Linguistic Development Research Paper Page 10
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374 WHAT IS IT THAT DEVELOPS?
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to tell us anything about the developmental processes in the areas that they scan. Many of the
discussions in this section will thus be either rather imprecise or the result of inference.
The key questions of this section are about the parts of the brain that are used in language, and how
they relate to other cognitive process. It also discusses the difficulties of trying to pin functionality
down to one area. For instance, Broca’s area, has been long associated with the muscular control
of speech processes. But before the turn of this century it was also said that if Broca’s region was
damaged all that we could conclude was that speech articulation was lost. It did not mean that
Broca’s region was doing the control, but only that Broca’s region was critical to the process of
articulation.
Our understanding of the distributed representation scheme used by neural networks only confirms
the above caution. If a single line of code is removed from a speech recognition program the whole
thing is likely to crash, but that does not mean that that line alone was responsible for speech
recognition, only that it was involved in the process.
How is the relationship defined between the complex symbolic system of language and the even more
complex biological structure of the brain? Most evidence for the relationship has been inferred from
language disorders caused by focal lesions on the brain, and other experimental techniques such as
brain scanning and dichotic listening tests. The bulk of the data is still gained from pathological
clinical cases to this day. The cautionary note raised above applies to such diagnostic techniques.
The study of the relationship assumes some knowledge of both the brain and language. How do we
define an adequate level of description for the knowledge that we have gained? Language implies a
complex set of mental processes such as the following:
1. Extraction of meaning from words and sentences.
2. Recalling verbal symbols from memory.
3. Associating verbal symbols with referents.
4. Organizing sentences that convey specific meaning and that follow prescribed syntactic orders,
and precise phonological rules etc.
In all of the processes the brain is equally engaged, but not necessarily in the same way. Brain scans
showing blood flow in an area, shows that there is more blood flow in the left hemisphere of the
brain during the execution of speech acts. Moreover the resolution is such that areas such as Broca’s
and Wernicke’s have been shown at work. The scanners do not show what part in the process each
patch plays.
The knowledge and functionality in the brain is often smeared out across a large patch of neurons.
Although neurons are located in different areas of the brain, their excision may cause equal damage
to a specific language function. Thus it is not necessarily possible to say that the functionality is
located in any one place. Given that there is no logical necessity for there to be any direct physical
counterpart to such grammatical rules as might be found in the formal description of grammar, it
is not necessary that the rules have direct psycho-biological reality.
For example, in Chomsky’s analysis of grammar, a speaker and hearer are mirror images of each
other. Generative grammar is the logical inverse of the comprehension process. Within the biological
reality there are distinctly different requirements of the systems. Thus there can be no biological
symmetry. The high degree of redundancy in spoken language allows for a certain amount of
imprecision within the decoding process. Such guesswork and filling-in does not prevent successful
comprehension. More precision is required in the production of sentences. It is necessary for us to
draw a distinction between the central cognitive processes behind the formulation of utterances and
the mode and method of communication whereby they get expressed and decoded.
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