Experience plays a crucial role for the normal development of many perceptual and cognitive functions, such as speech perception. For example, between 6 and 10 months of age, the infant's ability to discriminate among native speech sounds improves, whereas the ability to discriminate among foreign speech sounds declines. However, a recent investigation suggests that some experience with nonnative languages from 9 months of age facilitates the maintenance of this ability at 12 months. Nelson has suggested that the systems underlying face processing may be similarly sculpted by experience with different kinds of faces. In the current investigation, we demonstrate that, in human infants between 6 and 9 months of age, exposure to nonnative faces, in this case, faces of Barbary macaques (Macaca sylvanus), facilitates the discrimination of monkey faces, an ability that is otherwise lost around 9 months of age. These data support, and further elucidate, the role of early experience in the development of face processing.development ͉ early experience ͉ monkey ͉ recognition

Experience with certain types of faces during the first year of development defines which types of faces are more efficiently recognized later in life. In work described here, we found that infants who learned to recognize six monkey faces individually (i.e., each face was individually labeled) over a 3-month period maintained the ability to discriminate monkey faces. However, infants who learned these same six faces categorically (i.e., all faces were labeled "monkey") or were simply exposed to these faces (i.e., faces were not labeled) showed a decline in the ability to discriminate monkey faces. These results suggest that experience individuating faces from 6 to 9 months of age, via labeling, critically shapes the perceptual representation that is responsible for later recognition and discrimination of faces.