Opposite Hand Preferences in Two Sense-modalities

Abstract

HAND preferences have been recorded for 137 of the 150 monkeys used in behaviour experiments during 1958 to 1968. Eighty-seven of the 137 monkeys, however, were trained to make discriminations only in one sense-modality, or else were insufficiently assessed for hand preferences in two modalities. The following conditions obtain for all the remaining fifty monkeys: (1) no account was taken of an animal's first discrimination task (for which hand preferences tend to be atypical) unless the learning score exceeded five hundred trials; (2) treating the first task as described, discriminations were learnt at least twice in each of two sense-modalities (by thirty-nine monkeys through vision and touch, by eleven through vision and hearing); (3) hand preferences were systematically assessed during criterion performance on at least four training periods, distributed as described. Of the fifty monkeys adequately assessed in two sense-modalities thirty-eight preferred the same hand in both modalities, and (discounting the first task) eight changed preference within one or both modalities. The remaining four animals (that is, 8 per cent) showed regular alternations of preferences with change of modality from touch to vision. These alternations were to some extent transient in two, but have persisted unchanged in the other two monkeys.