Abstract

White's illusion is unique in that it differs from classical brightness contrast and assimilation illusions. Although White's illusion and brightness assimilation may appear similar, they are caused by different visual properties. This study aimed to investigate whether the mechanisms underlying White's illusion and brightness assimilation are the same. Experiment 1 investigated whether the length of the test stimulus and the thickness of the stimuli could affect brightness induction. The test stimulus was presented in the center of the inducing stimuli arranged in a square waveform. Experiment 2 investigated whether the number of inducing stimuli could affect brightness induction. The results showed that the perceived brightness of the test stimulus was systematically influenced by the length and thickness of the stimulus. This trend was maintained even when the number of inducing stimuli was controlled for. These results suggest that brightness induction could be explained by the responses of the primary visual cortex. Non-adjacent inducing stimuli also affected brightness perception, but the effect weakened as the distance from the test stimulus increased. This trend was observed in both White's illusion and classical brightness assimilation stimuli, indicating that White's illusion and classical brightness induction may occur due to a similar mechanism.