically equivalent choices are emphasised, influence people's decisions. When outcomes are uncertain, framing effects also induce patterns of choice reversal, where decisions tend to be risk averse when gains are emphasised and risk seeking when losses are emphasised. Studies of these effects typically use potent framing stimuli, such as the mortality of people suffering from diseases or personal financial standing. We examine whether these effects arise in users' decisions about interface features, which typically have less visceral consequences, using a crowd-sourced study based on snap-to-grid drag-and-drop tasks (n = 842). The study examined several framing conditions: those similar to prior psychological research, and those similar to typical interaction choices (enabling/disabling features). Results indicate that attribute framing strongly influences users' decisions, that these decisions conform to patterns of risk seeking for losses, and that patterns of choice reversal occur.

Comparative analysis in genomics involves comparing two or more genomes to identify conserved genetic information. These duplicated regions can indicate shared ancestry and can shed light on an organism's internal functions and evolutionary history. Due to rapid advances in sequencing technology, high-resolution genome data is now available for a wide range of species, and comparative analysis of this data can provide insights that can be applied in medicine, plant breeding, and many other areas. Comparative genomics is a strongly interactive task, and visualizing the location, size, and orientation of conserved regions can assist researchers by supporting critical activities of interpretation and judgment. However, visualization tools for the analysis of conserved regions have not kept pace with the increasing availability of genomic information and the new ways in which this data is being used by biological researchers. To address this gap, we gathered requirements for interactive exploration from three groups of expert genomic scientists, and developed a web-based tool called SynVisio with novel interaction techniques and visual representations to meet those needs. Our tool supports multi-resolution analysis, provides interactive filtering as researchers move deeper into the genome, supports revisitation to specific interface configurations, and enables loosely-coupled collaboration over the genomic data. An evaluation of the system with five researchers from three expert groups provides evidence about the success of our system's novel techniques for supporting interactive exploration of genomic conservation.

Learnability is important in graphical interfaces because it supports the user's transition to expertise. One aspect of GUI learnability is the degree to which the icons in toolbars and ribbons are identifiable and memorable - but current "flat" and "subtle" designs that promote strong visual consistency could hinder learning by reducing visual distinctiveness within a set of icons. There is little known, however, about the effects of visual distinctiveness of icons on selection performance and memorability. To address this gap, we carried out two studies using several icon sets with different degrees of visual distinctiveness, and compared how quickly people could learn and retrieve the icons. Our first study found no evidence that increasing colour or shape distinctiveness improved learning, but found that icons with concrete imagery were easier to learn. Our second study found similar results: there was no effect of increasing either colour or shape distinctiveness, but there was again a clear improvement for icons with recognizable imagery. Our results show that visual characteristics appear to affect UI learnability much less than the meaning of the icons' representations.

Touch interactions with current mobile devices have limited expressiveness. Augmenting devices with additional degrees of freedom can add power to the interaction, and several augmentations have been proposed and tested. However, there is still little known about the effects of learning multiple sets of augmented interactions that are mapped to different applications. To better understand whether multiple command mappings can interfere with one another, or affect transfer and retention, we developed a prototype with three pushbuttons on a smartphone case that can be used to provide augmented input to the system. The buttons can be chorded to provide seven possible shortcuts or transient mode switches. We mapped these buttons to three different sets of actions, and carried out a study to see if multiple mappings affect learning and performance, transfer, and retention. Our results show that all of the mappings were quickly learned and there was no reduction in performance with multiple mappings. Transfer to a more realistic task was successful, although with a slight reduction in accuracy. Retention after one week was initially poor, but expert performance was quickly restored. Our work provides new information about the design and use of chorded buttons for augmenting input in mobile interactions.

Finding and revisiting objects in visual content collections is common in many analytics tasks. For large collections, filters are often used to reduce the number of items shown, but many systems generate a new ordering of the items for every filter update - and these changes make it difficult for users to remember the locations of important items. An alternative is to show the entire dataset in a spatially-stable layout, and show filter results with highlighting. The spatial approach has been shown to work well with small datasets, but little is known about how spatial memory scales to tasks with hundreds of items. To investigate the scalability of spatial presentations, we carried out a study comparing finding and re-finding performance with two data organizations: pages of items that re-generate item ordering with each filter change, and a spatially-stable organization that presents all 700 items at once. We found that although overall times were similar, the spatial interface was faster for revisitation, and participants used fewer filters than in the paged interface as they gained familiarity with the data. Our results add to previous work by showing that spatial interfaces can work well with datasets of hundreds of items, and that they better support a transition to fast revisitation using spatial memory.

Emphasis effects - visual changes that make certain elements more prominent - are commonly used in information visualization to draw the user's attention or to indicate importance. Although theoretical frameworks of emphasis exist (that link visually diverse emphasis effects through the idea of visual prominence compared to background elements), most metrics for predicting how emphasis effects will be perceived by users come from abstract models of human vision which may not apply to visualization design. In particular, it is difficult for designers to know, when designing a visualization, how different emphasis effects will compare and how to ensure that the user's experience with one effect will be similar to that with another. To address this gap, we carried out two studies that provide empirical evidence about how users perceive different emphasis effects, using three visual variables (colour, size, and blur/focus) and eight strength levels. Results from gaze tracking, mouse clicks, and subjective responses in our first study show that there are significant differences between different kinds of effects and between levels. Our second study tested the effects in realistic visualizations taken from the MASSVIS dataset, and saw similar results. We developed a simple predictive model from the data in our first study, and used it to predict the results in the second; the model was accurate, with high correlations between predictions and real values. Our studies and empirical models provide new information for designers who want to understand how emphasis effects will be perceived by users.

All real-time computer games, particularly networked computer games, have a delay from when a player starts an action (e.g., clicking the mouse) until the game renders the result (e.g., firing a projectile). This delay can degrade both player performance (e.g., reduced game score) and quality of experience (e.g., the game is less fun). While previous work has studied the effects of delay on commercial games and individual game actions, a more detailed understanding is needed of the effects of delay on moving target selection with realistic target motion, a common scenario in many games. This paper presents an in-depth study of the effects of delay on the fundamental game action of selecting a moving target with a mouse while varying two parameters for the target motion – turn frequency and turn angle. We design and implement a custom game where players select moving targets using a mouse, while the game controls both the target motion and input delay. Analysis of data gathered in a 56-person user study shows both target selection time and accuracy degrade with delay. However, both selection time and accuracy increase with the frequency and angle of changes in the target’s movement, because turning slows targets down even while making them less predictable. We set these results in the context of other studies of delay and target selection by comparing our findings to those in seven other previously published papers that investigated the effects of delay on target selection.

Within-subjects experiments are prone to asymmetric transfer, which confounds results interpretation. While HCI researchers routinely test asymmetric transfer in objective data, doing so for subjective data is rare. Yet literature suggests that anchoring effects should make subjective measures particularly susceptible to asymmetric transfer. We report on four analyses of NASA-TLX data from four previously published HCI papers, with four main findings. First, asymmetric transfer is common, occurring in 42% of tests analysed. Second, the data conforms to predictions of anchoring effects. Third, the magnitude of the anchor's effect correlates with the magnitude of the difference between the interface ratings -- that is, the anchor's 'pull' correlates with the anchoring stimulus. Fourth, several of the previously published findings are changed when data are reanalysed using between-subjects treatment. We urge caution when analysing within-subjects subjective measures and recommend that researchers test for and report the occurrence of asymmetric transfer.

Time-lapse videos are often navigated by scrubbing with a slider. When networks are slow or images are large, however, even thumbnail versions load so slowly that scrubbing is limited to the start of the video. We developed a frame-loading technique called spread-loading that enables scrubbing regardless of delivery rate. Spread-loading orders frame delivery to maximize coverage of the entire sequence; this provides a temporal overview of the entire video that can be fully navigated at any time during delivery. The overview initially has a coarse temporal resolution, becoming finer-grained with each new frame. We compared spread-loading with traditional linear loading in a study where participants were asked to find specific episodes in a long time-lapse sequence, using three views with increasing levels of detail. Results show that participants found target episodes significantly and substantially faster with spread-loading, regardless of whether they could click to change the load point. Users rated spread-loading as requiring less effort, and strongly preferred the new technique.

Studies have shown certain game tasks such as targeting to be negatively and significantly affected by latencies as low as 41ms. Therefore it is important to understand the relationship between local latency - delays between an input action and resulting change in the display - and common gaming tasks such as targeting and tracking. In addition, games now use a variety of input devices, including touchscreens, mice, tablets and controllers. These devices provide very different combinations of direct/indirect input, absolute/relative movement, and position/rate control, and are likely to be affected by latency in different ways. We performed a study evaluating and comparing the effects of latency across four devices (touchscreen, mouse, controller and drawing tablet) on targeting and interception tasks. We analyze both throughput and path characteristics, identify differences between devices, and provide design considerations for game designers.

Visual notifications are integral to interactive computing systems. With large displays, however, much of the content is in the user's visual periphery, where human capacity to notice visual effects is diminished. One design strategy for enhancing noticeability is to combine visual features, such as motion and colour. Yet little is known about how feature combinations affect noticeability across the visual field, or about how peripheral noticeability changes when a user's primary task involves the same visual features as the notification. We addressed these questions by conducting two studies. Results of the first study showed that noticeability of feature combinations were approximately equal to the better of the individual features. Results of the second study suggest that there can be interference between the features of primary tasks and the visual features in the notifications. Our findings contribute to a better understanding of how visual features operate when used as peripheral notifications.

Full-coverage displays can place visual content anywhere on the interior surfaces of a room (e.g., a weather display near the coat stand). In these settings, digital artefacts can be located behind the user and out of their field of view - meaning that it can be difficult to notify the user when these artefacts need attention. Although much research has been carried out on notification, little is known about how best to direct people to the necessary location in room environments. We designed five diverse attention-guiding techniques for full-coverage display rooms, and evaluated them in a study where participants completed search tasks guided by the different techniques. Our study provides new results about notification in full-coverage displays: we showed benefits of persistent visualisations that could be followed all the way to the target and that indicate distance-to-target. Our findings provide useful information for improving the usability of interactive full-coverage environments.

All real-time computer games, particularly networked computer games, have a delay from when a player starts an action (e.g., clicking the mouse) until the game renders the result (e.g., firing a projectile). This delay can degrade both player performance (e.g., lower game score) and quality of experience (e.g., less fun). While previous work has studied the effects of delay on commercial games and individual game actions, a more detailed understanding is needed of the effects of delay on moving target selection with realistic target motion. This paper presents an in-depth study of the effects of delay on the fundamental game action of selecting a moving target with a mouse with parameters for the target motion - turn frequency and turn angle. We design and implement a custom game where players select moving targets using a mouse, while the game controls both the target motion and input delay. Analysis of data gathered in a 56-person user study shows both user time and accuracy in selecting the moving target degrade with delay. Target turn frequency and turn angle can make a target easier to select (i.e., selection accuracy increases), but take longer to do so (i.e., selection time increases), because turning slows targets down while making them less predictable.

Incorporating touchscreen interaction into cockpit flight systems offers several potential advantages to aircraft manufacturers, airlines, and pilots. However, vibration and turbulence are challenges to reliable interaction. We examine the design space for braced touch interaction, which allows users to mechanically stabilise selections by bracing multiple fingers on the touchscreen before completing selection. Our goal is to enable fast and accurate target selection during high levels of vibration, without impeding interaction performance when vibration is absent. Three variant methods of braced touch are evaluated, using doubletap, dwell, or a force threshold in combination with heuristic selection criteria to discriminate intentional selection from concurrent braced contacts. We carried out an experiment to test the performance of these methods in both abstract selection tasks and more realistic flight tasks. The study results confirm that bracing improves performance during vibration, and show that doubletap was the best of the tested methods.

Vehicle manufacturers are increasingly using touchscreens to support driver access to controls. However, input mechanisms displayed on touchscreens lack the tactile sensations of physical controls, creating risks of greater demand for visual attention. These risks can potentially be mitigated by restoring some degree of tactile feedback to touchscreen interaction. This paper describes a study that examines whether touchscreen target selection during simulated driving is improved by overlaying the touchscreen with a see-through 3D printed stencil that allows underlying touchscreen controls to be located or guided by feel. Results showed that touchscreen targets were selected more quickly and with shorter periods of visual attention towards the touchscreen when the stencil was present than when it was absent. Subjective preferences also favoured the stencil condition. The work demonstrates the value of adding tactile feedback to touchscreen interaction, and shows that stencils are a simple and effective way to reduce attentional demands.

Document readers with linear navigation controls do not work well when users need to navigate to previously-visited locations, particularly when documents are long. Existing solutions - bookmarks, search, history, and read wear - are valuable but limited in terms of effort, clutter, and interpretability. In this paper, we investigate artificial landmarks as a way to improve support for revisitation in long documents - inspired by visual augmentations seen in physical books such as coloring on page edges or indents cut into pages. We developed several artificial-landmark visualizations that can represent locations even in documents that are many hundreds of pages long, and tested them in studies where participants visited multiple locations in long documents. Results show that providing two columns of landmark icons led to significantly better performance and user preference. Artificial landmarks provide a new mechanism to build spatial memory of long documents - and can be used either alone or with existing techniques like bookmarks, read wear, and search.

Navigating to previously-visited pages is a trivial yet fundamental task in linear control-based document viewers. These widgets e.g., scrollbars often do not work well particularly for long documents. Existing solutions try to tackle this issue with bookmarks, search, history, and read wear but limited in terms of effort, clutter, and interpretability. To improve the revisitation support in long documents, we investigated the use of artificial landmarks similar to the visual augmentations available in physical books: coloring on page edges or indents cut into pages. We developed several artificial-landmark visualizations to represent page-locations in the scrollbar for many hundreds of pages long documents, and tested them in studies where participants visited multiple locations in long documents. Results indicate that using two columns of landmark icons significantly improved revisitation performance and preferred by users. Our two-level artificial-landmark augmented scrollbars can be a new way to support spatial memory development of long documents - and can be used either in isolation or in congregation with current techniques.

Experimental preregistration is required for publication in many scientific disciplines and venues. When experimental intentions are preregistered, reviewers and readers can be confident that experimental evidence in support of reported hypotheses is not the result of HARKing, which stands for Hypothesising After the Results are Known. We review the motivation and outcomes of experimental preregistration across a variety of disciplines, as well as previous work commenting on the role of evaluation in HCI research. We then discuss how experimental preregistration could be adapted to the distinctive characteristics of Human-Computer Interaction empirical research, to the betterment of the discipline.

