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%.

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.

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.

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).

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.

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.

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.

We introduce a new shortcut interface called KeyMap that is designed to leverage Norman's principle of natural mapping. Rather than displaying shortcut command labels in linear menus, KeyMap displays a virtual keyboard with command labels displayed directly on its keys. A crowdsourced experiment compares KeyMap to Malacria et al.'s ExposeHK using an extension of their protocol to also test recall. Results show KeyMap users remembered 1 more shortcut than ExposeHK immediately after training, and this advantage increased to 4.5 more shortcuts when tested again after 24 hours. KeyMap users also incidentally learned more shortcuts that they had never practised. We demonstrate how KeyMap can be added to existing web-based applications using a Chrome extension.

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.

We study interaction interferences, situations where an unexpected change occurs in an interface immediately before the user performs an action, causing the corresponding input to be misinterpreted by the system. For example, a user tries to select an item in a list, but the list is automatically updated immediately before the click, causing the wrong item to be selected. First, we formally define interaction interferences and discuss their causes from behavioral and system-design perspectives. Then, we report the results of a survey examining users' perceptions of the frequency, frustration, and severity of interaction interferences. We also report a controlled experiment, based on state-of-the-art experimental protocols from neuroscience, that explores the minimum time interval, before clicking, below which participants could not refrain from completing their action. Finally, we discuss our findings and their implications for system design, paving the way for future work.

Many interfaces attempt to assist users by offering suggestions, predicting actions, or correcting user input. Although these attempts may often be beneficial, they will occasionally fail, and prior research from psychology and behavioral economics on loss aversion suggests that such failures may have an overweighted impact on subjective preferences. To better understand the relationship between interface outcomes and subjective preferences, we adapted to interaction a model from behavioral economics describing reference-dependent preferences. Two experiments examined our model’s predictions: both involved word-snapping interface assistance during text selection, with subjects choosing whether they preferred unassisted text selection (no snapping) or assisted text selection (snapping). In Experiment 1, the word-snapping feature could be disabled when it was unhelpful by backtracking the selection, which required progress losses in terms of target characters selected. In Experiment 2, word-snapping could be disabled by pressing a modifier key and waiting for an animation to complete, without need for the loss of target characters. Time and error performance with both experimental methods were comparable. The model predicts an aversion to progress losses in Experiment 1 that should be neutralized in Experiment 2, and the results of both experiments conformed to these predictions. We discuss the implications of the model as a platform for understanding user preferences more broadly, especially when considering interfaces that risk periodically failing to meet user expectations.

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.

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.

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.

When task descriptions are precise they can be analysed to yield a variety of insights about interaction, such as the quantity of actions performed, the amount of information that must be perceived, and the cognitive workload involved. Task modelling notations and associated tools provide support for precise task description, but they generally provide a fixed set of constructs, which can limit their ability to model new and evolving application domains and technologies. This article describes challenges involved in using fixed notations for describing tasks. We use examples of recognized tasks analysis processes and their phases to show the need for customization of task notations, and through a series of illustrative examples, we demonstrate the benefits using our extensible task notation and tool (HAMSTERS-XL).

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.

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.

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.

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.

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.

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.

User interfaces often attempt to assist users by automating elements of interaction, but these attempts will periodically fail -- impeding user performance. To understand the design implications of correct and incorrect assistance, we conducted an experiment in which subjects selected their preferred of two interfaces (neutral and snapping) for a series of 10 drag-and-drop tasks. With neutral the dragged object moved pixel-by-pixel, and with snapping the object snapped to a grid. Snapping trials were engineered to provide controlled levels of objective performance gains and losses with respect to neutral: gains were achieved when the target was aligned with the grid, and losses were achieved through misalignment -- which required subjects to drop the object, hold a key, and complete the task using a finer movement resolution. Results showed a significant preference for the snapping interface, even when losses impaired performance.

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.

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.

Edge-scrolling allows users to scroll a viewport while simultaneously dragging near or beyond a window's edge. Common implementations rely on rate control, mapping the distance between the pointer and the edge of the viewport to the scrolling velocity. While ubiquitous in operating systems, edge-scrolling has received little attention, even though previous works suggest that (1) rate control may be suboptimal for isotonic pointing devices like mice and trackpads and (2) space beyond the window's edge might be scarce, limiting scrolling control. To address these problems, we developed Push-edge scrolling (and Slide-edge scrolling, its inertial variant), two novel position-based techniques that allow scrolling by "pushing" against the viewport edge. A controlled experiment shows that our techniques reduce overshoots and offer performance improvements by up to 13% over traditional edge-scrolling.

