Between-species variation in the development of hand preference among macaques

This research examined between-species variation in the development of hand preference among Macaca. Specifically, we examined hand preference using j uveniles and adults of three macaque species that differ in social and reac tive tendencies in order to examine whether the correlation between tempera ment and handedness that has been noted within Macaca mulatta occurs betwee n closely related species. Each of the species studied exhibited a differen t pattern of hand preference development. Both juvenile and adult M. mulatt a exhibited group-level left-hand bias. Juvenile Macaca nemestrina were not biased towards either hand at the group-level, whereas adults exhibited a group-level left-hand bias. Neither juvenile nor adult Macaca fascicularis exhibited manual bias at the group-level. Analysis of variance indicated st atistically significant main effects of species and age class on hand prefe rence measures. Post-hoc analysis indicated greater use of the left- versus right-hand, and greater hand preference strength independent of direction, among M. mulatta and M. nemestrina than among Af. fascicularis, and among adults than among juveniles. These results indicate significant between-spe cies variation in the development of hand preference within the genus Macac a, and are inconsistent with any one single-factor theory yet offered to ex plain the etiology of primate laterality. We hypothesize that the relations hip between handedness and temperament that has been shown within M. mulatt a may generalize across closely related primate species. (C) 2001 Elsevier Science Ltd. All rights reserved.