HAPTIC DISCRIMINATION IN CAPUCHIN MONKEYS (CEBUS-APELLA) - EVIDENCE OF MANUAL SPECIALIZATION

Two experiments investigated the effects of haptic and visual discrimi nation on hand preference in 22 brown capuchin monkeys (Cebus apella). The percentage of left-handed subjects in Experiment 1 were 63.6%, 45 .5%, and 18.2% for haptic, bipedal, and quadrupedal reaching, respecti vely. In Experiment 2, the haptic demands of the task were manipulated by using additional food types and another tactile medium. Left-hand preferences were further strengthened when reaching into water compare d to pine-shavings in Experiment 1. Reaching with no tactile interfere nce resulted in equal numbers of lateralized and nonlateralized subjec ts. These results show that when reaching demands the use of haptic cu es, as opposed to visual ones, monkeys shift towards greater left hand use. This is consistent with what is known about right hemisphere sup eriority for haptic discrimination in humans. Copyright (C) 1996 Elsev ier Science Ltd.