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.

Simple history systems such as Undo and Redo permit retrieval of earlier or later interaction states, but advanced systems allow powerful capabilities to reuse or reapply combinations of commands, states, or data across interaction contexts. Whether simple or powerful, designing interaction history mechanisms is challenging. We begin by reviewing existing history systems and models, observing a lack of tools to assist designers and researchers in specifying, contemplating, combining, and communicating the behaviour of history systems. To resolve this problem, we present CAUSALITY, a conceptual model of interaction history that clarifies the possibilities for temporal interactions. The model includes components for the work artifact (such as the text and formatting of a Word document), the system context (such as the settings and parameters of the user interface), the linear timeline (the commands executed in real time), and the branching chronology (a structure of executed commands and their impact on the artifact and/or context, which may be navigable by the user). We then describe and exemplify how this model can be used to encapsulate existing user interfaces and reveal limitations in their behaviour, and we also show in a conceptual evaluation how the model stimulates the design of new and innovative opportunities for interacting in time.

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.

We present SensaBubble, a chrono-sensory mid-air display system that generates scented bubbles to deliver information to the user via a number of sensory modalities. The system reliably produces single bubbles of specific sizes along a directed path. Each bubble produced by SensaBubble is filled with fog containing a scent relevant to the notification. The chrono-sensory aspect of SensaBubble means that information is presented both temporally and multimodally. Temporal information is enabled through two forms of persistence: firstly, a visual display projected onto the bubble which only endures until it bursts; secondly, a scent released upon the bursting of the bubble slowly disperses and leaves a longer-lasting perceptible trace of the event. We report details of SensaBubble's design and implementation, as well as results of technical and user evaluations. We then discuss and demonstrate how SensaBubble can be adapted for use in a wide range of application contexts -- from an ambient peripheral display for persistent alerts, to an engaging display for gaming or education.

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.

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.

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.

Touch scrolling systems use a transfer function to transform gestures on a touch sensitive surface into scrolling output. The design of these transfer functions is complex as they must facilitate precise direct manipulation of the underlying content as well as rapid scrolling through large datasets. However, researchers' ability to refine them is impaired by: (1) limited understanding of how users express scrolling intentions through touch gestures; (2) lack of knowledge on proprietary transfer functions, causing researchers to evaluate techniques that may misrepresent the state of the art; and (3) a lack of tools for examining existing transfer functions. To address these limitations, we examine how users express scrolling intentions in a human factors experiment; we describe methods to reverse engineer existing `black box' transfer functions, including use of an accurate robotic arm; and we use the methods to expose the functions of Apple iOS and Google Android, releasing data tables and software to assist replication. We discuss how this new understanding can improve experimental rigour and assist iterative improvement of touch scrolling.

Treemaps are a well known and powerful space-filling visualisation method for displaying hierarchical data. Many alternative treemap algorithms have been proposed, often with the aim being to optimise performance across several criteria, including spatial stability to assist users in locating and monitoring items of interest. In this paper, we demonstrate that spatial stability is not fully captured by the commonly used "distance change" (DC) metric, and we introduce a new "location drift" (LD) metric to more fully capture spatial stability. An empirical study examines the validity and usefulness of the location drift metric, showing that it explains some effects on user performance that distance change does not. Next, we introduce "Hilbert" and "Moore" treemap algorithms, which are designed to achieve high spatial stability. We assess their performance in comparison to other treemaps, showing that Hilbert and Moore treemaps perform well across all stability metrics.

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.

We introduce AccessRank, an algorithm that predicts revisitations and reuse in many contexts, such as file accesses, website visits, window switches, and command lines. AccessRank uses many sources of input to generate its predictions, including recency, frequency, temporal clustering, and time of day. Simulations based on log records of real user interaction across a diverse range of applications show that AccessRank more accurately predicts upcoming accesses than other algorithms. The prediction lists generated by AccessRank are also shown to be more stable than other algorithms that have good predictive capability, which can be important for usability when items are presented in lists as users can rely on their spatial memory for target location. Finally, we present examples of how real world applications might use AccessRank.

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.

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.

Touch interactions have refreshed some of the 'glowing enthusiasm' of thirty years ago for direct manipulation interfaces. However, today's touch technologies, whose interactions are supported by graphics, sounds or crude clicks, have a tactile sameness and gaps in usability. We use a Large Area Tactile Pattern Display (LATPaD) to examine design possibilities and outcomes when touch interactions are enhanced with variable surface friction. In a series of four studies, we first confirm that variable friction gives significant performance advantages in low-level targeting activities. We then explore the design space of variable friction interface controls and assess user reactions. Most importantly, we demonstrate that variable friction can have a positive impact on the enjoyment, engagement and sense of realism experienced by users of touch interfaces.