Atomic interactions in touch interfaces, like tap, drag, and flick, are well understood in terms of interaction design, but less is known about their physical performance characteristics. We carried out a study to gather baseline data about finger pitch and roll orientation during atomic touch input actions. Our results show differences in orientation and range for different fingers, hands, and actions, and we analyse the effect of tablet angle. Our data provides designers and researchers with a new resource to better understand what interactions are possible in different settings ( e.g. when using the left or right hand), to design novel interaction techniques that use orientation as input (e.g. using finger tilt as an implicit mode), and to determine whether new sensing techniques are feasible (e.g. using fingerprints for identifying specific finger touches).

Touch interactions are now ubiquitous, but few tools are available to help designers quickly prototype touch interfaces and predict their performance. For rapid prototyping, most applications only support visual design. For predictive modelling, tools such as CogTool generate performance predictions but do not represent touch actions natively and do not allow exploration of different usage contexts. To combine the benefits of rapid visual design tools with underlying predictive models, we developed the Storyboard Empirical Modelling tool (StEM) for exploring and predicting user performance with touch interfaces. StEM provides performance models for mainstream touch actions, based on a large corpus of realistic data. We evaluated StEM in an experiment and compared its predictions to empirical times for several scenarios. The study showed that our predictions are accurate (within 7% of empirical values on average), and that StEM correctly predicted differences between alternative designs. Our tool provides new capabilities for exploring and predicting touch performance, even in the early stages of design.

Text selection on touch devices can be a difficult task for users. Letters and words are often too small to select directly, and the enhanced interaction techniques provided by the OS -- magnifiers, selection handles, and methods for selecting at the character, word, or sentence level -- often lead to as many usability problems as they solve. The introduction of force-sensitive touchscreens has added another enhancement to text selection (using force for different selection modes); however, these modes are difficult to discover and many users continue to struggle with accurate selection. In this paper we report on an investigation of the design of touch-based and force-based text selection mechanisms, and describe two novel text-selection techniques that provide improved discoverability, enhanced visual feedback, and a higher performance ceiling for experienced users. Two evaluations show that one design successfully combined support for novices and experts, was never worse than the standard iOS technique, and was preferred by participants.

As display environments become larger and more diverse - now often encompassing multiple walls and room surfaces - it is becoming more common that users must find and manipulate digital artifacts not directly in front of them. There is little understanding, however, about what techniques and devices are best for carrying out basic operations above, behind, or to the side of the user. We conducted an empirical study comparing two main techniques that are suitable for full-coverage display environments: mouse-based pointing, and ray-cast 'laser' pointing. Participants completed search and pointing tasks on the walls and ceiling, and we measured completion time, path lengths and perceived effort. Our study showed a strong interaction between performance and target location: when the target position was not known a priori the mouse was fastest for targets on the front wall, but ray-casting was faster for targets behind the user. Our findings provide new empirical evidence that can help designers choose pointing techniques for full-coverage spaces.

In the physical world, teammates develop situation awareness about each other's location, status, and actions through cues such as gaze direction and ambient noise. To support situation awareness, distributed multiplayer games provide awareness cues - information that games automatically make available to players to support cooperative gameplay. The design of awareness cues can be extremely complex, impacting how players experience games and work with teammates. Despite the importance of awareness cues, designers have little beyond experiential knowledge to guide their design. In this work, we describe a design framework for awareness cues, providing insight into what information they provide, how they communicate this information, and how design choices can impact play experience. Our research, based on a grounded theory analysis of current games, is the first to provide a characterization of awareness cues, providing a palette for game designers to improve design practice and a starting point for deeper research into collaborative play.

The capacity of spatial multi-touch menus such as FastTap is limited by device screen size. We explore the idea of using multiple tabs to increase capacity - multiplexing the tablet's screen space so each location holds multiple items. Earlier work has shown potential of this idea for smartwatches, but no evaluations have considered larger devices. To assess issues with interference-based errors and spatial memory development, we built two FastTap systems with multiple tabs and conducted two studies. We first tested user learning of 16 targets with a training game, and found that participants easily adapted to the multi-tab model, were able to perform memory-based shortcuts, and made few interference-based errors. The second study used realistic drawing tasks and showed that people successfully used the multi-tab FastTap system, with 88% of selections made using shortcuts by the study's end. Our work demonstrates that spatial memory can successfully be multiplexed, and that tabs are a promising way to increase command set sizes for spatial interfaces.

Touchscreen input in commercial aircraft cockpits offers potential advantages, including ease of use, modifiability, and reduced weight. However, tolerance to turbulence is a challenge for their deployment. To better understand the impact of turbulence on cockpit input methods we conducted a comparative study of user performance with three input methods -- touch, trackball (as currently used in commercial aircraft), and a touchscreen stencil overlay designed to assist finger stabilization. These input methods were compared across a variety of interactive tasks and at three levels of simulated turbulence (none, low, and high). Results showed that performance degrades and subjective workload increases as vibration increases. Touch-based interaction was faster than the trackball when precision requirements were low (at all vibrations), but it was slower and less accurate for more precise pointing, particularly at high vibrations. The stencil did not improve touch selection times, although it did reduce errors on small targets at high vibrations, but only when finger lift-off errors had been eliminated by a timeout. Our work provides new information on the types of tasks affected by turbulence and the input mechanisms that perform best under different levels of vibration.

By exploiting visual popout effects, interface designers can rapidly draw a user's attention to salient information objects in a display. A variety of different visual stimuli can be used to achieve popout effects, including color, shape, size, motion, luminance, and flashing. However, there is a lack of understanding about how accurately different intensities of these effects support popout, particularly as targets move further from the center of the visual field. We therefore conducted a study to examine the accuracy of popout target identification using different visual variables, each at five different levels of intensity, and at a wide range of angles from the display center. Results show that motion is a strong popout stimulus, even at low intensities and wide angles. Identification accuracy decreases rapidly across visual angle with other popout stimuli, particularly with shape and color. The findings have relevance to a wide variety of applications, particularly as multi-display desktop environments increase in size and visual extent.

Finding (and re-finding) locations in text documents is a common activity for most computer users -- but tools for document navigation are still limited in many ways. Previous research has shown that a spatially-stable overview of the entire document can be substantially faster than any other navigation technique -- particularly when revisiting previous locations. However, the overview technique has only been tested in a limited laboratory study, so little is known about whether it works in more realistic contexts. To answer this question, we developed a PDF viewer that incorporates several document-navigation techniques, and carried out two studies. First, we ran a field experiment in which users carried out search tasks using an overview and other techniques -- on their own computers in a non-laboratory environment. Second, we ran a smaller field study in which people used our viewer (with choice of navigation techniques) for their own PDF tasks. In the field experiment, the overview was significantly and substantially faster than other techniques, and in the field study, the technique was frequently used for a wide variety of documents. Our work provides confirmation of the value of spatially stable overviews as a basis for document navigation.

Spatial memory is a powerful way for users to become expert with an interface, because remembering item locations means that users do not have to carry out slow visual search. Spatial learning in the real world benefits greatly from landmarks in the environment, but user interfaces often provide very few visual landmarks. In this paper we explore the use of artificial landmarks as a way to improve people's spatial memory in spatially-stable grid menus called CommandMaps. We carried out three studies to test the effects of three types of artificial landmarks (standard grid, simple anchor marks, and a transparent image) on spatial learning. We found that for small grid menus, the artificial landmarks had little impact on performance, whereas for medium and large grids, the simple anchor marks significantly improved performance. The simple visual anchors were faster and less error-prone than the visually richer transparent image. Our studies show that artificial landmarks can be a valuable addition to spatial interfaces.

Awareness information in shared-workspace groupware is often ephemeral, and when users are interrupted or look away from the system, they can miss important information about others' activities. These attentional disconnections are brief (generally less than ten seconds), are frequent in many work environments, and can occur for many reasons. In this paper, we provide visualization techniques that can help groupware users recover from these short absences. First, we provide a simple attention monitor that informs groupware systems whether a user is looking at the screen and whether the workspace is visible. Second, we provide a framework of catch-up techniques for visualizing missed activity -- including highlighting, motion traces, and replay. We implemented these techniques in three applications that cover different communication methods and interaction speeds, and explored the use of the effects in three studies. Participants clearly saw the value of catch-up techniques, and although different techniques were preferred in different situations, nearly all users strongly preferred the catch-up techniques. Our work shows that helping users deal with periods of attentional disconnection can substantially improve the usability of real-time groupware systems.

Expert interaction techniques enable users to greatly improve their performance; however, to realize these advantages, the user must first acquire the skill necessary to use a technique, then choose to use it over competing novice techniques. This article investigates several factors that may influence whether use of an expert technique persists when the context of use changes. Two studies examine the effect of changing performance requirements, and find that a high performance requirement imposed in a training context can effectively push users to adopt an expert technique, and that use of the technique is maintained when the requirement is subsequently reduced or removed. In a final study, performance requirement, high-level task, and environment of use are changed—participants played a training game to learn the menu for a drawing application, which they then used to complete a series of drawings over the following week. Participants exhibited a somewhat surprising “all-or-nothing” effect, using the expert technique nearly exclusively or not at all, and maintaining this behavior over a range of qualitatively different tasks. This suggests that switching to an expert technique involves a global change by the user, rather than an incremental change as suggested by previous work.

In social play settings, it can be difficult for people with different skill levels to play a game together. Player balancing that provides skill assistance for the weaker player can allow for enjoyable play experiences; however, previous research (and conventional wisdom) has suggested that skill assistance should be kept hidden to avoid perceptions of unfairness. We carried out a study to test how disclosing skill assistance affects player experience. We found -- surprisingly -- that disclosing assistance did not harm play experience; players were more influenced by the benefits of equalized performance resulting from assistance than by their knowledge of the assist. We introduce the idea of attribution biases to help explain why awareness was not harmful -- people tend to take credit for their successes, but attribute failures externally. We discuss how game designers can incorporate skill assistance to build multiplayer games that improve experiences for a wide range of players.

The peak-end rule is a psychological heuristic observing that people's retrospective assessment of an experience is strongly influenced by the intensity of the peak and final moments of that experience. We examine how aspects of game player experience are influenced by peak-end manipulations to the sequence of events in games that are otherwise objectively identical. A first experiment examines players' retrospective assessments of two games (a pattern matching game based on Bejeweled and a point-and-click reaction game) when the sequence of difficulty is manipulated to induce positive, negative and neutral peak-end effects. A second experiment examines assessments of a shootout game in which the balance between challenge and skill is similarly manipulated. Results across the games show that recollection of challenge was strongly influenced by peak-end effects; however, results for fun, enjoyment, and preference to repeat were varied -- sometimes significantly in favour of the hypothesized effects, sometimes insignificant, but never against the hypothesis.

Small touchscreens worn on the wrist are becoming increasingly common, but standard interaction techniques for these devices can be slow, requiring a series of coarse swipes and taps to perform an action. To support faster command selection on watches, we investigate two related interaction techniques that exploit spatial memory. WristTap uses multitouch to allow selection in a single action, and TwoTap uses a rapid combination of two sequential taps. In three quantitative studies, we investigate the design and performance of these techniques in comparison to standard methods. Results indicate that both techniques are feasible, able to accommodate large numbers of commands, and fast users are able to quickly learn the techniques and reach performance of ~1.0 seconds per selection, which is approximately one-third of the time of standard commercial techniques. We also provide insights into the types of applications for which these techniques are well-suited, and discuss how the techniques could be extended.

Hidden toolbars are becoming common on mobile devices. These techniques maximize the space available for application content by keeping tools off-screen until needed. However, current designs require several actions to make a selection, and they do not provide shortcuts for users who have become familiar with the toolbar. To better understand the performance capabilities and tradeoffs involved in hidden toolbars, we outline a design space that captures the key elements of these controls, and report on an empirical evaluation of four designs. Two of our designs provide shortcuts that are based on the user's spatial memory of item locations. The study found that toolbars with spatial-memory shortcuts had significantly better performance (700ms faster) than standard designs currently in use. Participants quickly learned the shortcut selection method (although switching to a memory-based method led to higher error rates than the visually-guided techniques). Participants strongly preferred one of the shortcut methods that allowed selections by swiping across the screen bezel at the location of the desired item. This work shows that shortcut techniques are feasible and desirable on touch devices, and shows that spatial memory can provide a foundation for designing shortcuts.

Command selection on large multi-touch surfaces can be difficult, because the large surface means that there are few landmarks to help users build up familiarity with controls. However, people's hands and fingers are landmarks that are always present when interacting with a touch display. To explore the use of hands as landmarks, we designed two hand-centric techniques for multi-touch displays -- one allowing 42 commands, and one allowing 160 -- and tested them in an empirical comparison against standard tab widgets. We found that the small version (HandMark-Fingers) was significantly faster at all stages of use, and that the large version (HandMark-Multi) was slower at the start but equivalent to tabs after people gained experience with the technique. There was no difference in error rates, and participants strongly preferred both of the HandMark menus over tabs. We demonstrate that people's intimate knowledge of their hands can be the basis for fast and feasible interaction techniques that can improve the performance and usability of interactive tables and other multi-touch systems.

Collaborative information seeking frequently occurs in an opportunistic and loosely-coupled fashion that is supported by awareness of others' activities on the web. Automatically sharing traces of information about web activity could substantially improve these collaborative information tasks, but conventional wisdom suggests that people are very reluctant to share information about web usage. Because work settings have different rules and practices about privacy, we carried out the first systematic study of people's privacy concerns about sharing web activity within workgroups. To provide a better understanding of privacy concerns about sharing web activity at work, we conducted a two-week diary study with 18 participants. Our study system asked participants to report on their search tasks and privacy concerns. Surprisingly, our results showed that people have little concern about sharing the majority of their activities with their work colleagues, and had even fewer concerns with sharing work-related activities. Our results provide new insights into the possibilities of sharing web activities within workgroups, and provide evidence that tools based on automatic sharing of awareness information can be feasible.

Although some forms of distributed groupware now enable fast-paced real-time collaboration (e.g., first-person shooter games), little work has been done to determine how coordination and interaction occur when people attempt to work together at high speed. Understanding the elements of high-speed coordination is important, because shared-workspace groupware systems offer opportunities for new kinds of high-speed work that is, they provide freedom from the physical constraints that can slow and restrict coordination in physical shared spaces. To better understand high-speed coordination, and to examine whether these opportunities can enable new kinds of interaction in groupware, we created and studied a new multi-player game (called RTChess) that is based on traditional chess, but adds multiple players and removes all turns from the gameplay. The result is a free-for-all game where people are limited only by their ability to move quickly and expertly a situation that is more like a team sport than a tabletop game. We carried out an observational study of 448 games of RTChess to look for the emergence of high-speed interaction, team coordination, and interactional expertise. We found that people can interact extremely quickly through distributed groupware, and saw evidence that people build expertise and develop several kinds of coordination in the game. Groupware systems like RTChess indicate that coordination and interaction in shared-workspace collaboration can occur at high speed, and suggest ways to free groupware users from the slow and stilted interactions that are common in many current multi-user systems.

