Stable Touch and Malleable Vision: Differential Priming Magnitudes in Virtual Reality

Visual dominance is a well-documented phenomenon, yet the reasons for such dominance remain unclear. We hypothesise that, specifically in visuo-haptic multisensory scenarios, part of the reason for this dominance is the ecological expectation for the perception of vision to temporally precede the perception of touch. This study investigated whether the order of presented stimuli impacts reaction times using a Virtual Reality (VR) oddball paradigm combined with ultrasound mid-air haptics. Twenty-eight participants responded to target stimuli across four conditions: touch-touch (TT), touch-vision (TV), vision-touch (VT), and vision-vision (VV). We hypothesized that, due to ecological expectation, Vision-then-Touch (VT) priming would be stronger than Touch-then-Vision (TV) due to its ecological expectancy, and that within-modality priming would generally exceed cross-modal priming. Results indicated that participants were significantly slower in VT conditions compared to TV conditions, contradicting the ecological hypothesis. We attribute this to visual dominance, where response times are faster whenever the target stimulus is visual, regardless of priming order. We also found that within-modality priming (VV and TT) elicited significantly faster responses than cross-modality conditions. Interestingly, exploratory analyses found that reaction time differences between conditions were significantly greater in trials where the participants responded to visual stimuli than in trials where participants responded to touch stimuli, suggesting that touch is perceptually more "stable" and less susceptible to priming effects than vision. Overall, visual dominance appears to override ecological sequential expectations in multisensory integration, though it is impacted more heavily by priming effects than touch.