Following repeated exposure to faces with contracted (or expanded) internal features, faces previously perceived as normal appear distorted in the opposite direction. These face aftereffects suggest that face-coding mechanisms adapt rapidly to changes in the configuration of the face. Past work with young adults has suggested that distinct coding mechanisms respond to faces that differ in orientation, gender, race, and eye gaze direction. The first aim of the present work was to determine whether coding of faces from different age categories (young and older adults) shows similar selectivity. Given evidence for age-related changes in face recognition, emotional expression recognition and configural information processing, we also tested aftereffects in older adults. Before and after an adaptation phase, participants rated the normality of morphed distorted faces ranging from 50% contracted through normal to 50% expanded. These test faces depicted young (18-32 years) and older (64+ years) individuals matched for distinctiveness and presented in equal numbers. In the adaptation phase, participants viewed either young or older faces with 60% contracted features. The size of the adapt and test faces was varied. For young participants (18-23 years), aftereffects occurred in all conditions but were significantly reduced when the age of the adapting face and test faces differed. These findings suggest that dissociable neural populations code young and older faces. For older adults (60-83 years), a different pattern of aftereffects was observed. When older adults were adapted to older faces, a significant aftereffect occurred with older but not young test faces, consistent with the age-contingent aftereffects observed with young adults. However, after adapting to young faces, older adults showed significant aftereffects of equal magnitude for young and older test faces. These findings suggest that changes in the perceptual or neural mechanisms that code faces take place as a function of the aging process.
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