Online board-game sites are popular settings for group activity. However, unlike many kinds of group interaction, previous research has found that there is often little verbal conversation during games, which seems strange in a social situation. One reason that has been suggested for the lack of talk is that actions in the game are themselves communicative acts that can replace verbal utterances. There is little known, however, about how games can substitute for verbal conversation. In this paper we carry out a study exploring meaning and shared understanding through the moves of a board game. Participants played a board game and then retrospectively analysed the communicative meaning of each move; we analysed their responses as indicative of "joint actions" in four layers of interaction. Our study shows that game moves can provide a great deal of communication, and that there are both similarities and differences to verbal conversations at each level. The physical layer, containing the board, is a foundation similar to that of people speaking the same language. The syntactic layer, consisting of the game rules, allows demonstration of expertise but is not noticed by players except in unusual circumstances. The strategic layer, consisting of competitive use of the syntactic rules, diverges considerably from a verbal conversation in terms of shared understanding, because players are actively attempting to avoid revealing their meaning. The personality layer allows players to make inferences about the other player as a person, just as in verbal communication. Our analysis provides new evidence that even simple turn-based games contain a great deal of interaction richness and subtlety, and that the different levels of communication should be considered by designers as a real and legitimate vehicle for social interaction.

Fast command selection is important for touch devices, but there are few techniques that allow accelerated selection while still providing a large command set. HandMark menus [25] propose the use of the hands as landmarks for fast memory-based selection. However, the original HandMark menus rely on bimanual operation, and earlier studies provided only limited evidence for the value of hand-based landmarks as a reference frame for spatial memory. In this paper we address these limitations. We introduce adapted HandMark menus that can be operated with one hand (while the other hand holds the tablet); the new version changes bimanual selection operations into sequential actions with one hand. We carried out three studies of these HandMark menus. The first study showed that the adapted menus still allowed fast performance and the development of spatial memory, even with one-handed use. The second study focused on the value of hands as landmarks, by comparing HandMark menus against a hidden popup menu. This study showed that using the hand as a reference frame significantly improved performance, and was strongly preferred by participants. Our work extends HandMark menus and shows that they are an effective selection method for tablets, and provides new evidence about the value of the hands as a spatial landmark for interaction.

Although rapid command selection is important for touch devices, only a few techniques allow accelerated selection while still providing a large command set. HandMark menus [3] propose the use of the hands as landmarks for fast memory-based selection. However, the original HandMark menus for tables rely on bimanual operation - not suitable for tablets, and earlier studies provided only limited evidence for the value of hand-based landmarks as a reference frame for spatial memory. We introduce adapted HandMark menus that can be operated with one hand (while the other hand holds the tablet); the new version changes bimanual selection operations into sequential actions with one hand. Three studies of these HandMark menus showed that using the hand as a landmark significantly improved performance and allowed fast spatial memory development, even with one-handed use. Our work extends HandMark menus and shows that they are an effective selection method for tablets, and provides new evidence about the value of the hands as a spatial landmark for interaction.

Abstract We provide afresh look at the use and prevalence of emphasis effects in Infovis. Through a survey of existing emphasis frameworks, we extract a set‐based approach that uses visual prominence to link visually and algorithmically diverse emphasis effects. Visual prominence provides a basis for describing, comparing and generating emphasis effects when combined with a set of general features of emphasis effects. Therefore, we use visual prominence and these general features to construct a new mathematical Framework for Information Visualization Emphasis, FIVE. The concepts we introduce to describe FIVE unite the emphasis literature and point to several new research directions for emphasis in information visualization.

Displaying 3D objects on horizontal displays can cause problems in the way that the virtual scene is presented on the 2D surface; inappropriate choices in how 3D is represented can lead to distorted images and incorrect object interpretations. We present four experiments that test 3D perception. We varied projection geometry in three ways: type of projection (perspective/parallel), separation between the observer's point of view and the projection's center (discrepancy), and the presence of motion parallax (with/without parallax). Projection geometry had strong effects different for each task. Reducing discrepancy is desirable for orientation judgments, but not for object recognition or internal angle judgments. Using a fixed center of projection above the table reduces error and improves accuracy in most tasks. The results have far-reaching implications for the design of 3D views on tables, in particular, for multi-user applications where projections that appear correct for one person will not be perceived correctly by another.

Psychological research has shown that 'peak-end' effects influence people's retrospective evaluation of hedonic and affective experience. Rather than objectively reviewing the total amount of pleasure or pain during an experience, people's evaluation is shaped by the most intense moment (the peak) and the final moment (end). We describe an experiment demonstrating that peak-end effects can influence a user's preference for interaction sequences that are objectively identical in their overall requirements. Participants were asked to choose which of two interactive sequences of five pages they preferred. Both sequences required setting a total of 25 sliders to target values, and differed only in the distribution of the sliders across the five pages -- with one sequence intended to induce positive peak-end effects, the other negative. The study found that manipulating only the peak or the end of the series did not significantly change preference, but that a combined manipulation of both peak and end did lead to significant differences in preference, even though all series had the same overall effort.

Real-time games such as first-person shooters (FPS) are sensitive to even small amounts of lag. The effects of net-work latency have been studied, but less is known about local latency, the lag caused by input devices and displays. While local latency is important to gamers, we do not know how it affects aiming performance and whether we can reduce its negative effects. To explore these issues, we tested local latency in a variety of real-world gaming scenarios and carried out a controlled study focusing on targeting and tracking activities in an FPS game with varying degrees of local latency. In addition, we tested the ability of a lag compensation technique (based on aim assistance) to mitigate the negative effects. Our study found local latencies in the real-world range from 23 to 243 ms which cause significant and substantial degradation in performance (even for latencies as low as 41 ms). The study also showed that our compensation technique worked extremely well, reducing the problems caused by lag in the case of targeting, and removing the problem altogether in the case of tracking. Our work shows that local latency is a real and substantial problem -- but games can mitigate the problem with appropriate compensation methods.

When player skill levels differ widely in a competitive First-Person Shooter (FPS) game, enjoyment suffers: weaker players become frustrated and stronger players become less engaged. Player balancing techniques attempt to assist the weaker player and make games more competitive, but these techniques have limitations for deployment when skill levels vary substantially. We developed new player balancing schemes to deal with a range of FPS skill difference, and tested these techniques in one-on-one deathmatches using a commercial-quality FPS game developed with the UDK engine. Our results showed that the new balancing schemes are extremely effective at balancing, even for players with large skill differences. Surprisingly, the techniques that were most effective at balancing were also rated as most enjoyable by both players -- even though these schemes were the most noticeable. Our study is the first to show that player balancing can work well in realistic FPS games, providing developers with a way to increase the audience for this popular genre. In addition, our results demonstrate the idea that successful balancing is as much about the way the technique is applied as it is about the specific manipulation.

Tabletop work surfaces have natural advantages for co-located collaboration, but also have physical constraints that can make group work difficult. View portals have been proposed as a way to provide access to other parts of a table surface, and as a way to re-orient content for group members in different locations; however, there is little research on whether portals really do improve group performance, how much they help, and whether they change other aspects of collaboration. We report on two studies that evaluate the effects of portals on group performance and behavior. Our first study showed significant performance advantages for portals: people were able to complete tasks more quickly and with more equal division of labor. Our second study, with a realistic design task, showed that people used portals extensively and saw them as valuable, but that they affected people's ability to maintain awareness, coordinate access to objects, and understand the organization of the workspace. Our work demonstrates benefits and potential drawbacks of portals for tables, and suggests that designers should carefully consider both individual and group needs before implementing these and other tabletop view augmentations.

Code clone visualizations (CCVs) are graphical representations of clone detection results provided by various state-of-the-art command line and graphical analysis tools. In order to properly analyze and manipulate code clones within a target system, these visualizations must be easily and efficiently comprehensible. We conducted an eye-tracking study with 20 participants (expert, intermediate, and novice) to assess how well people can comprehend visualizations such as Scatter plots, Treemaps, and Hierarchical Dependency Graphs provided by VisCad, a recent clone visualization tool. The goals of the study were to find out what elements of the visualizations (e.g., colors, shapes, object positions) are most important for comprehension, and to identify common usage patterns for different groups. Our results help us understand how developers with different levels of expertise explore and navigate through the visualizations while performing specific tasks. Distinctive patterns of eye movements for different visualizations were found depending on the expertise of the participants. Color, shape and position information were found to play vital roles in comprehension of CCVs. Our results provide recommendations that can improve the implementation of visualization techniques in VisCad and other clone visualization systems.

Identifying a target command can be difficult and time-consuming when the user is unfamiliar with a software system. One technique for assisting command identification is to provide a subset interface that contains only a limited set of the system's capabilities. We examine the design of subset interfaces, showing that subsets can be presented separately to the full user interface (UI) (e.g. in a palette) or in place, with in-place methods using either static or dynamic methods to identify the subset. We introduce the StencilMap and EphemeralMap as in-place subset UIs that, respectively, use static and dynamic highlighting. Both StencilMaps and EphemeralMaps make all of an application's commands concurrently available for selection within a grid. To highlight subset items StencilMaps use a static dark semi-transparent ‘stencil’ overlay to de-emphasise all but the subset items; EphemeralMaps, in contrast, use a short delay, with subset items shown immediately, and other items gradually faded in. A first experiment compares user performance with the in-place presentation of StencilMaps against that of the separate presentation of a subset palette. Results confirm the predicted spatial memory benefits for StencilMaps. A second experiment analyses the performance impact of three approaches to highlighting: none, static highlighting in StencilMaps, and dynamic highlighting in EphemeralMaps. Results show an interesting trade-off – while highlighting can offer benefits in assisting rapid target identification (particularly when the user is unfamiliar with the interface layout), there can also be longer-term performance benefits when highlighting is absent because the increased difficulty of visual search promotes the use and formation of spatial memory.

Navigating to files through a hierarchy is often a slow, laborious, and repetitive task. Recent lab studies showed that file browser interface augmentations, such as Icon Highlights and Search Directed Navigation, have the potential to reduce file retrieval times. However, for this potential to be realised in actual systems, further study is necessary to address two important issues. First, there are important design and implementation challenges in advancing the research prototypes previously evaluated into complete interactive systems that can be used for real work. Second, it is unknown how real users would employ these systems while engaged in actual work; would the potential performance improvements suggested by the earlier lab studies be realised? We therefore describe the design, implementation, and longitudinal field study evaluation of Finder Highlights, a file browser plugin for the OS X 'Finder' that adds support for Icon Highlights and Search Directed Navigation. Study results confirm that the augmentations are effective in reducing real-world file retrieval times, with retrieval times 13% faster when using Finder Highlights compared to the standard tool (10.6 s versus 12.2 s), while also emphasising important differences between lab and field studies. In summary, the paper strongly suggests that large-scale deployment of interface augmentations to file browsers, particularly Icon Highlights, will have a marked effect in improving users' real-world file retrieval.

Touch-based tablet UIs provide few shortcut mechanisms for rapid command selection; as a result, command selection on tablets often requires slow traversal of menus. We developed a new selection technique for multi-touch tablets, called FastTap, that uses thumb-and-finger touches to show and choose from a spatially-stable grid-based overlay interface. FastTap allows novices to view and inspect the full interface, but once item locations are known, FastTap allows people to select commands with a single quick thumb-and-finger tap. The interface helps users develop expertise, since the motor actions carried out as a novice rehearse the expert behavior. A controlled study showed that FastTap was significantly faster (by 33% per selection overall) than marking menus, both for novices and experts, and without reduction in accuracy or subjective preference. Our work introduces a new and efficient selection mechanism that supports rapid command execution on touch tablets, for both novices and experts.

Co-located work environments allow people to maintain awareness by observing others' actions (called consequen-tial communication), but the computerization of many tasks has dramatically reduced the observability of work actions. The recent interest in gestural interaction techniques offers the possibility of recreating some of the noticeability of previous work actions, but little is known about the observability and identifiability of command gestures. To investigate these basic issues, we carried out a study that asked people to observe and identify different sizes and morphologies of gestures from different locations, while carrying out an attention-demanding primary task. We studied small (tablet sized), medium (monitor-sized), and large (full-arm) gestures. Our study showed that although size did have significant effects, as expected, even small gestures were highly noticeable (rates above 75%) and identifiable (rates above 69%). Our results provide empirical guidance about the ways that gesture size, morphology, and location affect observation, and show that gestural interaction has potential for improving group awareness in co-located environments.

CommandMaps are a promising interface technique that flattens command hierarchies and exploits human spatial memory to provide rapid access to commands. CommandMaps have performed favorably in constrained cued-selection studies, but have not yet been tested in the context of real tasks. In this paper we present two real-world implementations of CommandMaps: one for Microsoft Word and one for an image editing program called Pinta. We use these as our experimental platforms in two experiments. In the first, we show that CommandMaps demonstrate performance and subjective advantages in a realistic task. In the second, we observe naturalistic use of CommandMaps over the course of a week, and gather qualitative data from interviews, questionnaires, and conversations. Our results provide substantial insight into users' reactions to CommandMaps, showing that they are positively received by users and allowing us to provide concrete recommendations to designers regarding when and how they should be implemented in real applications.

Many sports video games contain elements such as running or throwing that are based on real-world physical activities, but the translation of these activities to game controllers means that the original physicality is lost. This results in games where players have limited opportunity to improve their physical skills, where there is little differentiation in people's physical abilities, and where skills do not change over the course of a game. To explore ways of adding these elements back into sports games, we developed two games with small-scale physical controls for running and throwing -- one game was a simple running race, and one was a team-based handball-style game called Jelly Polo. In two studies (three track-and-field tournaments for the running game, and a four-week league for Jelly Polo), we observed the effects of physical controls on gameplay. Our studies showed that the physical controls enabled substantial individual differences in running and passing skill, allowed people to increase their expertise over time, and led to fatigue-based changes in performance during a game. Physical controls increased the games' challenge, complexity, and unpredictability, and dramatically improved player interest, expressiveness, and enjoyment. Our work shows that game designers should consider the idea of "exertion in the small" as a way to improve play experience in games based on physical activities.

Aim-assistance techniques have been shown to work for player balancing in 2D environments, but little information exists about how well these techniques will work in a 3D FPS game. We carried out three studies of the performance of five different aim assists in an Unreal-based game world. The assists worked well in a target-range scenario (study 1), but their performance was reduced when game elements were introduced in a walkthrough map (study 2). We systematically examined the relationships between realistic game elements and assist performance (study 3). These studies show that two techniques -- bullet magnetism and area cursor -- worked well in a wide variety of situations. Other techniques that worked well were too perceptible, and some previously-successful techniques did not work well in any game-like scenario. Our studies are the first to provide empirical evidence of the performance of aim assist techniques in 3D environments, and the first to identify the complexities in using these techniques in real FPS games.

