With the advent of large language models, creative writers can get support for refinement, co-writing, and text generation. Yet, writers often struggle to understand how model-driven rewrites affect the emotional trajectory of their narratives. We investigate how interactive visualizations can help writers gain awareness, agency, and control over the emotional flow of their texts. First, we designed an interactive visualization-based writing tool that allows writers to adjust emotional pacing, explore different emotional directions, and revise the emotional storyline in real time. Second, we conducted a user study with creative writers (N = 24) to evaluate its effectiveness. Our results show a significantly improved enjoyment, exploration, and perceived value. Writers highlighted increased emotional awareness and narrative coherence; simultaneously, they expressed concerns about authorship. Thus, support can enrich the creative process when designed with transparency, user agency, and adaptability in mind, contributing to the understanding of augmenting human writing creativity.

Voice assistants (VAs) are typically evaluated through task performance metrics and self-report questionnaires, but people’s voices themselves carry rich paralinguistic cues that reveal affect, effort, and interaction breakdowns. We present a within-subjects study (N=49) that systematically compared three VA personas across three usage scenarios to investigate whether speech-derived audio features can serve as a proxy for user experience (UX). Participants’ speech was analyzed for temporal, spectral, and linguistic markers, alongside standardized UX measures, brief mood and stress ratings, and a post-study questionnaire. We found correlations between specific speech features and self-reported satisfaction and experience. Furthermore, a machine learning model trained on speech features achieved promising accuracy in classifying UX levels, indicating that this might be a reasonable alternative to self-report instruments. Our findings establish speech as a viable, real-time signal for implicitly measuring UX and point toward adaptive VUIs that respond dynamically to emotional and usability-related vocal cues.

Transparency of a robot's actions and intentions is important for trustful human-robot collaboration. Current approaches for creating transparency through explanations mostly follow the approach "more information creates more transparency", assuming cognitive load remains manageable. However, this ignores human active reasoning, which can, if not too demanding, create a better understanding from less information, as found in education literature. To explore this self-explanation effect, we compared three explanation structures (fully-specified, under-specified, no explanation) that induced different levels of active reasoning demand (low, medium, high). In a controlled laboratory study, 36 participants observed a robot completing rule-based classification tasks of varying difficulty (easy, moderate, hard) across all explanation conditions. We found that a moderate reasoning demand, elicited through under-specified explanations, produced the best understanding of the robot's actions compared to full or no explanations. This challenges the current "more helps more" approach and may help design more effective explanations for creating transparency.

We introduce PromptCanvas, a UI concept that transforms prompting into a composable, widget-based experience on an infinite canvas. Users can generate, customize, and arrange interactive widgets that represent various facets of their text, offering greater control over AI-generated content. PromptCanvas allows to create widgets through system suggestions, user prompts, or manual input, providing a flexible environment tailored to individual needs. This enables deeper engagement with the creative process. In two lab studies, PromptCanvas outperformed both the conversational UI (lab study 1) and the structured baseline, Wordcraft (lab study 2) on the Creativity Support Index. Participants found that it reduced cognitive load, while at the same time providing better performance. Qualitative feedback revealed that the visual organization of thoughts and easy iteration encouraged new perspectives and ideas. The field study ( \(N=10\) ) also confirmed these results, showcasing the potential of dynamic, customizable interfaces to improve collaborative writing with AI.

Virtual reality training systems require the careful design of content presentation, user embodiment, and overall user experience. We explore the impact of different perspectives (first-person and third-person) and virtual self-visualization techniques (VSVTs: mirrors and external avatars) on user embodiment, performance and experience. In a study with 28 participants learning karate movements, we tested four combinations of these factors. Results indicate that perspective influences visual focus and embodiment, while VSVTs affect movement execution, particularly in the third-person avatar condition. Measurements of physiological activity, workload, presence, and enjoyment found no significant overall advantages for any of the conditions. Interviews revealed that most participants preferred the familiar first-person mirror combination, although participants in third-person perspective focused more on their own body and noted the helpfulness of this viewpoint. The study demonstrates that alternative perspectives and visualization techniques offer valuable training options, as these conditions did not produce significant differences in measured cognitive load when compared with each other. Future VR training systems should incorporate interactive feedback and customization options to accommodate individual preferences and optimize learning experiences.

Effective self-reflection is crucial for motor skill acquisition, yet it is challenging to facilitate in single-user VR training environments. We investigate this through a method where users are embodied as a virtual trainer and prompted to actively evaluate a recorded performance. In an empirical study, we systematically varied the trainee’s appearance and their movements. Our mixed-methods analysis reveals that confronting one’s own performance triggers a fundamental role conflict between the user’s identity as the performer and their new role as the evaluator. Most importantly, this conflict challenges a binary view of embodiment. Participants experienced a multi-faceted sense of self, oscillating between identifying with the trainee and detaching as the trainer. Our work contributes a novel characterization of embodied self-evaluation, revealing a psychological duality at its core and offering clear design implications for VR systems that foster self-insight in training and therapy.

Meaningful interactions positively impact users’ meaning-making and feeling socially and culturally connected with their surroundings. However, creating such interactions is a continuous, complex challenge. We present the Traces in Use design concept supporting interface contextualization for meaningful human–environment interactions in public places. The concept was developed and evaluated in three steps: (I) exploring traces of use characteristics as inspiration for design, (II) introducing the concept definition, its theoretical evaluation, and a supporting framework, and (III) practically evaluating the concept by developing, contextualizing, and testing three interfaces (a lion interface, a drum, and a storyteller) in two empirical field studies (N = 40). The results show that the concept promotes meaningful interaction by supporting users’ feelings of socio-cultural connectedness and meaning-making. With this, our work contributes the Traces in Use design concept, its development, and its methodological application for meaningful human–environment interactions and interface contextualization in public places.

Object detection tasks still often require manual image analysis. Using Machine Learning (ML) instead creates accountability challenges, necessitating experts for model refinement, which is costly and takes time. We investigate integrating crowd knowledge as a cost-effective alternative. While human capabilities in recognizing complex patterns and perceiving variations can still outperform machines and improve an imperfect ML model, ML predictions can compensate for the crowd’s lack of expertise. Our investigation (N=28 non-expert) in oil spill detection shows that adopting an ML-assisted UI elevates precision and recall by over 11% and increases efficiency by 29% compared to a non-assisted UI. Considering agreement among non-expert crowd workers further improved precision by 8% and recall by almost 5%, which is also substantially beyond pure ML performance. Our work contributes an approach for combining crowd knowledge and ML to advance human-AI collaboration in oil spill detection.

In traffic engineering, cities rely on large detector datasets to manage traffic. Visualizing these big, multi-dimensional datasets poses challenges such as overplotting and dimension reduction, often rendering traditional visualization techniques inadequate. To address this, we added two machine learning (ML) algorithms (Local Outlier Factor algorithm and K-Prototypes clustering) to an interactive time series visualization to improve exploration by both domain experts and non-experts. We used an original detector dataset of a mid-sized German city. Our findings reveal that the ML algorithms greatly enhanced data exploration in these interactive visualizations, particularly for users with limited domain knowledge. This research directly contributes to the design of traffic data analysis tools, offering a foundation for traffic detection hardware and software improvements but also advancing complex dataset visualization in general. It will ultimately lead to more informed decisions, improved traffic management, and has the potential to reduce air pollutants, thus counteracting climate change.

Physical training in virtual environments, such as VR, has gained popularity, especially due to the coronavirus pandemic. VR training offers new opportunities compared to traditional methods, including the use of different perspectives, mirrors, and avatars to enhance the understanding of personal movements. However, the interaction of these elements has been less studied. To address this, we developed VReflect, a VR environment that uses mirrors and avatars as virtual self-visualization techniques (VSVT) to improve self-awareness during movement training. In a preliminary study on learning beginner karate movements, we tested four combinations of perspectives and VSVTs. The results indicate that neither first-person nor third-person perspectives can be universally recommended, which is in alignment with previous work. Interviews revealed a preference for the traditional combination of mirrors and first-person perspective.

AI is anticipated to enhance human decision-making in high-stakes domains like aviation, but adoption is often hindered by challenges such as inappropriate reliance and poor alignment with users' decision-making. Recent research suggests that a core underlying issue is the recommendation-centric design of many AI systems, i.e., they give end-to-end recommendations and ignore the rest of the decision-making process. Alternative support paradigms are rare, and it remains unclear how the few that do exist compare to recommendation-centric support. In this work, we aimed to empirically compare recommendation-centric support to an alternative paradigm, continuous support, in the context of diversions in aviation. We conducted a mixed-methods study with 32 professional pilots in a realistic setting. To ensure the quality of our study scenarios, we conducted a focus group with four additional pilots prior to the study. We found that continuous support can support pilots' decision-making in a forward direction, allowing them to think more beyond the limits of the system and make faster decisions when combined with recommendations, though the forward support can be disrupted. Participants' statements further suggest a shift in design goal away from providing recommendations, to supporting quick information gathering. Our results show ways to design more helpful and effective AI decision support that goes beyond end-to-end recommendations.

