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Abstract:
To understand language, children must learn to
listen for meaning in sequences of speech sounds that unfold
rapidly in time. Fluent understanding requires "listening
ahead", continually anticipating what is coming next using
linguistic and nonlinguistic information from the context in
which words are spoken. Skilled adults draw on multiple
sources of knowledge to process speech with remarkable speed and
efficiency, but research on the early development of this
critical capacity is just beginning (1-4). We review
several recent studies of early word recognition and sentence
comprehension using eye-tracking methods for measuring the time
course of children's understanding. Efficiency in
comprehension increases as the inexperienced listener learns to
exploit regularities in the structure of continuous speech,
enabling the child to anticipate upcoming words and relate word
meanings to one another. Even with limited experience of
language and the world, infants can rely on two main sources of
knowledge in listening for meaning in speech. The first is
their attention to the local redundancies provided by caretakers
who use a special form of infant-directed (ID) speech, i.e., who
repeat themselves frequently, emphasize focussed words by placing
them in perceptually prominent positions, and lighten the load of
monitoring speech by presenting new information in predictable
formats. The second is their early sensitivity to
regularities in the speech they hear that are correlated with
structural aspects of the ambient language.
First we show how infants benefit from
predictability in speech at a perceptual level. Certain
characteristic features of ID speech enable the inexperienced
listener to anticipate the onset of focussed words, including (1)
the positioning of focused words in sentence-final position, and
(2) the high level of prosodic and segmental redundancy across
utterances. In two studies with 18-month-olds (n=120), we
found that familiar words were recognized more quickly and
reliably in final than in medial position, and that the
redundancy of the carrier phrase influenced the efficiency of
recognition. Next we show how infants benefit from
predictability at a linguistic level, as they learn to make use
of language-specific cues in understanding. Further
research with 18- to 26-month-olds (n=150) reveals dramatic
developmental gains in the ability to exploit phonetic,
morphological, and semantic cues to word identity across the
second year. Even for infants with lexicons of only a few
hundred words, the interpretation of sentence meaning is
predictive, and linking spoken language to a mental model of the
world is an active, continuous process.
References
(1) Fernald, A., Pinto, J.P., Swingley, D.,
Weinberg, A., & McRoberts, G.W. (1998). Rapid gains in
speed of verbal processing by infants in the second year.
Psychological Science, 9:72-75.
(2) Fernald, A., Swingley, D., & Pinto, J.P.
(2001). When half a word is enough: Infants can recognize
spoken words using partial phonetic information. Child
Development, 72:1003-1015.
(3) Swingley, D. & Fernald, A. (in
press). Recognition of words referring to present and
absent objects by 24-month-olds. Journal of Memory and
Language.
(4) Swingley, D., Pinto, J.P., & Fernald, A.
(1999). Continuous processing in word recognition at 24
months. Cognition, 71, 73-108.
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