Characters in games such as World of Warcraft allow players to act in the game world and to interact with others. Game characters and avatars are a mediated form of self-representation for the player, but some research suggests that players also view characters in other ways that have to do with the kinds of value that the characters provide. To better understand the ways that players value their characters in an online environment, we carried out a semi-structured interview study of twenty World of Warcraft players. From our data we identify ten kinds of value that characters can provide -- including utility, investment, communication, memory, enjoyment, and representations of relationships, as well as value as an opportunity for experience, creativity, sociability, and self-expression. The analytical lens of value provides a new understanding of the ways that players appreciate characters in online multi-user worlds. Our results can help developers understand and enhance an element of multi-player games that contributes greatly to player experience and satisfaction.

Network lag is a fact of life for networked games. Lag can cause game states to diverge at different nodes in the network, making it difficult to maintain the illusion of a single shared space. Traditional lag compensation techniques help reduce inconsistency in networked games; however, these techniques do not address what to do when states actually have diverged. Traditional consistency maintenance (CM) does not specify how to make game- critical decisions when players' views of the shared state are different, nor does it indicate how to repair inconsistencies. These two issues -- decision-making and error repair -- can have substantial effects on players' gaming experience. To address this shortcoming, we have characterized a range of algorithmic choices for decision- making and error repair. We report on a study confirming that these algorithms can have significant effects on player experience and performance, and showing that they are often more important than degree of consistency itself.

Pointing gestures -- particularly deictic references -- are ubiquitous in face-to-face communication. However, deictic pointing can be much more difficult in collaborative virtual environments (CVEs) than in everyday life -- early studies found that the 'fragmentation' caused by the environment greatly complicated object-based communication. In the fifteen years since these studies appeared, the technologies used in CVEs have improved substantially, and several techniques for improving pointing have been proposed or implemented. What these advances mean for the problems of fragmentation and deictic gesture, however, is not clear. To find out, we conducted a new observational study of deictic pointing in a CVE with several techniques that may reduce fragmentation: extra-wide and third-person views, precise control over an avatar's pointing arm, and visual enhancements such as object highlighting and laser pointing. Our study shows that although pointing has come a long way, problems of fragmentation still occur, and that visual and view enhancements can cause new problems for collaboration, even as they solve others. In addition, the visibility of a gesture's preparatory actions remained important to study participants, even when pointing was augmented. These results provide a richer understanding of the subtlety in avatar-based deictic communication, and of the ways that this critical communication mechanism can be better supported in CVEs.

Collaborative tabletop systems can employ direct touch, where people's real arms and hands manipulate objects, or indirect input, where people are represented on the table with digital embodiments. The input type and the resulting embodiment dramatically influence tabletop interaction: in particular, the touch avoidance that naturally governs people's touching and crossing behavior with physical arms is lost with digital embodiments. One result of this loss is that people are less aware of each others' arms, and less able to coordinate actions and protect personal territories. To determine whether there are strategies that can influence group interaction on shared digital tabletops, we studied augmented digital arm embodiments that provide tactile feedback or movement alterations when people touched or crossed arms. The study showed that both augmentation types changed people's behavior (people crossed less than half as often) and also changed their perception (people felt more aware of the other person's arm, and felt more awkward when touching). This work shows how groupware designers can influence people's interaction, awareness, and coordination abilities when physical constraints are absent.

Navigating through a file hierarchy is one of the most common methods for accessing files, yet it can be slow and repetitive. New algorithms that predict upcoming file accesses have the potential to improve navigation-based file retrieval, but it is unknown how best to present their predictions to users. We present three design goals aiming to improve navigation-based file retrieval interfaces: minimise the time spent at each hierarchical level en route to the target file; reduce the number of levels traversed by providing shortcuts; and promote rehearsal of the retrieval mechanics to facilitate expertise. We introduce three interfaces that augment standard file browsers based on each of these goals: Icon Highlights give greater prominence to predicted items in the current folder; Hover Menus provide shortcuts to predicted folder content; and Search Directed Navigation uses predictive highlighting to guide users through the hierarchy in response to query terms. Results from a user evaluation show that all three interfaces improve file retrieval times, with Icon Highlights and Hover Menus best suited for frequently accessed items and Search Directed Navigation best suited for infrequent ones. We also show that the benefits are larger when folder content is spatially unstable. Finally, we discuss how the interfaces could be combined and deployed in existing file browsers.

Colours are an important part of user experiences on the Web. Colour schemes influence the aesthetics, first impressions and long-term engagement with websites. However, five percent of people perceive a subset of all colours because they have colour vision deficiency (CVD), resulting in an unequal and less-rich user experience on the Web. Traditionally, people with CVD have been supported by recolouring tools that improve colour differentiability, but do not consider the subjective properties of colour schemes while recolouring. To address this, we developed SPRWeb, a tool that recolours websites to preserve subjective responses and improve colour differentiability - thus enabling users with CVD to have similar online experiences. To develop SPRWeb, we extended existing models of non-CVD subjective responses to CVD, then used this extended model to steer the recolouring process. In a lab study, we found that SPRWeb did significantly better than a standard recolouring tool at preserving the temperature and naturalness of websites, while achieving similar weight and differentiability preservation. We also found that recolouring did not preserve activity, and hypothesize that visual complexity influences activity more than colour. SPRWeb is the first tool to automatically preserve the subjective and perceptual properties of website colour schemes thereby equalizing the colour-based web experience for people with CVD.

Keyboard shortcuts allow fast interaction, but they are known to be infrequently used, with most users relying heavily on traditional pointer-based selection for most commands. We describe the goals, design, and evaluation of ExposeHK, a new interface mechanism that aims to increase hotkey use. ExposeHK's four key design goals are: 1) enable users to browse hotkeys; 2) allow non-expert users to issue hotkey commands as a physical rehearsal of expert performance; 3) exploit spatial memory to assist non-expert users in identifying hotkeys; and 4) maximise expert performance by using consistent shortcuts in a flat command hierarchy. ExposeHK supports these objectives by displaying hotkeys overlaid on their associated commands when a modifier key is pressed. We evaluated ExposeHK in three empirical studies using toolbars, menus, and a tabbed \'18ribbon' toolbar. Results show that participants used more hotkeys, and used them more often, with ExposeHK than with other techniques; they were faster with ExposeHK than with either pointing or other hotkey methods; and they strongly preferred ExposeHK. Our research shows that ExposeHK can substantially improve the user's transition from a \'18beginner mode' of interaction to a higher level of expertise.

Relative spatial consistency - that is, the stable arrangement of objects in a 2D presentation - provides several benefits for interactive interfaces. Spatial consistency allows users to develop memory of object locations, reducing the time needed for visual search, and because spatial memory is long lasting and has a large capacity these performance benefits are enduring and scalable. This suggests that spatial consistency could be used as a fundamental principle for the design of interfaces. However, there are many display situations where the standard presentation is altered in some way: e.g., a window is moved to a new location, scaled, or rotated on a mobile or tabletop display. It is not known whether the benefits of spatial organization are robust to these common kinds of view transformation. To assess these effects, we tested user performance with a spatial interface that had been transformed in several ways, including different degrees of translation, rotation, scaling, and perspective change. We found that performance was not strongly affected by the changes, except in the case of large rotations. To demonstrate the value of spatial consistency over existing mechanisms for dealing with view changes, we compared user performance with a spatially-stable presentation (using scaling) with that of a 'reflowing' presentation (widely used in current interfaces). This study showed that spatial stability with scaling dramatically outperforms reflowing. This research provides new evidence of spatial consistency's value in interface design: it is robust to the view transformations that occur in typical environments, and it provides substantial performance advantages over traditional methods.

Object handoff - that is, passing an object or tool to another person - is an extremely common activity in collaborative tabletop work. On digital tables, object handoff is typically accomplished by sliding them on the table surface - but surface-only interactions can be slow and error-prone, particularly when there are multiple people carrying out multiple handoffs. An alternative approach is to use the space above the table for object handoff; this provides more room to move, but requires above-surface tracking. We have developed two above-the-surface handoff techniques that use simple and inexpensive tracking: a force-field technique that uses a depth camera to determine hand proximity, and an electromagnetic-field technique called ElectroTouch that provides positive indication when people touch hands over the table. We compared the new techniques to three kinds of surface-only handoff (sliding, flicking, and surface-only Force-Fields). The study showed that the above-surface techniques significantly improved both speed and accuracy, and that ElectroTouch was the best technique overall. This work provides designers with practical new techniques for substantially increasing performance and interaction richness on digital tables.

Many web-based information-seeking tasks are set in a social context where other people's knowledge and advice improves success in finding information. However, when tightly-knit contacts (friends, family, colleagues) are not available, information seeking becomes more difficult. Inspired by previous work in social navigation, we developed WebWear, a system that collects and displays traces of activity for tightly-knit groups. WebWear allows people to use contextual knowledge of contacts' interests and activities to interpret the meaning of the traces, improving their usefulness. In a comparative study, we found that WebWear helped people complete information-seeking tasks more accurately, without requiring additional effort. A one-week field trial found that WebWear was both usable and useful, and that privacy concerns were reduced in the small-group context. WebWear shows that small-scale social navigation systems are feasible, and that they can improve the effectiveness of information seeking on the World-Wide Web.

In tabletop work with direct input, people avoid crossing each others' arms. This natural touch avoidance has important consequences for coordination: for example, people rarely grab the same item simultaneously, and negotiate access to the workspace via turn-taking. At digital tables, however, some situations require the use of indirect input (e.g., large tables or remote participants), and in these cases, people are often represented with virtual arm embodiments. There is little information about what happens to coordination and reaching when we move from physical to digital arm embodiments. To gather this information, we carried out a controlled study of tabletop behaviour with different embodiments. We found dramatic differences in moving to a digital embodiment: people touch and cross with virtual arms far more than they do with real arms, which removes a natural coordination mechanism in tabletop work. We also show that increasing the visual realism of the embodiment does not change behaviour, but that changing the thickness has a minor effect. Our study identifies important design principles for virtual embodiments in tabletop groupware, and adds to our understanding of embodied interaction in small groups.

Gestures are a ubiquitous part of human communication over tables, but when tables are distributed, gestures become difficult to capture and represent. There are several problems: extracting arm images from video, representing the height of the gesture, and making the arm embodiment visible and understandable at the remote table. Current solutions to these problems are often expensive, complex to use, and difficult to set up. We have developed a new toolkit - KinectArms - that quickly and easily captures and displays arm embodiments. KinectArms uses a depth camera to segment the video and determine gesture height, and provides several visual effects for representing arms, showing gesture height, and enhancing visibility. KinectArms lets designers add rich arm embodiments to their systems without undue cost or development effort, greatly improving the expressiveness and usability of distributed tabletop groupware.

Applications typically provide ways for expert users to increase their performance, such as keyboard shortcuts or customization, but these facilities are frequently ignored. To help address this problem, we introduce skillometers -- lightweight displays that visualize the benefits available through practicing, adopting a better technique, or switching to a faster mode of interaction. We present a general framework for skillometer design, then discuss the design and implementation of a real-world skillometer intended to increase hotkey use. A controlled experiment shows that our skillometer successfully encourages earlier and faster learning of hotkeys. Finally, we discuss general lessons for future development and deployment of skillometers.

Colour vision deficiencies (CVD) affect the everyday lives of a large number of people, but it is difficult for others - even friends and family members - to understand the experience of having CVD. Simulation tools can help provide this experience; however, current simulations are based on general models that have several limitations, and therefore cannot accurately reflect the perceptual capabilities of most individuals with reduced colour vision. To address this problem, we have developed a new simulation approach that is based on a specific empirical model of the actual colour perception abilities of a person with CVD. The resulting simulation is therefore a more exact representation of what a particular person with CVD actually sees. We tested the new approach in two ways. First, we compared its accuracy with that of the existing models, and found that the personalized simulations were significantly more accurate than the old method. Second, we asked pairs of participants (one with CVD, and one close friend or family member without CVD) to discuss images of everyday scenes that had been simulated with the CVD person's particular model. We found that the personalized simulations provided new insights into the details of the CVD person's experience. The personalized-simulation approach shows great promise for improving understanding of CVD (and potentially other conditions) for people with ordinary perceptual abilities.

We describe a method for applying gain to events reported by scrolling input devices such as scroll wheels. By treating document length as an input to our gain functions, the method allows rapid document traversal regardless of document length; it also allows slow and precise scroll control at shorter distances. An initial experiment characterises four diverse scrolling input devices -- a standard 'notched' scroll wheel, a high performance 'inertial' wheel, an isometric scrolling joystick, and a trackpad -- and the results are used to calibrate several gain function parameters. A second experiment validates the method, showing that it allows faster scrolling in long and short documents than current scrolling-device gain methods, and that subjective preferences favour it.

Color is commonly used to convey information in digital environments, but colors can be difficult to distinguish for many users -- either because of a congenital color vision deficiency (CVD), or because of situation-induced CVDs such as wearing colored glasses or working in sunlight. Tools intended to improve color differentiability (recoloring tools) exist, but these all use abstract models of only a few types of congenital CVD; if the user's color problems have a different cause, existing recolorers can perform poorly. We have developed a recoloring tool (SSMRecolor) based on the idea of situation-specific modeling -- in which we build a performance-based model of a particular user in their specific environment, and use that model to drive the recoloring process. SSMRecolor covers a much wider range of CVDs, including acquired and situational deficiencies. We evaluated SSMRecolor and two existing tools in a controlled study of people's color-matching performance in several environmental conditions. The study included participants with and without congenital CVD. Our results show both accuracy and response time in color-matching tasks were significantly better with SSMRecolor. This work demonstrates the value of a situation-specific approach to recoloring, and shows that this technique can substantially improve the usability of color displays for users of all types.

Designers of GUI applications typically arrange commands in hierarchical structures, such as menus, due to screen space limitations. However, hierarchical organisations are known to slow down expert users. This paper proposes the use of spatial memory in combination with hierarchy flattening as a means of improving GUI performance. We demonstrate these concepts through the design of a command selection interface, called CommandMaps, and analyse its theoretical performance characteristics. We then describe two studies evaluating CommandMaps against menus and Microsoft's Ribbon interface for both novice and experienced users. Results show that for novice users, there is no significant performance difference between CommandMaps and traditional interfaces -- but for experienced users, CommandMaps are significantly faster than both menus and the Ribbon.

