How do babies know their friends and foes?

The study of infant social cognition is the study of how human infants acquire information about people. By examining infants' sensory abilities and the stimulus characteristics of people, research can determine what information is available to infants from their social world. We can then consider what social environments are appropriate for infants of different ages. This paper examines the sociocognitive competencies of human infants during the first 6 months of their lives and asks how these competencies are functional in the daily social ecology of the human infant. Select examples of research with other species are used to illustrate how the adaptive significance of sociocognitive abilities could be more fruitfully explored in studies of human infancy.