Several enhanced pointing techniques aim to reduce the Fitts' law targeting distance by providing multiple target trajectories in the hope that a shorter path is available. However, these techniques introduce a search or decision component to pointing users must examine the alternatives available and decide upon the trajectory to use. We analyse these difficulties, present a methodology for examining them as well as other behaviour issues, and report empirical results of performance with pointer wrapping and Ninja cursors. Results show that offering multiple trajectories incurs a significant search or decision cost, and that users are therefore poor at capitalising on the theoretical benefits of reduced target distance.

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.

The limited viewport size of mobile devices requires that users continuously acquire information that lies beyond the edge of the screen. Recent hardware solutions are capable of continually tracking a user's finger around the device. This has created new opportunities for interactive solutions, such as direct off-screen pointing: the ability to directly point at objects that are outside the viewport. We empirically characterize user performance with direct off-screen pointing when assisted by target cues. We predict time and accuracy outcomes for direct off-screen pointing with existing and derived models. We validate the models with good results (R2 ≥ 0.9) and reveal that direct off-screen pointing takes up to four times longer than pointing at visible targets, depending on the desired accuracy tradeoff. Pointing accuracy degrades logarithmically with target distance. We discuss design implications in the context of several real-world applications.

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.

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.

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.

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.

Selecting items in cascading pull-down menus is a frequent task in most GUIs. These selections involve two major components: steering and selection, with the steering component being the most time-consuming and error-prone. We describe a new technique, called Adaptive Activation-Area Menu (AAMU) that eliminate corner steering. AAMUs contain an enlarged activation area which dynamically resizes itself providing a broader steering path for menu navigation. We also combined AAMUs with Force-field menus, to create Force-AAMUs. We empirically demonstrate that AAMUs and Force-AAMUs outperformed the current default menu. We also compared performances of various other menus including Enlarged activation area menus (EMUs) and Gesture based selection with mouse as an input device. Overall, users show higher satisfaction rates for AAMUs over other menu designs.

We theoretically and empirically examine the impact of control display (CD) gain on mouse pointing performance. Two techniques for modifying CD gain are considered: constant gain (CG) where CD gain is uniformly adjusted by a constant multiplier, and pointer acceleration (PA) where CD gain is adjusted using a nonuniform function depending on movement characteristics. Both CG and PA are evaluated at various levels of relationship between mouse and cursor movement: from low levels, which have a near one-to-one mapping, through to high levels that aggressively amplify mouse movement. We further derive a model predicting the modification in motor-space caused by pointer acceleration. Experiments are then conducted on a standard desktop display and on a very large high-resolution display, allowing us to measure performance in high index of difficulty tasks where the effect of clutching may be pronounced. The evaluation apparatus was designed to minimize device quantization effects and used accurate 3D motion tracking equipment to analyze users' limb movements. On both displays, and in both gain techniques, we found that low levels of CD gain had a marked negative effect on performance, largely because of increased clutching and maximum limb speeds. High gain levels had relatively little impact on performance, with only a slight increase in time when selecting very small targets at high levels of constant gain. On the standard desktop display, pointer acceleration resulted in 3.3% faster pointing than constant gain and up to 5.6% faster with small targets. This supported the theoretical prediction of motor-space modification but fell short of the theoretical potential, possibly because PA caused an increase in target overshooting. Both techniques were accurately modeled by Fitts' law in all gain settings except for when there was a significant amount of clutching. From our results, we derive a usable range of CD gain settings between thresholds of speed and accuracy given the capabilities of a pointing device, display, and the expected range of target widths and distances.

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.

Interface designers normally strive for a design that minimises the user's effort. However, when the design's objective is to train users to interact with interfaces that are highly dependent on spatial properties (e.g. keypad layout or gesture shapes) we contend that designers should consider explicitly increasing the mental effort of interaction. To test the hypothesis that effort aids spatial memory, we designed a "frost-brushing" interface that forces the user to mentally retrieve spatial information, or to physically brush away the frost to obtain visual guidance. We report results from two experiments using virtual keypad interfaces -- the first concerns spatial location learning of buttons on the keypad, and the second concerns both location and trajectory learning of gesture shape. The results support our hypothesis, showing that the frost-brushing design improved spatial learning. The participants' subjective responses emphasised the connections between effort, engagement, boredom, frustration, and enjoyment, suggesting that effort requires careful parameterisation to maximise its effectiveness.

