Abstract # 114:

Scheduled for Saturday, August 26, 2017 03:15 PM-03:30 PM: (National Ballroom Salon A) Oral Presentation


IDENTIFYING DISTINGUISHING FEATURES OF PERCEPTUOMOTOR CONTROL OF STONE TOOLS IN HUMANS AND BEARDED CAPUCHIN MONKEYS

M. Mangalam, L. K. Roles and D. M. Fragaszy
University of Georgia, Department of Psychology, 125 Baldwin Street, Athens, Georgia 30602, USA
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     The manufacture of flaked stone tools from about 2.5 Mya profoundly altered the course of human evolution. We propose that differences in perceptuomotor cordination in humans compared to other primates contributed to this transition. In the present study, using kinematic analysis of video records, we compared patterns of variability in movements while cracking palm nuts (Astrocaryum spp.) among wild bearded capuchin monkeys, Sapajus libidinosus at Fazenda Boa Vista, Brazil, that routinely crack these nuts, and humans—novices (scientists) and experts (residents). The monkeys struck a nut repeatedly with consistent moderate force and consistent movements. The residents regulated their body movements after an initial strike and subsequently struck the nut with the kinetic energy adequate to crack it open in one or two more strikes. They showed the largest variability in movements. The scientists employed neither strategy. They produced an intermediate variability in movements and the largest variability in performance (all mentioned contrasts p < 0.05, mixed effect Poisson regression analyses). These results suggest humans regulate kinetic energy of the stone, an integrated property of the stone's mass and its velocity, whereas monkeys regulate amplitude and velocity of their strikes, which can be perceived through kinesthesis. Extending kinesthesis to include properties of objects in motion may have enabled our ancestors to discover effective movement solutions for knapping stones, and for other instrumental actions with objects.