Effects of test stimulus size on motion aftereffects to illusory motion

Abstract

After viewing a stimulus moving in one direction (adaptation stimulus) for dozens of seconds to minutes, an observer perceives a stationary stimulus (test stimulus) to be moving in the opposite direction. This phenomenon is known as the motion aftereffect (MAE). Many studies have examined various features of the stimuli that affect MAE, such as size, contrast, and velocity and have discussed MAE in relation to neural mechanisms. Harrison et al. (2016) demonstrated illusory global motion by drifting a stationary Gabor patch array. The Gabor patch array consists of horizontally or vertically drifting Gabor patches arranged on an imaginary square. An observer perceives rotational motion to the Gabor array although each patch does not rotate. Using this illusory rotation as an adaptation stimulus, we previously reported that this illusion induced rotational MAE in the opposite direction (ECVP2021). The aim of the current study was to investigate the effect of the size of a test stimulus, a black filled square, on the duration of MAE induced by illusory rotational motion. In an experiment, participants viewed the adaptation stimulus for 30 seconds and a test stimulus was then presented. The participants reported whether the test stimulus was perceived as moving by pressing and holding a key corresponding to the direction of rotation (clockwise or counterclockwise). The results showed that the MAE durations changed with the size of the test stimulus.