Face perception in monkeys reared with no exposure to faces

TLDR

Infants were raised without face exposure for 6–24 months, then given a month of exposure to either human or monkey faces. Even without prior exposure, the monkeys preferred and could discriminate both human and monkey faces, but after a month of exposure they only discriminated the familiar species and struggled with the other, demonstrating an innate face‑processing ability and a sensitive period for prototype refinement.

Abstract

Infant monkeys were reared with no exposure to any faces for 6-24 months. Before being allowed to see a face, the monkeys showed a preference for human and monkey faces in photographs, and they discriminated human faces as well as monkey faces. After the deprivation period, the monkeys were exposed first to either human or monkey faces for a month. Soon after, the monkeys selectively discriminated the exposed species of face and showed a marked difficulty in regaining the ability to discriminate the other nonexposed species of face. These results indicate the existence of an experience-independent ability for face processing as well as an apparent sensitive period during which a broad but flexible face prototype develops into a concrete one for efficient processing of familiar faces.