The study attempted to reconstruct changes in naturalistic interactions between mother and child while children gained competence in three basic developmental tasks, namely, while they were learning to walk, eat, and dress themselves alone. Cross-sequentially organised observations focused on independent and dependent child behaviours and corresponding supportive mother reactions. At four measurement points across a period of 100 days, six children, two each at the age of 9, 12, and 21 months, were videotaped at home interacting with their mothers; at each point, mothers were interviewed about children's competencies. Changes in behaviour frequencies and interaction patterns were consistent with hypotheses that mothers adjust their socialising interactions to children's growing competencies in developmental tasks. Before tasks were begun, interactions could be characterised as nurturant (contingent maternal support for dependent behaviour only); when children were actively learning in a task, interactions evolved into complementary patterns (maternal support for both dependent and independent behaviours); and when competence was firmly established, mothers rarely showed contingent support for either dependent or independent task-related behaviours. The discussion contrasts processes of developmental change in socialising contexts with assumptions about the stability of childrearing practices.