Social media platforms use short, highly engaging videos to catch users’ attention. While the short-form video feeds popularized by TikTok are rapidly spreading to other platforms, we do not yet understand their impact on cognitive functions. We conducted a between-subjects experiment (N = 60) investigating the impact of engaging with TikTok, Twitter, and YouTube while performing a Prospective Memory task (i.e., executing a previously planned action). The study required participants to remember intentions over interruptions. We found that the TikTok condition significantly degraded the users’ performance in this task. As none of the other conditions (Twitter, YouTube, no activity) had a similar effect, our results indicate that the combination of short videos and rapid context-switching impairs intention recall and execution. We contribute a quantified understanding of the effect of social media feed format on Prospective Memory and outline consequences for media technology designers to not harm the users’ memory and wellbeing.

Human-in-the-loop optimization utilizes human expertise to guide machine optimizers iteratively and search for an optimal solution in a solution space. While prior empirical studies mainly investigated novices, we analyzed the impact of the levels of expertise on the outcome quality and corresponding subjective satisfaction. We conducted a study (N=60) in text, photo, and 3D mesh optimization contexts. We found that novices can achieve an expert level of quality performance, but participants with higher expertise led to more optimization iteration with more explicit preference while keeping satisfaction low. In contrast, novices were more easily satisfied and terminated faster. Therefore, we identified that experts seek more diverse outcomes while the machine reaches optimal results, and the observed behavior can be used as a performance indicator for human-in-the-loop system designers to improve underlying models. We inform future research to be cautious about the impact of user expertise when designing human-in-the-loop systems.

Intelligent decision support tools (DSTs) hold the promise to improve the quality of human decision-making in challenging situations like diversions in aviation. To achieve these improvements, a common goal in DST design is to calibrate decision makers’ trust in the system. However, this perspective is mostly informed by controlled studies and might not fully reflect the real-world complexity of diversions. In order to understand how DSTs can be beneficial in the view of those who have the best understanding of the complexity of diversions, we interviewed professional pilots. To facilitate discussions, we built two low-fidelity prototypes, each representing a different role a DST could assume: (a) actively suggesting and ranking airports based on pilot-specified criteria, and (b) unobtrusively hinting at data points the pilot should be aware of. We find that while pilots would not blindly trust a DST, they at the same time reject deliberate trust calibration in the moment of the decision. We revisit appropriation as a lens to understand this seeming contradiction as well as a range of means to enable appropriation. Aside from the commonly considered need for transparency, these include directability and continuous support throughout the entire decision process. Based on our design exploration, we encourage to expand the view on DST design beyond trust calibration at the point of the actual decision.

Social games benefit from social connectedness between players because it improves the gaming experience and increases enjoyment. In virtual reality (VR), various approaches, such as avatars, are developed for multi-player games to increase social connectedness. However, these approaches are lacking in single-player games. To increase social connectedness in such games, our work explores the visualization of physiological data from asynchronous players, i.e., electrocardiogram (ECG). We identified two visualization dimensions, the number of players, and the visualization style, after a design workshop with experts (N=4) and explored them in a single-user virtual escape room game. We spatially and temporally integrated the visualizations and compared two times two visualizations against a baseline condition without visualization in a within-subject lab study (N=34). All but one visualization significantly increased participants’ feelings of social connectedness. Heart icons triggered the strongest feeling of connectedness, understanding, and perceived support in playing the game.

Prior research explored ways to alert virtual reality users of bystanders entering the play area from afar. However, in confined social settings like sharing a couch with seatmates, bystanders' proxemic cues, such as distance, are limited during interruptions, posing challenges for proxemic-aware systems. To address this, we investigated three visualizations, using a 2D animoji, a fully-rendered avatar, and their combination, to gradually share bystanders' orientation and location during interruptions. In a user study (N=22), participants played virtual reality games while responding to questions from their seatmates. We found that the avatar preserved game experiences yet did not support the fast identification of seatmates as the animoji did. Instead, users preferred the mixed visualization, where they found the seatmate's orientation cues instantly in their view and were gradually guided to the person's actual location. We discuss implications for fine-grained proxemic-aware virtual reality systems to support interaction in constrained social spaces.

COVID-19 caused an abrupt switch from face-to-face to online teaching. This led to unknown challenges and consequences for students and lecturers. In the first semester after its outbreak, we developed a messenger-based chatbot to perform an experience sampling study to evaluate students’ well-being and experiences (n = 31) with the radical changes in higher education. Finding a decrease in students’ perceived motivation but an increase in productivity, we conducted a follow-up survey to compare the development a year later (n = 41). Our results revealed two main student profiles, one feeling severely impacted by the persisting social distance in their study performance and the other appreciating the flexibility and expended free time due to the changes in the teaching formats. Based on our findings, we introduce implications for the overall design of higher education and show the benefits and challenges of combining chatbot-enabled experience sampling with traditional surveys.

Embedded interfaces support active indexing, the process of making sense of the experienced. While this supports the creation of meaningful relationships, findings are limited on how it could support sustaining the significance of historical places. We selected two historical places of daily use and developed two AR apps for each. The apps aimed at fostering participants’ indexing and meaningful connection to the places by presenting their history. One app offered passive, informative content. The other displayed an interactive, moral dilemma emphasizing the places’ social values. We tested the apps in two between-subjects studies with N=42 participants in total. We explored how participants ’ historical understanding can be improved by embedding our interfaces on five levels (spatially, physically, contextually, historically, and morally). We found that the morally embedded AR stories supported active indexing stronger than the passive ones and argued that they could foster meaningful relationships between users and historical places.

Dynamic balance is an essential skill for the human upright gait; therefore, regular balance training can improve postural control and reduce the risk of injury. Even slight variations in walking conditions like height or ground conditions can significantly impact walking performance. Virtual reality is used as a helpful tool to simulate such challenging situations. However, there is no agreement on design strategies for balance training in virtual reality under stressful environmental conditions such as height exposure. We investigate how two different training strategies, imitation learning, and gamified learning, can help dynamic balance control performance across different stress conditions. Moreover, we evaluate the stress response as indexed by peripheral physiological measures of stress, perceived workload, and user experience. Both approaches were tested against a baseline of no instructions and against each other. Thereby, we show that a learning-by-imitation approach immediately helps dynamic balance control, decreases stress, improves attention focus, and diminishes perceived workload. A gamified approach can lead to users being overwhelmed by the additional task. Finally, we discuss how our approaches could be adapted for balance training and applied to injury rehabilitation and prevention.

Virtual Reality (VR) is increasingly used in everyday contexts for a variety of tasks. We particularly look at the confined space for passengers inside cars, where head-mounted displays (HMDs) could complement the prevalent use of mobile devices for work. In a field study (N=19), we tested three mobile workspace setups along the reality-virtuality continuum (Mounted Tablet, Augmented Focus Bubble, and Virtual Office) and let users re-position the virtual keyboard and display while typing on a physical keyboard in a parked car. The results revealed that using HMDs lowered users' awareness of their real surroundings but increased their perceived workload with a performance impairment of text entry rate compared to just using a tablet. Letting users customize their workspace layout improved their perceived performance and decreased pitch-axis head movements for switching between the virtual display and keyboard. This paper discusses challenges and strategies for future work regarding dynamic incorporation of productivity tools, adaptive mixed reality (MR) work environment designs, and optimizing upper thresholds of physical discomfort in mobile MR workspaces.

Creating social Virtual Environments (VEs) is an ongoing challenge. Traces of prior human interactions, or traces of use, are used in Physical Environments (PEs) to create more meaningful relationships with the PE and the people within it. In this paper, we explore how the concept of traces of use can be transferred from PEs to VEs to increase known success factors for social VEs, such as increased social presence. First, we introduce a conceptualization and discussion ($N=4$ expert interviews) of a "Traces in VEs" framework. Second, we evaluate the framework in two lab studies ($N=46$ in total), exploring the effect of traces in (i) VE vs. PE, and (ii) on social presence. Our findings confirm that traces increase the feeling of social presence. However, their meaning may differ depending on the environment. Our framework offers a structured overview of relevant components and relationships that need to be considered when designing meaningful user experiences in VE using traces. Thus, our work is valuable for practitioners and researchers who systematically want to create social VEs.

In autonomous cars, drivers will spend more time on non-driving-related activities. Getting their hands off the wheel and eyes off the road, the driver, similar to a rear-seat passenger today, can use multiple built-in displays for such activities or even mobile head-mounted displays (HMDs) in virtual reality (VR). A wider motion range is known to increase engagement, but might also amplify the risk of motion sickness while switching between displays. In a rear-seat VR field study (N=21) on a city highway, we found a head movement range of ± 50° with a speed of 1.95m/s to provide the best trade-off between motion sickness and engagement. Compared to the pitch (Y) axis, movement around the yaw (X) axis induced less discomfort and more engagement with less motion sickness. Our work provides a concrete starting point for future research on self-driving carsickness, starting from today’s rear-seat passengers.

