Virtual reality (VR) allows to embody avatars. Coined the Proteus effect, an avatar’s visual appearance can influence users’ behavior and perception. Recent work suggests that athletic avatars decrease perceptual and physiological responses during VR exercise. However, such effects can fail to occur when users do not experience avatar ownership and identification. While customized avatars increase body ownership and identification, it is unclear whether they improve the Proteus effect. We conducted a study with 24 participants to determine the effects of athletic and non-athletic avatars that were either customized or randomly assigned. We developed a customization editor to allow creating customized avatars. We found that customized avatars reduced perceived exertion. We also found that athletic avatars decreased heart rate while holding weights, however, only when being customized. Results indicate that customized avatars can positively influence users during physical exertion. We discuss the utilization of avatar customization in VR exercise systems.

Perceived temperature and thermoregulation are not only influenced by actual temperature but also by visual perception. For instance, the hue-heat hypothesis posits that warm-colored lighting can increase perceived temperature. Recent work indicates that embodying avatars with visual cues suggesting extreme temperatures influences thermal perception and thermoregulation. However, recent work is limited by short exposure times, inconsistent temperature effects, and the absence of a baseline comparison. Thus, we conducted a study where participants embodied ice, neutral, and fire hands in virtual reality for 15 minutes. We show that thermal sensation is significantly higher with fire hands compared to ice hands, but found no consistent effects on skin temperature. As the effects on thermal sensation remain consistent at least over 15 minutes, we conclude that avatars’ appearance can be used to systematically influence users’ thermal perception.

Designers of virtual characters use facial expressions to display avatar emotions. Previous work revealed connections between emotions and thermoregulatory, e.g., happiness increases and sadness decreases skin temperature. As virtual reality (VR) enables embodying avatars with any facial expression, it is unclear whether embodying avatars with different emotions also affect users’ thermophysiological and emotional responses. We conducted a study with 24 participants who embodied customized avatars displaying happy, neutral, and sad facial expressions in VR. We found that participants’ skin temperature was higher with sad avatars than with happy ones while resting. Despite non-significant pairwise comparisons, descriptive statistics suggest an opposite trend for skin temperature responses during grabbing interactions. We also show that participants felt happier while embodying happy avatars compared to sad avatars. Results indicate that avatars’ emotions impact users’ thermoregulation and affective states. We discuss underlying mechanisms and potential applications.

Obtaining informed consent is a fundamental ethical requirement in research involving human subjects, designed to ensure autonomy, respect, and the protection of participants. However, new technologies and research methodologies in Human–Computer Interaction (HCI) present unique challenges in maintaining ethical standards and require a deeper understanding of how consent practices are implemented. This scoping review provides a detailed examination of the frameworks, methodologies, and practices for obtaining informed consent in HCI. We present recognized universal principles while also discussing the ethical guidelines, and legal frameworks that underpin consent processes. Furthermore, we analyze the practices of disclosure, screening, consenting, and confirmation to assess how researchers ensure voluntary participation. The review addresses key criticisms and challenges identified in the literature, suggesting improvements and exploring alternative approaches. By offering comprehensive insights into the complexities of informed consent, we underscore the ongoing need for ethical awareness and continuous refinement of ethical conduct in HCI.

Electromyography (EMG) enables hands-free interactions by detecting muscle activity at different human body locations. Previous studies have demonstrated that input performance based on isometric contractions is muscle-dependent and can benefit from synchronous biofeedback. However, it remains unknown whether stimulation before interaction can help to localize and tense a muscle faster. In a response-based VR experiment (N=21), we investigated whether prior stimulation using visual or tactile cues at four different target muscles (biceps, triceps, upper leg, calf) can help reduce the time to perform isometric muscle contractions. The results show that prior stimulation decreases EMG reaction times with visual, vibrotactile, and electrotactile cues. Our experiment also revealed important findings regarding learning and fatigue at the different body locations. We provide qualitative insights into the participants’ perceptions and discuss potential reasons for the improved interaction. We contribute with implications and use cases for prior stimulated muscle activation.

