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Deacon, T. W. (1999) Chapter 13: Language evolution and neuromechanisms. In A Companion to Cognitive Science, Bechtel, W. & Graham, G. (eds) Blackwell, Malden MA.

Author of the summary: Debajyoti Pati, 2000, gte811q@prism.gatech.edu

The idea that the structure of the human brain is somehow linked to language abilities first evolved from observations where damage to certain parts of the brain resulted in the impairment of certain language abilities. The findings of Paul Broca (1861) and Carl Wernicke (1874) were the pioneering ones which led to further research in this area. The classical approach identified language processing centers (with links) and higher cortical centers in the brain, which they ascribed solely to language processing abilities. Contemporary theories, while retaining some of the original thoughts, have come up with explanations where they rejected the ideal of language centers, and hypothesized on more distributed functional locations within the brain which might be doing more activities besides language processing. Some of the major findings in this area comes from electrical cortical stimulation, and neuroimaging. In the former, low-level electrical stimulation is introduced on exposed cortical surfaces. The latter process involves sending signals which reflect relative metabolic demands of various areas. The major finding is that language tasks involves the coordinated involvement of multiple brain systems (as opposed to language centers in the classical theory). Also, there seem to be considerable differences based on individual"s attributes including sex and the language spoken.

It is, however, agreed by all that the human language processing abilities are unique. While many species demonstrate certain language functions, the uniqueness of human beings arise form the complications involved in language communication, which is dependent on associations between sound, meanings, and referents. This uniqueness has been attempted to be explained through several hypothesis. One hypothesis explains the difference through greater general intelligence of human beings. They rely on evidence that the human brain has increased considerably in size over 2 million years, and argue that theories on language specialization of brains are not necessary for explaining the difference. A second theory challenges the intelligence theory by arguing that languages are too complex to be acquired by general learning processes. They believe in the existence of innate language templates which helps human beings to learn language (faster than any other skill). They show the examples of instinct in other species to bolster their argument. A third hypothesis bases its arguments on the uniqueness of the vocal skill and the descent of the larynx, but not many strong evidences are available to support it. A fourth hypothesis points out to the of the symbolic aspects of human language, and makes that assertion that it is this system which accounts for the uniqueness of language.

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