Plaster busts are common exhibition pieces in museums, but they usually are off-limits for touch. While modern exhibition concepts increasingly involve interaction, this rarely includes touching a plaster bust. However, there may be a wealth of information associated with these cultural heritage objects, e.g., their making and their creator’s craftsmanship, which tangible interaction could make accessible right on the object. We equipped plaster replicas of such a bust with capacitive sensors and developed a tangible prototype in collaboration with two domain experts from the art museum “Staatliche Antikensammlungen” (Munich, Germany), a curator and a sculptor, in an iterative design approach. Then we tested it in a lab study (N=12) and an in situ study in the museum (N=20). We describe our technical approach, which we also made public as a git project1, and discuss our study results about busts as tangible interfaces in the art of sculpting.

Virtual Reality (VR) technologies can counteract stress or fatigue and restore attention, e.g., by recreating the beauty of nature in a Virtual Restorative Environment (VRE). This has gained additional relevance in the current pandemic: When facing the stress of physical restrictions and a limited activity space, how can VR technologies provide the individual experience of being away? We created a VRE that can be used during trips in automated cars using a captured natural environment and simulated artifacts that communicate vehicle information during VR relaxation. In a user study (N = 21), we compared the proposed in-car VRE to simply closing the eyes. We found that the VRE strongly improved the subjective ratings of mood and slightly increased attentional capacity and the objectively measured performance in a working memory test. Our results provide a concrete starting point for exploring calming VR experiences for future passengers, but also users at home.

Recent automotive research often focuses on automated driving, including the interaction between automated vehicles (AVs) and so-called “vulnerable road users” (VRUs). While road safety statistics and traffic psychology at least define VRUs as pedestrians, cyclists, and motorcyclists, many publications on human-vehicle interaction use the term without even defining it. The actual target group remains unclear. Since each group already poses a broad spectrum of research challenges, a one-fits-all solution seems unrealistic and inappropriate, and a much clearer differentiation is required. To foster clarity and comprehensibility, we propose a literature-based taxonomy providing a structured separation of (vulnerable) road users, designed to particularly (but not exclusively) support research on the communication between VRUs and AVs. It consists of two conceptual hierarchies and will help practitioners and researchers by providing a uniform and comparable set of terms needed for the design, implementation, and description of HCI applications.

Unintended consequences of deployed AI systems fueled the call for more interpretability in AI systems. Often explainable AI (XAI) systems provide users with simplifying local explanations for individual predictions but leave it up to them to construct a global understanding of the model behavior. In this work, we examine if non-technical users of XAI fall for an illusion of explanatory depth when interpreting additive local explanations. We applied a mixed methods approach consisting of a moderated study with 40 participants and an unmoderated study with 107 crowd workers using a spreadsheet-like explanation interface based on the SHAP framework. We observed what non-technical users do to form their mental models of global AI model behavior from local explanations and how their perception of understanding decreases when it is examined.

The urban realm is currently undergoing a transformation in which cities are being laced with sensors and networks of ever-connected devices. At the same time, more and more novel and advanced materials are finding their way into interaction design and Human-Computer Interaction (HCI) research, offering us new interaction possibilities. In this half-day online studio, attendees will have the opportunity to exchange and reflect on urban interaction designs for user engagement based on a set of novel, unconventional, or omnipresent materials in urban environments. We will further collect historical, public, and community locations of different social and societal meaning. Participants will be asked to develop hands-on concepts and use cases for the selected locations through a material-centered approach and think about new levels of user-environment engagement to extend and explore the current design space. The formulated concepts and use cases will be recorded in an online collaboration tool with the prospect to publish them as enhances for the new generation of media architecture.

Concrete is a ubiquitous material in urban environments and increasingly used by industry and the maker movement. However, there is little research about its affordance and its potential for embedded User Interfaces (UI). In our ongoing work, we investigate different manufacturing processes and design strategies to change and adapt the affordances of concrete to make it appear interactive. We tested three interface elements, a button, a scroll wheel, and a slider, with 33 participants in a lab elicitation study. Each was created in two versions following two design strategies, one with a more natural look, the other more abstract. Five participants then bodystormed ideas with the prototypes in an outdoor environment. Based on our explorations, we discuss design considerations for creating concrete interfaces including the potential of both design strategies and present different application scenarios.

We explore the concept of a Spherical World in Miniature (SWIM) for discrete locomotion in Virtual Reality (VR). A SWIM wraps a planar WIM around a physically embodied sphere and thereby implements the metaphor of a tangible Tiny Planet that can be rotated and moved, enabling scrolling, scaling, and avatar teleportation. The scaling factor is set according to the sphere's distance from the head-mounted display (HMD), while rotation moves the current viewing window. Teleportation is triggered with a dwell time when looking at the sphere and keeping it still. In a lab study (N=20), we compare our SWIM implementation to a planar WIM with an established VR controller technique using physical buttons. We test both concepts in a navigation task and also investigate the effects of two different screen sizes. Our results show that the SWIM, despite its less direct geometrical transformation, performed superior in most evaluations. It outperformed the planar WIM not only in terms of task completion time (TCT) and accuracy but also in subjective ratings.

Intensive Care Unit (ICU) professionals have to make lifesaving therapy decisions promptly under high stress and uncertainty. Clinical Decision Support Systems (CDSS) can improve the quality of healthcare by identifying complex statistical connections between patients' parameters and by rapidly presenting the statistically most promising treatment options to physicians. However, HCI aspects are rarely considered when developing CDSSs. This paper describes a field study conducted in three ICUs investigating how physicians and nurses form (volume) therapy decisions and monitor their success. Our findings reveal a continuous decision cycle in which nurses and physicians collaborate synchronously and asynchronously to provide optimal care. Furthermore, the desire to understand how a CDSS generated recommendations varies depending on the user's goals and other contextual factors such as workload. These findings show that CDSSs for ICUs need to (1) specifically facilitate collaboration and (2) support adaptation of the interface to both context and users.

Psychological targeting tries to influence and manipulate users' behaviour. We investigated whether users can protect themselves from being profiled by a chatbot, which automatically assesses users' personality. Participants interacted twice with the chatbot: (1) They chatted for 45 minutes in customer service scenarios and received their actual profile (baseline). (2) They then were asked to repeat the interaction and to disguise their personality by strategically tricking the chatbot into calculating a falsified profile. In interviews, participants mentioned 41 different strategies but could only apply a subset of them in the interaction. They were able to manipulate all Big Five personality dimensions by nearly 10%. Participants regarded personality as very sensitive data. As they found tricking the AI too exhaustive for everyday use, we reflect on opportunities for privacy protective designs in the context of personality-aware systems.

We investigate the use of a handheld spherical object as a controller for locomotion in VR. Rotating the object controls avatar movement in two different ways: As a zero order controller, it is continuously rotated to the target position as if rolling a ball on the floor. As a first order controller, it is tilted like a joystick to determine the direction and speed of movement. We describe how our prototype was built from low-cost commercially available hardware and discuss our design decisions. Then we evaluate both locomotion techniques in a user study (N=20) and compare them to established methods using handheld VR controllers. Our prototype matched and in some cases outperformed these methods regarding task time and accuracy. All results were obtained without any usage instructions, indicating easy learnability. Some of our insights may transfer to interaction with other naturally shaped objects in VR experiences.

In this paper we present use cases for affective user interfaces (UIs) in cars and how they are perceived by potential users in China and Germany. Emotion-aware interaction is enabled by the improvement of ubiquitous sensing methods and provides potential benefits for both traffic safety and personal well-being. To promote the adoption of affective interaction at an international scale, we developed 20 mobile in-car use cases through an inter-cultural design approach and evaluated them with 65 drivers in Germany and China. Our data shows perceived benefits in specific areas of pragmatic quality as well as cultural differences, especially for socially interactive use cases. We also discuss general implications for future affective automotive UI. Our results provide a perspective on cultural peculiarities and a concrete starting point for practitioners and researchers working on emotion-aware interfaces.

Using a smartphone while walking in urban traffic is dangerous. Pedestrians might become distracted and have to split their attention between traffic, walking and using the mobile device. The increasing level of automation in vehicles introduces novel challenges and opportunities for pedestrian-vehicle interaction, e.g external displays attached to automated vehicles. However, these approaches are hardly scalable and fail to provide clear information in a multi-user environment. We investigate whether a smartphone app could provide individual guidance to enhance pedestrian safety in future traffic. To this end, we tested three app concepts in a user study (N=24) and found that on-screen guidance increases the frequency of successful crossing decisions significantly. In addition, all participants indicated that they would use the proposed system, preferably with an unobtrusive colored bar indicating the safest crossing decision in real-time. Integrating smartphones into the interaction between vehicles and pedestrians could increase situational awareness while crossing roads, solve the scalability problem and thus foster pedestrian safety in future traffic scenarios.

Traces of use in public environments show the behaviour patterns of the masses. Taking advantage of this quality, we want to use such traces as design tool to indicate possible interactions in e.g. newly built areas while keeping a natural and calm environment. Due to current lacking knowledge about such traces, this work aims at understanding the perception of traces of use in public places. Therefore we collected a total of 182 pictures of traces of use in urban environments. A focus group discussed and classified a preselected set of pictures. In an online picture viewing survey, 18 different pictures were reviewed for pattern identification (N= 32-52). Overlaps were visualized in heatmaps. We contribute an analysis of which public traces of use are easy to recognize with great agreement and which are not.

