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Abstract:
Perceptual identification of speech sounds is greatly
influenced by spectral characteristics of adjacent sound. For
example, listeners will label an ambiguous syllable as /da/ when it
is preceded by /ar/ and as /ga/ when it is preceded by /al/. Recent
work demonstrates that context effects in speech identification can
be induced by adjacent non-speech sounds that mimic spectral
characteristics of /al/ and /ar/ (Lotto & Kluender, 1998).
Non-human animals trained to "label" syllables as /ga/ or /da/ also
exhibit context-dependent response shifts (Lotto, Kluender &
Holt, 1997). These results have led to speculation that speech
context effects arise from general perceptual mechanisms. To
examine the nature of these putative mechanisms, the temporal
course and frequency range of this context effect was examined.
Identification functions for varied context conditions were
collected from adult native-English-speaking listeners. Results
suggest peripheral sensory processes play little or no role. Shifts
in identification are present even when context and target syllable
are separated by 400 ms and nearly identical shifts are obtained
for dichotic presentation of target and context. Also, the context
effect is strongly related to spectral content of the context and
not to the phonemic label assigned to the context, suggesting that
the effect is due to general auditory mechanisms and not to
cognitive or speech-specific processes. These data will be
discussed in terms of possible physiological explanations.
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