Sensitivity to changes in identity, caricature and sex in face recognition

It is known that we are quite accurate at judging the sex of unfamiliar faces [1]. Furthermore sex categorization is performed more rapidly, on average, than familiarity or identity decisions [2]. In one of our recent studies on face perception, with unfamiliar faces [3] we were surprised to find that discrimination performance was much lower for faces differing in sex quality than when the facial features were morphed between two identities. Here, we investigated if this observation holds also for familiar faces. The motivation for this series of experiments was to find out if memory of familiar faces was showing similar differences; participants being more inaccurate when they had to remember the specific feminity or masculinity of a well known face than when identity-related changes of facial features were involved. Participants had to identify the veridical faces of familiar work colleagues among ten distractor faces that were morphing variations of the original faces. Distractor faces varied either in identity, caricature or sex. In the identity face sets, distractor faces were morphs between the original face and unfamiliar faces mixed in different proportions. In the caricature face sets, distractors were different caricatures of the original face. Finally, in the sex face sets, distractor faces were different feminized and masculinized versions of the veridical face. Participants performed best when the original face was presented among identity distractors. They had a tendency to choose feature enhancing caricatures over the original faces in caricature sets. Participants were very poor at finding the original faces in the sex sets. Generally our findings with unfamiliar faces show that sex-related changes in facial features are less obvious to the observers than identity-related changes. Furthermore our study on familiar faces suggests that we do not retain sex-related facial information in memory as accurately as identity-related information. These results have important implications for models of face recognition and how facial features are represented in the brain