In this paper, we explore how a familiarly shaped object can serve as a physical proxy to manipulate virtual objects in Augmented Reality (AR) environments. Using the example of a tangible, handheld sphere, we demonstrate how irregularly shaped virtual objects can be selected, transformed, and released. After a brief description of the implementation of the tangible proxy, we present a buttonless interaction technique suited to the characteristics of the sphere. In a user study (N = 30), we compare our approach with three different controller-based methods that increasingly rely on physical buttons. As a use case, we focused on an alignment task that had to be completed in mid-air as well as on a flat surface. Results show that our concept has advantages over two of the controller-based methods regarding task completion time and user ratings. Our findings inform research on integrating tangible interaction into AR experiences.

The intentions of an automated vehicle are hard to spot in the absence of eye contact with a driver or other established means of communication. External car displays have been proposed as a solution, but what if they malfunction or display misleading information? How will this influence pedestrians' trust in the vehicle? To investigate these questions, we conducted a between-subjects study in Virtual Reality (N = 18) in which one group was exposed to erroneous displays. Our results show that participants already started with a very high degree of trust. Incorrectly communicated information led to a strong decline in trust and perceived safety, but both recovered very quickly. This was also reflected in participants' road crossing behavior. We found that malfunctions of an external car display motivate users to ignore it and thereby aggravate the effects of overtrust. Therefore, we argue that the design of external communication should avoid misleading information and at the same time prevent the development of overtrust by design.

Communicating uncertainty has been shown to provide positive effects on user understanding and decision-making. Surprisingly however, most personal health tracking applications fail to disclose the accuracy of their measurements and predictions. In the case of fertility tracking applications (FTAs), inaccurate predictions have already led to numerous unwanted pregnancies and law suits. However, integrating uncertainty into FTAs is challenging: Prediction accuracy is hard to understand and communicate, and its effect on users' trust and behavior is not well understood. We created a prototype for uncertainty visualizations for FTAs and evaluated it in a four-week field study with real users and their own data (N=9). Our results uncover far-reaching effects of communicating uncertainty: For example, users interpreted prediction accuracy as a proxy for their cycle health and as a security indicator for contraception. Displaying predicted and detected fertile phases next to each other helped users to understand uncertainty without negative emotional effects.

The emerging possibilities of data analysis and exploration in virtual reality raise the question of how users can be best supported during such interactions. Spherical visualizations allow for convenient exploration of certain types of data. Our tangible sphere, exactly aligned with the sphere visualizations shown in VR, implements a very natural way of interaction and utilizes senses and skills trained in the real world. This work is motivated by the prospect to create in VR a low-cost, tangible, robust, handheld spherical display that would be difficult or impossible to implement as a physical display. Our concept enables it to gain insights about the impact of a fully tangible embodiment of a virtual object on task performance, comprehension of patterns, and user behavior. After a description of the implementation we discuss the advantages and disadvantages of our approach, taking into account different handheld spherical displays utilizing outside and inside projection.

Recent developments in the commercialization of virtual reality open up many opportunities for enhancing human interaction with three-dimensional objects and visualizations. Spherical visualizations allow for convenient exploration of certain types of data. Our tangible sphere, exactly aligned with the sphere visualizations shown in VR, implements a very natural way of interaction and utilizes senses and skills trained in the real world. In a lab study, we investigate the effects of the perception of actually holding a virtual spherical visualization in hands. As use cases, we focus on surface visualizations that benefit from or require a rounded shape. We compared the usage of two differently sized acrylic glass spheres to a related interaction technique that utilizes VR controllers as proxies. On the one hand, our work is motivated by the ability to create in VR a tangible, lightweight, handheld spherical display that can hardly be realized in reality. On the other hand, gaining insights about the impact of a fully tangible embodiment of a virtual object on task performance, comprehension of patterns, and user behavior is important in its own right. After a description of the implementation we discuss the advantages and disadvantages of our approach, taking into account different handheld spherical displays utilizing outside and inside projection.

User experience (UX) evaluation is a growing field with diverse approaches. To understand the development since previous meta-review efforts, we conducted a state-of-the-art review of UX evaluation techniques with special attention to the triangulation between methods. We systematically selected and analyzed 100 papers from recent years and while we found an increase of relevant UX studies, we also saw a remaining overlap with pure usability evaluations. Positive trends include an increasing percentage of field rather than lab studies and a tendency to combine several methods in UX studies. Triangulation was applied in more than two thirds of the studies, and the most common method combination was questionnaires and interviews. Based on our analysis, we derive common patterns for triangulation in UX evaluation efforts. A critical discussion about existing approaches should help to obtain stronger results, especially when evaluating new technologies.

Empowering people through technology is of increasing concern in the HCI community. However, there are different interpretations of empowerment, which diverge substantially. The same term thus describes an entire spectrum of research endeavours and goals. This conceptual unclarity hinders the development of a meaningful discourse and exchange. To better understand what empowerment means in our community, we reviewed 54 CHI full papers using the terms empower and empowerment. Based on our analysis and informed by prior writings on power and empowerment, we construct a framework that serves as a lens to analyze notions of empowerment in current HCI research. Finally, we discuss the implications of these notions of empowerment on approaches to technology design and offer recommendations for future work. With this analysis, we hope to add structure and terminological clarity to this growing and important facet of HCI research.

In this paper we investigate whether a helmet-mounted display for motorcyclists can provide similar benefits as the established head-up display (HUD) in cars. HUDs can increase driving safety by efficiently informing the driver. Given their high safety risks, such a technology seems overdue for motorcyclists. Only recently, several crowdfunding projects have raised substantial funding for helmet-mounted displays, however, none of them has released a commercial product yet. In order to investigate display concepts, we developed an easy-to-reproduce and low-cost helmet-mounted display prototype and compared it to a conventional display setup. The helmet-mounted display was rated more attractive and induced a lower workload. Those motorcyclists who generally exceeded the speed limit before also rode significantly slower when using the head-mounted display. We argue that an intelligent HUD application that adapts to the rider»s behavior and preferences could further enhance safety and improve user experience for motorcyclists. We encourage other researchers to replicate our setup and to investigate the impact of HUDs on motorcyclists' behavior and road safety.

The ever-increasing amount of information in cars demands novel and safer displays, such as head-up or windshield displays. We present two studies that investigate the recognition of stimuli presented on a windshield display. Using a divided attention task and a driving simulator, we first compared four types of stimuli which are common in traffic signs: text, circles, triangles, and squares. We measured the response times at 17 positions within an extended field of regard of 35°x15°. The follow-up study validated our results by replicating the first study with two changes: We investigated the influence of peripheral workload with a more diverse simulated environment and tested for training effects by converting the setup to a left-hand drive car. We contribute response times and sizing recommendations for a field of regard of 35°x15°. These recommendations will help designers of large head-up displays to create interfaces which are well-legible and avoid both cluttering the driver's view and occluding the road scene.

Autonomous cars will likely hit the market soon, but trust into such a technology is one of the big discussion points in the public debate. Drivers who have always been in complete control of their car are expected to willingly hand over control and blindly trust a technology that could kill them. We argue that trust in autonomous driving can be increased by means of a driver interface that visualizes the car's interpretation of the current situation and its corresponding actions. To verify this, we compared different visualizations in a user study, overlaid to a driving scene: (1) a chauffeur avatar, (2) a world in miniature, and (3) a display of the car's indicators as the baseline. The world in miniature visualization increased trust the most. The human-like chauffeur avatar can also increase trust, however, we did not find a significant difference between the chauffeur and the baseline.

User studies and expert reviews are established methods for evaluating usability and user experience (UX) in user-centered design. However, practitioners often struggle to integrate these often time-consuming and costly methods in their design processes. As technological products and services are becoming increasingly mobile, their contexts of use are increasingly diverse and less predictable. While this changing context is hard to capture in lab studies, the same mobile technologies also provide possibilities for new study methods. In this paper we advocate lightweight mobile tools for crowdsourcing UX feedback. In cooperation with a design agency, we built two apps that allow users to express feedback with text, ratings and pictures whenever using a product. The second app assigns feedback to categories, while the first does not. In a case study we compared the quantity, relevance, and nature of the feedback collected with both UX evaluation apps to traditional evaluation methods. The feedback collected with the apps was considered highly useful by designers and provided more user stories and context than traditional evaluations.

Windshield displays (WSDs) are the big siblings of Head-up displays (HUDs). They are assumed to cover the entire windshield and to allow displaying content at continuous depth, eventually. This creates a large and unstructured 3D space for information display -- raising the question what to display where. To address this question, we developed a view management concept for WSDs in left hand drive cars which proposes zones and areas for specific information. As driving is a safety-critical task, we designed the initial concept with the driver's perceptual abilities in mind. Subsequently, we gathered insights into the driver's needs and desires from a formative study. We asked participants where they would place different types of information after inspiring their imagination by a 3D driving scene and WSD information on a Google Cardboard. The improved concept respects both the drivers' needs and desires and their perceptual abilities and can serve as a basis for view management concepts of future WSD.

