This paper offers a review of the literature on the role of imitation in the earliest stages of social interaction between babies and familiar partners. The review focuses on the ways in which reciprocal imitation marks familiar relationships that provide special contexts for babies to engage actively and exuberantly in the construction of a shared culture. Because adults' perception of a baby's actions and intentions are filtered by the adult's experience of living within a particular culture, babies can obtain valuable information about this culture from the differences between what they do and how familiar adults respond to them. As they become increasingly interested in the social meaning of people's behaviour, infants also become more sensitive about how their own actions may be interpreted, showing pride and delight when their intentions are realised and embarrassed withdrawal when their efforts fail. When very young children are observed in unfamiliar contexts and when they are cared for and educated in professional settings, they may have relatively few opportunities for lively, joyful exchanges with reassuringly familiar partners and this can distort adults' perceptions of "normal" infant behaviour. It is argued that adults' attentive interest in mutually enjoyable exchanges with young children is an important difference between humans and other apes and provides an essential foundation for pedagogy and for children's active participation in a shared culture.