Learning Tool Use: Body Scheme Recalibration and the Development of Hand Skill

Abstract

Skill at using tools depends on somatosensory and visual information being integrated into a body schema. “Calibration,” defined as the ability to accurately localize a limb in space, and “recalibration,” the ability to accurately localize a limb plus tool in space, are proposed as intermediate stages between the development of manipulative prehension and the acquisition of skilled tool usage. Each of these depends upon body scheme information. The ability to recalibrate muscular output for different weights and lengths of tools was investigated. It was hypothesized that such recalibration is an intermediate stage of skill that should be developed prior to extensive practice with tools themselves. A total of 48 normal children, ranging in age from 4.0 to 8.11 years, served as subjects. Test instruments included the Southern California Motor Accuracy Test (MAC) and three tests of recalibration skills. These three tests involved touching a target with the tip of the index finger and with the tips of both a short and a long tool. Results were as hypothesized. Older children performed significantly better than younger children on all tests of hand and tool skill. Ability to use a tool appears to increase with increased ability to recalibrate. Skill in using the hand as a tool appears to develop earlier than skill in recalibrating for short / light tools, which precedes skill at recalibrating for longer / heavier tools.