Spontaneous hand usage and handedness in a troop of baboons

Hand usage was studied in a troop of 18 Guinea baboons (10 adults and 8 young) for spontaneous activities. Handedness was determined by an analysis of unimanual activities and bimanual asymmetric activities. The distribution of preferential biases gave 5 right-handers and 2 left-handers, other subjects being ambidextrous. Main effects were age related: the strength of the preference was greater for adults than for young; moreover, bimanual activities performed by the adult group were more asymmetric than those realized by the subgroup of young. Laterality thus appears to develop during ontogeny in baboons.