Vibrotactile-Only Virtual Reality Target Selection

Empirical VR Study with 32 BVI Users

Project Overview

Virtual reality (VR) mixed method study with 32 blind and visually impaired (BVI) participants, exploring unimodal vibrotactile spatial target acquisition in peripersonal space across lateral and depth axes.

2nd ACM Europe Summer School on Accessible and Inclusive Technologies: Doctoral Lightning Talk (opens in a new tab)
MINDS Workshop: Invited speaker (opens in a new tab)
Open access repository (opens in a new tab) for Unity project

2025

Year

BCU PhD

Institution

Empirical
(mixed-methods)

Type

Problem

The absence of accommodations and standardised non-visual guidelines has resulted in widespread exclusion from VR for BVI users. Prior VR work has explored haptic feedback supplementing visuals or audio, yet its effectiveness as a standalone sensory substitution channel has not been thoroughly examined.

Key Finding

(1) An axis-dependent speed-accuracy trade-off where lateral selections were faster but less accurate, (2) evidence that standard unimodal vibrotactile guidance is insufficient for high-precision targeting without supplementary cues, and (3) qualitative feedback indicating high participant enthusiasm and potential psychological benefits.

Problem Definition

Evaluating fundamental tasks, such as pointing and selection, informs understanding of more complex high-level interactions like spatial orientation and wayfinding. Restricting the VR environment to lateral and depth movements within a seated peripersonal space isolates the core selection skills required for consumer-level VR interactions.

This study explores mapping this space onto an off-the-shelf vibrotactile vest to guide precise hand movements for 32 BVI participants. The design deliberately decouples the vibrotactile feedback: the vest provides global awareness directions, while the handheld controller provides local guidance binary target collision signals, avoiding sensory overload at the hand.

A bHaptics TactSuit x40 vest displaying multiple vibration motors — bHaptics vest used in study

The literature demonstrates the utility of vibrotactile feedback for guiding BVI users in 2D interfaces and for augmenting sighted user performance in spatial target selection. However, a significant gap exists in translating these principles to fully non-visual VR contexts, effectively excluding BVI users from the spatial interactions that define modern VR.

While vibrotactile cues often supplement visual information or provide alerts for obstacle avoidance in virtual environments, their use as the sole sensory substitution channel for BVI users in VR is a critical, unexplored area. Although prior work suggests unimodal cues may be preferred and BVI participants have expressed a desire for more vibrotactile depth information, there is a lack of empirical data on how vibrotactile-only cues perform in VR target selection scenarios.

Meta Quest Pro VR headset and two controllers floating against a light background — Meta Quest Pro used in the study

We asked:

To what extent do unimodal vibrotactile cues facilitate accurate lateral and depth-based VR pointing movements?
How does performance differ between lateral and depth axes?
How does vibrotactile modulation influence performance, preference, and usability?

The mixed methods approach, combining standardised performance data analysis and semi-structured interview thematic analysis, provides actionable recommendations for the design of accessible VR interfaces for BVI users.

Methodology

Participants used a single controller in their preferred hand for target selection with a trigger press, with selection errors permissible. The bHaptics TactSuit x40 vest provided global directional cues, while the Meta Quest Touch Pro Controller provided local binary vibration upon object contact. The task involved reciprocal selection between 3D targets along either the lateral or depth axis.

Testing occurred with 32 unpaid participants (20 males, 12 females, 0 non-binary/other), aged 24-84 (M = 49.75 ± 16.12), recruited from across the UK to ensure evaluations could be conducted in locations and according to schedules suitable for the BVI participants.

Diagram showing four different vest vibration patterns mapping to different angles — Vest vibration patterns

A dense table displaying demographic information for 32 participants including age, gender, visual impairment level, and technical experience — Table with demographic information for the participants

Top down view diagram of the target layout showing targets at different distances along a cross formation — Target layout top down view

A 2x2 within-subject repeated-measures design explored movement direction (lateral vs. depth) and haptic growth modulation (quadratic vs. pulse) with six commonly used indices of difficulty (IDs). Participants alternated between targets appearing along the movement axis. Instructions followed standard task procedures, with continuous movement between targets as quickly and accurately as possible.

In summary, the experimental design was as follows:

Total blocks per participant: 4 (one for each direction × feedback method combination)
Total trials per block: 108 (6 IDs × 9 trials × 2 repetitions)
Total trials per participant: 432 (4 blocks × 108 trials)
Total dataset: 13,824 trials (432 trials × 32 participants)

Results

Key significant results include:

Significant speed-accuracy trade-off: faster lateral movements but substantially more errors than depth
High overall error rates (mean 63.19%) indicating off-the-shelf vibrotactile cues are insufficient for precision
Counter-intuitive distance effect: smaller and closer targets yielded more errors
No significant differences between continuous quadratic and intermittent pulse modulation
Minimal learning effect as users rapidly hit a performance ceiling
Subtle demographic patterns highlighting high individual variability

Users systematically overshot targets, particularly for short distances, suggesting a hardware-perception bottleneck where mechanical latency impacted fine-motor precision.

There was a strong mismatch between perceived accuracy and statistical results, with users believing they performed better laterally than in depth, whilst the results showed the opposite.

Several bar charts showing significant performance differences across movement time, error rate, and throughput — Significant performance differences

Two boxplots showing endpoint distributions that indicate systematic overshooting past the target centers — Endpoint boxplots showing systematic overshooting

Qualitative summary:

Difficulty and Familiarity: Initial high cognitive load decreased with time, but physical fatigue was prominent for unusual depth movements
Sense of Achievement and Fun: Participants framed the task as a game, frequently reporting enjoyment and strong motivation
Refinement and Customisation: Strong desire for system control, multiple options, and multimodal feedback (such as audio cues)
Psychological and Practical Benefits: High enthusiasm for the technology's potential in independent navigation, sports, and reducing social isolation

Conclusion

Key Takeaways:

Large Accuracy Challenges - standard vibrotactile-only interaction is exceptionally difficult
Speed-Accuracy Trade-off Across Axes - faster but significantly less accurate lateral movements
Neither Modulation Type Overcame Task Difficulty - both quadratic and pulse struggled with fine-grained precision
Mismatch in Accuracy and Confidence - high confidence in lateral motion despite worse performance
Inverse Distance-Accuracy Relationship - closer targets were significantly harder, indicating a hardware-perception bottleneck
Minimal Learning Effect - users rapidly hit a performance ceiling
Subtle Demographic Patterns - highlighted the necessity for personalised design tolerances
Participant Enthusiasm - high psychological impacts, enjoyment, and practical use-case suggestions
Alternative Designs Needed - multi-stage feedback or force feedback is essential for the final approach