Predictions about the role of contingency, imitation, and affect sharing in the development of social awareness were tested in infants during natural, imitative, and yoked conditions with their mothers at 5 and 13 weeks of age. Results showed that at both ages, infants of highly attuned mothers gazed, smiled, and vocalized positively more during the natural than during the imitative and yoked conditions, whereas they increased negative vocalizations during the yoked conditions. In contrast, infants of less attuned mothers did not differentiate between the conditions, except at 13 weeks when these infants increased their gazes during the imitative condition. Whereas contingency and imitation draw infant attention to conspecifics, affective communication appears to lay the foundation for infants' social awareness.