Categorical perception of unfamiliar facial identities, the face-space metaphor, and the morphing technique

Abstract

Categorization is a fundamental property of the human brain. We used an image-morphing procedure to investigate the categorical perception of unfamiliar and familiar facial identities. Two delayed matching tasks are reported here. First, independently of face familiarity, subjects discriminate more easily two different morphed faces belonging to two different identities than two different morphed faces belonging to the same one, even if the physical distance within the pairs is identical. Second, this holds on only when faces are upright. The results are interpreted in terms of how representations of faces are encoded and stored in long-term memory. The inability of the face-space metaphor, developed by Valentine (1991), is discussed. An alternative explanation, based on the morphing characteristics and the concept of typicality, is proposed.