Preliminary quantitative studies of prehension in squirrel monkeys (Saimiri sciureus).

Squirrel monkeys were filmed in the act of prehending objects of various sizes, shapes, and states of motion. Subsequent three-dimensional analyses indicated that general aspects of prehension do not vary grossly across individuals nor as a function of the object to be prehended, at least at the level of measurement used in these studies. The monkeys exhibited only whole-hand control, even with small or moving objects. However, in comparison with stationary objects, moving objects did elicit variations of arm and hand positions, and were associated with higher frequencies of blinking than nonmoving objects. Some stationary objects also elicited subtle adjustments of movement and form. Sex differences were found in several aspects of prehensive movement and passive joint mobility, but the significance of these findings is not yet clear.