A Faster VR Body to Speed Up ChoicesA VR body can move faster than its user, making actions like reaching more efficient. We propose a VR body that not only moves faster during reaching, but also starts moving before the user has decided which target to reach for. However, it is unclear whether such a VR body would speed up choices, since moving towards a wrong target might cause confusion, or influence users' choices. To explore these questions, we built a faster VR body prototype, focusing on an accelerated hand and arm, in a choice task. Thirty-four participants viewed random-dot displays to judge the overall motion direction and indicated their choice by pressing the corresponding button. Task difficulty was varied to influence choice uncertainty. Results showed that choice time decreased when the virtual body was 0.1 seconds ahead of the physical body, but increased when it was 0.3 seconds ahead. Users' choice distributions showed no significant differences.2026DYDifeng Yu et al.University of CopenhagenImmersion & Presence ResearchFull-Body Interaction & Embodied InputEye Tracking & Gaze InteractionCHI
A Design Space of Virtual Bodies: Their Types, Effects, and Theoretical FoundationsIn virtual reality, users are typically represented by and interact through a virtual body. Research frequently manipulates different features of these bodies. We analyze 208 studies to identify what aspects of virtual bodies are manipulated, how these manipulations affect interaction and other outcomes, and why they are assumed to do so. Based on the analysis, we propose a design space comprising seven types of visual manipulations: appearance, size, morphology, viewpoint, transfer, remapping, and control. We also synthesize findings on their effects—ranging from task performance to physiological responses and social outcomes—and examine the theories used to explain them, such as embodiment, Proteus effect, and presence. The design space helps researchers identify key variables and their interconnections in design and empirical research of virtual bodies. The synthesis further reveals unexplored causal connections and highlights theories that may account for observed effects.2026JBJoanna Bergström et al.University of CopenhagenIdentity & Avatars in XRImmersion & Presence ResearchSocial & Collaborative VRCHI
From Movement Adaptation to De Novo Learning: A Design Space of VR Interaction TechniquesVR interaction techniques define mappings between physical movements and virtual outcomes. While some mappings are learned through the adaptation of existing movement strategies, others require acquiring entirely new control policies. Drawing on motor learning theory, we introduce a design space that organizes these mappings into three families and provides a basis for reasoning about how the mappings are learned. To examine learning within individual families and their compositions, we start with two simple hand-based mappings, mirror reversal and cross-hand control, and their combination, allowing us to probe the design space in a controlled experiment with 96 participants. The mappings differ in initial difficulty, but participants achieve comparable overall learning. In the combined condition, prior exposure produces mapping specific start-up advantages. We discuss how this design space can support the analysis and design of VR mapping techniques.2026CXCleo Xiao et al.University of CopenhagenImmersion & Presence ResearchFull-Body Interaction & Embodied InputSocial & Collaborative VRCHI
Illusory-UMH: A Systematic Comparison of Tactile Illusions and Modulation Techniques in Ultrasonic Mid-air HapticsSpatiotemporal modulation (STM) is the current de facto standard technique for generating continuous tactile sensations in Ultrasonic Mid-Air Haptics (UMH). However, like other techniques, it assumes a uniform sensitivity distribution across the hand. Tactile illusions, such as the funneling effect (FE) and cutaneous rabbit effect (CRE) create continuous sensations by stimulating only a few points along the shape, which could be strategically selected at highly sensitive points in the hand for stronger effects, but such effects remain unexplored in UMH. This paper investigates tactile illusions (FE, CRE) as potential alternatives for STM, comparing their ability to produce continuous and intense shapes at regions on the palm with different skin sensitivity. Our results reveal significantly superior performance for CRE, when compared to FE and STM in the tested parameter range. FE in turn provides slightly higher continuity, even across sensitivity regions, while STM provides higher intensity.2025ZSZhouyang Shen et al.Mid-Air Haptics (Ultrasonic)Vibrotactile Feedback & Skin StimulationUIST
A Concept at Work: A Review of Motivations, Operationalizations, and Conclusions in VR Research about PresencePresence appears an important concept for virtual reality (VR): It is frequently measured with questionnaires, and theory and methods about it have been discussed in numerous works. Yet, it is unclear how to actually work with this concept: Why is presence important to measure, how to choose an appropriate questionnaire, and what to conclude about it based on findings? To answer these questions, we review how the concept is put to work in 288 VR papers from 2023 measuring presence with questionnaires. Our findings include that measuring presence is often motivated by another construct, such as user experience; the reasons for choosing a specific questionnaire are often weak or not reported at all; and high presence values are frequently used simply to validate an interaction technique. We propose recommendations for working with presence and formulate questions to direct future research.2025CXCleo Xiao et al.University of Copenhagen, Department of Computer ScienceImmersion & Presence ResearchCHI
