2017 年 88 巻 5 号 p. 504-517
The tau and kappa effects are perceptual illusions involved with spatiotemporal interactions. In the tau (kappa) effect, the spatial distance (duration) between two stimuli is perceived as longer when the duration (spatial distance) between these stimuli is made physically longer. The occurrence of these effects is explained by two hypotheses, both assuming the perception of motion between locations in which the stimuli are presented. Additionally, the first hypothesis posits that the motion speed is kept constant, whereas the second hypothesis is based on a Bayesian model with prior knowledge that the speed is slow. Perceived spatial distance and duration are estimated from the predicted motion velocity, resulting in the tau and kappa effects. This article aims to discuss the validity of each hypothesis, as well as future avenues, through a review of recent studies related to the tau and kappa effects.