Laterality in Animals

Abstract

The International Journal of Comparative Psychology, Vol. 3, No. LATERALITY IN Fall 1989 ANIMALS Lesley University of We now know that laterality in various forms is Rogers England J. New a characteristic and that it apparently developed very early in evolution. Yet, some hundred years had to elapse after the discov- ery that there was lateralization, or asymmetry, for control of speech in the human brain, before any earnest attempts were made to dis- of a wide range of species, cover or recognise the presence of laterality in nonhuman species (see Robinson, Becker & Camp, 1983). The reason for this delay appears to have been the belief that lateralization of brain function was a char- to the human species, placing our species above all other species. This belief had been preceded by a well-developed mythology sur- rounding the sinistral-dextral dichotomy of handedness in humans acteristic unique (Corballis, 1983, pp. 1-9), and the belief that dextrality was also a uniquely human characteristic. It has been argued that shared tool use by humans caused laterality of limb use and, in turn, specializa- tion of the left hemisphere for language (Frost, 1980; Bradshaw & Nettleton, 1982). Thus, the population bias in handedness in humans was seen to be intimately related to our superior ability to use tools, and the pop- ulation bias in lateralization of function in the cerebral hemispheres was seen to be the basis of our superior ability for language. Not surprisingly, these unique attributes afforded to the human species were reluctantly relinquished by many psychologists, some (e.g. Levy, 1974, 1979) clinging to them well after lateralization of function in the nervous system had been clearly demonstrated in more than one nonhuman species, in particular for control of singing in song-birds (Nottebohm, 1971; see later). Address correspondence to Lesley J. Rogers, Physiology Department, University of England, Armidale, NSW 2351, Australia. New Human Sciences Press