Verbal regulation of grip force in preschoolers.

The purpose of this study was to clarify the developmental processes in verbal regulation by preschool children. Participants were 152 typically developing children (74 boys, 78 girls) between 4 and 6 years of age (M = 5.3, SD = .8), and 30 healthy adults (15 men, 15 women) between 19 and 26 years of age (M = 20.8, SD = 1.4). In Exp. 1, the task was to regulate grip force based on quantitative instruction which implies using a scale for regulation. Participants were required to produce a half-grip force of the maximum (Task 1). In Exp. 2, the task was grip-force regulation based on nonquantitative instruction. The participants were asked to respond with a slightly weaker grip force than the maximum (Task 2) and then a further weaker grip force (Task 3) than that used on Task 2. The regulation rates produced the extent of regulation and suggest regulation by quantitative instruction may develop earlier than by nonquantitative instruction. Also, precise grip-force regulation based on the semantic aspect of instruction may be difficult for young children. The developmental changes in the rate of performance especially observed in children of 4 to 6 years indicate that the tendency to use too much grip force disappears during this preschool period. In addition, too little grip force in regulation may reflect the developmental process toward fine grasping movements.