The relationship between the effect of hand visibility on visuotactile temporal resolution and autistic traits.

Individuals with autism spectrum disorder (ASD) have atypical sensory processing, particularly when sensory stimuli are delivered from different modalities with a temporal lag of subseconds. Previous studies have suggested that individuals with ASD require a longer temporal lag to judge temporal orders of successive audiovisual stimuli than neurotypical individuals; however, it remains unclear whether a lower temporal resolution in the visuotactile domain is associated with an individual's autistic traits. In addition, a previous study demonstrated that visuotactile temporal resolution degraded when the participants saw a hand image on a display. In this study, we investigated whether the temporal resolution of the visuotactile stimuli degrades when the participant's own hand or rubber hands are visible, and whether the effect of the hand's visibility on the temporal resolution decreases according to an individual's autistic traits. We used the temporal order judgment (TOJ) of the vibrotactile stimulus delivered to the participant's index finger and an LED attached above their own hand or rubber hand. Our findings suggest that when participants could not see their hand, temporal order judgment tended to be coarser in participants with higher autistic traits. However, this tendency was not observed when they could see both their own or the rubber hands. Moreover, temporal resolution degraded when the participants could see their own hands. These results indicate that autistic traits influence the temporal resolution of visuotactile stimuli if they are delivered as external signals in TOJ.