RESEARCH ARTICLE Modulation of Emotional Category Induced by Temporal Factors in Emotion Recognition

Categorical perception (CP), the perceptual experience whereby continuous sensory phe-nomena are perceived as distinct and separate percepts, is one of the most characteristic features of information processing in human cognition. CP is considered as the result of the integration of the top-down processing including background knowledge and verbal labeling and the bottom-up processing such as physical characteristics of the sensory signal. How-ever, the underlying mechanisms governing the integration remain unclear. To address this issue, we focused on the temporal characteristics of CP of facial expression. In the current study, we investigated the contributions of temporal factors in CP processes, using facial expression recognition tasks as an example of CP. Participants completed an identification task and a discrimination task, well-established tasks for evaluating CP of facial expres-sions, with variable temporal parameters, that is, duration of stimulus presentation and delay time (interval between stimulus and response). The results demonstrated that the emotionally ambiguous stimuli are categorized more distinctively with the extension of delay length, not of stimulus duration. In contrast, the category boundary for facial expres