Neural Correlates of Individuation and Subordinate-Level Categorization of Other-Race Faces in Infancy

Perceptual narrowing is a domain-general process in which infants move from a broad sensitivity to a wide range of stimuli to developing expertise within often experienced native stimuli (Maurer & Werker, 2014). One outcome of this is the own-race bias, characterized by an increasing difficulty in discriminating other-race faces with age and experience for those raised in a racially homogenous environment (Anzures, Quinn, Pascalis, Slater, Tanaka, & Lee, 2013). Recent theorists have proposed that this is due to a categorization-individuation process, wherein infants begin to categorize non-native stimuli, such as other-species’ faces, but individuate native stimuli, such as often-experienced human faces (Hugenberg, Young, Bernstein, & Sacco, 2010; Nelson, 2001; Reynolds & Roth, 2018). Previous work has shown that exposure to multiple exemplars during initial learning facilitates categorization of other-species faces while exposure to a single exemplar does not (Dixon, Reynolds, Romano, Roth, Stumpe, Guy, & Mosteller, 2019). The goal of this study was to investigate the effects of initial learning conditions on infants’ ability to individuate and categorize own- and other-race faces. Ten-month-old infants were familiarized with either a single exemplar or multiple exemplars of either own- or other-race faces. Event-related potentials (ERP) were recorded while infants were presented with the familiar face(s) they were exposed to during familiarization, a novel face from the same race used during familiarization, and a novel face from a race other than the one used in familiarization. Infants familiarized with a single face, either own-race or other-race, were able to discriminate between faces at the categorical level of race, but not at an individual level. Infants familiarized with multiple exemplars failed to discriminate at the categorical or individual level, regardless of race. Results suggest that in contrast to other-species faces, infants at this age may be focused on individuating own-species faces, regardless of race. The implications of the current findings are discussed in relation to the impact of initial learning conditions on infants’ ability to individuate and categorize own- and other-species faces, the developmental timeline of own-species face processing, and social implications of infants’ and older children’s processing of other-race faces.