While we know that persuasive system design matters, we barely understand when persuasive strategies work and why they only work in some cases. We propose an approach to systematically understand and design for motivation, by studying the fundamental building blocks of motivation, according to the theory of planned behavior (TPB): attitude, subjective norm, and perceived control. We quantitatively analyzed (N=643) the attitudes, beliefs, and values of mobile fitness coach users with TPB. Capacity (i.e., perceived ability to exercise) had the biggest effect on users' motivation. Using individual differences theory, we identified three distinct user groups, namely followers, hedonists, and achievers. With insights from semi-structured interviews (N=5) we derive design implications finding that transformation videos that feature other users' success stories as well as suggesting an appropriate workout can have positive effects on perceived capacity. Practitioners and researchers can use our theory-based mixed-method research design to better understand user behavior in persuasive applications.

This paper describes a study comparing the information recall of participants using 2D and 3D physical visualizations. Specifically, it focuses on physical bar charts and evaluates the difference between a paper-based visualization and a version built with wooden blocks. We conducted a repeated measures study involving 16 participants in which we measured the recall of information immediately after the exploration and with a delay of one week. We used questionnaires and semi-structured interviews to obtain more information about the process of recall and participants' opinions whether and how the visualizations differ in their potential for memorizing information. The results point out that participants believe to remember the 3D visualizations better, but besides the recall of extreme values the quantitative data cannot completely verify this appreciation. Furthermore the results highlight that the in the study used physical interaction techniques are not able to compensate lacking visual differentiation. One surprising finding was the strong dependency of the different data sets on the recall performance.

Drivers attend to a lot of information at various locations inside and outside the car as well as on external devices (e.g. smart phones). Head-Up Displays (HUDs) support keeping drivers' visual focus directed towards the street; as they present virtual information in the windshield area on top of the physical world within the field of view of the driver. Displayed information, however, is often spatially dissociated with its cause in the physical world: for example a warning is displayed, yet drivers still require time searching for the hazard causing it. Windshield displays (WSDs) allow virtual warnings being displayed at the position of the hazard. We compared HUD and WSD with the baseline no-display and found that drivers demonstrate a calm gaze behavior with WSDs; they keep their visual attention in average 1.5 s longer focused on the leading car. However, we also found no significant faster reaction time compared to HUDs. We discuss our findings comparing HUDs to WSDs, present potential limitations of our study and point out future steps in order to further investigate the advantages of WSDs.

With recent progress in display technology, visual see-through head-mounted displays are beginning to enter our everyday lives. Especially in cars they may replace head-up displays, as they can theoretically perfectly imitate them but are more flexible to use. However, prior work has shown that both screen- and vehicle-stabilized content suffer from drawbacks such as occlusion or technological limitations. As a potential alternative, we propose three concept alternatives, in which head rotation is used to manipulate the displayed content differently from both of the known stabilization techniques. In a qualitative user study, we identify the best concept proposal and then evaluate it against the established content stabilization techniques. The presented concept is perceived to be more applicable for the proposed use case and effectively reduces some of the known problems of both stabilization techniques.

Physical Visualizations are currently mostly used in casual contexts, e.g., as artistic data sculptures. However, their measurable benefits for traditional information visualization are largely unexplored. As a step in this direction, we compared the memorability of physical visualizations to that of digital visualizations. We conducted a user study with 40 participants in which we measured the recall of three types of information immediately after exploration and with a delay of two weeks. The results show that the physical visualization led to significantly less information decay within this time span. Our results build on known effects from cognitive psychology and provide a first indicator for measurable benefits of physical visualizations regarding memorability.

Windshield displays (WSDs) are information displays covering the entire windshield. Current WSD test setups place information at different distances, but always within the driver's foveal field of view. We built two WSD test setups, which present information not only at various distances within the driver's visual focus, but also in the peripheral field of view. Then we evaluated the display of information in the periphery on both WSD setups in a user study. While making sure the participants would look at the peripheral information, we measured the display's impact on driving performance. Subjects were also asked about their driving experience with the windshield displays and their preference among the two setups.

Mid-air gestures are initial hand poses with a subsequent movement. Existing gesture guides reveal this dynamic part of a gesture. Initial poses, however, are either revealed by space-consuming cheat sheets or time-consuming demonstration videos. Mime is a novel interaction concept that (1) reveals how to form complex hand poses and (2) teaches pose-command mappings: Mime reduces hand poses to space-efficient line figures that users mime with their hands; these abstract lines are embedded into command icons or names to create a mnemonic. We present several applications of the Mime concept, and implemented a prototype based on mid-air back-of-device interaction on off-the-shelf mobile phones. We compared both mnemonics, iconic and textual, to a baseline without embedding to test learnability and memorability of a 12-item vocabulary. Users in the iconic condition required significantly less training than both other conditions and recalled significantly more items after one week compared to the no-cue baseline.

We present a wide interactive banner display installed at a city sidewalk and the findings from two long-term field studies investigating the opportunities of public displays to actively shape the audience. In order to improve parallel usage and dissolve crowds, our wide display subtly directs individual users by visual stimuli and manipulates the audience like a puppeteer, thus reversing the notion of adaptive content being implicitly manipulated by the users.

Touch screens are increasingly used for secondary in-vehicle controls. While they are more flexible than traditional knobs and dials, interacting with them requires more visual attention. In this paper, we propose several variations of a concept we call "What You See Is What You Touch" (WYSIWYT), which allows touch screen interaction without removing one's eyes from the road. This becomes possible by showing both, the current content of the touch screen as well as the position of the user's hand in relation to it, within the car's head-up display (HUD). In an initial study we compared six different variations of this concept in a driving simulation mockup. After excluding some concept variations, we conducted a second study comparing the remaining ones with traditional touch interaction. The best performing variation obtains better subjective ratings without any significant disadvantages in driving performance.

Head-mounted displays (HMDs) have great potential to improve the current situation of car drivers. They provide every benefit of a head-up display (HUD), while at the same time showing more flexibility in usage. We built an infotainment system specifically designed to be displayed in an HMD. With this system, we then conducted a dual task study in a driving simulation, comparing different techniques of content stabilization (head- and cockpit stabilized visualizations). Interaction with the system took place via a physical input device (rotary controller) or indirect pointing gestures. While cockpit-stabilized content generally resulted in a slightly better driving performance, HMD visualizations suffered from technological limitations, partly reflected in the secondary task performance and subjective feedback. Regarding input modality, we found that horizontal gesture interaction significantly influenced the quality of lane keeping. Apparently, horizontal interaction with the one hand caused unintentional steering with the other.

Electric Vehicles (EVs) are an emerging technology and open up an exciting new space for designing in-car interfaces. This technology enhances driving experience by a strong acceleration, regenerative breaking and especially a reduced noise level. However, engine vibrations and sound transmit valuable feedback to drivers of conventional cars, e.g. signaling that the engine is running and ready to go. We address this lack of feedback with Heartbeat, a multimodal electric vehicle information system. Heartbeat communicates (1) the state of the electric drive including energy flow and (2) the energy level of the batteries in a natural and experienceable way. We enhance the underlying Experience Design process by formulating working principles derived from an experience story in order to transport its essence throughout the following design phases. This way, we support the design of a consistent experience and resolve the tension between implementation constraints (e.g., space) and the persistence of the underlying story while building prototypes and integrating them into a technical environment (e.g., a dashboard).

One unique property of head-mounted displays (HMDs) is that content can easily be displayed at a fixed position within the user's field of view (head-stabilized). This ensures that critical information (e.g. warnings) is continuously visible and can, in principle, be perceived as quickly as possible. We examined this strategy with a physically and visually distracted driver. We ran two consecutive studies in a driving simulator, comparing different warning visualizations in a head-up display (HUD) and a HMD. In an initial study, we found no significant effects of warning type or display technology on the reaction times. In a second study, after modifying our visualization to include a visual reference marker, we found that with only this minor change, reaction times were significantly lower in the HMD when compared to the HUD. Our insights can help others design better head-stabilized notifications.

Peripheral interaction, like ambient information systems (AIS), aims at leveraging the periphery of our attention. While ambient information systems address the perception of information, peripheral interaction targets lightweight interaction outside of the current focus of attention. A number of prototypes have demonstrated the value of peripheral interaction through long-term in-situ deployments. Such studies are particularly suited to evaluate peripheral interaction since they enable the integration of devices into daily routines and thereby move interaction to the periphery of attention. However, they do not lend themselves well to early design phases. In fact, the design process completely lacks early evaluation tools to assess design choices.

Touch screens are on the rise and replace traditional knobs and buttons at a fast pace. However, their lack of tangible guidance and feedback can become a problem in scenarios where visual attention is scarce. Besides dynamic tactile feedback by vibrations, the usability of touch screens can be improved by static haptic structures such as shaped or structured surfaces. In this paper we describe the prototype of an in-vehicle application using unimanual four-finger interaction and haptic guidance in order to avoid visual distraction from the primary task of driving. We built a low fidelity prototype with static haptics using an Android tablet and silicone foil. A user study showed that flexible positioning of touch buttons mapped to the user's fingers was more convenient and produced fewer errors than fixed positioning. A curved haptic border provided the user with orientation and allowed a new selection mode: dragging buttons over the edge resulted in a reduced interaction time when compared to double tapping. We present several different variants for unimanual multifinger interaction on planar and non-planar surfaces. Our results can support the development of future concepts for blind interaction.