Humans’ thermal regulation and subjective perception of temperature is highly plastic and depends on the visual appearance of the surrounding environment. Previous work shows that an environment’s color temperature affects the experienced temperature. As virtual reality (VR) enables visual immersion, recent work suggests that a VR scene’s color temperature also affects experienced temperature. It is, however, unclear if an avatar’s appearance also affects users’ thermal perception and if a change in thermal perception even influences the body temperature. Therefore, we conducted a study with 32 participants performing a task in an ice or fire world while having ice or fire hands. We show that being in a fire world or having fire hands increases the perceived temperature. We even show that having fire hands decreases the hand temperature compared to having ice hands. We discuss the implications for the design of VR systems and future research directions.

Using biosignals through electromyography (EMG) and rendering them as feedback for hands-free interaction finally migrates to engaging virtual reality (VR) experiences for health and fitness-related applications. Previous work proposes various body locations as input sources and different output modalities for creating effective biofeedback loops. However, it is currently unknown which muscles and sensory modalities can provide optimal real-time interaction regarding the performance and perceived workload of the users. In two VR studies (N=18 and N=40) based on a Fitts’ law target selection task, we explored sensor placement at different body locations and investigate auditory, tactile, and visual feedback modalities. Objective and subjective results indicate that input performance can be improved by presenting muscle tension as simultaneous tactile and visual feedback. We contribute with recommendations for registration of isometric muscle contraction at different body locations and conclude that reproducing physiological feedback through multimodal channels can assist users interacting with EMG devices.

Previous work shows that high latency, a prolonged delay between player in- and system output, negatively affects player experience and performance. However, previous work also comes to contrary conclusions about how the in-game perspective alters the latency sensitivity of video games. Currently, it is unclear if the in-game perspective independently modulates latency's effects. To investigate how a game's in-game perspective interacts with latency, we developed a shooting game incorporating three perspectives (First-Person-, Third-Person-, and Bird's-Eye-View). In a study, participants (N = 36) played with two levels of latency (low and high) and the three perspectives. We show that latency reduces performance and experience, independent of the perspective. Moreover, Bayesian analysis suggests that the in-game perspective does not interact with latency and does not affects performance or experience. We conclude that more robust means to categorize latency sensitivity of video games than the in-game perspective are required.

Privacy policies (PPs) are currently the only way to inform users about their rights and choices during web browsing and searching. However, users avoid engaging with them, because of their length and abstract legal language, which makes them hard to read and understand. We propose to support the understanding of PPs by using modular icons. Icons have already proven to be helpful in visualizing concepts with high information density. However, the value of using icons to supplement PPs lacks a scientific foundation. Thus, we conducted two studies to evaluate existing icon sets for their understandability and to teach participants their meaning in situ. We show that modular privacy icons can be taught using our process, which has the potential to aid quicker and easier comprehension of PPs. We contribute a set of tested modular privacy icons and a verified process on how to teach them to users incidentally during web browsing.

Avatars are used to represent users in virtual reality (VR) and create embodied experiences. Previous work showed that avatars’ stereotypical appearance can affect users’ physical performance and perceived exertion while exercising in VR. Although sweating is a natural human response to physical effort, surprisingly little is known about the effects of sweating avatars on users. Therefore, we conducted a study with 24 participants to explore the effects of sweating avatars while cycling in VR. We found that visualizing sweat decreases the perceived exertion and increases perceived endurance. Thus, users feel less exerted while embodying sweating avatars. We conclude that sweating avatars contribute to more effective exergames and fitness applications.

Feeling ownership of a virtual body is crucial for immersive experiences in VR. Knowledge about body ownership is mainly based on rubber hand illusion (RHI) experiments in the real world. Watching a rubber hand being stroked while one’s own hidden hand is synchronously stroked, humans experience the rubber hand as their own hand and underestimate the distance between the rubber hand and the real hand (proprioceptive drift). There is also evidence for a decrease in hand temperature. Although the RHI has been induced in VR, it is unknown whether effects in VR and the real world differ. We conducted a RHI experiment with 24 participants in the real world and in VR and found comparable effects in both environments. However, irrespective of the RHI, proprioceptive drift and temperature differences varied between settings. Our findings validate the utilization of the RHI in VR to increase our understanding of embodying virtual avatars.

