It is a widely held view that mother‐infant vocal engagements provide a foundation for children's development of communication and language abilities. In this paper we consider how the maternal covocalisation and alternating patterns of temporal dependence between the vocal behaviours of mothers and infants might facilitate such development. Two related issues are examined in relation to the choice of these patterns: first, the means by which temporal dependence is determined; second, the appropriateness of the selected units of analysis for the investigation of the effect of mothers' behaviour on infant communication development. Regarding the first of these issues, we propose that dependence between the actions of mothers and infants can be determined by a procedure which randomly permutes the behavioural records of both mother and infant. In considering the second, we use pragmatic and ecological criteria to evaluate units of analysis for the investigation of temporal patterning, and borrow the concepts ofaffordanceandencounterfrom ecological perspectives on human perception to examine the role of maternal behaviour in the emergence of communication and language abilities in infant