Data sculptures are a promising type of visualizations in which data is given a physical form. In the past, they have mostly been used for artistic, communicative or educational purposes, and designers of data sculptures argue that in such situations, physical visualizations can be more enriching than pixel-based visualizations. We present the design of Activity Sculptures: data sculptures of running activity. In a three-week field study we investigated the impact of the sculptures on 14 participants' running activity, the personal and social behaviors generated by the sculptures, as well as participants' experiences when receiving these individual physical tokens generated from the specific data of their runs. The physical rewards generated curiosity and personal experimentation but also social dynamics such as discussion on runs or envy/competition. We argue that such passive (or calm) visualizations can complement nudging and other mechanisms of persuasion with a more playful and reflective look at ones' activity.

Large touch screens are recently appearing in the automotive market, yet their usability while driving is still controversial. Flat screens do not provide haptic guidance and thus require visual attention to locate interactive elements that are displayed. Thus, we need to think about new concepts to minimize the visual attention needed for interaction, to keep the driver's focus on the road and ensure safety.

In this paper, we investigate pointing as a lightweight form of gestural interaction in cars. In a pre-study, we show the technical feasibility of reliable pointing detection with a depth camera by achieving a recognition rate of 96% in the lab. In a subsequent in-situ study, we let drivers point to objects inside and outside of the car while driving through a city. In three usage scenarios, we studied how this influenced their driving objectively, as well as subjectively. Distraction from the driving task was compensated by a regulation of driving speed and did not have a negative influence on driving behaviour. Our participants considered pointing a desirable interaction technique in comparison to current controller-based interaction and identified a number of additional promising use cases for pointing in the car.

There is a well-established culture of early prototyping when designing digital interactive systems, such as paper prototyping and wireframe methods. The culture of designing physical objects is somewhat different: early explorations of form is still prototyped via 2D sketches or renderings, but - mostly because of the construction effort involved - prototyping of actual physical objects is deferred to later stages. A problem occurs when designing mixed physical-digital systems, such as tangible user interfaces (TUIs) on interactive surfaces: the high degree of interactivity means that early prototyping is vital, yet there is no viable process for prototyping both the physical and digital aspects simultaneously on a low-fidelity (low-fi) level. Our solution is Paperbox, a toolkit for exploring design ideas for tangible interaction on interactive surfaces. It supports the early exploration of different form factors and immediately provides digital interactivity for the low-fidelity TUI prototypes built with it. We observed our toolkit in use in various settings: as a brainstorming tool by junior designers; in the development of a consumer electronics product in a large industrial company by senior designers; and in a usability study comparing the effect of different levels of fidelity on the outcome. The lessons learnt will enable others to replicate and extend our approach.

Recent research has presented large public displays in novel non-flat shapes such as spheres, curved planes and cylinders, and looked at the influence of the form factor on user behavior. Yet, the basic shape cannot be considered in isolation when interpreting the behavior of passers-by around such displays. In this paper we investigate two further display factors, framedness and seamlessness, that have to be considered in conjunction with the form factor to understand user behavior in front of large non-flat displays. We present the findings from a field study with an interactive column display and take a closer look at how these factors influence actor and bystander behavior. Our results show that rectangular frames act as a sort of funnel for user position and can easily override effects of the non-flat shape on user position and interaction, even though the users didn't recall the presence of these frames.

Head-mounted displays (HMDs) have the potential to overcome some of the technological limitations of currently existing automotive head-up displays (HUDs), such as the limited field of view and the restrictive boundaries of the windshield. In an initial study we evaluated the use of HMDs in cars by means of a typical HUD visualization, using a HUD as baseline output technology. We found no significant differences in terms of driving performance, physical uneasiness or visual distraction. User statements revealed several advantages and drawbacks of the different output technologies apart from technological maturity and ergonomics. These results will hopefully inspire researchers as well as application developers and even might lead us to novel HMD visualization approaches.

Head-mounted displays (HMDs) have the potential to overcome some of the technological limitations of currently existing automotive head-up displays (HUDs), such as the limited field of view and the restrictive boundaries of the windshield. However, in a formative study, we identified other, partially known problems with HMDs regarding content stability and occlusion. As a counter-measure we propose a novel layout mechanism for HMD visualization, which, on the one hand, benefits from the unique characteristics of HMDs and, on the other, combines the advantages of head-stabilized and cockpit-stabilized content. By subdividing the HMD's field of view into different slots to which the content is dynamically assigned depending on the user's head rotation, we ensure that the driver's vision is effectively augmented in every possible direction.

Contemporary car design must not only focus on technology supporting the driver and the driving task: it needs to create positive experiences for drivers and passengers alike. This case study, the Clique Trip, is an example of designing a positive social (i.e. relatedness) experience in the automotive context, addressing the analysis, the design, and the evaluation of the experience. The Clique Trip experience creates a feeling of closeness and relatedness among friends when being in a "motorcade". It is derived from experience reports, implemented in the car and evaluated on the road. Qualitative and quantitative results revealed its capability to create the targeted social experience.

There are about as many strategies for listening to music as there are music enthusiasts. This makes learning about overarching patterns and similarities difficult. In this paper, we present an empirical analysis of long-term music listening histories from the last.fm web service. It gives insight into the most distinguishing factors in music listening behavior. Our sample contains 310 histories with up to six years duration and 48 associated variables describing various user and music characteristics. Using a principal components analysis, we aggregated these variables into 13 components and found several correlations between them. The analysis especially showed the impact of seasons and a listener's interest in novelty on music choice. Using this information, a sample of a user's listening history or even just demographical data could be used to create personalized interfaces and novel recommendation strategies. We close with derived design considerations for future music interfaces.

Digital office environments often integrate multiple displays in a variety of arrangements. We investigated the combination of a horizontal and a directly connected vertical display, which together form a digital workspace. In particular, we were interested in the effect of the physical transition (bezel, edge or curve) on dragging. In a study participants performed dragging tasks across both display planes with direct touch as well as a pointing device. Contrary to our expectations, we found no significant effect on task completion time. Only regarding accuracy the curved transition performed better than edge and bezel. Interestingly, the subjective judgment did generally not match the objective results. These findings suggest that we need to rethink our understanding of display continuities in terms of usability as well as user satisfaction.

In our everyday life, the perception of thermal cues plays a crucial role for the identification and discrimination of materials. When touching an object, the change of temperature in the skin of our fingertips is characteristic for the touched material and can help to discriminate objects with the same texture or hardness. However, this useful perceptual channel is disregarded for interactive elements on standard touchscreens. In this paper, we present a study in which we compared the rate of object discrimination for stand-alone thermal stimuli as well as supplemental thermal stimuli characterizing virtual materials on a touchscreen. Our results show that five materials could be discriminated at a stable rate using either stand-alone or supplemental thermal stimuli. They suggest that thermal cues can enable material discrimination on touch surfaces, which gives way for expanded use of thermal stimuli on interactive surfaces.

We present GISpL, the Gestural Interface Specification Language. GISpL is a formal language which allows both researchers and developers to unambiguously describe the behavior of a wide range of gestural interfaces using a simple JSON-based syntax. GISpL supports a multitude of input modalities, including multi-touch, digital pens, multiple regular mice, tangible interfaces or mid-air gestures.

Instant messaging systems, such as Skype, offer text, audio and video channels for one-on-one and group conversations, both for personal and professional communication. They are commonly used at a distance, i.e., across countries and continents. To avoid disrupting other tasks, they display personal states to signal others when to contact someone and when not. This mechanism, however, heavily relies on users setting their own state correctly. In an online survey with 46 participants we found that neglecting state updates leads to unwanted messages, either because the state is incorrect or others disrespect it because they assume it to be wrong anyway. We address this situation with the StaTube, a tangible object offering (1) peripheral interaction for setting one's own state and (2) peripheral awareness of selected others' state. In an in-situ evaluation we found first indicators that (1) peripheral interaction fosters more frequent state updates and more accurate state information, and (2) that our participants felt more aware of their contacts' states due to the physical ambient representation.

We present Vertibles, a set of Tangible User Interface (TUI) objects employing a vacuum-based adhesion effect. This effect allows attaching them to arbitrarily inclined surfaces, bringing the benefit of TUIs to vertical interactive surfaces. In contrast to other vertically attachable TUIs, Vertibles stick to a wide range of surface materials and work with optical as well as electric object tracking techniques for interactive surfaces. We present an overview of approaches for sticking objects onto vertical surfaces, describe the technical principle and properties of our solution, and document implementation details of a number of Vertibles prototypes.