Tendon Vibration for Creating Movement Illusions in Virtual RealityTendon vibration can create movement illusions: vibrating the biceps tendon induces an illusion of extending the arm, while vibrating the triceps tendon induces an illusion of flexing the arm. However, it is unclear how to create and integrate such illusions shown in neuroscience to interaction techniques in virtual reality (VR). We first design a motor setup for tendon vibration. Study 1 validates that the setup induces movement illusions which on average create a 5.26 cm offset in active arm movements. Study 2 shows that tendon vibration improves the detection thresholds of visual motion gains often used in VR interaction techniques by 0.22. A model we developed in Study 2 predicts the effects of tendon vibration and is used in a biomechanical simulation to demonstrate the detection thresholds across typical reaching tasks in VR.2025MCMantas Cibulskis et al.University of CopenhagenVibrotactile Feedback & Skin StimulationShape-Changing Interfaces & Soft Robotic MaterialsImmersion & Presence ResearchCHI
Deriving Selection Techniques for GUIs based on the Multiple Process ModelDesigning efficient selection techniques for graphical user interfaces (GUIs) is fundamental in HCI research. We derive selection techniques based on the multiple process model, a theory that details the motor control processes during goal-directed movements. Specifically, we deduce three theoretical assumptions on how control processes of pre-planning, impulse control, and limb-target control could influence selection movements when adjusting GUI elements, including visual feedback, cursor position, and target position. Corresponding to our assumptions, we develop three techniques that hide the cursor when a target is highlighted, snap the cursor when selection begins, and expand clustered objects during selection movements. After that, we pre-register the assumptions and research methodology and evaluate the techniques in three crowdsourcing-based pointing studies. Our results show that all techniques improved the selection efficiency compared to established baselines. We further discuss the design implications and reflect on how we derived techniques from theory.2025DYDifeng Yu et al.University of Copenhagen, Department of Computer ScienceUser Research Methods (Interviews, Surveys, Observation)Prototyping & User TestingCHI
Doorways Do Not Always Cause Forgetting: Studying the Effect of Locomotion Technique and Doorway Visualization in Virtual RealityThe “doorway effect” predicts that crossing an environmental boundary affects memory negatively. In virtual reality (VR), we can design the crossing and the appearance of such boundaries in non-realistic ways. However, it is unclear whether locomotion techniques like teleportation, which avoid crossing the boundary altogether, still induce the effect. Furthermore, it is unclear how different appearances of a doorway act as a boundary and thus induce the effect. To address these questions, we conducted two lab studies. First, we conceptually replicated prior doorway effect studies in VR using natural walking and teleportation. Second, we investigated the effect of five doorway visualizations, ranging from doors to portals. The results show no difference in object recognition performance due to the presence of a doorway, locomotion technique, or doorway visualization. We discuss the implications of these findings on the role of boundaries in event-based memory and the design of boundary interactions in VR.2024TGThomas van Gemert et al.University of CopenhagenSocial & Collaborative VRImmersion & Presence ResearchCHI
Sicknificant Steps: A Systematic Review and Meta-analysis of VR Sickness in Walking-based Locomotion for Virtual RealityWalking-based locomotion techniques in virtual reality (VR) can use redirection to enable walking in a virtual environment larger than the physical one. This results in a mismatch between the perceived virtual and physical movement, which is known to cause VR sickness. However, it is unclear if different types of walking techniques (e.g., resetting, reorientation, or self-overlapping spaces) affect VR sickness differently. To address this, we conducted a systematic review and meta-analysis of 96 papers published in 2016–2022 that measure VR sickness in walking-based locomotion. We find different VR sickness effects between types of redirection and between normal walking and redirection. However, we also identified several problems with the use and reporting of VR sickness measures. We discuss the challenges in understanding VR sickness differences between walking techniques and present guidelines for measuring VR sickness in locomotion studies.2024TGThomas van Gemert et al.University of CopenhagenMotion Sickness & Passenger ExperienceImmersion & Presence ResearchCHI
Towards a Bedder Future: A Study of Using Virtual Reality while Lying DownMost contemporary Virtual Reality (VR) experiences are made for standing users. However, when a user is lying down---either by choice or necessity---it is unclear how they can walk around, dodge obstacles, or grab distant objects. We rotate the virtual coordinate space to study the movement requirements and user experience of using VR while lying down. Fourteen experienced VR users engaged with various popular VR applications for 40 minutes in a study using a think-aloud protocol and semi-structured interviews. Thematic analysis of captured videos and interviews reveals that using VR while lying down is comfortable and usable and that the virtual perspective produces a potent illusion of standing up. However, commonplace movements in VR are surprisingly difficult when lying down, and using alternative interactions is fatiguing and hampers performance. To conclude, we discuss design opportunities to tackle the most significant challenges and to create new experiences.2023TGThomas van Gemert et al.University of CopenhagenFull-Body Interaction & Embodied InputImmersion & Presence ResearchCHI
