Effects of multiple planning constraints on the development of grasp posture planning in 6- to 10-year-old children.

This experiment examined how multiple planning constraints affect grasp posture planning in 6- to 10-year-old children (n = 16 in each group) by manipulating the intended object end-orientation (left end-down, right end-down) and initial precision demands (standard, initial precision) of a bar transport task. Results indicated that grasp posture planning was strongly influenced by multiple planning constraints. During the standard condition the sensitivity toward comfortable final hand postures (end-state comfort) was similar for all age groups in right end-down trials, and corresponded to values reported in adult populations. In contrast, there was an age-related increase in end-state comfort compliance during left end-down trials. During the initial precision condition end-state comfort was similar across all groups for left end-down trials. However, end-state comfort compliance was significantly lower for the 6-year-old children than in all other age groups for right end-down trials. In sum, the ability of children to plan their goal-related movements is influenced by the presence of task-related constraints that increase the overall cognitive demands of the task. The demands associated with selecting the appropriate grasp posture during the most cognitive demanding condition required more cognitive resources than 6- to 10-year-old children possess. Removing the conflict between the goal-directed and habitual systems reduces some of these costs, with data indicating that the ability to integrate multiple planning constraints first emerges at 7 years of age, and improves over the developmental spectrum.