Graspable tangibles are now being explored on the current generation of capacitive touch surfaces, such as the iPad and the Android tablet. Because the size and form factor is relatively new, early and low fidelity prototyping of these TUIs is crucial in getting the right design. The problem is that it is difficult for the average interaction designer to develop such physical prototypes. They require a substantial amount time and effort to physically model the tangibles, and expertise in electronics to instrument them. Thus prototyping is sometimes handed off to specialists, or is limited to only a few design iterations and alternative designs. Our solution contributes a low fidelity prototyping approach that is time and cost effective, and that requires no electronics knowledge. First, we supply non-specialists with cardboard forms to create tangibles. Second, we have them draw lines on it via conductive ink, which makes their objects recognizable by the capacitive touch screen. They can then apply routine programming to recognize these tangibles and thus iterate over various designs.

We present a network visualization design study focused on supporting automotive engineers who need to specify and optimize traffic patterns for in-car communication networks. The task and data abstractions that we derived support actively making changes to an overlay network, where logical communication specifications must be mapped to an underlying physical network. These abstractions are very different from the dominant use case in visual network analysis, namely identifying clusters and central nodes, that stems from the domain of social network analysis. Our visualization tool RelEx was created and iteratively refined through a full user-centered design process that included a full problem characterization phase before tool design began, paper prototyping, iterative refinement in close collaboration with expert users for formative evaluation, deployment in the field with real analysts using their own data, usability testing with non-expert users, and summative evaluation at the end of the deployment. In the summative post-deployment study, which entailed domain experts using the tool over several weeks in their daily practice, we documented many examples where the use of RelEx simplified or sped up their work compared to previous practices.

The increasing number of media facades in urban spaces offers great potential for new forms of interaction especially for collaborative multi-user scenarios. In this paper, we present a way to directly interact with them through live video on mobile devices. We extend the Touch Projector interface to accommodate multiple users by showing individual content on the mobile display that would otherwise clutter the facade's canvas or distract other users. To demonstrate our concept, we built two collaborative multi-user applications: (1) painting on the facade and (2) solving a 15-puzzle. We gathered informal feedback during the ARS Electronica Festival in Linz, Austria and found that our interaction technique is (1) considered easy-to-learn, but (2) may leave users unaware of the actions of others.

We present Cardiogram, a visual analytics system that supports automotive engineers in debugging masses of traces each consisting of millions of recorded messages from in-car communication networks. With their increasing complexity, ensuring these safety-critical networks to be error-free has become a major task and challenge for automotive engineers. To overcome shortcomings of current analysis tools, Cardiogram combines visualization techniques with a data preprocessing approach to automatically reduce complexity based on engineers' domain knowledge. In this paper, we provide the findings from an exploratory, three-year field study within a large automotive company, studying current practices of engineers, the challenges they meet and the characteristics for integrating novel visual analytics tools into their work practices.

Multi-touch screens and surfaces for manipulating digital content play a crucial role in mobile and ubiquitous computing. Augmenting these interactive surfaces with tactile feedback has been found to increase interaction speed, reduce operating errors and minimize visual and cognitive load. Communicating detailed tactile characteristics of virtual elements, however, requires complex electromechanical or electrostatic actuator setups. This increase in complexity makes tactile interfaces intricate, costly or poorly scalable. In order to provide sophisticated tactile sensations with simple actuator technology, we exploit a haptic psychophysical phenomenon called Phantom Sensation. We present a comparison of three standard tactile actuator technologies to see which one can recreate the Phantom Sensation with maximum effect. Our results show the way to a simple and scalable implementation of illusion-based tactile feedback for interactive surfaces. We explore the notion of the Phantom Sensation and its possible applications within a ubicomp scenario.

Currently available user interfaces for playlist generation allow creating playlists in various ways, within a spectrum from fully automatic to fully manual. However, it is not entirely clear how users interact with such systems in the field and whether different situations actually demand different interfaces. In this paper we describe Rush 2, a music interface for mobile touch-screen devices that incorporates three interaction modes with varying degrees of automation: Adding songs manually, in quick succession using the rush interaction technique or filling the playlist automatically. For all techniques various filters can be set. In a two- week diary study (with in-depth interaction logging) we gained insight into how people interact with music in their everyday lives and how much automation and interactivity are really necessary.

Careful use of the limited remaining fossil energy resources is important for both ecological and economical reasons. In addition to technical improvements, fuel consumption of a vehicle is influenced significantly by the driving behavior. Currently, only few in-car user interfaces are trying to promote a more fuel-efficient driving behavior. We propose EcoChallenge, a community- and location-based in-car persuasive game with the goal to motivate and support a behavioral change towards a fuel-saving driving style. We implemented and integrated EcoChallenge in an experimental vehicle and evaluated it in a field study. The results regarding acceleration, deceleration, breaking and coasting show the effectiveness of our approach. In addition, users confirmed a very positive experience with our system.

In this paper we present inTUIt experience prototyping approach to investigate different simple identification techniques for tangible user interfaces (TUI) on digital surfaces. We have developed four different experience prototypes, proposing alternative approaches to the establishment of temporary ownership of digital content and TUIs in public environments.

Recent in-vehicle information systems are increasingly equipped with touch screens. While classic (i.e. point-based) direct touch interaction has known benefits in non-automotive environments, it primarily relies on visual attention, which makes it a bad candidate for interaction in the car, where visual attention should be on the road. We have designed an interaction scheme for IVIS based on touch gestures and pie menus and implemented several versions of it featuring visual cues as improvements to the original idea. In an extensive user study with a primary driving task, we were able to show that our interaction scheme is significantly faster than classic touch interaction and that it demands shorter gesture using visual cues.

Haptic feedback on touch-sensitive displays provides significant benefits in terms of reducing error rates, increasing interaction speed and minimizing visual distraction. This particularly holds true for multitasking situations such as the interaction with mobile devices or touch-based in-vehicle systems. In this paper, we explore how the interaction with tactile touchscreens can be modeled and enriched using a 2+1 state transition model. The model expands an approach presented by Buxton. We present HapTouch -- a force-sensitive touchscreen device with haptic feedback that allows the user to explore and manipulate interactive elements using the sense of touch. We describe the results of a preliminary quantitative study to investigate the effects of tactile feedback on the driver's visual attention, driving performance and operating error rate. In particular, we focus on how active tactile feedback allows the accurate interaction with small on-screen elements during driving. Our results show significantly reduced error rates and input time when haptic feedback is given.

In 1992, Tani et al. proposed remotely operating machines in a factory by manipulating a live video image on a computer screen. In this paper we revisit this metaphor and investigate its suitability for mobile use. We present Touch Projector, a system that enables users to interact with remote screens through a live video image on their mobile device. The handheld device tracks itself with respect to the surrounding displays. Touch on the video image is projected onto the target display in view, as if it had occurred there. This literal adaptation of Tani's idea, however, fails because handheld video does not offer enough stability and control to enable precise manipulation. We address this with a series of improvements, including zooming and freezing the video image. In a user study, participants selected targets and dragged targets between displays using the literal and three improved versions. We found that participants achieved highest performance with automatic zooming and temporary image freezing.

We present rush as a recommendation-based interaction and visualization technique for repeated item selection from large data sets on mobile touch screen devices. Proposals and choices are intertwined in a continuous finger gesture navigating a two-dimensional canvas of recommended items. This provides users with more flexibility for the resulting selections. Our design is based on a formative user study regarding orientation and occlusion aspects. Subsequently, we implemented a version of rush for music playlist creation. In an experimental evaluation we compared different types of recommendations based on similarity, namely the top 5 most similar items, five random selections from the list of similar items and a hybrid version of the two. Participants had to create playlists using each condition. Our results show that top 5 was too restricting, while random and hybrid suggestions had comparable results.

The history of songs, to which a person has listened, is a very personal piece of information. It is a rich data set that comes as a byproduct of the use of digital music players and can be obtained without interfering with the user.

In music information retrieval (MIR), there are two main research directions, which are based either on a folder hierarchy and metadata, or on the actual acoustic content. We believe that both content-based and hierarchy-based retrieval have their respective strengths for browsing and organizing music collections, and that the integration of content analysis techniques in metadata-based media UIs can lead to more powerful UIs. In this paper we present a prototype, in which audio analysis techniques and user feedback are integrated into an interactive UI for browsing and organizing large music collections. We also provide visual assistance to support non-visual perception of music. We discussed our system with test users and received encouragement as well as valuable suggestions for future re-search.

The MOST bus is a current bus technology for connecting multimedia components in cars, such as radios, navigation systems, or media players. The bus functionality is described in a large hierarchically structured catalog of some 4psila000 entries. Browsing this catalog has become infeasible on paper as well as with currently used textual database interfaces. An observation of current work practices has revealed many problems and inefficiencies. We describe the (iteratively developed) design of MostVis, a visual tool for exploring MOST function catalogs, as well as an evaluation of our implemented prototype. Our design carefully adapts existing visualization techniques and combines them in a multiple coordinated view (MCV) approach to satisfy the specific needs of our target group. With this paper, we hope to provide a living example of how existing general-purpose techniques can be successfully trimmed and tailored for a very specific audience.

