Encouraging head movements can be beneficial for safety maneuvers, such as shoulder checking, providing realistic haptic feedback in virtual reality, or guiding attention. While weight-shifting offers opportunities to provide proprioceptive feedback that aligns with encouraged body movement, its integration in helmet interfaces remains largely unexplored. To investigate how weight-shifting can encourage head motion through proprioceptive feedback, we developed a weight-shifting mechanism that integrates a motorized weight to shift the helmet's center of gravity, prompting head rotation without adding visual or auditory load. A user study (n = 24) compared three weight-shifting patterns, rotation (continuous motion), swing (covering 130 degrees), and step (covering 20 degrees), measuring accuracy, response time, confidence, and workload. Accuracy was consistent across conditions (approximate to 78%), but participants completed tasks significantly faster with the rotation pattern. Qualitative reports confirmed that this motion elicited head movements. This study demonstrates the potential of proprioceptive feedback provided to head-worn devices to reduce reliance on visual or auditory cues.

Avatar appearance can influence users’ behaviour within Virtual Reality (VR), a phenomenon known as the Proteus effect. Prior work suggests that walking behavior after VR exposure is affected by the previously embodied avatar’s apparent age. However, little is known about how such effects unfold during ongoing avatar embodiment in VR. We conducted a study where 32 full-body tracked participants embodied young- and old-looking avatars and repeatedly completed a walking route in VR. Results show that participants walked significantly slower when embodying old-looking avatars. Presence and body ownership increased over time. Interestingly, embodiment duration did not significantly affect the magnitude of the Proteus effect on walking speed, with descriptive differences remaining largely stable. These results suggest that the behavioral impact of avatar age persists without substantial change over a 15 to 20-minute VR session. Our findings contribute to a deeper understanding of avatar age as a design parameter in VR.

Interacting with smart environments through gestures faces the challenge of false positives, also known as the Midas touch problem. To enable seamless and robust gesture activation, we selected activation microgestures performed simultaneously on a ring during gesture execution. A user study revealed a clear preference for activating the ring with the thumb over the middle finger, based on usability and physical demand. Interestingly, while activating a push button requires more force than pressing a smooth pressure sensor, the soft button caused significantly higher physical demand than pressing a push button, which provides clear passive haptic force feedback indicating when the button has been pushed. The lack of force feedback from the pressure sensor appears to cause users to continue pressing after the sensor has been activated. In summary, activating index-finger gestures using a thumb press is a promising technique for easy, usable, and robust ubiquitous gesture interaction.

With growing exertion, effortful actions become increasingly difficult, shaping how people pace and perform physical tasks. To realistically convey this experience in Virtual Reality (VR), systems must replicate not only the visual but also the physical sensations of exhaustion. We propose a technique for conveying avatars' exhaustion by leveraging weight-changing VR controllers (PumpVR) to align their physical weight with the avatars' stamina. As stamina decreases, controller weight increases to simulate the rising effort required for movement, and vice versa. We integrated this mechanism into a VR climbing game and conducted a user study (n = 24) comparing stamina-mirroring weight feedback to controllers with static weight. Results showed that stamina-mirroring weight significantly enhanced users' perceived realism and enjoyment, while increasing perceived exertion. Our findings demonstrate the potential of weight feedback to convey physiological states in VR, offering a more embodied and realistic alternative to purely visual representations.

Mid-air gestures often suffer from low learnability and high error rates, particularly in the absence of visual feedback. As an alternative, sequential vibrotactile feedback on the forearm can convey directional cues for spatial hand guidance. We investigate the human ability to discriminate the direction of successive vibrotactile stimuli applied to the forearm. Our results show that longitudinal directions (forward/backward) are perceived more reliably than transverse directions (clockwise/counterclockwise). Moreover, directional discrimination significantly improves for actuator distances of 45 mm or more along the longitudinal axis. In addition, posterior and lateral forearm regions yield higher perceptual performance than anterior and medial regions.

We present MovPad, a novel concept of feeling holes and bumps on a flat touch surface that is moving up and down. An experiment showed that users could perceive bumps and holes when the touchpad, on which their finger slides across, moved. Interestingly, we found no performance difference in distinguishing holes from bumps when seeing the moving pad versus being blindfolded. Generally, shapes with a width of 18 mm and above, representing the average digit’s width, could be better perceived than smaller ones. Our approach enables users to feel surface textures and structures, and thus, has huge potential to enrich touch interaction on mobile devices through embedding a movable touchpad or touchscreen into tablets, phones, and smartwatches.