Latency is inherently part of every interactive computing system and particularly important for video games. Previous work shows that constant latency above 25 ms reduces game experience and player performance. However, latency in the wild varies and is never constant due to multiple factors, such as updates in routing tables, users changing their location, or the system's workload. It is unclear if switching latency impairs the gaming experience stronger than a constant high latency. To elucidate, we conducted an experiment with 264 participants playing a shooting video game induced with 0 ms, 33 ms, and 66 ms controlled latency. While playing, the game switched between different latency levels based on three frequencies. Our analysis shows that switching latency significantly impaired the participants' flow. Additionally, we found effects on the perceived tension, the experienced challenge, and the players' performance. We conclude that games should prioritize constant latency, even if that entails artificially adding latency.

Avatars in virtual reality (VR) enable embodied experiences and induce the Proteus effect—a shift in behavior and attitude to mimic one’s digital representation. Previous work found that avatars associated with physical strength can decrease users’ perceived exertion when performing physical tasks. However, it is unknown if an avatar’s appearance can also influence the user’s physiological response to exercises. Therefore, we conducted an experiment with 24 participants to investigate the effect of avatars’ athleticism on heart rate and perceived exertion while cycling in VR following a standardized protocol. We found that the avatars’ athleticism has a significant and systematic effect on users’ heart rate and perceived exertion. We discuss potential moderators such as body ownership and users’ level of fitness. Our work contributes to the emerging area of VR exercise systems.

Reading is a fundamental activity to obtain information both in the real and the digital world. Virtual reality (VR) allows novel approaches for users to view, read, and interact with a text. However, for efficient reading, it is necessary to understand how a text should be displayed in VR without impairing the VR experience. Therefore, we conducted a study with 18 participants to investigate text presentation type and location in VR. We compared world-fixed, edge-fixed, and head-fixed text locations. Texts were displayed using Rapid Serial Visual Presentation (RSVP) or as a paragraph. We found that RSVP is a promising presentation type for reading short texts displayed in edge-fixed or head-fixed location in VR. The paragraph presentation type using world-fixed or edge-fixed location is promising for reading long text if movement in the virtual environment is not required. Insights from our study inform the design of reading interfaces for VR applications.

Cloud gaming services and remote play offer a wide range of advantages but can inherent a considerable delay between input and action also known as latency. Previous work indicates that deep learning algorithms such as artificial neural networks (ANN) are able to compensate for latency. As high latency in video games significantly reduces player performance and game experience, this work investigates if latency can be compensated using ANNs within a live first-person action game. We developed a 3D video game and coupled it with the prediction of an ANN. We trained our network on data of 24 participants who played the game in a first study. We evaluated our system in a second user study with 96 participants. To simulate latency in cloud game streaming services, we added 180 ms latency to the game by buffering user inputs. In the study we predicted latency values of 60 ms, 120 ms and 180 ms. Our results show that players achieve significantly higher scores, substantially more hits per shot and associate the game significantly stronger with a positive affect when supported by our ANN. This work illustrates that high latency systems, such as game streaming services, benefit from utilizing a predictive system.

Online services collect an increasing amount of data about their users. Privacy policies are currently the only common way to inform users about the kinds of data collected, stored and processed by online services. Previous work showed that users do not read and understand privacy policies, due to their length, difficult language, and often non-prominent location. Embedding privacy-relevant information directly in the context of use could help users understand the privacy implications of using online services. We implemented Contextual Privacy Policies (CPPs) as a browser extension and provide it to the community to make privacy information accessible for end-users. We evaluated CPPs through a one-week deployment and in situ questionnaires as well as pre- and post-study interviews. We found that CPPs were well received by participants. The analysis revealed that provided information should be as compact as possible, be adjusted to user groups and enable users to take action.

Collaborative Virtual Environments (CVEs) offer unique opportunities for human communication. Humans can interact with each other over a distance in any environment and visual embodiment they want. Although deictic gestures are especially important as they can guide other humans' attention, humans make systematic errors when using and interpreting them. Recent work suggests that the interpretation of vertical deictic gestures can be significantly improved by warping the pointing arm. In this paper, we extend previous work by showing that models enable to also improve the interpretation of deictic gestures at targets all around the user. Through a study with 28 participants in a CVE, we analyzed the errors users make when interpreting deictic gestures. We derived a model that rotates the arm of a pointing user's avatar to improve the observing users' accuracy. A second study with 24 participants shows that we can improve observers' accuracy by 22.9%. As our approach is not noticeable for users, it improves their accuracy without requiring them to learn a new interaction technique or distracting from the experience.