NFC and RFID technologies have found their way into current mobile phones and research has presented a variety of applications using NFC/RFID tags for interaction between physical objects and mobile devices. Since this type of interaction is widely novel for most users, there is a considerable initial inhibition threshold for them. In order to get novice users started with this physical interaction and its applications, we have designed different ways to increase the learnability and guidance of such applications. Their effectiveness was evaluated in a qualitative and quantitative user study with 40 participants, who interacted with NFC-equipped posters in different ways. We report on the types of usage errors observed and show that future designs of NFC/RFID-based mobile applications should consider using a dedicated start-tag for interaction.

Touch-sensitive displays seem like a natural and promising option for dealing with the increasing complexity of current in-vehicle information systems (IVIS), but since they can hardly be used without visual attention conventional point touch systems are rarely considered in cars. To ensure road safety, the drivers' visual attention needs to be focused almost entirely to the road. In order to integrate touch screens successfully into cars, new concepts are needed to reduce visual demand. The adaptation of pie menus serving as a visualisation of gestures reduces the user's cognitive load, and we were able to achieve an almost blind interaction with the IVIS. We compared our design to a generic touch system using a dual task evaluation method (Lane Change Task [18][20]), and the results regarding total task completion time, lane deviation and subjective preferences confirm a higher usability and efficiency, as well as an added hedonic quality of pieTouch.

Although interactive surfaces have many unique and compelling qualities, the interactions they support are by their very nature bound to the display surface. In this paper we present a technique for users to seamlessly switch between interacting on the tabletop surface to above it. Our aim is to leverage the space above the surface in combination with the regular tabletop display to allow more intuitive manipulation of digital content in three-dimensions. Our goal is to design a technique that closely resembles the ways we manipulate physical objects in the real-world; conceptually, allowing virtual objects to be 'picked up' off the tabletop surface in order to manipulate their three dimensional position or orientation. We chart the evolution of this technique, implemented on two rear projection-vision tabletops. Both use special projection screen materials to allow sensing at significant depths beyond the display. Existing and new computer vision techniques are used to sense hand gestures and postures above the tabletop, which can be used alongside more familiar multi-touch interactions. Interacting above the surface in this way opens up many interesting challenges. In particular it breaks the direct interaction metaphor that most tabletops afford. We present a novel shadow-based technique to help alleviate this issue. We discuss the strengths and limitations of our technique based on our own observations and initial user feedback, and provide various insights from comparing, and contrasting, our tabletop implementations

In this paper we investigate tangible interaction on interactive tabletops. These afford the support and integration of physical artefacts for the manipulation of digital media. To inform the design of interfaces for interactive surfaces we think it is necessary to deeply understand the benefits of employing such physical handles, i.e., the benefits of employing a third spatial dimension at the point of interaction.To this end we conducted an experimental study by designing and comparing two versions of an interactive tool on a tabletop display, one with a physical 3D handle, and one purely graphical (but direct touch enabled). Whilst hypothesizing that the 3D version would provide a number of benefits, our observations revealed that users developed diverse interaction approaches and attitudes about hybrid and direct touch interaction.

With the increasing complexity of in-car communication architectures, their diagnostics have become essential for automotive development and maintenance. In order to help engineers to detect and analyze the potential sources and consequences of errors, it is crucial to provide both comprehensive and detailed insight into the communication processes and their contexts. Two important aspects of these are the dependencies and correlations between onboard functions. In this paper we present a dual-view visualization for exploring the functional dependency chains of in-car communication processes. One view presents the dependencies of hardware components using a space filling approach similar to a treemap, whereas the other view displays the functional correlations as an interactive sequence chart. The views are coupled via color coding and show the dependencies of an interactively selectable functional unit. In an expert evaluation, we assessed the benefits of using this visualization technique for in-car communication diagnostics with very positive results.

Collaborative creativity is traditionally supported by formal techniques, such as brainstorming. These techniques improve the idea-generation process by creating group synergies, but also suffer from a number of negative effects. Current electronic tools to support collaborative creativity overcome some of these problems, but introduce new ones, by either losing the benefits of face-to-face communication or the immediacy of simultaneous contribution. Using an interactive environment as a test bed, we are investigating how collaborative creativity can be supported electronically while maintaining face-to-face communication. What are the design-factors influencing such a system? We have designed a brainstorming application that uses an interactive table and a large wall display, and compared the results of using it to traditional paper-based brainstorming in a user study with 30 participants. From the considerations that went into the design and the observations during the study we derive a number of design guidelines for collaborative systems in interactive environments.

In this paper we present a wall-sized input system with high accuracy input in the center and lower precision tracking on the remaining parts of the wall. This work complements the concept of focus plus context displays where output quality in the center is better than in the periphery. Our contribution is to realize a similar concept for the input direction. A high precision tracking unit in the center provides a workspace with high interactivity, while four additional cameras placed in the corners of the wall provide lower precision tracking and hence much coarser interactivity on the entire wall. In our prototype this multi-precision input solution is combined with a focus plus context display, thus providing two levels of interactivity in both the input and output direction. With this setup, we have implemented two example applications to demonstrate the benefits of variable precision input

The main objective of the third workshop on Multi-User and Ubiquitous User Interfaces (MU3I 2006) is to bring people with relevant backgrounds (e.g. interface design, CSCW, ubiquitous computing) together to discuss two key questions in this field: How can we build interfaces, which span multiple devices so that the user knows that they can be used to control a specific application? How can we build interfaces for public displays? Therefore, the main outcome of the workshop is expected to consists of further insights into those problems, potential solutions and a research agenda to investigate these further.

We describe the design and implementation of graphical interaction widgets for use with a steerable projector-camera unit. The design of our widgets is adapted to provide the right visual cues when projected and they are controlled by the user's hand. The widgets' input regions are arranged in an ergonomic way and they use a simple but robust computer vision technique for interaction.

We describe a method for notifying users through auditory cues embedded in an ambient soundscape in the environment. It uses pieces of music which are composed in such a way, that particular instruments or motifs can be added or omitted without losing the aesthetic quality of the overall composition. This allows for very subtle modifications in the soundscape which are only noticed by those users who have chosen this particular instrument or motif as "their" notification instrument before. As a side effect, the soundscape itself can be used to subtly influence the mood of users. The method has been implemented in a prototype, which we briefly discuss. The prototype is implemented using a spatial audio framework and can hence notify users from particular directions.

This second workshop on Multi-User and Ubiquitous User Interfaces aims at further investigating two major issues identified at last year's MU3I: control and consistency. The former relates to how a user gains control of devices in a ubiquitous computing environment, how control is passed, and how it is shared in such a setting. The second one concerns interfaces that span multiple devices or move from one set of devices to another. Both issues will be discussed in this year's workshop (with a focus on consistency.

Tangible user interfaces provide access to virtual information through intuitive physical manipulation. However, feedback is mostly provided by displays in the environment instead of the TUI itself. In this paper we describe the design of Tuister, a tangible user interface with multiple embedded displays and sensors. We explain how Tuister can be used to browse and access hierarchical structures and briefly describe the current state of a prototype we're building.

Navigation services can be found in different situations and contexts: while connected to the web through a desktop PC, in cars, and more recently on PDAs while on foot. These services are usually well designed for their specific purpose, but fail to work in other situations. In this paper we present an approach that connects a variety of specialized user interfaces to achieve a personal navigation service spanning different situations. We describe the concepts behind the \bf BPN (BMW Personal Navigator), an entirely implemented system that combines a desktop event and route planner, a car navigation system, and a multi-modal, in- and outdoor pedestrian navigation system for a PDA. Rather than designing for one unified UI, we focus on connecting specialized UIs for desktop, in-car and on-foot use.

We are exploring a class of decision-theoretic handheld systems that give a user personalized advice about how to explore an indoor area in search of products or information. An initial user test in a simple mockup of a shopping mall showed that even novice PDA users accepted the system immediately and were able to achieve their shopping goals faster than when using a paper map of the mall. A key issue is the extent to which spontaneous user behavior can be accommodated within this framework.

We describe a hybrid building navigation system consisting of stationary information booths and a mobile communication infrastructure feeding small portable devices. The graphical presentations for both the booths and the mobile devices are generated from a common source and for the common task of way finding, but they use different techniques to convey possibly different subsets of the relevant information. The form of the presentations is depending on technical limitations of the output media, accuracy of location information, and cognitive restrictions of the user. We analyze what information needs to be conveyed, how limited resources influence the presentation of this information, and argue, that by generating all different presentations in a common framework, a consistent appearance across devices can be achieved and that the different device classes can complement each other in facilitating the navigation task.

While car navigation systems are widely commercialized already today, pedestrian information systems are still in the early research stage. However, recent progress in mobile computing has opened perspectives for pedestrian navigation systems. In this context, graphics is and will still be an important modality to convey all types of route information. This paper will address the question how to generate graphics for navigation systems that help pedestrians, e.g., airport passengers, city tourists or conference attendees, to find their way in complex environments. We will discuss how the presentation of graphics can be tailored to various technical and cognitive constraints, and we will demonstrate our ideas within a scenario where a passenger of an airport gets navigational help from a stationary info booth and afterwards on her way via a handheld device (PDA). Both the 3D visualization at the info booth and the sketch-like presentation on the PDA are generated from the same data and by the same system, yet are adapted to the specific situation, output medium and user as far as possible.

No abstract available.