Maternal responsive-didactic caregiving (RDC) and infant advanced object play were investigated in a sample of 400 mothers and their 10-month-old infants during video-recorded semi-structured play interactions. Three maternal behaviours: contingent response, cognitively stimulating language and autonomy-promoting speech were coded and infant object play. Factor analysis confirmed the three maternal behaviours loaded onto one underlying factor, labelled RDC. Based on ecological and transactional theories of development, associations between RDC and infant (advanced object play), maternal (age, education, ethnicity and first language) and family (size and home adversity) factors were investigated. Multiple regressions (1) explored the predictors of maternal RDC and (2) tested the possible role of maternal RDC in predicting infant intellectual development at 18 months. At 10 months, infants showing higher levels of play maturity experienced more maternal responsive and didactic feedback. All mother and family characteristics predicted variations in maternal RDC. Predicting 18-month cognitive development, RDC had significant effect over and above maternal education, home adversity and infant play. Mother's first language remained significant, reflecting that RDC, in this investigation, relies heavily on language input. The findings highlight the importance of both contingent response and didactic contributions in interactions to subsequent cognitive development as early as the first year.