OVRlap: Perceiving Multiple Locations Simultaneously to Improve Interaction in VRWe introduce OVRlap, a VR interaction technique that lets the user perceive multiple places simultaneously from a first-person perspective. OVRlap achieves this by overlapping viewpoints. At any time, only one viewpoint is active, meaning that the user may interact with objects therein. Objects seen from the active viewpoint are opaque, whereas objects seen from passive viewpoints are transparent. This allows users to perceive multiple locations at once and easily switch to the one in which they want to interact. We compare OVRlap and a single-viewpoint technique in a study where 20 participants complete object-collection and monitoring tasks. We find that participants are significantly faster and move their head significantly less with OVRlap in both tasks. We propose how the technique might be improved through automated switching of the active viewpoint and intelligent viewpoint rendering.2022JSJonas Schjerlund et al.University of CopenhagenFull-Body Interaction & Embodied InputImmersion & Presence ResearchCHI
How to Evaluate Object Selection and Manipulation in VR? Guidelines from 20 Years of StudiesThe VR community has introduced many object selection and manipulation techniques during the past two decades. Typically, they are empirically studied to establish their benefits over the state-of-the-art. However, the literature contains few guidelines on how to conduct such studies; standards developed for evaluating 2D interaction often do not apply. This lack of guidelines makes it hard to compare techniques across studies, to report evaluations consistently, and therefore to accumulate or replicate findings. To build such guidelines, we review 20 years of studies on VR object selection and manipulation. Based on the review, we propose recommendations for designing studies and a checklist for reporting them. We also identify research directions for improving evaluation methods and offer ideas for how to make studies more ecologically valid and rigorous.2021JBJoanna Bergström et al.University of CopenhagenImmersion & Presence ResearchPrototyping & User TestingCHI
Ninja Hands: Using Many Hands to Improve Target Selection in VRSelection and manipulation in virtual reality often happen using an avatar's hands. However, objects outside the immediate reach require effort to select. We develop a target selection technique called Ninja Hands. It maps the movement of a single real hand to many virtual hands, decreasing the distance to targets. We evaluate Ninja Hands in two studies. The first study shows that compared to a single hand, 4 and 8 hands are significantly faster for selecting targets. The second study complements this finding by using a larger target layout with many distractors. We find no decrease in selection time across 8, 27, and 64 hands, but an increase in the time spent deciding which hand to use. Thereby, net movement time still decreases significantly. In both studies, the physical motion exerted also decreases significantly with more hands. We discuss how these findings can inform future implementations of the Ninja Hands technique.2021JSJonas Schjerlund et al.University of CopenhagenFull-Body Interaction & Embodied InputCHI
Iteratively Adapting Avatars using Task-Integrated OptimisationVirtual Reality allows users to embody avatars that do not match their real bodies. Earlier work has selected changes to the avatar arbitrarily and it therefore remains unclear how to change avatars to improve users’ performance. We propose a systematic approach for iteratively adapting the avatar to perform better for a given task based on users’ performance. The approach is evaluated in a target selection task, where the forearms of the avatar are scaled to improve performance. A comparison between the optimised and real arm lengths shows a significant reduction in average tapping time by 18.7%, for forearms multiplied in length by 5.6. Additionally, with the adapted avatar, participants moved their real body and arms significantly less, and subjective measures show reduced physical demand and frustration. In a second study, we modify finger lengths for a linear tapping task to achieve a better performing avatar, which demonstrates the generalisability of the approach.2020JMJess McIntosh et al.Full-Body Interaction & Embodied InputIdentity & Avatars in XRUIST
Tool Extension in Human–Computer InteractionTool use extends people's representations of the immediately actionable space around them. Physical tools thereby become integrated in people's body schemas. We introduce a measure for tool extension in HCI by using a visual-tactile interference paradigm. In this paradigm, an index of tool extension is given by response time differences between crossmodally congruent and incongruent stimuli; tactile on the hand and visual on the tool. We use this measure to examine if and how findings on tool extension apply to interaction with computer-based tools. Our first experiment shows that touchpad and mouse both provide tool extension over a baseline condition without a tool. A second experiment shows a higher degree of tool extension for a realistic avatar hand compared to an abstract pointer for interaction in virtual reality. In sum, our measure can detect tool extension with computer-based tools and differentiate interfaces by their degree of extension.2019JBJoanna Bergström et al.University of CopenhagenHaptic WearablesFull-Body Interaction & Embodied InputCHI