Methodology of motor skill and laterality: New test of hand preference in Macaca nemestrina

Ten female pig-tailed macaques (Macaca nemestrina) were tested for hand pre ference and hand skill (i.e., speed of performance and error rate). The exp erimental task was naturalistic, calling for adaptive manual skills and fin e manipulation: the monkeys had to remove small food rewards embedded in a vertical array, and precision opposition of thumb and forefinger was needed to extract each pellet. Each monkey was tested 10 times on 10 different da ys. The results indicated individual hand preference rather than population -level handedness; however, a tendency toward right predominance was found. The results on hand skill showed a relation between error rate and hand pr eference, as the preferred hand made fewer errors. A different and unexpect ed finding was obtained when skill was evaluated in terms of speed of perfo rmance: in adult subjects the left hand was quicker than the right. Therefo re, different kinds of skill showed different patterns in relation to hand preference.