Multisensory temporal processing in own-body contexts: plausibility of hand ownership does not improve visuo-tactile asynchrony detection.

Tracking one's own body is essential for environmental interaction, and involves integrating multisensory cues with stored information about the body's typical features. Exactly how multisensory information is integrated in own-body perception is still unclear. For example, Ide and Hidaka (Exp Brain Res 228:43-50, 2013) found that participants made less precise visuo-tactile temporal order judgments (TOJ) when viewing hands in a plausible orientation (upright; typical for one's own hand) compared to an implausible orientation (rotated 180°). This suggests that viewing one's own body relaxes the precision for perceived visuo-tactile synchrony. In contrast, visuo-proprioceptive research shows improvements for multisensory temporal perception near one's own body in asynchrony detection tasks, implying an increase in precision. Hence, it is unclear whether viewed hand orientation generally modulates the ability to detect small asynchronies between vision and touch, or if this effect is specific to TOJ tasks. We investigated whether viewed hand orientation affects detection of visuo-tactile asynchrony. In two experiments, participants viewed model hands in anatomically plausible or implausible orientations. In one experiment, we stroked the hands to induce the rubber hand illusion. Participants were asked to detect short delays (40-280 ms) between vision (an LED flash on the model hand) and touch (a tap to fingertip of the participant's hidden hand) in a two-interval forced-choice task. Bayesian analyses show that our data provide strong evidence that viewed hand orientation does not affect visuo-tactile asynchrony detection. This study suggests the mechanisms for fine-grained time perception differ between visuo-tactile and visuo-proprioceptive contexts.