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As the world holds its breath the state of synchronicity increases. A friend
whom I haven't spoken with in months sent me this today without knowing
anything about this thread. On one of his science lists a similar discussion
has been raging for a couple of weeks centered upon this article.


EARLY LANGUAGE ACQUISITION: CRACKING THE SPEECH CODE

Patricia K. Kuhl

Abstract

Infants learn language with remarkable speed, but how they do it remains a
mystery. New data show that infants use computational strategies to detect
the statistical and prosodic patterns in language input, and that this leads
to the discovery of phonemes and words. Social interaction with another
human being affects speech learning in a way that resembles communicative
learning in songbirds. The brain's commitment to the statistical and
prosodic patterns that are experienced early in life might help to explain
the long-standing puzzle of why infants are better language learners than
adults. Successful learning by infants, as well as constraints on that
learning, are changing theories of language acquisition.

Summary


*    Infants learn their native language quickly and effortlessly, and
follow the same developmental path regardless of culture. However, it has
proved difficult to understand how they do this, or to build computers that
can reproduce this feat.
*    An early and essential task for infants is to make sense of the speech
that they hear. Each language uses a unique set of about 40 phonemes, and
infants must learn to partition varied speech sounds into these phonemic
categories. Young infants are sensitive to subtle differences between all
phonetic units, whereas older children lose their sensitivity to
distinctions that are not used in their native language. The loss of
discrimination for foreign-language distinctions is paralleled by an
increase in sensitivity to native-language phonetic units.
*    There is evidence that infants analyse the statistical distributions of
sounds that they hear in ambient language, and use this information to form
phonemic categories. They also learn phonotactic rules  language-specific
rules that govern the sequences of phonemes that can be used to compose
words.
*    To identify word boundaries, infants can use both transitional
probabilities between syllables, and prosodic cues, which relate to
linguistic stress. Most languages are dominated by either trochaic words
(with the stress on the first syllable) or iambic ones (with the stress on
later syllables). Infants seem to use a combination of statistical and
prosodic cues to segment words in speech.
*    Social influences are important in speech learning. Infants learn more
easily from interactions with human beings speaking another language than
they do from audiovisual exposure to the same language material, and their
speech is strongly influenced by the response of others around them, such as
their mothers. The importance of social input in language learning has some
similarities to social influences on song learning in birds.
*    Language experience causes neural changes. One hypothesis, native
language neural commitment (NLNC), proposes that language learning produces
dedicated neural networks that code the patterns of native-language speech.
As these networks develop, they make it easier for new speech elements and
patterns to be learned if they are consistent with the existing patterns,
but place constraints on the learning of foreign-language patterns. NLNC
might explain the closing of the 'sensitive period' for language learning;
once a certain amount of learning has occurred, neural commitment interferes
with the learning of new languages so they cannot be learned as easily.