Abstract
Visual adaptation offers a behavioural window into neural processes underlying a perceptual representation. Studies have demonstrated that adaptation changes the apparent duration of a subsequent sensory event, pointing to the involvement of sensory processing in duration perception. Here we demonstrate a novel adaptation effect where adaptation to a human face distorts the perceived duration of a subsequent face in different categories but not that of another human face. In Experiment 1, participants compared the duration of a comparison against a standard face after a 2100-ms adaptation period. The adaption and the standard stimuli were the same human face, and the comparison stimuli were other faces of human, monkey, or cat. The results showed that the monkey comparison faces and the cat comparison faces were perceived as longer in duration than the human comparison faces, suggesting the face category specificity in the adaptation-based duration distortion. Experiment 2 demonstrated that the adaptation effect of face category on perceived duration was eliminated when the adaption stimulus was rendered unrecognisable by phase-scrambling. This suggests the involvement of configural information in the adaptation effect. Experiment 3 revealed that the category-based adaptation effect persisted for at least 1000-ms after the adaptation stimulus disappeared. This may imply that the category-based face adaptation is based on cognitive processes higher than simple sensory processes. Our results point to the possibility that the adaptation-based duration distortion may involves not only sensory processing but also categorical processing at higher visual stages.