Preparation for grasping an object: A developmental study.

• An optoelectronic technique (SELSPOT) was used to monitor the opening and closing of the hand during reaching actions by measuring the change in the distance between thumb and index finger. Exp 1 established an adult criterion for the development. Adults started closing the hand around the target well before touch, and the timing was dependent on the size of the target. The hand started to close earlier when grasping a small rather than a large target. In addition, the degree of hand opening was also less for a small than for a large target. In Exp 2, infants who were 5–6, 9, and 13 months of age also controlled their grasping actions visually and started closing the hand around the target in anticipation of the encounter rather than as a reaction to the encounter. The strategy of the two younger age groups was different from that of adults. They started closing the hand closer to the time of contact with the target than did the 13-month-olds, who were comparable to adults in this respect. In all age groups, reaching and grasping were most commonly organized in a continuous way; the hand started to close without any interruption in the approach. The opening of the hand was adjusted to target size in the 9- and 13-month-olds but not in the 5–6 month olds.

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Psychology

psykologi

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