Humans can distinguish two short simultaneous touches on the forearm, called Two-Point Discrimination (2PD), starting at a distance of approximately 40 mm. However, similar insights are lacking for vibrotactile stimuli, which would be essential for designing ergonomic gesture wristbands. Thus, an oriented 2PD test was performed using vibrotactile actuators on the forearm placed around the wrist (transverse) and along the forearm (longitudinal). The results indicate that the orientation between two actuators cannot be robustly distinguished. Two simultaneous stimuli on the forearm can best be detected at 90 mm distance, with a success rate of up to 96% for transverse placement when the actuators are arranged around the wrist. In this case, the actuators are approximately placed opposite each other, looking at the wrist as a circle. Thus, an actuator arrangement around the wrist is most sufficient to distinguish between a single and two simultaneous vibrotactile stimuli.

We introduce FeelCoilins, a prototype for midair drumming in Virtual Reality (VR) that incorporates ungrounded force feedback to improve realism and presence. The system employs solenoid actuators on 3D-printed drumstick controllers to produce force feedback during drum hits. An exploratory formative study with 10 participants compared drumming experience under two conditions: with and without force feedback. While quantitative performance metrics were largely similar between conditions, qualitative data suggest that the force feedback was perceived to enhance realism. However, the weight and form factor were seen as factors that reduced the perceived realism. These findings inform the next design iteration, fostering the potential of FeelCoilins for enhancing VR drumming practice.

Creativity is increasingly essential, especially as automation and artificial intelligence replace routine tasks. Previous work suggests that the physical environment, for example, room size and object presence, might influence our creativity. Virtual Reality (VR) enables working in any environment and thereby allows optimizing the environment to foster creativity. Previous research on creativity, however, did not systematically control room size and object presence. As their isolated effects are unclear, we explore the effects of room size and objects on creativity in VR. Participants completed an alternative uses task in small and large virtual rooms that were empty or filled with objects. We found that the presence of objects increases subjective creative performance but found no effects of room size or objects on objective creativity. We derive implications to enhance the subjective experience in creative VR workspaces and discuss that the effects of room size might be smaller than previously thought.

In Virtual Reality (VR), users frequently interact through pointing movements. The accuracy and speed of such goal-directed movements depend on their estimated energy and time costs. In VR, vision is stimulated separately from tactile and kinesthetic sensory modalities. For instance, a virtual pointing device can be visually presented as heavy while being physically lightweight. Yet, it is unknown how visual and physical weight cues contribute to our strategy to optimize movements in terms of accuracy and speed. In a study with 32 participants, we found physical weight (additional weight of the controller) increases precision and movement time when pointing in VR. Interestingly, we found that visually conveyed weight (additional volume at the controller's 3d model) also increases movement time, suggesting that adjusting the appearance of virtually held objects can affect the performance of pointing movements. We interpret our findings in light of motor-cognitive models and discuss implications for VR designers.

MorphGrip is a novel shape-changing grip that aims to guide the pose and position of controllers or handheld devices or tools. In a user study, we explored how well such directional shape changes felt at the user’s palms and fingers can serve as guidance. The results indicate that haptic cues in horizontal and vertical guide users significantly better than cues that suggest moving MorphGrip in tilt and roll direction. While haptics have lower bandwidth than vision and auditory feedback, MorphGrip can be supportive in scenarios with a risk of audiovisual overload. Accordingly, we identify promising use cases for integrating MorphGrip into the grips of handheld devices for applications, such as rehabilitation therapy, smart tools, and guidance in special environments, like underwater.

A growing body of work in human-computer interaction (HCI), particularly work on haptic feedback and haptic displays, relies on sensory illusions, which is a phenomenon investigated in perception research. However, an overview of which illusions are prevalent in HCI for generating haptic feedback in computing systems and which remain underrepresented, as well as the rationales and possible undiscovered potentials therein, have not yet been provided. Existing surveys on human-computer interfaces using sensory illusions are not only outdated but, more importantly, they do not consider literature across disciplines, namely, perception research and HCI. This article provides a systematic literature review of haptic feedback generated by sensory illusions. By reporting and discussing the findings of 90 publications, we provide an overview of how sensory illusions can be used and adapted to produce haptic feedback and how they are implemented and evaluated in HCI. We moreover identify current trends and research gaps and discuss ideas for possible research directions worth investigating.

We use simple stickers on a wooden board to create ubiquitous touch interaction. Resonant frequencies make the board vibrate, creating tactile feedback when touching the stickers. In an experiment, we used stickers of three sizes to create Resonant Sticker Buttons and varied the delay of the feedback. Both size and feedback delay influenced the perceived weight of the buttons. While higher latencies result in a heavier perceived button, larger button sizes result in lighter perceived buttons and perceived feedback strength, and vice versa. Our findings suggest that touch interfaces with buttons of varying sizes, weights, and vibration strengths can be created on everyday surfaces, such as tables, by simply using stickers and speakers.

