Male and female faces are only perceived categorically when linked to familiar identities - And when in doubt, he is a male

Categorical perception (CP) is a fundamental cognitive process that enables us to sort similar objects in the world into meaningful categories with clear boundaries between them. CP has been found for high-level stimuli like human faces, more precisely, for the perception of face identity, expression and ethnicity. For sex however, which represents another important and biologically relevant dimension of human faces, results have been equivocal so far. Here, we reinvestigate CP for sex using newly created face stimuli to control two factors that to our opinion might have influenced the results in earlier studies. Our new stimuli are (a) derived from single face identities, so that changes of sex are not confounded with changes of identity information, and (b) “normalized” in their degree of maleness and femaleness, to counteract natural variations of perceived masculinity and femininity of faces that might obstruct evidence of categorical perception. Despite careful normalization, we did not find evidence of CP for sex using classical test procedures, unless participants were specifically familiarized with the face identities before testing. These results support the single-route hypothesis, stating that sex and identity information in faces are not processed in parallel, in contrast to what was suggested in the classical Bruce and Young model of face perception. Besides, interestingly, our participants show a consistent bias, before and after perceptual normalization of the male–female range of the test morph continua, to judge faces as male rather than female

A Familiarity Disadvantage for Remembering Specific Images of Faces

Familiar faces are remembered better than unfamiliar faces. Furthermore, it is much easier to match images of familiar than unfamiliar faces. These findings could be accounted for by quantitative differences in the ease with which faces are encoded. However, it has been argued that there are also some qualitative differences in familiar and unfamiliar face processing. Unfamiliar faces are held to rely on superficial, pictorial representations, whereas familiar faces invoke more abstract representations. Here we present 2 studies that show, for 1 task, an advantage for unfamiliar faces. In recognition memory, viewers are better able to reject a new picture, if it depicts an unfamiliar face. This rare advantage for unfamiliar faces supports the notion that familiarity brings about some representational changes, and further emphasizes the idea that theoretical accounts of face processing should incorporate familiarity. (PsycINFO Database Recor

The influence of familiarity on the neural coding of face sex

Foster C, Schultz J, Munzing M, Bülthoff I, Armann R. The influence of familiarity on the neural coding of face sex. bioRxiv. 2022.**Abstract** In behaviour, humans have been shown to represent the sex of faces categorically when the faces are familiar to them. This leads to them judging faces crossing the category boundary (i.e. from male to female) as more different than faces that are within the same category. In this study, we investigated how faces of different sexes are encoded in the brain, and how familiarity changes the neural coding of sex. We recorded participants’ brain activity using fMRI while they viewed both familiar and unfamiliar faces that were morphed in their sex characteristics (i.e. between male and female). Participants viewed pairs of faces that were either identical, or differed in their sex morph level, with or without a categorical change in perceived sex (i.e. crossing the perceived male/female category boundary). This allowed us to disentangle physical and categorical neural coding of face sex, and to investigate if neural coding of face categories was enhanced by face familiarity. Our results show that the sex of familiar, but not unfamiliar, faces was encoded categorically in the medial prefrontal and orbitofrontal cortex as well as in the right intraparietal sulcus. In contrast, the fusiform face area showed a sensitivity to the physical changes in the sex of faces that was unaffected by face familiarity. The occipital face area showed its highest responses to faces towards the ends of the sex morph continuum (i.e. the most male or most female faces), and these responses were also unaffected by face familiarity. These results suggest that there is a dissociation between the brain regions encoding physical and categorical representations of face sex, with occipital and fusiform face regions encoding physical face sex properties and frontal and parietal regions encoding high-level categorical face sex representations that are linked to face identity