Presence in virtual reality (VR) is typically assessed through questionnaires in the real world and after leaving an immersive experience. Previous research suggests that questionnaires in VR reduce biases caused by the real-world setup. However, it remains unclear whether presence questionnaires still provide valid results when subjects are being surveyed while the construct is perceived. In a user study with 36 participants, two standardized presence questionnaires (IPQ, SUSa) were either completed in the real lab, in a virtual lab scene, or in the actual scene after a virtual gaming experience. Our results show inconsistencies between the measurements and that main scores, as well as subscales of the presence measures are significantly affected by the subjects’ environment. As presence questionnaires have been designed to be answered after an immersive experience, we recommend revising those tools for measuring presence in VR.

Avatars in virtual reality (VR) can have body structures that differ from the physical self. Game designers, for example, often stylize virtual characters by reducing the number of fingers. Previous work found that the sensation of presence in VR depends on avatar realism and the number of limbs. However, it is currently unknown how the removal of individual fingers affects the VR experience, body perception, and how fingers are used instead. In a study with 24 participants, we investigate the effects of missing fingers and avatar realism on presence, phantom pain perception, and finger usage. Our results show that particularly missing index fingers decrease presence, show the highest phantom pain ratings, and significantly change hand interaction behavior. We found that relative usage of thumb and index fingers in contrast to middle, ring, and little finger usage was higher with abstract hands than with realistic ones – even when the fingers were missing. We assume that dominant fingers are firstly integrated into the own body schema when an avatar does not resemble one’s own appearance. We discuss cognitive mechanisms in experiencing virtual limb loss.

Virtual reality (VR) allows embodying any possible avatar. Known as the Proteus effect, avatars can change users’ behavior and attitudes. Previous work found that embodying Albert Einstein can increase cognitive task performance. The behavioral confirmation paradigm, however, predicts that our behavior is also affected by others’ perception of us. Therefore, we investigated the cognitive performance in collaborative VR when self-perception and external perception of the own avatar differ. 32 male participants performed a Tower of London task in pairs. One participant embodied Einstein or a young adult while the other perceived the participant as Einstein or a young adult. We show that the perception by others affects cognitive performance. The Einstein avatar also decreased the perceived workload. Results imply that avatars’ appearance to both, the user and the others must be considered when designing for cognitively demanding tasks.

Motion tracking technologies and avatars in virtual reality (VR) showing the movements of the own body enable high levels of presence and a strong illusion of body ownership (IBO) – key features of immersive systems and gaming experiences in virtual environments. Previous work suggests using software-based algorithms that can not only compensate system latency but also predict future movements of the user to increase input performance. However, the effects of movement prediction in VR on input performance are largely unknown. In this paper, we investigate neural network-based predictions of full-body avatar movements in two scenarios: In the first study, we used a standardized 2D Fitts’ Law task to examine the information throughput in VR. In the second study, we utilized a full-body VR game to determine the users’ performance. We found that both performance and subjective measures in a standardized 2D Fitts’ law task could not benefit from the predicted avatar movements. In an immersive gaming scenario, however, the perceived accuracy of the own body location improved. Presence and body assessments remained more stable and were higher than during the Fitts’ task. We conclude that machine-learning-based predictions could be used to compensate system-related latency but participants only subjectively benefit under certain conditions.

As touchscreens are the most successful input method of current mobile devices, touch gestures became a widely used input technique. While gestures provide users with advantages to express themselves, they also introduce challenges regarding accuracy and memorability. In this paper, we investigate the effect of a gesture's orientation on how well the gesture can be performed. We conducted a study in which participants performed systematically rotated unistroke gestures. For straight lines as well as for compound lines, we found that users tend to align gestures with the primary axes. We show that the error can be described by a Clausen function with R² = .93. Based on our findings, we suggest design implications and highlight the potential for recognizing flick gestures, visualizing gestures and improving recognition of compound gestures.

