The Japanese Society for Cognitive Psychology

When single flash is simultaneously presented with two short beeps, two flashes are often perceived. This phenomenon is called as fission illusion. The occurrence rates of fission illusion are modulated by visual characteristics. The present study investigated the effects of visual stimuli with emotional valence on fission illusion using signal detection theory. Facial expression stimuli were presented in Experiment 1. The results indicated that angry and happy faces modulated criterion scores compared with neutral face under fission illusion condition. Simple geometric shapes were presented in Experiment 2. The results indicated that inverted-triangle and circle, which included negative and positive valence, respectively, decreased d-prime scores: thus, larger fission illusion is induced by these visual stimuli compared with triangle as neutral stimulus. Therefore, different effects were observed in the process of fission illusion between facial expressions and simple geometric shapes with emotional valence.