In co-located collaboration, people use the space above the table for deictic gestures, and height is an important part of these gestures. However, when collaborators work at distributed tables, we know little about how to convey information about gesture height. A few visualizations have been proposed, but these have not been evaluated in detail. To better understand how remote embodiments can show gesture height, we developed several visualizations and evaluated them in three studies. First, we show that touch visualizations significantly improve people's accuracy in identifying the type and target of a gesture. Second, we show that visualizations of height above the table help to convey gesture qualities such as confidence, emphasis, and specificity. Third, we show that people quickly make use of height visualizations in realistic collaborative tasks, and that height-enhanced embodiments are strongly preferred. Our work illustrates several designs for effective visualization of height, and provides the first comprehensive evidence of the value of height information as a way to improve gestural communication in distributed tabletop groupware.

There are many web sites that allow people to play board or card games against other human players. These sites offer tools and opportunities for social interaction, but little is known about how people really interact on these sites. To learn more about social dynamics on game sites, we analysed three months of log files from a large site to explore three themes: permanence (whether people formed a long-term association with the site); social interaction (in terms of shared activity and verbal communication); and formation of ties (whether people made contacts with others). Our analyses showed that while the site seems very social when we consider gameplay, the population was highly transient, and people talked very little. To explain these behaviours, we suggest that games and game-based activity should be considered as a legitimate form of human interaction. Our analysis provides new information and new ways of thinking about how game environments can be designed to support many kinds of sociability.

Disconnection and reconnection are common problems for users of synchronous groupware, but these problems are not easy for developers to handle because of the wide range of scenarios and timeframes that must be considered. We have developed a new toolkit called DiscoTech that helps programmers deal with disconnection. The toolkit is based on five design dimensions that determine how stored information can be manipulated as the system waits for an absent user to rejoin, and how information should be replayed upon reconnection. DiscoTech provides a plug-in architecture to handle a wide variety of behaviours that developers may need during disconnection; these plug-ins range from fully generic tools to customized strategies with full knowledge of the groupware application. We present the design of the DiscoTech toolkit, show examples of its use, and provide evidence that it covers a broad range of situations, imposes minimal performance overhead, and is easy for programmers to learn. DiscoTech handles a wider range of issues than previous toolkits, without requiring undue effort, and provides a practical way to improve the real-world usability of synchronous groupware.

Player coordination is a key element in many multi-player real-time digital games, and control over the design of these coordination requirements is an important part of developing successful games. However, it is currently difficult to describe or analyze coordination requirements in game situations, because current frameworks and theories do not mesh with the realities of video game design. We developed a new framework (called PLATO) that can help game designers understand and manipulate coordination episodes. The framework deals with five atomic aspects of coordinated activity: Players, Locations, Actions, Time, and Objects. PLATO provides a vocabulary, methodology and diagram notation for describing and analyzing coordination. We demonstrate the framework's utility by describing coordination situations from existing games, showing how PLATO can be used to understand and redesign coordination requirements.

Real-time distributed groupware sends several kinds of messages with varying quality-of-service requirements. However, standard network protocols do not provide the flexibility needed to support these different requirements (either providing too much reliability or too little), leading to poor performance on real-world networks. To address this problem, we investigated the use of an application-level networking technique called adaptive forward error correction (AFEC) for real-time groupware. AFEC can maintain a predefined level of reliability while avoiding the overhead of packet acknowledgement or retransmission. We analysed the requirements of typical real-time groupware systems and developed an AFEC technique to meet these needs. We tested the new technique in an experiment that measured message reliability and latency using TCP, plain UDP, UDP with non-adaptive FEC, and UDP with our AFEC scheme, under several simulated network conditions. Our results show that for awareness messages that can tolerate some loss, FEC approaches keep latency at nearly the plain-UDP level while dramatically improving reliability. In addition, adaptive FEC is the only technique that can maintain a specified level of reliability and also minimize delay as network conditions change. Our study shows that groupware AFEC can be a useful tool for improving the real-world performance and usability of real-time groupware.

Collaborative Virtual Environments (CVEs) allow people to interact with each other in virtual worlds through computer-generated avatars. Avatars are much less expressive than real bodies, and one main limitation is their lack of support for non-verbal communication such as pointing gestures. Part of the problem is that these gestures must be created through an input device, but the user is already busy controlling the avatar's location, rotation, and view direction. Pointing gestures are only useful for collaborative communication if they can be controlled simultaneously with all other avatar actions. To determine whether there are input configurations that make pointing gestures feasible, we carried out a study that compared five different widely-available input devices in three non-verbal communication tasks. We found that users were able to successfully incorporate pointing gestures into tasks that already involved moving, turning, and looking, but that there were significant and substantial differences between devices. Two configurations performed best: a mode-switched version of standard mouse-and-keyboard control, and a direct-pointing scheme using a Wii remote. There were also minor effects of gender and video-game experience. Our study suggests that users will be able to successfully create free pointing gestures in CVEs, greatly improving the communicative richness of these environments.

This paper considers the issue of the locus of control in adaptive e-learning environments from the perspective of a new stakeholder; the instructional expert. With an ever increasing ability to gain insight into learners based on their online activities, instructors and instructional designers are poised to add value to the process of adaptation, a process normally reserved for either systems designers or the end user. This work describes the design of an e-learning system which provides automated analytics information to these experts for consideration, and then leverages the insights these experts have made as the basis for content and feature adaptation.

Scrolling is controlled through many forms of input devices, such as mouse wheels, trackpad gestures, arrow keys, and joysticks. Performance with these devices can be adjusted by introducing variable transfer functions to alter the range of expressible speed, precision, and sensitivity. However, existing transfer functions are typically "black boxes" bundled into proprietary operating systems and drivers. This presents three problems for researchers: (1) a lack of knowledge about the current state of the field; (2) a difficulty in replicating research that uses scrolling devices; and (3) a potential experimental confound when evaluating scrolling devices and techniques. These three problems are caused by gaps in researchers' knowledge about what device and movement factors are important for scrolling transfer functions, and about how existing devices and drivers use these factors. We fill these knowledge gaps with a framework of transfer function factors for scrolling, and a method for analysing proprietary transfer functions---demonstrating how state of the art commercial devices accommodate some of the human control phenomena observed in prior studies.

Color vision deficiencies (CVDs) cause problems in situations where people need to differentiate the colors used in digital displays. Recoloring tools exist to reduce the problem, but these tools need a model of the user's color-differentiation ability in order to work. Situation-specific models are a recent approach that accounts for all of the factors affecting a person's CVD (including genetic, acquired, and environmental causes) by using calibration data to form the model. This approach works well, but requires repeated calibration - and the best available calibration procedure takes more than 30 minutes. To address this limitation, we have developed a new situation-specific model of human color differentiation (called ICD-2) that needs far fewer calibration trials. The new model uses a color space that better matches human color vision compared to the RGB space of the old model, and can therefore extract more meaning from each calibration test. In an empirical comparison, we found that ICD-2 is 24 times faster than the old approach, and had small but significant gains in accuracy. The efficiency of ICD-2 makes it feasible for situation-specific models of individual color differentiation to be used in the real world.

In games where skills such as targeting are critical to winning, it is difficult for players with different skill levels to have a competitive and engaging experience. Although several mechanisms for accommodating different skill levels have been proposed, traditional approaches can be too obvious and can change the nature of the game. For games involving aiming, we propose the use of target assistance techniques (such as area cursors, target gravity, and sticky targets) to accommodate skill imbalances. We compared three techniques in a study, and found that area cursors and target gravity significantly reduced score differential in a shooting-gallery game. Further, less skilled players reported having more fun when the techniques helped them be more competitive, and even after they learned assistance was given, felt that this form of balancing was good for group gameplay. Our results show that target assistance techniques can make target-based games more competitive for shared play.

Interface guidelines encourage designers to include shortcut mechanisms that enable high levels of expert performance, but prior research has demonstrated that few users switch to using them. To help understand how interfaces can better support a transition to expert performance we develop a framework of the interface and human factors influencing expertise development. We then present a system called Blur that addresses three main problems in promoting the transition: prompting an initial switch to expert techniques, minimising the performance dip arising from the switch, and enabling a high performance ceiling. Blur observes the user's interaction with unaltered desktop applications and uses calm notification to support learning and promote awareness of an alternative hot command interface. An empirical study validates Blur's design, showing that users make an early and sustained switch to hot commands, and that doing so improves their performance and satisfaction.

Standard web browsers are becoming a common platform for delivering groupware applications, but until recently, the only way to support real-time collaboration was with browser plug-ins. New networking approaches have recently been introduced - based on re-purposed techniques for delivering web pages (Comet), or integration of real-time communication directly into the browser (HTML5 WebSockets). Little is currently known, however, about whether these new approaches can support real-time groupware. We carried out a study to assess the performance of the three different networking approaches, based on a framework of groupware requirements, in several network settings. We found that web-based networking performs well - better than plug-in approaches in some cases - and can support the communication requirements of many types of real-time groupware. We also developed two groupware applications using Comet and WebSockets, and showed that they provided fast and consistent performance on the real-world Internet. Our studies show that web-based networking can support real-time collaboration, and suggest that groupware developers should consider the browser as a legitimate vehicle for real-time multi-user systems.

Awareness of other people's activity is an important part of shared-workspace collaboration, and is typically supported using visual awareness displays such as radar views. These visual presentations are limited in that the user must be able to see and attend to the view in order to gather awareness information. Using audio to convey awareness information does not suffer from these limitations, and previous research has shown that audio can provide valuable awareness in distributed settings. In this paper we evaluate the effectiveness of synthesized dynamic audio information, both on its own and as an adjunct to a visual radar view. We developed a granular-synthesis engine that produces realistic chalk sounds for off-screen activity in a groupware workspace, and tested the audio awareness in two ways. First, we measured people's ability to identify off-screen activities using only sound, and found that people are almost as accurate with synthesized sounds as with real sounds. Second, we tested dynamic audio awareness in a realistic groupware scenario, and found that adding audio to a radar view significantly improved awareness of off-screen activities in situations where it was difficult to see or attend to the visual display. Our work provides new empirical evidence about the value of dynamic synthesized audio in distributed groupware.

Interactive systems often require calibration to ensure that input and output are optimally configured. Without calibration, user performance can degrade (e.g., if an input device is not adjusted for the user's abilities), errors can increase (e.g., if color spaces are not matched), and some interactions may not be possible (e.g., use of an eye tracker). The value of calibration is often lost, however, because many calibration processes are tedious and unenjoyable, and many users avoid them altogether. To address this problem, we propose calibration games that gather calibration data in an engaging and entertaining manner. To facilitate the creation of calibration games, we present design guidelines that map common types of calibration to core tasks, and then to well-known game mechanics. To evaluate the approach, we developed three calibration games and compared them to standard procedures. Users found the game versions significantly more enjoyable than regular calibration procedures, without compromising the quality of the data. Calibration games are a novel way to motivate users to carry out calibrations, thereby improving the performance and accuracy of many human-computer systems.

We consider different hierarchical menu and toolbar-like interface designs from a theoretical perspective and show how a model based on visual search time, pointing time, decision time and expertise development can assist in understanding and predicting interaction performance. Three hierarchical menus designs are modelled -- a traditional pull-down menu, a pie menu and a novel Square Menu with its items arranged in a grid -- and the predictions are validated in an empirical study. The model correctly predicts the relative performance of the designs -- both the eventual dominance of Square Menus compared to traditional and pie designs and a performance crossover as users gain experience. Our work shows the value of modelling in HCI design, provides new insights about performance with different hierarchical menu designs, and demonstrates a new high-performance menu type.

Guidelines for designing information charts (such as bar charts) often state that the presentation should reduce or remove 'chart junk' - visual embellishments that are not essential to understanding the data. In contrast, some popular chart designers wrap the presented data in detailed and elaborate imagery, raising the questions of whether this imagery is really as detrimental to understanding as has been proposed, and whether the visual embellishment may have other benefits. To investigate these issues, we conducted an experiment that compared embellished charts with plain ones, and measured both interpretation accuracy and long-term recall. We found that people's accuracy in describing the embellished charts was no worse than for plain charts, and that their recall after a two-to-three-week gap was significantly better. Although we are cautious about recommending that all charts be produced in this style, our results question some of the premises of the minimalist approach to chart design.

Color is commonly used to represent categories and values in many computer applications, but differentiating these colors can be difficult in many situations (e.g., for users with color vision deficiency (CVD), or in bright light). Current solutions to this problem can adapt colors based on standard simulations of CVD, but these models cover only a fraction of the ways in which color perception can vary. To improve the specificity and accuracy of these approaches, we have developed the first ever individualized model of color differentiation (ICD). The model is based on a short calibration performed by a particular user for a particular display, and so automatically covers all aspects of the user's ability to see and differentiate colors in an environment. In this paper we introduce the new model and the manner in which differentiability limits are predicted. We gathered empirical data from 16 users to assess the model's accuracy and robustness. We found that the model is highly effective at capturing individual differentiation abilities, works for users with and without CVD, can be tuned to balance accuracy and color availability, and can serve as the basis for improved color adaptation schemes.

Deictic reference -- pointing at things during conversation -- is ubiquitous in human communication, and should also be an important tool in distributed collaborative virtual environments (CVEs). Pointing gestures can be complex and subtle, however, and pointing is much more difficult in the virtual world. In order to improve the richness of interaction in CVEs, it is important to provide better support for pointing and deictic reference, and a first step in this support is to determine how well people can interpret the direction that another person is pointing. To investigate this question, we carried out two studies. The first identified several ways that people point towards distant targets, and established that not all pointing requires high accuracy. This suggested that natural CVE pointing could potentially be successful; but no knowledge is available about whether even moderate accuracy is possible in CVEs. Therefore, our second study looked more closely at how accurately people can produce and interpret the direction of pointing gestures in CVEs. We found that although people are more accurate in the real world, the differences are smaller than expected; our results show that deixis can be successful in CVEs for many pointing situations, and provide a foundation for more comprehensive support of deictic pointing.

Synchronous groupware depends on the assumption that people are fully connected to the others in the group, but there are many situations (network delay, network outage, or explicit departure) where users are disconnected for various periods. There is little research dealing with disconnection in synchronous groupware from a user and application perspective; as a result, most current groupware systems do not handle disconnection events well, and several user-level problems occur. To address this limitation, we developed the Disco framework, a model for handling several types of disconnection in synchronous groupware. The framework considers how disconnections are identified, what senders and receivers should do during an absence, and what should be done with accumulated data upon reconnection. We have implemented the framework in three applications that show the feasibility, generality, and functionality of our ideas. Our framework is the first to deal with a full range of disconnection issues for synchronous groupware, and shows how groupware can better support the realities of distributed collaboration.

