November 6 Elizabeth Bates, UCSD Cognitive Science
A new View of Language Evolution (If That's Possible)
The term "phrenology" refers to Franz Gall's 18th century theory of human brain organization, in which each cognitive or moral faculty (from benevolence to music to language) was attributed to a distinct, dedicated area in the brain. This seductive notion is still with us, reappearing continually on book jackets and the Science pages of the NY Times. It is an easy way to think about brain organization for higher human faculties, and it has become the public¹s first way of trying to understand findings using new neural imaging techniques. However, several converging lines of evidence challenge the notion of an innate, fixed and localized "mental organ" for language. First, studies of children with early focal brain injury demonstrate that brain organization for language is highly plastic: these children develop alternative neural systems that sustain language abilities well within the normal range, and are equally good following left or right hemisphere damage. Second, cross-linguistic studies of adult patients with aphasia demonstrate that extraordinarily detailed, language-specific knowledge is retained despite their impairments in real-time use of that knowledge ("It is hard to take the Turkish out of the Turk, and the English out of the Englishman"). These results demonstrate that brain organization for language in normal adults is highly distributed. Third, studies using functional brain imaging techniques indicate that language is handled in many different areas of the brain, and that profiles of activation change markedly in accord with changes in the task, and the subject's expertise in that task. All of these results suggest that language is superimposed (through evolution and development) on neural tissue that also carries out phylogenetically ancient non-linguistic functions. Furthermore, the system can be configured in a number of different ways. This dynamic, plastic and distributed view of brain organization for language is much more compatible than the phrenological view with new findings in developmental neurobiology, and with our current understanding of how genes contribute to the construction of bodies and brains. I end by sketching out an alternative approach to the evolution and development of language, based on selection for cognitive and social 'infrastructure', functions that are not unique language or to humans, but have been quantitatively tuned in humans to make language, culture and technology possible.