Brain Laterality in Signed and Spoken Language: A Synthetic Theory of Language Use

Abstract

First, the hypothesis is examined that right hemispheric cognitive processes underlie human language in a fundamental way, and specifically, that the right hemisphere is implicated in the semantic processes underlying the establishment of meaning and in processing of linguistic “gestalts” generally. In this respect, several lines of evidence are examined, including the performance of aphasics, commisurotomy patients, native deaf signers, and users of Japanese and Chinese ideographs. A right hemispheric basis for various aspects of language use having been established, a second hypothesis is examined: that differences in societal complexity are related to differences in relative dependence upon cognitive processes controlled by the right and the left cerebral hemispheres. More specifically, we examine the hypothesis that growth in societal complexity has been accompanied by increased dependence upon left hemisphere processes. We present quantitative evidence from studies of differences in language structure to support the hypothesis. More broadly, what we are attempting here is to construct a synthetic theory of language use that incorporates information from the neurological and the social sciences.