Understanding social perception is important for designing mobile devices that are socially acceptable. Previous work not only investigated the social acceptability of mobile devices and interaction techniques but also provided tools to measure social acceptance. However, we lack a robust model that explains the underlying factors that make devices socially acceptable. In this paper, we consider mobile devices as social objects and investigate if the stereotype content model (SCM) can be applied to those devices. Through a study that assesses combinations of mobile devices and group stereotypes, we show that mobile devices have a systematic effect on the stereotypes' warmth and competence. Supported by a second study, which combined mobile devices without a specific stereotypical user, our result suggests that mobile devices are perceived stereotypically by themselves. Our combined results highlight mobile devices as social objects and the importance of considering stereotypes when assessing social acceptance of mobile devices.

Virtual Reality (VR) is gaining increasing importance in science, education, and entertainment. A fundamental characteristic of VR is creating presence, the experience of 'being' or 'acting', when physically situated in another place. Measuring presence is vital for VR research and development. It is typically repeatedly assessed through questionnaires completed after leaving a VR scene. Requiring participants to leave and re-enter the VR costs time and can cause disorientation. In this paper, we investigate the effect of completing presence questionnaires directly in VR. Thirty-six participants experienced two immersion levels and filled three standardized presence questionnaires in the real world or VR. We found no effect on the questionnaires' mean scores; however, we found that the variance of those measures significantly depends on the realism of the virtual scene and if the subjects had left the VR. The results indicate that, besides reducing a study's duration and reducing disorientation, completing questionnaires in VR does not change the measured presence but can increase the consistency of the variance.

Empirical studies are a cornerstone of HCI research. Technical progress constantly enables new study methods. Online surveys, for example, make it possible to collect feedback from remote users. Progress in augmented and virtual reality enables to collect feedback with early designs. In-situ studies enable researchers to gather feedback in natural environments. While these methods have unique advantages and disadvantages, it is unclear if and how using a specific method affects the results. Therefore, we conducted a study with 60 participants comparing five different methods (online, virtual reality, augmented reality, lab setup, and in-situ) to evaluate early prototypes of smart artifacts. We asked participants to assess four different smart artifacts using standardized questionnaires. We show that the method significantly affects the study result and discuss implications for HCI research. Finally, we highlight further directions to overcome the effect of the used methods.

Museums are essential to make culture accessible to the mass audience. Human museum guides are important to explain the presented artifacts to the visitors. Recently, museums started to experiment with enhancing exhibitions through mixed reality. It enables cultural exhibitors to provide each visitor with an individualized virtual guide that adapts to the visitor's interests. The effect of the presence and appearance of a virtual museum guide is, however, unclear. In this paper, we compare a real-world guide with a realistic, an abstract, and an audio-only representation of the virtual guide. Participants followed four multimodal presentations while we investigated the effect on comprehension and perceived co-presence. We found that a realistic representation of a virtual guide increases the perceived co-presence and does not adversely affect the comprehension of learning content in mixed reality exhibitions. Insights from our study inform the design of virtual guides for real-world exhibitions.

Navigating on large high-resolution displays (LHRDs) using devices built for traditional desktop computers can be strenuous and negatively impact user experience. As LHRDs transition to everyday use, new user-friendly interaction techniques need to be designed to capitalise on the potential offered by the abundant screen space on LHRDs. We conducted a study which compared mouse pointing and eye-tracker assisted pointing (MAGIC pointing) on LHRDs. In a controlled experiment with 35 participants, we investigated user performance in a one-dimensional pointing task and a map-based search task. We determined that MAGIC pointing had a lower throughput, but participants had the perception of higher performance. Our work contributes insights for the design of pointing techniques for LHRDs. The results indicate that the choice of technique is scenario-dependent which contrasts with desktop computers.

Hand tracking and haptics are gaining more importance as key technologies of virtual reality (VR) systems. For designing such systems, it is fundamental to understand how the appearance of the virtual hands influences user experience and how the human brain integrates vision and haptics. However, it is currently unknown whether multi-sensory integration of visual and haptic feedback can be influenced by the appearance of virtual hands in VR. We performed a user study in VR to gain insight into the effect of hand appearance on how the brain combines visual and haptic signals using a cue-conflict paradigm. In this paper, we show that the detection of surface irregularities (bumps and holes) sensed by eyes and hands is affected by the rendering of avatar hands. However, sensitivity changes do not correlate with the degree of perceived limb ownership. Qualitative feedback provides insights into potentially distracting cues in visual-haptic integration.

