HAND PREFERENCE IN INFANT RHESUS MACAQUES (MACACA-MULATTA)

In this research we examined hand preference in infant rhesus macaques (Macaca mulatta). The subjects were 20 Macaca mulatta, each aged betw een 4 and 11 months. We assessed hand preference using both a unimanua l reaching task and a bimanual coordination task. In the unimanual rea ching task, we presented subjects with raisins and noted which hand th e animals used to retrieve the food. In the bimanual coordination task , we presented the same subjects with plastic tubes filled with raisin paste and noted which hand the animals used to hold the tubes and whi ch hand the animals used to remove the food. We noted a population-lev el bias toward use of the left hand for both tasks. These results sugg est early right hemisphere advantage for reaching and bimanual coordin ation in Macaca mulatta, although we acknowledge that this issue needs to be examined more directly through neuroimaging procedures such as Positron Emission Tomography (PET) or functional Magnetic Resonance im aging (fMRI). We speculate that early right hemisphere advantage contr ibutes to differential patterns of hand preference development for uni manual and bimanual action, and Mat the development of hand preference for bimanual coordination is related to the emergence of hemispheric specialization for processing species-specific vocalizations.