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Abstract
During the first six months of life, infants are able to make fine distinctions in a broad range of stimuli. Between six and nine months of age, however, infants abilities to identify subtle differences in irrelevant stimuli decline, while improve upon their abilities to distinguish between socially relevant stimuli. This phenomenon can be observed in regard to speech (the ability to discriminate native vs. non-native phonemes), identity discrimination (the ability to discriminate faces of ones own species and race vs. faces of other species and races), and a variety of other perceptual schemas. Following this pattern, six month old humans are able to discriminate equally among human faces and Tonkean macaque monkey (Macaca fuscata) faces, whereas nine month olds have reduced abilities to discriminate macaque monkey faces and enhanced abilities in discrimination of human faces. The purpose of this study was to test the same phenomenon using a phylogenetically more distant species of monkey: capuchin monkeys (Cebus apella). We took advantage of infants preference for novel stimuli to determine how quickly infants are able to recognize a familiar face and distinguish it from unfamiliar faces. Our results were in agreement with the claim that younger infants are able to discriminate capuchin monkey faces more quickly than older infants and adults can.