AGE-RELATED DIFFERENCES IN PREHENSION - THE INFLUENCE OF TASK GOALS

A single study is reported in which the influence of age and task goal on reaching and grasping movements were examined. Ten young and 10 el derly subjects reached and grasped a disk (4.5-cm diameter) and then e ither (a) placed it in a well, (b) placed it in a box, or (c) threw it in a box, all located 30 cm to the left of the disk. The reach-to-gra sp movements were analyzed over two phases: the approach to capture th e disk and the transporting of the disk. Differential effects were obs erved over the two phases as a function of age. Over the approach, the movement times of the elderly subjects were comparable with those of the young subjects, but their relative deceleration and hand enclosing times took longer. During object transport, however, the elderly subj ects moved more slowly than the young subjects did, but there were no differences in relative timing. In both phases, the precision required of the task influenced the duration of movement and the relative timi ng of arm deceleration, suggesting that subjects accurately anticipate d the demands of the task. Those results, which are discussed in relat ion to hardware and software Limitations on performance, suggest that the age-related differences reflect changes in the use of software str ategies over the two phases of movement.