On traditional tables, people frequently use the third dimension to pile, sort and store objects. However, while effective and informative for organization, this use of the third dimension does not usually extend far above the table. To enrich interaction with digital tables, we present the concept of shallow-depth 3D -- 3D interaction with limited depth. Within this shallow-depth 3D environment several common interaction methods need to be reconsidered. Starting from any of one, two and three touch points, we present interaction techniques that provide control of all types of 3D rotation coupled with translation (6DOF) on a direct-touch tabletop display. The different techniques exemplify a wide range of interaction possibilities: from the one-touch technique, which is designed to be simple and natural, but inherits a degree of imprecision from its simplicity; through to three-touch interaction, which allows precise bimanual simultaneous control of multiple degrees of freedom, but at the cost of simplicity. To understand how these techniques support interaction in shallow-depth 3D, we present a user study that examines the efficiency of, and preferences for, the techniques developed. Results show that users are fastest and most accurate when using the three-touch technique and that their preferences were also strongly in favour of the expressive power available from three-touch.

Using a stylus on a tablet computer to acquire small targets can be challenging. In this paper we present pointing lenses -- interaction techniques that help users acquire and select targets by presenting them with an enlarged visual and interaction area. We present and study three pointing lenses for pen-based systems and find that our proposed Pressure-Activated Lens is the top overall performer in terms of speed, accuracy and user preference. In addition, our experimental results not only show that participants find all pointing lenses beneficial for targets smaller than 5 pixels, but they also suggest that this benefit may extend to larger targets as well.

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.

In this paper, we explore ways to combine the video of a remote person with a shared tabletop display to best emulate face-to-face collaboration. Using a simple photo application we compare a variety of social and performance measures of collaboration of a standard non-spatial 2D interface with two approaches for adding spatial cues to videoconferencing: one based on simulated immersive 3D, the other based on video streams in a physically fixed arrangement around an interactive table. A face-to-face condition is included as a 'gold-standard' control. As expected, social presence and task measures were superior in the face-to-face condition, but there were also important differences between the 2D and spatial interfaces. In particular, the spatial interfaces positively influenced social presence and copresence measures in comparison to 2D, but the task measures favored the two-dimensional interface.

Speed dependent automatic zooming (SDAZ) is a promising refinement to scrolling in which documents are automatically zoomed-out as the scroll rate increases. By automatically zooming, the visual flow rate is reduced enabling rapid scrolling without motion blur. In order to aid SDAZ calibration we theoretically and empirically scrutinise human factors of the speed/zoom relationship. We then compare user performance with four alternative text-document scrolling systems, two of which employ automatic zooming. One of these systems, which we term 'DDAZ', is based on van Wijk and Nuij's recent and important theory that calculates optimal pan/zoom paths between known locations in 2D space. van Wijk and Nuij suggested that their theory could be applied to scrolling, but did not implement or test their formulaic suggestions. Participants in our evaluation (n=27) completed scrolling tasks most rapidly when using SDAZ, followed by DDAZ, normal scrollbars, and traditional rate-based scrolling. Workload assessments and preferences strongly favoured SDAZ. We finish by examining issues for consideration in commercial deployments.

This paper describes the design and evaluation of a gesture-based scheme for issuing the back and forward commands in web browsers. In designing our gesture recogniser we conducted several experiments to determine metrics associated with the magnitude, timing and stereotypical errors of ‘natural’ linear flick gestures using stylus and mouse input devices. These low-level metrics are important to software designers who must implement algorithms that discriminate between gestures and other actions such as mouse clicks and drags. As well as empirically characterising gestures, the metrics provide various insights into stereotypical behaviour with gestures, including the facts that angular errors are larger in the left and right directions with the pen, that vertical gestures are ‘awkward’ with the mouse, and that downwards gestures are slower than other directions. An evaluation of gestures for web browsing shortcuts shows that they enhance navigation efficiency, and that participants were extremely enthusiastic about them.

Text elision is a user interface technique that aims to improve the efficiency of navigating through information by allowing regions of text to be ‘folded’ into and out of the display. Several researchers have argued that elision interfaces are particularly suited to source code editing because they allow programmers to focus on relevant code regions while suppressing the display of irrelevant information. Elision features are now appearing in commercial systems for software development. There is, however, a lack of empirical evidence of the technique's efficiency. This paper presents an empirical evaluation of source code elision using a Java program editor. The evaluation compared a normal ‘flat text’ editor with two versions that diminished elided text to levels that were ‘just legible’ and ‘illegible’. Performance was recorded in four tasks involving navigation through programs. Results show that programmers were able to complete their tasks more rapidly when using the elision interfaces, particularly in larger program files. Although several participants indicated a preference for the just legible elision interface, performance was best with illegible elision.