Consistency maintenance (CM) techniques are a crucial part of many distributed systems, and are particularly important in networked games. In this paper we describe a framework of the human factors of CM, to help designers of networked games make better decisions about its use. The framework shows that there is wide variance in the CM requirements of different game situations, identifies the types of requirements that can be considered, and analyses the effects of several consistency schemes on user experience factors. To further explore these issues, we carried out a simulation study that compared four CM algorithms. The experiment confirms many of the predictions of the framework, and reveals additional subtleties of the algorithms. Our work is the first to look comprehensively at the tradeoffs and costs of CM, and our results are a strong starting point that will help designers improve on the user's quality of experience in distributed shared environments.

Many interactive systems require users to navigate through large sets of data and commands using constrained input devices—such as scroll rings, rocker switches, or specialized keypads—that provide less power and flexibility than traditional input devices like mice or touch screens. While performance with more traditional devices has been extensively studied in human-computer interaction, there has been relatively little investigation of human performance with constrained input. As a result, there is little understanding of what factors govern performance in these situations, and how interfaces should be designed to optimize interface actions such as navigation and selection. Since constrained input is now common in a wide variety of interactive systems (such as mobile phones, audio players, in-car navigation systems, and kiosk displays), it is important for designers to understand what factors affect performance. To aid in this understanding, we present the Constrained Input Navigation (CIN) model, a predictive model that allows accurate determination of human navigation and selection performance in constrained-input scenarios. CIN identifies three factors that underlie user efficiency: the performance of the interface type for single-level item selection (where interface type depends on the input and output devices, the interactive behavior, and the data organization), the hierarchical structure of the information space, and the user's experience with the items to be selected. We show through experiments that, after empirical calibration, the model's predictions fit empirical data well, and discuss why and how each of the factors affects performance. Models like CIN can provide valuable theoretical and practical benefits to designers of constrained-input systems, allowing them to explore and compare a much wider variety of alternate interface designs without the need for extensive user studies.

In this paper, we show that people frequently return to previously-visited regions within their documents, and that scrollbars can be enhanced to ease this task. We analysed 120 days of activity logs from Microsoft Word and Adobe Reader. Our analysis shows that region revisitation is a common activity that can be supported with relatively short recency lists. This establishes an empirical foundation for the design of an enhanced scrollbar containing scrollbar marks that helps people return to previously visited document regions. Two controlled experiments show that scrollbar marks decrease revisitation time, and that a large number of marks can be used effectively. We then design an enhanced Footprints scrollbar that supports revisitation with several features, including scrollbar marks and mark thumbnails. Two further experiments show that the Footprints scrollbar was frequently used and strongly preferred over traditional scrollbars.

Networked multiplayer games must support a much wider variety of interactions than single-player games because networked games involve communication and coordination between players. This means that designers must consider additional usability issues that relate to group play - but there are currently no usability engineering methods that are specifically oriented towards the needs of multiplayer games. To address this problem, we developed a new set of usability heuristics, called Networked Game Heuristics (NGH), which can be used in the design and evaluation of networked multiplayer games. The new heuristics were identified by analyzing problem reports from 382 reviews of networked PC games, covering six main genres. We aggregated problem reports into ten problem categories (covering issues from session management to cheating to training for novice players) and developed heuristics that describe how these usability problems can be avoided. We tested the new heuristics by having evaluators use them and an existing set to assess the usability of two networked games. Evaluators found more usability problems with NGH, and stated that the new heuristics were better for evaluating multiplayer game usability. Our research is the first to present networked game heuristics that are derived from real problem reports, and the first to evaluate the heuristics' effectiveness in a realistic usability test.

Many interactive tasks in graphical user interfaces involve finding an item in a list but with the item not currently in sight. The two main ways of bringing the item into view are scrolling of one-dimensional lists and expansion of a level in a hierarchical list. Examples include selecting items in hierarchical menus and navigating through “tree” browsers to find files, folders, commands, or e-mail messages. System designers are often responsible for the structure and layout of these components, yet prior research provides conflicting results on how different structures and layouts affect user performance. For example, empirical research disagrees on whether the time to acquire targets in a scrolling list increases linearly or logarithmically with the length of the list; similarly, experiments have produced conflicting results for the comparative efficacy of “broad and shallow” versus “narrow and deep” hierarchical structures. In this article we continue in the human–computer interaction tradition of bringing theory to the debate, demonstrating that prior results regarding scrolling and hierarchical navigation are theoretically predictable and that the divergent results can be explained by the impact of the dataset's organization and the user's familiarity with the dataset. We argue and demonstrate that when users can anticipate the location of items in the list, the time to acquire them is best modeled by functions that are logarithmic with list length and that linear models arise when anticipation cannot be used. We then propose a formal model of item selection from hierarchical lists, which we validate by comparing its predictions with empirical data from prior studies and from our own. The model also accounts for the transition from novice to expert behavior with different datasets.

Multi-display environments (MDEs) are now becoming common, and are becoming more complex, with more displays and more types of display in the environment. One crucial requirement specific to MDEs is that users must be able to move objects from one display to another; this cross-display movement is a frequent and fundamental part of interaction in any application that spans two or more display surfaces. Although many cross-display movement techniques exist, the differences between MDEs—the number, location, and mixed orientation of displays, and the characteristics of the task they are being designed for—require that interaction techniques be chosen carefully to match the constraints of the particular environment. As a way to facilitate interaction design in MDEs, we present a taxonomy that classifies cross-display object movement techniques according to three dimensions: the referential domain that determines how displays are selected, the relationship of the input space to the display configuration, and the control paradigm for executing the movement. These dimensions are based on a descriptive model of the task of cross-display object movement. The taxonomy also provides an analysis of current research that designers and researchers can use to understand the differences between categories of interaction techniques.

Browsing a blog archive is currently not well supported. Users cannot gain an overview of a blog easily, nor do they receive adequate support for finding potentially interesting entries in the blog. To overcome these problems, we developed a visualization tool that offers a new way to browse a blog archive. The main design principles of the tool are twofold. First, a blog should provide a rich overview to help users reason about the blog at a glance. Second, a blog should utilize social interaction history preserved in the archive to ease exploration and navigation. The tool was evaluated using a tool-specific questionnaire and the Questionnaire for User Interaction Satisfaction. Responses from the participants confirmed the utility of the design principles: the user satisfaction was high, supported by a low error rate in the given tasks. Qualitative feedback revealed that the decision to select which entry to read was multidimensional, involving factors such as the topic, the posting time, the length, and the number of comments on an entry. We discuss the implications of these findings for the design of navigational support for blogs, in particular to facilitate exploratory tasks.

It is easy for users to lose awareness of their location and orientation when navigating large information spaces. Providing landmarks is one common technique that helps users remain oriented, alleviating the mental workload and reducing the number of redundant interactions. But how many landmarks should be displayed? We conducted an empirical evaluation of several relationships between the number of potential landmarked items in the display and the number of landmarks rendered at any one time, with results strongly favouring a logarithmic relationship.

The initiation of interaction in face-to-face environments is a gradual process, and takes place in a rich information landscape of awareness, attention, and social signals. One of the main benefits of this process is that people can be more sensitive to issues of privacy and interruption while they are moving towards interaction. However, on-line communication tools do not provide this subtlety, and often lead to unwanted interruptions. We have developed a prototype message system called OpenMessenger (OM) that adds the idea of gradual initiation of interaction to on-line communication. OpenMessenger provides multiple levels of awareness about people, and provides notification to those about whom information is being gathered. OpenMessenger allows people to negotiate interaction in a richer fashion than is possible with any other current messaging system. Preliminary evaluation data suggest the utility of the approach, but also shows that there are a number of issues yet to be resolved in this area.

To overcome display limitations of small-screen devices, researchers have proposed techniques that point users to objects located off-screen. Arrow-based techniques such as City Lights convey only direction. Halo conveys direction and distance, but is susceptible to clutter resulting from overlapping halos. We present Wedge, a visualization technique that conveys direction and distance, yet avoids overlap and clutter. Wedge represents each off-screen location using an acute isosceles triangle: the tip coincides with the off-screen locations, and the two corners are located on-screen. A wedge conveys location awareness primarily by means of its two legs pointing towards the target. Wedges avoid overlap programmatically by repelling each other, causing them to rotate until overlap is resolved. As a result, wedges can be applied to numbers and configurations of targets that would lead to clutter if visualized using halos. We report on a user study comparing Wedge and Halo for three off-screen tasks. Participants were significantly more accurate when using Wedge than when using Halo.

Multi-monitor displays and multi-display environments are now common. Cross-display cursor movement, in which a user moves the pointer from one display to another, occurs frequently in these settings. There are several techniques for supporting this kind of movement, and these differ in the way that they deal with displayless space (the physical space between displays). Stitching is the method used by most operating systems; in this technique, the cursor jumps from the edge of one display directly into the next display. In contrast, Mouse Ether maps the motor space of the mouse exactly to the physical space of the displays, meaning that the cursor has to travel across displayless space until it reaches the next display. To determine which of these approaches is best for cross-display movement, we carried out a study comparing Stitching, Mouse Ether, and a variant of Mouse Ether with Halo for off-screen feedback. We found that Stitching is equivalent to or faster than any variant of Mouse Ether, and that Halo improves Ether’s performance (but not enough to outperform Stitching). Results also indicate that the larger the gap between displays, the longer the targeting takes – even for Stitching. These findings provide valuable guidance for practitioners and raise new interesting questions for research.

Tightly-coupled interaction is shared work in which each person's actions immediately and continuously influence the actions of others. Tightly-coupled collaboration is a hallmark of expert behavior in face-to-face activity, but becomes extremely difficult to accomplish over distributed groupware. The main cause of this difficulty is network delay that disrupts people's ability to synchronize their actions with another person. In this paper we report on two studies that explore local lag as a way of reducing this problem. When applied to visual feedback, local lag synchronizes the visual environments of the local and remote clients, preventing one person from getting ahead of the other. We tested the effects of local lag in several delay conditions: we found that the technique significantly improved performance, and that users did not rate local lag as more difficult or frustrating to use. Our studies improve our understanding of local lag and of how it improves tightly-coupled interaction in distributed groupware.

VoodooSketch is a system that extends interactive surfaces with physical interface palettes on which users can dynamically deploy controls as shortcut to application functionality. The system provides physical 'plug and play' controls as well as support for sketching of controls, and allows controls to be associated with application functions via handwritten labels. The system uses a special digital pen, which writes 'real' ink on the palettes while functioning as a digital input device on the interactive surfaces. The palettes can be seamlessly integrated into existing applications, be appropriated by the user to suit different input requirements, and support new interaction styles across multiple surfaces, palettes and users.

Menus are a primary control in current interfaces, but there has been relatively little theoretical work to model their performance. We propose a model of menu performance that goes beyond previous work by incorporating components for Fitts' Law pointing time, visual search time when novice, Hick-Hyman Law decision time when expert, and for the transition from novice to expert behaviour. The model is able to predict performance for many different menu designs, including adaptive split menus, items with different frequencies and sizes, and multi-level menus. We tested the model by comparing predictions for four menu designs (traditional menus, recency and frequency based split menus, and an adaptive 'morphing' design) with empirical measures. The empirical data matched the predictions extremely well, suggesting that the model can be used to explore a wide range of menu possibilities before implementation.

Multi-point interaction tasks involve the manipulation of several mutually-dependent control points in a visual workspace -- for example, adjusting a selection rectangle in a drawing application. Multi-point interactions place conflicting requirements on the interface: the system must display objects at sufficient scale for detailed manipulation, but it must also provide an efficient means of navigating from one control point to another. Current interfaces lack any explicit support for tasks that combine these two requirements, forcing users to carry out sequences of zoom and pan actions. In this paper, we describe three novel mechanisms for view control that explicitly support multi-point interactions with a single mouse, and preserve both visibility and scale for multiple regions of interest. We carried out a study to compare two of the designs against standard zoom and pan techniques, and found that task completion time was significantly reduced with the new approaches. The study shows the potential of interfaces that combine support for both scale and navigation.

Embodiments are visual representations of people in a groupware system. Embodiments convey awareness information such as presence, location, and movement -- but they provide far less information than what is available from a real body in a face-to-face setting. As a result, it is often difficult to recognize and characterize other people in a groupware system without extensive communication. To address this problem, information-rich embodiments use ideas from multivariate information visualization to maximize the amount of information that is represented about a person. To investigate the feasibility of rich embodiment and their effects on group interaction, we carried out three studies. The first shows that users are able to recall and interpret a large set of variables that are graphically encoded on an embodiment. The second and third studies demonstrated rich embodiments in two groupware systems -- a multiplayer game and a drawing application -- and showed that the enhanced representations do improve recognition and characterization, and that they can enrich interaction in a variety of ways.

The interaction techniques that are used in tabletop groupware systems (such as pick-and-drop or pantograph) can affect the way that people collaborate. However, little is known about these effects, making it difficult for designers to choose appropriate techniques when building tabletop groupware. We carried out an exploratory study to determine how several different types of interaction techniques (pantograph, telepointers, radar views, drag-and-drop, and laser beam) affected coordination and awareness in two tabletop tasks (a game and a storyboarding activity). We found that the choice of interaction technique significantly affected coordination measures, performance measures, and preference - but that the effects were different for the two different tasks. Our study shows that the choice of tabletop interaction technique does indeed matter, and provides insight into how tabletop systems can better support group work.

Many visualizations use smoothly animated transitions to help the user interact with information structures. These transitions are intended to preserve perceptual constancy during viewpoint transformations. However, animated transitions also have costs -- they increase the transition time, and they can be complicated to implement -- and it is not clear whether the benefits of smooth transitions outweigh the costs. In order to quantify these benefits, we carried out two experiments that explore the effects of smooth transitions. In the first study, subjects were asked to determine whether graph nodes were connected, and navigated the graph either with or without smooth scene transitions. In the second study, participants were asked to identify the overall structure of a tree after navigating the tree through a viewport that either did or did not use smooth transitions for view changes. The results of both experiments show that smooth transitions can have dramatic benefits for user performance -- for example, participants in smooth transition conditions made half the errors of the discrete-movement conditions. In addition, short transitions were found to be as effective as long ones, suggesting that some of the costs of animations can be avoided. These studies give empirical evidence on the benefits of smooth transitions, and provide guidelines about when designers should use them in visualization systems.