This work aims to provide tactile feedback when touching elements on everyday surfaces using their resonant frequencies. We used a remote speaker to bring a thin wooden surface into vibration for providing haptic feedback when a small graphical fly glued on the board was touched. Participants assigned the vibration to the fly instead of the board it was glued on. We systematically explored when that assignment illusion works best. The results indicate that additional sound, as well as vibration, lasting as long as the touch, are essential factors for having an assignment of the haptic feedback to the touched graphical object. With this approach, we contribute to ubiquitous and calm computing by showing that resonant frequency can provide vibrotactile feedback for images on thin everyday surfaces using only a minimum of hardware.

The need for remote collaborative work is constantly increasing. Collaboratively adapting digital content, such as documents and images, has come to a stage where it is part of our daily lives. In comparison, remote collaboration on physical objects has matured at a slower pace, even though this is a possible step towards location-independent cooperation and therefore equality in work. In this paper, we present a structured literature review on computer-supported remote collaboration on physical objects from the last 23 years. Our contribution is threefold: First, we provide a comprehensive analysis of the current state of research on the topic of remote collaboration on physical objects. Second, we identify multiple research gaps, such as inclusion of haptic sense, mutual collaboration, and asynchronous collaboration. Third, we analyze code relationships in the selected publications and provide directions for future work in the form of exploratory research questions.

Vibrations are the dominant way to create haptic feedback for interactive systems and are most often induced by vibrotactile actuators. However, virtual content created for augmented reality usually does not support that modality, instead relying mainly on visual and auditive output. Aiming to provide haptic feedback for augmented reality in cases where real vibrations cannot be used, we explore how vibrations can be felt using vision and audio only. In a user study, a virtual 10 x 10 cm white square-shaped cuboid was influenced by animation and/or sound to induce a haptic illusion when being touched. We were able to identify a specific range where the perception of vibration was significantly stronger and more realistic compared to all other values. This was the case if the virtual object’s edges were blurred up to a range of 0.4 cm or 0.6 cm, correspondingly accompanied by sounds, where the spectrum was cut off at a frequency of 256 Hz (for 0.4 cm) or 966 Hz (for 0.6 cm). With that, we aim to enrich augmented reality systems.

Many standard AR devices, such as the HoloLens 2, have limitations in displaying fast motions, like the ones required to visualize moving or vibrating objects. One reason for this is the low computing power compared to other technologies, resulting in frame rate drops. Further, established visualization enhancement methods, such as anti-aliasing, cannot be applied because of their high computational demands. Therefore, we have looked at possible alternatives on the HoloLens 2 for displaying vibrations more realistically as long as these technical limitations exist. We have chosen to examine vibrations as they are widely used for different use cases, like creating feedback, communicating the success of interactions, and generating a better scene understanding. In a user study, three different effects were evaluated against a baseline method, which was the representation of a vibration using a sinus function to calculate the displacement of the object. We found that an effect where the edges of the AR object are blurred (continuously with changing intensity) is perceived as significantly more realistic than other effects and the baseline method.

The use of mid-air gestures to control interactive systems is becoming increasingly important, particularly in mixed reality scenarios. However, these gestures are not always intuitive and can be challenging to learn as they lack visual guidance. Therefore, it is crucial to explore strategies to improve the learnability of these gestures. In this work, it is investigated how a vibration stimulus can be applied at the forearm to guide a person in performing a gesture. Utilizing a prototypical wristband with 24 vibrotactile actuators, the metaphors pull and push, representing attractive and repulsive feedback, were compared against each other. Results of a controlled user study show that participants perform significantly better with the pull metaphor, completing gestures faster, and make fewer errors. In line with this, the majority stated a subjective preference towards pull after experiencing both metaphors.

Besides referring to digital twins, the iterative development of physical objects cannot be easily managed in version control systems. However, physical content also could benefit from versioning for structured work and collaborative uses, thereby increasing equality between digital and physical design. Hence, it needs to be investigated what kind of system is most suitable for supporting a physical object version control. Focusing on the visualization of differences between states of a physical artifact, two systems were compared against each other in a lab study: a screen-based solution optimized for 3D models as baseline and an approach that augments a physical artifact with digital information as hypothesis. Our results indicate that the Augmented Artifact system is superior in task completion time but scores a lower usability rating than the baseline. Based on the results, we further provide design considerations for building a physical object version control system.