Hand preference in fast-moving versus slow-moving actions in capuchin, Sapajus spp., and squirrel monkeys, Saimiri sciureus

Among the many hand preference studies on nonhuman primates, several have demonstrated the effect of diverse action demands on the direction and magnitude of hand preference. However, few studies have assessed hand preference in the natural repertoire of motor behaviours in nonhuman primates, especially in actions that differ in velocity. Nevertheless, velocity is involved in the coordination between the upper limb joints and could be related to cerebral hemispheric specialization. Indeed, depending on the velocity, some joints, and so some muscles, are used more than others. The purpose of this study was to quantify hand preference across various natural actions to evaluate how the nature of the action modifies hand preference in capuchin and squirrel monkeys. First, we observed seven female tufted capuchin monkeys during spontaneous foraging, performing fast actions (pounding and capturing fast-moving prey) and slow actions (picking fruit, carrying, tapping and catching slow-moving prey). Second, we observed seven squirrel monkeys performing fast actions (capturing fast-moving prey) and slow actions (picking fruit and catching slow-moving prey) in their enclosure. The results showed that (1) capturing fast-moving prey and pounding were associated with a left-hand preference and (2) slow actions were associated with variable hand preferences. Fast manual actions may elicit consistent hand preference. Given that many nonhuman primates use fast actions to capture prey, this possibility deserves further investigation. If this finding is confirmed, a novel link between motor control processes and hand preference can be pursued.