The perception of facial expressions by the three-month-old.

We used habituation to investigate 3-month-olds' abilities to discriminate and recognize smiling and frowning expressions posed by the mother or by a female stranger. Infants discriminated between the expressions and recognized which expression they had seen during the habituation trials; they did so whether the expressions were posed by the mother or by the stranger. However, when the expressions were posed by the mother, more infants showed the discrimination, and boys looked at her pictures longer than girls. These differences suggest that infants' previous experiences with faces influence their perceptions of the facial expressions.