Differences in perceived duration between plausible biological and non-biological stimuli

Visual motion stimuli can sometimes distort our perception of time. This effect is dependent on the apparent speed of the moving stimulus, where faster stimuli are usually perceived lasting longer than slower stimuli. Although it has been shown that neural and cognitive processing of biological motion stimuli differ from non-biological motion stimuli, no study has yet investigated whether perceived durations of biological stimuli differ from non-biological stimuli across different speeds. Here, a prospective temporal reproduction task was used to assess that question. Biological motion stimuli consisted in a human silhouette running in place. Non-biological motion stimuli consisted in a rectangle moving in a pendular way. Amount and plausibility of movement for each stimulus and frame-rate (speed) were evaluated by an independent group of participants. Although amount of movement was positively correlated to frame rate, movie clips involving biological motion stimuli were judged to last longer than non-biological motion stimuli only at frame rates in which movement was rated as plausible. These results suggest that plausible representations of biomechanical movement induce additional temporal distortions to those modulated by increases in stimulus speed. Moreover, most studies that have reported neural and cognitive differences in the processing of biological and non-biological motion stimuli acquired neurophysiological data using fMRI. The present study aimed additionally to report differences in the processing of biological and non-biological motion stimuli across different speeds using functional near infrared spectroscopy (fNIRS), a less costly and portable form of neurophysiological data acquisition.