The tension between privacy and awareness has been a persistent difficulty in distributed environments that support opportunistic and informal interaction. For example, many awareness systems that display 'always-on' video links or PC screen contents have been perceived as too invasive, even though functional real-world analogues, like open-plan offices, may provide even less privacy than their online counterparts. In this paper we explore the notion of privacy in open-plan real-world environments, in order to learn more about how it might be supported in distributed systems. From interviews and observations in four open-plan offices, we found that attention plays an important role in the management of both confidentiality and solitude. The public nature of paying attention allows people to build understandings of what objects in a space are legitimate targets for attention and allows people to advertise their interest in interaction. Our results add to what is known about how privacy works in real-world spaces, and suggest valuable design ideas that can help improve support for natural privacy control and interaction in distributed awareness systems.

Networked games can provide groupware developers with important lessons in how to deal with real-world networking issues such as latency, limited bandwidth and packet loss. Games have similar demands and characteristics to groupware, but unlike the applications studied by academics, games have provided production-quality real-time interaction for many years. The techniques used by games have not traditionally been made public, but several game networking libraries have recently been released as open source, providing the opportunity to learn how games achieve network performance. We examined five game libraries to find networking techniques that could benefit groupware; this paper presents the concepts most valuable to groupware developers, including techniques to deal with limited bandwidth, reliability, and latency. Some of the techniques have been previously reported in the networking literature; therefore, the contribution of this paper is to survey which techniques have been shown to work, over several years, and then to link these techniques to quality requirements specific to groupware. By adopting these techniques, groupware designers can dramatically improve network performance on the real-world Internet.

The windows and doorways that connect offices to public spaces are a site for people to gather awareness information and initiate interaction. However, these portals often reveal more information to the public area than the office occupant would like. As a result, people often keep doors and window blinds closed, which means that nobody can gather awareness information, even those with whom the occupant would be willing to share. One solution to this problem is a co-present media space - a computer-mediated video connection at the boundary between an office and a public area. These systems can provide both greater privacy control to the occupant and greater overall awareness information to observers. To see how co-present media spaces would work in real world settings, we built what we believe are the first ever co-present media spaces, and deployed them in two offices. From observations gathered over fifteen months, it is clear that the systems can do a better job of balancing the occupant's need for privacy and the observers' need for awareness better, than a standard window. However, we also identified a number of issues that affected the use and the success of the systems: the existence of alternate information sources, confusion with existing social norms, disparities between effort and need, and reduced interactional subtlety for observers in the public area. Our work contributes both a novel arrangement of a media space for co-present collaborators, and the first investigation into the design factors that affect the use and acceptance of these systems.

Multi-display environments compose displays that can be at different locations from and different angles to the user; as a result, it can become very difficult to manage windows, read text, and manipulate objects. We investigate the idea of perspective as a way to solve these problems in multi-display environments. We first identify basic display and control factors that are affected by perspective, such as visibility, fracture, and sharing. We then present the design and implementation of E-conic, a multi-display multi-user environment that uses location data about displays and users to dynamically correct perspective. We carried out a controlled experiment to test the benefits of perspective correction in basic interaction tasks like targeting, steering, aligning, pattern-matching and reading. Our results show that perspective correction significantly and substantially improves user performance in all these tasks.

Several researchers have recently proposed technology for crowd-and-DJ interactions in nightclub environments. However, these attempts have not always met with success. In order to design better technologies and systems in this area, it is important to start with an understanding of how nightclub interaction currently happens. To build this understanding, we carried out an interview study focusing on DJ-audience interactions. We interviewed eleven DJs from several different cities, and asked them to discuss the ways that they interact with the audience, and the ways that they maintain and use awareness of the audience. We found that DJs gather a wide variety of information about their audiences, and that this information is important to them as they plan and shape the evening's musical experience. DJs are adept at gathering visual information about the audience, despite poor lighting conditions and a heavy workload of selecting and mixing music. Despite the difficulties, DJs took a dim view of technology designed to let crowds exert more control over the music. This study is one of the first to look closely at the interactive relationship between the DJ and the nightclub audience through the lens of HCI, and our findings provide a number of guidelines for the design of new DJ-focused nightclub technologies.

The rapid increase in display sizes and resolutions has led to the re-emergence of many pen-based interaction systems like tabletop and wall display environments. Pointing in these environments is an important task, but techniques have not exploited the manipulation of control and display parameters to the extent seen in desktop environments. We have overcome these in the design of a new pen-based interaction technique -- Bubble Radar. Bubble Radar allows users to reach both specific targets and empty space, and supports dynamic switching between selecting and placing. The technique is based on combining the benefits of a successful pen-based pointing technique, the Radar View, with a successful desktop object pointing technique -- the Bubble Cursor. We tested the new technique in a user study and found that it was significantly faster than existing techniques, both for overall pointing and for targeting specific objects.

Designers and architects regularly use piles to organise visual artifacts. Recent efforts have now made it possible for users to create piles in digital systems as well. However, there is still little understanding of how users shouldinteract with digital piles. In this paper we investigate this issue. We first identify three tasks that must be supported by a digitalpile—navigation, reorganisation and repositioning. We then present three interaction techniques—called HoverDeck, DragDeck and ExpandPile that meet these requirements. The techniques allow users to easily browse the piles, and also allow them to move elements between and within piles in an ad-hoc manner. In a user study that compared the different interaction techniques, we found that ExpandPile was significantly faster than the other techniques over all tasks. There were differences, however, in individual tasks. We discuss the benefits and limitations of the different techniques and identify several situations where each of them could prove useful.

Selecting items from lists is a common task in many applications. Alphabetically-sorted listboxes are the most common interface widget used to accomplish this selection, but although general they can be slow and frustrating to use, particularly when the lists are long. In addition, when the user regularly revisits a small set of items, listboxes provide little support for increased performance through experience. To address these shortcomings, we developed a new list selection device called a ListMap, which organizes list items into a space-filling array of buttons. Items never move in a ListMap, which allows people to make use of spatial memory to find common items more quickly. We carried out a study to compare selection of font names from a set of 220 fonts using both ListMaps and standard listboxes. We found that although listboxes are faster for unknown items, revisitation leads to significant performance gains for the ListMap.

Scrolling is the standard way to navigate through many types of digital documents. However, moving more than a few pages can be slow because all scrolling techniques constrain visual search to only a small document region. To improve document navigation, we developed Space-Filling Thumbnails (SFT), an overview display that eliminates most scrolling. SFT provides two views: a standard page view for reading, and a thumbnail view that shows all pages. We tested SFT in three experiments that involved finding pages in documents. The first study (n=13) compared seven current scrolling techniques, and showed that SFT is significantly faster than the other methods. The second and third studies (n=32 and n=14) were detailed comparisons of SFT with thumbnail-enhanced scrollbars (TES), which performed well in the first experiment. SFT was faster than TES across all document types and lengths, particularly when tasks involved revisitation. In addition, SFT was strongly preferred by participants.

Many systems provide the user with a limited viewport of a larger graphical workspace. In these systems, the user often needs to find and select targets that are in the workspace, but not visible in the current view. Standard methods for navigating to the off-screen targets include scrolling, panning, and zooming; however, these are laborious when users cannot see a target's direction or distance. Techniques such as halos can provide awareness of targets, but actually getting to the target is still slow with standard navigation. To improve off-screen target selection, we developed a new technique called hop, which combines halos with a teleportation mechanism that shows proxies of distant objects. Hop provides both awareness of off-screen targets and fast navigation to the target context. A study showed that users are significantly faster at selecting off-screen targets with hopping than with two-level zooming or grab-and-drag panning, and it is clear that hop will be faster than either halos or proxy-based techniques (like drag-and-pop or vacuum filtering) by themselves. Hop both improves on halo-based navigation and extends the value of proxies to small-screen environments.

Multi-display environments and smart meeting rooms are now becoming more common. These environments build a shared display space from variety of devices: tablets, projected surfaces, tabletops, and traditional monitors. Since the different display surfaces are usually not organized in a single plane, traditional schemes for stitching the displays together can cause problems for interaction. However, there is a more natural way to compose display space -- using perspective. In this paper, we develop interaction techniques for multi-display environments that are based on the user's perspective on the room. We designed the Perspective Cursor, a mapping of cursor to display space that appears natural and logical from wherever the user is located. We conducted an experiment to compare two perspective-based techniques, the Perspective Cursor and a beam-based technique, with traditional stitched displays. We found that both perspective techniques were significantly faster for targeting tasks than the traditional technique, and that Perspective Cursor was the most preferred method. Our results show that integrating perspective into the design of multi-display environments can substantially improve performance.

Groupware communicates by sending messages across the network, and groupware programmers use a variety of formats for these messages, such as XML, plain text, or serialized objects. Although these formats have many advantages, they are often so verbose that they overload the system's network resources. Groupware programmers could improve efficiency by using more compact formats, but this efficiency comes at the cost of increased complexity, reduced convenience, and reduced readability. In this paper we propose an alternate approach for improving efficiency -- an automatic compression system that transparently minimizes verbose formats. Our general message compressor -- GMC -- automatically finds and removes redundancy in message streams, without any knowledge of the contents or structure of the message, and without any need for the programmer to change the way they work. In tests with realistic message traces, GMC reduced text messages to 20% of their original size, XML messages to 8% of the original, and serialized objects to 9%. Although not as compact as a hand-coded representation, GMC provides most of the compression benefits with almost none of the work -- it allows groupware programmers to use convenient message formats without compromising transport efficiency.

Despite the availability of awareness servers and casual interaction systems, distributed groups still cannot maintain artifact awareness – the easy awareness of the documents, objects, and tools that other people are using – that is a natural part of co-located work environments. To address this deficiency, we designed an awareness tool that uses screen sharing to provide information about other people’s artifacts. People see others’ screens in miniature at the edge of their display, can selectively raise a larger view of that screen to get more detail, and can engage in remote pointing if desired. Initial experiences show that people use our tool for several purposes: to maintain awareness of what others are doing, to project a certain image of themselves, to monitor progress and coordinate joint tasks, to help determine when another person can be interrupted, and to engage in serendipitous conversation and collaboration. People have also been able to balance awareness with privacy, by using the privacy protection strategies built into our system: restricting what parts of the screen others can see, specifying update frequency, hiding image detail, and getting feedback of when screenshots are taken.

Designers of children's technology are often more interested in user motivation than those who design systems for adults. Since children's technology often has aims such as education or practice, keeping the user engaged and interested is an important objective. The Media Equation - the idea that people respond socially to computers - shows potential for improving engagement and motivation. Studies have shown that people are more positive about both themselves and the computer when software exhibits certain social characteristics. To explore the possible value of the Media Equation as a design concept for children's software, we replicated two of the original Media Equation studies, concerning the effects of praise and team formation. Our results, however, were contrary to our expectations: we did not find evidence that children were significantly affected by social characteristics in software, and adults were influenced in only a few cases. These results raise questions about using the Media Equation as a design principle for children's software.

Recent advances in multi-user collaboration have seen a proliferation of interaction techniques for moving digital objects from one device to another. However, little is known about how these techniques work in realistic situations, or how they compare to one another. We conducted a study to compare the efficiency of six techniques for moving objects from a tablet to a tabletop display. We compared the techniques in four different distance ranges and with three movement directions. We found that techniques like the Radar View and Pick-and-Drop, that have a control-to-display ratio of 1, are significantly faster for object movement than techniques that have smaller control-to-display ratios. We also found that using spatial manipulation of objects was faster than pressure-based manipulation.

The distortion caused by an interactive fisheye lens can make it difficult for people to remember items and locations in the data space. In this paper we introduce the idea of visit wear - a visual representation of the places that the user has previously visited - as a way to improve navigation in spaces affected by distortion. We outline the design dimensions of visit wear, and report on two studies. The first shows that increasing the distortion of a fisheye view does significantly reduce people's ability to remember object locations. The second study looks at the effects of visit wear on performance in revisitation tasks, and shows that both completion time and error rates are significantly improved when visit wear is present. Visit wear works by changing the revisitation problem from one of memory to one of visual search. Although there are limitations to the technique, visit wear has the potential to substantially improve the usability both of fisheye views and of graphical information spaces more generally.

Website privacy policies state the ways that a site will use personal identifiable information (PII) that is collected from fields and forms in web-based transactions. Since these policies can be complex, machine-readable versions have been developed that allow automatic comparison of a site's privacy policy with a user's privacy preferences. However, it is still difficult for users to determine the cause and origin of conformance conflicts, because current standards operate at the page level - they can only say that there is a conflict on the page, not where the conflict occurs or what causes it. In this paper we describe fine-grained policy anchors, an extension to the way a website implements the Platform for Privacy Preferences (P3P), that solves this problem. Fine grained policy anchors enable field-level comparisons of policy and preference, field-specific conformance displays, and faster access to additional conformance information. We built a prototype user agent based on these extensions and tested it with representative users. We found that fine-grained anchors do help users understand how privacy policy relates to their privacy preferences, and where and why conformance conflicts occur.

Alpha blending allows the simultaneous display of overlapping windows-such as palette windows in visual workspaces. Although alpha blending has been used in some applications, such as games, it has not been widely adopted. One reason for the limited acceptance is that in many scenarios, alpha blending compromises the readability of content. We introduce a new blending mechanism called multiblending that uses a vector of blending weights, one for each class of features, rather than a single transparency value. Multiblending can in most cases be automatically optimized to preserve the most relevant features of both the palette and the background window. We present the results of a user study in which multiblended palettes provided higher recognizability of both the background and the palette than the best participating version of alpha blending.

Delay is an unavoidable reality in collaborative environments. We propose an approach to dealing with delay in which 'decorators' are introduced into the interface. Decorators show the presence, magnitude and effects of delay so that participants can better understand its consequences and adopt their own natural coping strategies. Two experiments with different decorators show that this approach can significantly reduce errors in specific collaborative activities. We conclude that revealing delays is one way in which groupware can benefit from accepting and working with the reality of distributed systems, rather than trying to maintain the illusion of copresent interaction.

Although telepointers are valuable for supporting real-time collaboration, they are rarely seen in commercial groupware applications that run on the Internet. One reason for their absence is that current telepointer implementations perform poorly on real-world networks with varying traffic, congestion, and loss. In this paper, we report on a new implementation of telepointers (HPT) that is designed to provide smooth, timely, and accurate telepointers in real-world groupware: on busy networks, on cable and dialup connections, and on wireless channels. HPT maintains performance at usable levels with a combination of techniques from multimedia and distributed systems research, including UDP transport, message compression, motion prediction, adaptive rate control, and adaptive forward error correction. Although these techniques have been seen before, they have never been combined and tailored to the specific requirements of telepointers. Tests of the new implementation show that HPT provides good performance in a number of network situations where other implementations do not work at all - we can provide usable telepointers even over a lossy 28K modem connection. HPT sets a new standard for telepointers, and allows designers to greatly improve the support that groupware provides for real-time interaction over distance.

