Neural Correlates of Face Processing: Perceptual Narrowing and Categorization

Perceptual narrowing is a developmental process that occurs between 6 and 9 months of age, during which infants transition from having more general perceptual abilities to more specific abilities. An example of this would be the other-species effect, in which infants experience a decline in the ability to individuate other species’ faces. It has been suggested that an infant’s growing ability to categorize could lead to a decline in their ability to discern individuals within other-species groups (Scott & Monesson, 2009), and that this difference is related to processing styles. In this study, 9-month-old infants were tested on their subordinate-level categorization ability with different species of monkey faces. Subordinate-level categorization is categorization on the species level. ERP data was recorded while the infants were shown presentations of the novel face/familiar species category and the novel face/novel species category after being familiarized to either a single face or a group of exemplars. It was predicted that the 9-month-olds in the categorization group would have a greater amplitude ERP response, namely the P400 component, to the Novel Other face category versus the Novel Same and Familiar face categories. This would provide evidence that infants at this age are not processing individual faces from other-species but are categorizing other species faces. It was also predicted that there would be differences in the Nc component between groups based on condition type. It was found that the categorization group showed an ability to categorize the monkey faces by species, as shown by a larger amplitude Nc and P400 for the Novel Other face category, whereas the individuation group did not. These findings add support to the idea that subordinate-level categorization could be a mechanism behind the effects seen from perceptual narrowing of other-species faces.