The Effects of a Multi-Point Thermal Haptic Ring System on Presence in a VR Environment

Technical Summary: The Effects of a Multi-Point Thermal Haptic Ring System on Presence in a VR Environment

Problem Statement
While contemporary Virtual Reality (VR) systems offer convincing visual and auditory stimuli, interaction with virtual objects often lacks physical completeness. Haptic feedback is essential for addressing this limitation, yet thermal feedback—a key property for material discrimination and object identification—remains underexplored regarding its specific contribution to "presence" (the subjective experience of being in a virtual environment). Previous thermal haptic research has largely focused on device performance, stimulus detection, or material identification rather than the experiential impact of contact-triggered thermal feedback. Furthermore, existing studies often combine environmental cues with object-specific cues, making it difficult to isolate the effects of localized thermal contact. There is a need to determine whether localized, contact-triggered thermal feedback delivered via wearable devices enhances specific dimensions of presence, such as spatial presence and experienced realism, without altering the general sense of involvement.

Methodology
The study employed a counterbalanced, within-subjects experimental design with 30 participants (students and staff from the University of the West of Scotland). Participants interacted with a VR environment using a Meta Quest 2 headset and a custom-built thermal haptic apparatus.

• Apparatus: The system consisted of two independently controlled ring modules worn on the index and ring fingers of the right hand. Each ring integrated a thermoelectric (Peltier) module, a thermoplastic elastomer interface, an embedded temperature sensor, and a heat dissipation system (aluminium heat sink and graphene layer). The rings were connected to an external control unit that regulated thermal output based on sensor feedback.
• Virtual Environment: The environment contained three visually identical grey cylinders. Participants were required to grasp them without visual temperature cues.
• Conditions:
  • Active Condition: Grasping a cylinder triggered specific thermal commands. The left cylinder provided uniform cold (5°C command to both rings); the middle cylinder provided spatially differentiated feedback (5°C to the index finger, 42°C to the ring finger); the right cylinder provided uniform warm (42°C to both rings).
  • Inactive Condition: Participants wore the identical apparatus and performed the same task, but no thermal output was activated.
• Procedure: The order of conditions was counterbalanced. During interactions, participants maintained contact for at least 5 seconds. Thermal perception (intensity and differentiation) was queried during the active condition.
• Measures:
  • Presence: Measured using the Igroup Presence Questionnaire (IPQ), analyzing four dimensions: General Presence (PRES), Spatial Presence (SP), Involvement (INV), and Experienced Realism (REAL).
  • Retrospective Evaluation: Post-experiment ratings on a 7-point Likert scale assessed the contribution of thermal feedback to realism, immersion, and cue appropriateness.
  • Thermal Perception: 7-point ratings of cold intensity, warm intensity, and the clarity of thermal differentiation between fingers.

Key Results

• Presence Metrics: The active thermal condition showed positive mean differences compared to the inactive condition for Spatial Presence ($M_{diff} = 1.17$, $p = .047$, $d_z = 0.38$) and Experienced Realism ($M_{diff} = 1.00$, $p = .048$, $d_z = 0.38$). Conversely, General Presence and Involvement showed negligible differences ($M_{diff} = 0.17$ and $-0.23$, respectively).
• Retrospective Ratings: Participants provided positive evaluations for the contribution of thermal feedback to realism ($M=5.07$), immersion ($M=5.03$), and cue appropriateness ($M=4.93$).
• Thermal Perception: In the active condition, the mean rating for warming intensity ($M=5.20$) exceeded that of cooling intensity ($M=3.97$). Thermal differentiation was perceived by 66.7% of participants (rating $\ge 4$), though with higher variability than warming.
• Statistical Context: The authors note that four IPQ outcomes were examined without multiplicity adjustment, and the two significant $p$-values were close to the .05 threshold. Consequently, these findings are interpreted as preliminary.

Significance and Claims
The paper claims that localized thermal feedback delivered through a multi-point wearable system may support the spatial and realistic qualities of virtual object contact. The results suggest that thermal cues, when spatially and temporally aligned with visual object interaction, can enhance the plausibility of the interaction (Experienced Realism) and the feeling of being located within the environment (Spatial Presence), without necessarily changing the overall level of engagement (Involvement).

The study demonstrates the technical feasibility of integrating independently controlled finger-worn thermal modules into a VR workflow. However, the authors explicitly state that the results do not establish an advantage of spatially differentiated feedback over uniform feedback, as the IPQ outcomes represented the aggregate active condition rather than a direct comparison of mapping types. The findings are treated as preliminary evidence that warrants further hypothesis-driven research, specifically studies that directly compare uniform and differential mappings and include behavioral measures alongside self-reports.