Children's self-control behavior in motor and cognitive tasks was examined in a series of two studies in which modeling and self-regulatory mechanisms were varied to assess the influence of each. In the first study, 6-, 7-, 9-, and 11-year-old children individually played a 20-trial game of 'Simon Says' (involving activation and inhibition trials) with a male model who (1) conducted the game in the traditional manner, (2) introduced the sanction, "Don't", on the inhibition trials, (3) performed an action that differed from the instructions, or (4) gave instructions only without action. Results indicated that activation latency and inhibition errors were influenced by age of the child and self-control condition. Activation errors also were affected by self-control condition, but not by age. The same motor self-control task ("Simon Says") and a cognitive task (picture arrangement) were used as performance measures in a second study with children aged 5, 7, and 9 who were assigned to one of three self-regulation conditions (external control, cognitive modeling, or self-reinforcement) or a control condition. For the motor task of "Simon Says", activation latency, activation errors, and inhibition errors decreased across age. Inhibition errors also were influenced by the specific self-regulation treatment. Solution times and accuracy scores for the cognitive self-control task improved with age and were influenced somewhat by self-regulatory mechanisms. Age similarities across self-control tasks seemed to fit the notion of a developmental function. Differential effects of the self regulatory mechanisms are discussed in the context of cognitive and behavioral competencies. (Author/MS)