Parent-child mutually responsive, binding, reciprocal orientation, or a system of reciprocity has been implicated as fundamental in socialization, particularly by Maccoby, but it remains poorly understood. In this study, two posited components of such orientation, mother-child shared cooperation with each other and mother-child shared positive affect, were measured in multiple contexts of daily interactions using a combination of micro- and macroscopic behavioral coding systems, and subsequently aggregated. Mothers’ self-reports were also used. Two implications of thus conceptualized mutually responsive orientation were examined: mothers’ use of power in disciplinary interactions and children’s degree of internalization of maternal rules, both assessed using multiple observational and mother-reported measures. Mothers and children were studied twice, when children were 26-41 months (Time 1, N = 103), and when they were 43-56 months (Time 2, N = 99). In the dyads high on the mutually responsive orientation (particularly those who maintained such orientation throughout early childhood), mothers resorted to less power and children were more internalized regarding maternal values and rules, in the contemporaneous and longitudinal sense. Mothers high on empathic perspective taking were more likely to establish a system of reciprocity with their children. The importance of such systems for social development is discussed.