Abstract
Humans have shown to effectively estimate material roughness using both vision and/or touch. If both modalities receive conflicting information (i.e., sensory conflict), the perceptual system tends to use a weighted combination of the available cues depending on their reliability. While previous studies have primarily focussed on participants’ roughness perception in manual exploration tasks, we examined whether and how experiencing visuohaptic conflicts change roughness estimation during more natural object interactions (i.e., grasping). For stimuli selection, participants rated the visual and haptic roughness of a range of stimuli on a continuous rating scale (i.e., 0-100%). Based on these ratings, we identified three roughness levels (i.e., rough/medium/smooth) for three material categories (Wood, Sandpaper, Natural). In the main experiment, we dissociated the visual and haptic experience in three participant groups by using different sets of those stimuli and presenting them in a mirror setup. That is, all participants viewed the same three medium stimuli visually (placed in front of the mirror), but grasped either the same, the smoother, or the rougher version of the same object category (placed behind the mirror). Participants rated the perceived roughness of the stimuli, separately for visual and haptic sensation, on the same rating scale before and after the grasping task. Our findings (N=18) showed that participants exposed to rougher haptic experiences rated medium visual stimuli as looking rougher after grasping. Similarly, participants who touched smoother stimuli during grasping perceived medium stimuli as looking smoother. In contrast, we observed no visual bias on the haptic estimations of roughness. The findings suggest that visual perception of material properties can be biased by the haptic experience of everyday manual interactions.
Acknowledgement: Eastbio BBSRC [BB/M010996/1]