Abstract
Our perception of time is known to systematically regress toward the mean of recent stimulus distribution. This phenomenon, known as central tendency, has been viewed as a product of assimilative recalibration to preceding stimuli in order to improve the overall performance of timing behavior. Here, however, we show that central tendency is a consequence of assimilative recalibration to past decisions rather than to past stimuli. In our psychophysical procedure, we measured the apparent durations of static sinusoidal gratings (1.0 c/deg) with various durations (0.2-0.9 sec) by means of a reproduction method (N=10). Using multiple regression analysis, we calculated the impact of preceding stimulus duration (Ws) and preceding reproduced duration (Wr) upon the response error in the current trial. Analysis showed that current response is strongly assimilated to preceding responses (Wr= 0.42; p< .0001) and contrasted from preceding stimuli (Ws= -0.25; p< .0001). The relative amount of assimilation and repulsion was well correlated with the amount of central tendency in individual observers, and the effect of a previous trial on current-trial bias decreased with inter-trial distance regardless of bias direction. Similar patterns of results were obtained if observers reproduced duration as indicated by a digit figure (0.2-0.9) that was shown with a fixed duration (0.7 sec), thereby suggesting that the repulsive component is unlikely to be a product of adaptation to physical stimulus duration. In an additional experiment, we found no clear evidence for such two distinct effects in the serial dependence of orientation perception which has been known for exhibiting an assimilative effect from preceding stimuli. These results suggest that our perceptual decision of event time is continually adjusted via two distinct adaptive processes: assimilative recalibration which retains consistency with past decisions (Bayesian) and repulsive recalibration which emphasizes the difference from past sensory inputs (anti-Bayesian).
Meeting abstract presented at VSS 2018