Hand Preference in the Use and Manufacture of Tools by Tufted Capuchin (Cebus apella) and Lion-Tailed Macaque (Macaca silenus ) Monkeys

The purpose of this study was to examine hand preference in the use and manufacture of probing tools by tufted capuchin and lion-tailed macaque monkeys ( Cebus apella and Macaca silenus ). Hand preference for the tool-using sequence was noted in 4 of 5 capuchins (a left-hand preference was noted in 3 ss) and 3 of 4 macaques (a left-hand preference was noted in 2 ss). The monkeys frequently used bimanual action in the initial and final segments of the 3-component task and typically modified tools through coordinated action of the hands and teeth. These data provide evidence consistent with the hypotheses that (a) hemisphere specialization for manual control evolved in primates prior to intensive use of tools by early hominids and (b) monkeys prefer the left hand for precise, visually guided, manipulative actions.