User interfaces can improve task performance by exploiting the powerful human capabilities for spatial cognition. This opportunity has been demonstrated by many prior experiments. It is tempting to believe that providing greater spatial flexibility-by moving from flat 2D to 3D user interfaces-will further enhance user performance. This paper describes an experiment that investigates the effectiveness of spatial memory in real-world physical models and in equivalent computer-based virtual systems. The different models vary the user's freedom to use depth and perspective in spatial arrangements of images representing web pages. Results show that the subjects' performance deteriorated in both the physical and virtual systems as their freedom to locate items in the third dimension increased. Subjective measures reinforce the performance measures, indicating that users found interfaces with higher dimensions more 'cluttered' and less efficient

Computer Science researchers are investigating systems that exploit the benefits of collaborative computing technology in learning. There is, however little empirical evidence of the benefits and costs associated with different modes of computer support for collaborative learning. The authors describe an experiment that compares how well 51 children (aged ten and eleven) learnt to solve a small puzzle in three different collaborative learning conditions. Results showed no significant difference in learning outcomes among the three conditions, but revealed that girls solved the puzzle more slowly when collaborating.

Several recent research systems have provided interactive three-dimensional (3D) visualisations for supporting everyday work such as file and document management. But what improvements do these 3D interfaces offer over their traditional 2D counterparts? This paper describes the comparative evaluation of two document management systems that differ only in the number of dimensions used for displaying and interacting with the data. The 3D system is heavily based on Robertson et al.'s Data Mountain, which supports users in storing, organising and retrieving “thumbnail” representations of documents such as bookmarked Web-pages. Results show that our subjects were faster at storing and retrieving pages in the display when using the 2D interface, but not significantly so. As expected, retrieval times significantly increased as the number of thumbnails increased. Despite the lack of significant differences between the 2D and 3D interfaces, subjective assessments showed a significant preference for the 3D interface.

This article reviews models and theoretical frameworks of collaborative awareness in the use of real-time groupware systems. The review is used to motivate and guide an investigation of distortion-oriented mechanisms for supporting collaborators' fluid and dynamic awareness requirements. We describe our development and evaluation of DOME, a distortion-oriented multiuser editor. Although we designed DOME to provide a realistic and useful platform for the investigation of awareness concepts, our evaluation revealed major flaws in its support for distortion-oriented awareness. We analyze the cause of these errors, some of which were not detected in prior work, and provide precise formulations that will overcome them.

Article CEVA: a tool for collaborative video analysis Share on Authors: Andy Cockburn Department of Computer Science, University of Canterbury, Christchurch, New Zealand Department of Computer Science, University of Canterbury, Christchurch, New ZealandView Profile , Tony Dale Department of Computer Science, University of Canterbury, Christchurch, New Zealand Department of Computer Science, University of Canterbury, Christchurch, New ZealandView Profile Authors Info & Claims GROUP '97: Proceedings of the international ACM SIGGROUP conference on Supporting group work: the integration challengeNovember 1997 Pages 47–55https://doi.org/10.1145/266838.266857Published:16 November 1997 9citation465DownloadsMetricsTotal Citations9Total Downloads465Last 12 Months7Last 6 weeks0 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 SiteGet Access

This paper examines the usability of the hypertext navigation facilities provided by World Wide Web client applications. A notation is defined to represent the user's navigational acts and the resultant system states. The notation is used to report potential, or “theoretical” problems in the models of navigation supported by three web client applications. A usability study confirms that these problems emerge in actual use, and demonstrates that incorrect user models of the clients' facilities are common. A usability analysis identifies inadequacies in the clients' interfaces. Motivated by the analysis of usability problems, we propose extensions to the design of WWW client applications. These proposals are demonstrated by our system WEBNET which uses dynamic graphical overview diagrams to extend the navigational facilities of conventional World Wide Web client applicaions. Related work on graphical overview diagrams for web navigation is reviewed.

Groupware design is at a stage where identification, clarification and validation of best practice is critical if its potential is to be realised. The paper examines and records the major causes of groupware failure, and provides four groupware design principles that encapsulate the problems and guide design teams around them. The principles provide an extendable framework that is a synthesis of design lessons recorded in CSCW literature.