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.