Prehension in infant capuchins (Cebus apella) from six weeks to twenty-four weeks: video analysis of form and symmetry.

We analyzed the spontaneous prehensile activity of two infants living with their mothers in social groups, using videotapes taken once weekly from weeks 5 to 24. Prehensile activities were laterally symmetric. Unimanual activity predominated, although bimanual activity appeared at the same ages as unimanual activity. In most bimanual activity the two hands performed the same action, but complementary actions occurred from the onset of bimanual activity. Extrusion of the tongue towards objects out of reach was observed occasionally, as was precision grasping. Early prehension in capuchins is organized, as in human infants, in a matrix of exploratory activity integrated with vision and oral exploration. Capuchins present a useful model system for the study of manipulative development.