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Regarding the Neural Plasticity thread, we should agree
with Pinker's comment that neural plasticity does not
refute evolutionary psychology, in particular in relation
with language mechanisms. However, it makes a case
to raise some serious suspicions about some of its
fundamental tenets.

The first point is about the concept of plasticity itself.
While learning can be said to be subsumed by plasticity,
the opposite is not correct. Plasticity denotes at least
two processes: a) the increase or decrease in synaptic
efficacy and b) the growth of new synaptic connections
(axonal and dendritic growth).

While item a) can be said to be directly associated with
learning in the usual sense, item b) reflects a more profound
reorganization of the brain. It is the latter that must
be seen as impacting the emergence of language in humans.

It is known that language learning is a process that is
more efficient in children than in adults. It may be just
a coincidence, but exactly during childhood, plasticity
(the item b aspect) is at its peek. The coincidence is
further supplemented by other evidences.

Proponents of genetically determined and domain-specific
language organs should, then, try to explain what happens
with hemispherectomy. Adults with serious epileptic seizures
often are submitted to the removal of one of the brain's
hemispheres. When the hemisphere is the left, adults are
significantly language-impaired, showing only mild recovery
during the following years, and at the expense of intense
retraining. When this operation is performed on children
with similar epileptic problems, they are able to develop
their language abilities to an almost normal
state ([1], [2], [3]).

Again, this does not demonstrate that there isn't any
genetically determined mechanism for language, but it
gives weight to other hypotheses that face the brain as
a self-organizing and adaptable mechanism, ready from
childhood to construct impressive perceptual structures
from everything that is captured by the senses.

What appears to be the difficult idea to sustain is
the domain-specificity of any genetically determined
mechanism, related only with linguistic abilities.


[1] Stark, R. E. et. al (1995) Speech-Language Outcomes
of Hemispherectomy in Children and Young Adults", Brain
and Language 51: 406-421

[2] Deutsch, George and Springer, Sally (1997) Left Brain,
Right Brain, Perspectives from Cognitive Neuroscience, W. H.
Freeman and Company, NY.

[3] Kolb, Brian (1995) Brain Plasticity and Behavior, Lawrence
Erlbaum Assoc.

Sergio Navega
Intelliwise Research

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