Sex Differences in Early Infancy

Sex-linked behaviors in infancy have generated a great deal of interest, in part because they offer a way of assessing the extent to which sexually dimorphic behaviors exist before extensive social and educational experiences. This article reviews sex differences in basic and sensory processes, social behavior, and cognitive behavior that have been reported during the 1st year of life, and discusses current knowledge about the underlying basis for these differences and the extent to which they contribute to later behavior. Careful investigation of the interaction between social and biological factors in infancy will be necessary to fully understand the nature and development of human sex differences.