Open-source software development projects are almost always collaborative and distributed. Despite the difficulties imposed by distance, these projects have managed to produce large, complex, and successful systems. However, there is still little known about how open-source teams manage their collaboration. In this paper we look at one aspect of this issue: how distributed developers maintain group awareness. We interviewed developers, read project communication, and looked at project artifacts from three successful open source projects. We found that distributed developers do need to maintain awareness of one another, and that they maintain both a general awareness of the entire team and more detailed knowledge of people that they plan to work with. Although there are several sources of information, this awareness is maintained primarily through text-based communication (mailing lists and chat systems). These textual channels have several characteristics that help to support the maintenance of awareness, as long as developers are committed to reading the lists and to making their project communication public.

Fisheye views use distortion to provide both local detail and global context in a single continuous view. However, the distorted presentation can make it more difficult to interact with the data; it is therefore not clear whether fisheye views are good choices for interactive tasks. To investigate this question, we tested the effects of magnification and representation on user performance in a basic pointing activity called steering - where a user moves a pointer along a predefined path in the workspace. We looked specifically at magnified steering, where the entire path does not fit into one view. We tested three types of fisheye at several levels of distortion, and also compared the fisheyes with two non-distorting techniques. We found that increasing distortion did not reduce steering performance, and that the fisheyes were faster than the non-distorting techniques. Our results show that in situations where magnification is required, distortion-oriented views can be effective representations for interactive tasks.

Telepointers are an important type of embodiment in real-time distributed groupware. Telepointers can increase the presence of remote participants and can provide considerable awareness information about people's locations and activities. However, the motion of a telepointer is often disrupted by network jitter. Although some strategies exist for dealing with jitter, none of these techniques are able to restore the immediacy and smoothness of a real cursor. In this paper we investigate the use of prediction - commonly used in networked simulations and games - to reduce the effects of jitter on telepointer motion. To determine whether prediction can be effective for improving telepointers, we carried out two experiments that tested the effects of different prediction schemes (some real and some artificial) on people's ability to interpret telepointer gestures. These studies show that although cursor prediction is still a difficult problem, there are both potential performance improvements, and definite preference advantages. Our studies suggest that telepointer prediction should be routinely used to increase the immediacy and naturalness of remote interaction, and suggest that prediction can also improve interpretation in certain situations.

Group awareness is an important part of synchronous collaboration, and support for group awareness can greatly improve groupware usability. However, it is still difficult to build groupware that supports group awareness. To address this problem, we have developed the MAUI toolkit, a Java toolkit with a broad suite of awareness-enhanced UI components. The toolkit contains both extensions of standard Swing widgets, and groupware-specific components such as telepointers. All components have added functionality for collecting, distributing, and visualizing group awareness information. The toolkit packages components as JavaBeans, allowing wide code reuse, easy integration with IDEs, and drag-and-drop creation of working group-aware interfaces. The toolkit provides the first ever set of UI widgets that are truly collaboration-aware, and provides them in a way that greatly simplifies the construction and testing of rich groupware interfaces.

Loose coupling is a common way of organizing collaboration in work groups, but it has not been studied extensively in CSCW. In this paper, we consider the patterns of work that are seen in mobile groups that adopt a loosely coupled collaboration style. We report findings from interviews and fieldwork with teams of workers who deliver home healthcare services. In these teams, workers are mobile, widely dispersed, and autonomous, and team members communicate with each other only intermittently. Based on these findings, we identify and discuss four work patterns that occur in loosely coupled mobility: discretionary collaboration and effort thresholds, implicitly shared information, asynchronous communication and coordination, and barriers to synchrony. We consider the implications of these findings for the design of CSCW technologies.

Researchers in Computer Supported Cooperative Work have recently developed discount evaluation methods for shared-workspace groupware. Most discount methods rely on some understanding of the context in which the groupware systems will be used, which means that evaluators need to model the tasks that groups will perform. However, existing task analysis schemes are not well suited to the needs of groupware evaluation: they either do not deal with collaboration issues, do not use an appropriate level of analysis for concrete assessment of usability in interfaces, or do not adequately represent the variability inherent in group work. To fill this gap, we have developed a new modeling technique called Collaboration Usability Analysis. CUA focuses on the teamwork that goes on in a group task rather than the taskwork. To enable closer links between the task representation and the groupware interface, CUA grounds each collaborative action in a set of group work primitives called the mechanics of collaboration . To represent the range of ways that a group task can be carried out, CUA allows variable paths through the execution of a task, and allows alternate paths and optional tasks to be modeled. CUA's main contribution is to provide evaluators with a framework in which they can simulate the realistic use of a groupware system and identify usability problems that are caused by the groupware interface.

Fisheye views allow people to see both a focus region and the surrounding context in the same window. However, the magnification effects of the fisheye lens can cause several problems for users. One of these is focus-targeting, where a user moves the focus to a new location. Magnification makes focus-targeting difficult because objects appear to move as the focus point approaches them. This paper examines how the distortion of a fisheye view affects focus-targeting performance, and present a technique called speed-coupled flattening (SCF) as a way to improve focus targeting in distortion-oriented views. SCF dynamically reduces the distortion level of a fisheye based on pointer velocity and acceleration. In an experiment, the technique resulted in significant reductions in both targeting time and targeting errors. By adjusting distortion based on the user's activity, we can improve usability without requiring the user to manipulate any additional view controls

Discount usability evaluation methods have recently been introduced as a way to assess groupware systems. However, one criticism of these techniques is that they do not make use of information about users and their work contexts. To address this problem, we developed groupware walkthrough, a new usability inspection technique for groupware. The technique is a substantive modification of cognitive walkthrough to include consideration for the complexities of teamwork. The two components of groupware walkthrough are a task model for identifying and analysing real-world collaborative tasks, and a walkthrough process for assessing a system's support for those tasks. Groupware walkthrough is a low-cost technique that can identify collaboration-specific usability problems and can find problems that would not be revealed through other inspection methods

Good real time groupware products are hard to develop, in part because evaluating their support for basic teamwork activities is difficult and costly. To address this problem, we are developing discount evaluation methods that look for groupware-specific usability problems. In a previous paper, we detailed a new set of usability heuristics that evaluators can use to inspect shared workspace groupware to see how they support teamwork. We wanted to determine whether the new heuristics could be integrated into a low-cost methodology that parallels Nielsen's traditional heuristic evaluation (HE). To this end, we examined 27 evaluations of two shared workspace groupware systems and analysed the inspectors' relative performance and variability. Similar to Nielsen's findings for traditional HE, individual inspectors discovered about a fifth of the total known teamwork problems, and that there was only modest overlap in the problems they found. Groups of three to five inspectors would report about 40-60% of the total known teamwork problems. These results suggest that heuristic evaluation using our groupware heuristics can be an effective and efficient method for identifying teamwork problems in shared workspace groupware systems.

Gestural communication is an important part of shared work, both in face-to-face settings and distributed environments. However, gestures in groupware are often difficult to see and interpret because of disruptions to their motion caused by network jitter. One way to improve the visibility of remote gestures is by using traces-visualizations of the last few moments' of a remote pointer's motion. We carried out an experiment to test the effectiveness of traces in helping people interpret gestures. We found that telepointer traces dramatically improved people's accuracy and confidence in their decisions as jitter delays grew larger. Our results suggest that telepointer traces and other visualizations of interaction history can be used to enrich communication among remote collaborators.

Network delays are a fact of life when using real-time groupware over a wide area network such as the Internet. This paper looks at how network delays affect closely-coupled group work in real-time distributed groupware. We first determine the types and amounts of delay that can happen on the Internet, and then identify types of collaborative interactions that are affected by delay. We then examine two interaction types more closely: predicting others’ movements, and coordinating shared access to artifacts. We carried out experiments to measure the effects of two kinds of delay (latency and jitter). When these interactions are isolated and repeated, we found that even small delays can lead to significant increases in completion time and errors. Although people in real-world tasks are often able to adapt their actions to accommodate network delays, we conclude that designing groupware to minimise the effects of delay can improve usability for closely-coupled collaboration. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Many researchers believe that groupware can only be evaluated by studying real collaborators in their real contexts, a process that tends to be expensive and time-consuming. Others believe that it is more practical to evaluate groupware through usability inspection methods. Deciding between these two approaches is difficult, because it is unclear how they compare in a real evaluation situation. To address this problem, we carried out a dual evaluation of a groupware system, with one evaluation applying user-based techniques, and the other using inspection methods. We compared the results from the two evaluations and concluded that, while the two methods have their own strengths, weaknesses, and trade-offs, they are complementary. Because the two methods found overlapping problems, we expect that they can be used in tandem to good effect, e.g., applying the discount method prior to a field study, with the expectation that the system deployed in the more expensive field study has a better chance of doing well because some pertinent usability problems will have already been addressed.

Manipulating a mouse pointer is often difficult for the low vision computer user. Working with such a small, mobile screen object is very visually demanding. Although several techniques have been used to address this problem, the design space of assistive pointers has not been fully explored by the current state of the art. This paper proposes a four dimensional framework to fully articulate the design space of assistive pointers for low vision users. The dimensions of the framework describe the key attributes of assistance offered to users by any pointing solution: the perceptual channel that carries the assistance, the stage of targeting supported by the assistance, the relationship between the assistance and the interface, and the degree of availability associated with the assistance.

Real-time collaboration in current distributed groupware workspaces is often an awkward and clumsy process.We hypothesize that better support for workspace awareness-the understanding of who is in the workspace, where they are working, and what they are doing-can improve the usability of these shared computational workspaces.We conducted an experiment that compared people's performance on two versions of a groupware interface.The interfaces used workspace miniatures to provide different levels of support for workspace awareness.The basic miniature showed information only about the local user, and the enhanced miniature showed the location and activity of other people in the workspace as well.We examined five aspects of groupware usability: task completion times, communication efficiency, the participants' perceived-effort, overall preference, and strategy use.In two of three task types tested, completion times were lower in the awareness-enhanced system, and in one task type, communication was more efficient.The additional awareness information also allowed people to use different and more effective strategies to complete the tasks.Participants greatly preferred the awareness-enhanced system.The study provides empirical evidence that support for workspace awareness improves the usability of groupware, and uncovers some of the reasons underlying this improvement.

Collaboration in current real-time groupware systems is often an awkward and clumsy process. We hypothesize that better support for workspace awareness can improve the usability of these shared computational workspaces. We conducted an experiment that compared people's performance on two versions of a groupware interface. The interfaces used workspace miniatures to provide different levels of support for workspace awareness. The basic miniature showed information only about the local user, and the enhanced miniature showed the location and activity of others in the workspace as well. In two of three task types tested, completion times were lower with increased awareness support, and in one task type, communication was more efficient. Participants also greatly preferred the awareness-enhanced system. The study provides empirical evidence of, and underlying reasons for, the value of supporting workspace awareness in groupware. Keywords workspace awareness, groupware, usability INTRODU...

Article Free Access Share on Design for individuals, design for groups: tradeoffs between power and workspace awareness Authors: Carl Gutwin Department of Computer Science, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada Department of Computer Science, University of Saskatchewan, Saskatoon, SK, S7N 5A9, CanadaView Profile , Saul Greenberg Department of Computer Science, University of Calgary, Calgary, AB, T2N 1N4, Canada Department of Computer Science, University of Calgary, Calgary, AB, T2N 1N4, CanadaView Profile Authors Info & Claims CSCW '98: Proceedings of the 1998 ACM conference on Computer supported cooperative workNovember 1998 Pages 207–216https://doi.org/10.1145/289444.289495Published:01 November 1998Publication History 213citation2,057DownloadsMetricsTotal Citations213Total Downloads2,057Last 12 Months159Last 6 weeks15 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

We outline the need for search engines to provide user feedback on the expected time for a query, describe a scheme for learning a model of query time by observing sample queries, and discuss the results obtained for a set of actual user queries on a document collection using the MG search engine.

Real time groupware systems are now moving away from strict view-sharing and towards relaxed “what-you-see-is-what-I-see” interfaces, where distributed participants in a real time session can view different parts of a shared visual workspace. As with strict view-sharing, people using relaxed-WYSIWIS require a sense of workspace awareness—the up-to-the-minute knowledge aobut another person's interactions with the shared workspace. The problem is deciding how to provide a user with an appropriate level of awareness of what other participants are doing when they are working in different areas of the workspace. In this video, we illustrate distortion oriented displays as a novel way of providing this awareness. These displays, which employ magnification lenses and fisheye view techniques, show global context and local detail within a single window, both peripheral and detailed awareness of other participants' actions. Three prototypes are presented as examples of groupware distortion-oriented displays. The head-up lens uses a see-through lens to show full-sized local detail in the foreground, and a miniature overview showing global context in the background. The offset lens employs a magnifying lens to show detail over a miniature overview. The fisheye text viewer provides people with detail of what everyone is doing through multiple focal points, one for each participant.

No abstract available.

Real-time groupware systems often let each participant control their own view into a shared workspace. However, when collaborators do not share the same view they lose their awareness about where and how others are interacting with the workspace artifacts. We have designed a number of add-on awareness windows that help people regain this awareness. Two general strategies and several variations are illustrated in this video that extend work done in a few other groupware systems. First, radar overviews shrink the entire workspace to fit within a single window. Awareness is indicated by overlaying the overview with boxes representing others' viewports, by telepointers that show where they are working, and by seeing changes to objects in the workspace as they are made. The workspace can be represented within the radar overview as a scaled miniature, by stylized objects, or by its semantic structure. Second, two types of detailed views show some or all of what another person can see, providing awareness of fine-grained details of others' actions.

Workspace awareness is knowledge about others' interaction with a shared workspace. Groupware systems provide only limited information about other participants, often compromising workspace awareness. This paper describes a usability study of several widgets designed to help maintain awareness in a groupware workspace. These widgets include a miniature view, a radar view, a multiuser scrollbar, a glance function, and a "what you see is what I do" view. The study examined the widgets' information content, how easily people could interpret them, and whether they were useful or distracting. Observations, questionnaires, and interviews indicate that the miniature and radar displays are useful and valuable for tasks involving spatial manipulation of artifacts. Keywords Workspace awareness, shared workspaces, usability study. INTRODUCTION People maintain an ongoing awareness of others in physical workspaces like whiteboards and tabletops, and they do this using everyday perceptual abilit...

In this paper we discuss a mechanism for modifying context in a tutorial dialogue. The context mechanism imposes a pedagogically motivated misrepresentation (PMM) on a dialogue to achieve instructional goals. In the paper, we outline several types of PMMs and detail a particular PMM in a sample dialogue situation. While the notion of PMMs are specifically oriented towards tutorial dialogue, misrepresentation has interesting implications for context in dialogue situations generally, and also suggests that Grice's maxim of quality needs to be modified.