Perceptual Narrowing in Face Processing: Reviewing the Factors Influencing its Onset and Offset

An infant's face- and speech-processing system develops during the first year from broad and non-specific to becoming a system that is tuned to the faces and languages to which they are most exposed. This phenomenon is called perceptual narrowing. Before 9 months of age, infants are capable of discriminating and recognizing individuals from any type of race/species faces. However, with increased exposure to own-race and own-species faces and lack of exposure to other types of faces, by 9 months of age, they have improved their ability to discriminate own-race faces, while they show increased difficulty in the discrimination of faces from other races and species. According to the literature, we can conclude that, by 12 months of age, most human perceptual systems have become perceptually tuned and adult-like; however, this is not true. In the following sections, we will argue that perceptual narrowing for faces occurs during the same developmental period as it does for language, and that it can be prevented or modulated with sufficient exposure to unfamiliar sounds or face types. We conclude that narrowing has been designed by natural selection to tailor an individual's cognition to their local social context. It might occur for every domain pertaining to social communication-from speech processing to emotion or gesture perception-in a process that gradually adapts the infant to their native social group.