Entering text is one of the most common tasks when interacting with computing systems. Virtual Reality (VR) presents a challenge as neither the user's hands nor the physical input devices are directly visible. Hence, conventional desktop peripherals are very slow, imprecise, and cumbersome. We developed a apparatus that tracks the user's hands, and a physical keyboard, and visualize them in VR. In a text input study with 32 participants, we investigated the achievable text entry speed and the effect of hand representations and transparency on typing performance, workload, and presence. With our apparatus, experienced typists benefited from seeing their hands, and reach almost outside-VR performance. Inexperienced typists profited from semi-transparent hands, which enabled them to type just 5.6 WPM slower than with a regular desktop setup. We conclude that optimizing the visualization of hands in VR is important, especially for inexperienced typists, to enable a high typing performance.

Pointing at remote objects to direct others' attention is a fundamental human ability. Previous work explored methods for remote pointing to select targets. Absolute pointing techniques that cast a ray from the user to a target are affected by humans' limited pointing accuracy. Recent work suggests that accuracy can be improved by compensating systematic offsets between targets a user aims at and rays cast from the user to the target. In this paper, we investigate mid-air pointing in the real world and virtual reality. Through a pointing study, we model the offsets to improve pointing accuracy and show that being in a virtual environment affects how users point at targets. In the second study, we validate the developed model and analyze the effect of compensating systematic offsets. We show that the provided model can significantly improve pointing accuracy when no cursor is provided. We further show that a cursor improves pointing accuracy but also increases the selection time.

Rendering the user's body in virtual reality increases immersion and presence the illusion of "being there". Recent technology enables determining the pose and position of the hands to render them accordingly while interacting within the virtual environment. Virtual reality applications often use realistic male or female hands, mimic robotic hands, or cartoon hands. However, it is unclear how users perceive different hand styles. We conducted a study with 14 male and 14 female participants in virtual reality to investigate the effect of gender on the perception of six different hands. Quantitative and qualitative results show that women perceive lower levels of presence while using male avatar hands and male perceive lower levels of presence using non-human avatar hands. While women dislike male hands, men accept and feel presence with avatar hands of both genders. Our results highlight the importance of considering the users' diversity when designing virtual reality experiences.

The latency of current mobile devices' touchscreens is around 100ms and has widely been explored. Latency down to 2ms is noticeable, and latency as low as 25ms reduces users' performance. Previous work reduced touch latency by extrapolating a finger's movement using an ensemble of shallow neural networks and showed that predicting 33ms into the future increases users' performance. Unfortunately, this prediction has a high error. Predicting beyond 33ms did not increase participants' performance, and the error affected the subjective assessment. We use more recent machine learning techniques to reduce the prediction error. We train LSTM networks and multilayer perceptrons using a large data set and regularization. We show that linear extrapolation causes an 116.7% higher error and the previously proposed ensembles of shallow networks cause a 26.7% higher error compared to the LSTM networks. The trained models, the data used for testing, and the source code is available on GitHub.

Although interaction with computing systems has become remarkably diverse in recent years, the computer mouse remained the primary pointing device for daily computer use. Being solely an input device, the classical mouse decouples input from output. In this paper, we propose to extend the mouse to a device that can be actuated by the user and the computer. We developed a mouse that allows its position and button state to be actuated. In a technical evaluation, we test the spatial resolution of our system and how effectively feedback is communicated to the user. In a subjective assessment, we explore users' reactions to four use cases including games and office applications, highlighting the potential of the device. Through a quantitative assessment, we investigate whether perceiving the movement of the mouse helps to learn gestures. Finally, we discuss how a mouse providing feedback can be used to build novel interaction techniques.

Touchscreens are the dominant input mechanism for a variety of devices. One of the main limitations of touchscreens is the latency to receive input, refresh, and respond. This latency is easily perceivable and reduces users' performance. Previous work proposed to reduce latency by extrapolating finger movements to identify future movements - albeit with limited success. In this paper, we propose PredicTouch, a system that improves this extrapolation using inertial measurement units (IMUs). We combine IMU data with users' touch trajectories to train a multi-layer feedforward neural network that predicts future trajectories. We found that this hybrid approach (software: prediction, and hardware: IMU) can significantly reduce the prediction error, reducing latency effects. We show that using a wrist-worn IMU increases the throughput by 15% for finger input and 17% for a stylus.