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Among
the many puzzles that language presents to the developmental psychologist,
perhaps
the most fascinating is the relative ease with which a toddler picks up
a first
language.
Although infants know nothing of the rules of grammar and have only a
fragmentary
understanding of the physical and social world, they are able to master
the
core
structures of language by the age of three. The ease with which children
master their
first
language contrasts with the more painful and incomplete process of learning
a second
language
in adulthood.
My
approach to this problem views language acquisition as an emergent process.
Eschewing
the traditional opposition betwee nativism and empiricism, I believe that
we
can
better understand language learning as a process grounded on competitive
Darwinian
processes
that operate across a variety of time scales, including a phylogenetic
scale, an
ontogenetic
scale, and a synchronic processing scale.
On
the synchronic time scale of online language processing, I view utterances
as
providing
cues that adjudicate the competition between alternative interpretations.
Beginning
in 1978, Elizabeth Bates and I worked with over 20 colleagues studying
processing
in 18 different languages to elaborate what we call the Competition Model.
The
Competition Model views language processing as a series of competitions
between
lexical
items, phonological forms, and syntactic patterns. Competition Model studies
have
shown
that learning of language forms is based on the accurate recording of many
exposures
to words and patterns in different contexts. If a pattern is reliably present
in
the
adult input, the child picks it up quickly. Rare and unreliable patterns
are learned late
and
are relatively weaker even in adults.
More
recently, I have attempted to relate the communicative functions postulated
by the
Competition
Model to the process of perspective-taking. This process allows the human
mind
to construct an ongoing cognitive simulation based on linguistic abstractions
grounded
on perceptual realities. The perspective-taking approach views the forms
of
grammar
as emerging from repeated acts of perspective-taking and perspective-switching.
Grammatical
devices such as pronouns, case, voice, and attachment can all be seen as
ways
of expressing shifts in a basically ego-centered perspective. One major
goal in this
new
line of research is to better understand the brain mechanisms underlying
perspective-shifting.
On
the ontogenetic time scale, we can examine language emergence in at least
two ways.
One
methodology uses neural network models to simulate the acquisition of detailed
grammatical
structures. Beginning in 1989, I have worked on building conectionist models
for
the acquisition of morphology, syntax, and lexicon in English, German,
and Hungarian.
More
recently, I have examined the ontogenetic emergence of language from a
more
biological
viewpoint, using data on language processing from child with early focal
lesions.
The
results of studies of these children using reaction-time methodologies
and
standardized
tests indicate that, although they have completely normal functional use
of
language, detailed aspects of processing are slower in some cases. Using
functional
magnetic
resonance imaging technology, we have pinpointing areas of activation involved
in
specific linguistic tasks. These results have allowed us to evaluate a
series of
hypotheses
regarding sensitive periods for the emergence of language in the brain.
Models
of language learning need to account not only for the acquisition of a
first
language
by children, but also for the learning of second languages. The connectionist
perspective
on second language learning emphasizes the role of transfer and interference.
Empirical
studies in the Competition Model framework have supported these predictions.
We
still need to construct a clearer view of the ways in which declines in
brain plasticity
lead
to a loss in language learning ability over time. However, for adults who
are able to
activated
underlying compensatory processes such as the phonological loop and
motivational
supports, language learning is still possible in adulthood.
Finally,
on the phylogenetic time scale, researchers have begun to examine the ways
in
which
language has emerged through competitive Darwinian processes. My work on
perspective-taking,
competition, and brain mechanisms suggests that the most likely
account
of the origin of language is one grounded on social mechanisms. In this
sense,
the
elaboration of an emergent account of perspective-taking suggests a Vygotskyan
approach
to language evolution.
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