EFFECTS OF UPRIGHT POSTURE ON HAND PREFERENCE FOR REACHING VS. THE USE OF PROBING TOOLS BY TUFTED CAPUCHINS (CEBUS-APELLA)

This research examined the effects of task (reaching vs. tool use) and posture (quadrupedal vs. bipedal) on hand preference in tufted capuch ins (Cebus apella). Regarding direction of hand preference, we found a significant main effect of posture, as the bipedal stance elicited gr eater use of the right hand than did the quadrupedal stance, and a sig nificant posture x task interaction, as bipedal reaching elicited grea ter use of the right hand than did other postural and task conditions. Further, we found a significant main effect of task on strength of ha nd preference, as tool use elicited more consistent use of one hand ov er the other than did reaching. Our findings indicate that bipedal rea ching facilitates a mild right-hand bias in intensely manipulative pri mates. We speculate that this moderate bias may have been pushed in th e direction of nearly exclusive right-hand preference in most humans w ith the development of complex tool use. (C) 1998 Wiley-Liss, Inc.dagg er.