Speech and bottom-up processes

["BRUNO H. Repp" <repp@xxxxxxxxxxxxxxxxxxxxxx>]

Although the discussion is beginning to veer away from the original topic,
I would like to add some relevant references that modesty forbade me
to include with my earlier message. With my dear colleague Neil Todd's
messages having relieved me of that inhibition, here I go:

Repp, B. H., & Frost, R. (1988). Detectability of words and nonwords
in two kinds of noise. Journal of the Acoustical Society of America,
84, 1929-1932.

        This study was concerned with the detection threshold for the
presence of speech in noise, not with the much higher intelligibility
threshold. It showed that there is no threshold difference between
English words and nonwords, which suggests that the detection process
was purely bottom-up.

Repp, B. H., Frost, R., & Zsiga, E. (1992). Lexical mediation between
sight and sound in speechreading. The Quarterly Journal of Experimental
Psychology, 45A, 1-20.

        There we showed that the detectability of the presence of speech
in noise was not influenced by simultaneous visual exposure to matching or
nonmatching articulations (lipreading), which again implies an autonomous
auditory bottom-up process for speech detection. The lexical status of
the stimuli (words or nonwords) affected response bias, but not sensitivity.
A similar finding for printed words as the visual stimuli, rather than
lipreading, was reported by

Frost, R., Repp, B. H., & Katz, L. (1988). Can speech perception be
influenced by simultaneous presentation of print? Journal of Memory and
Language, 27, 741-755.

        All three studies provide evidence that the presence of speech
can be detected on the basis of acoustic cues long before it is even
partially recognized. The detection threshold (70% correct, with 50%
being chance) for speech in broadband noise is about -28 dB of S/N ratio,
and that in amplitude-modulated (signal-correlated) noise is about
-13 dB (Repp & Frost, 1988). Both thresholds are well below the
intelligibility thresholds.


Bruno H. Repp
Haskins Laboratories
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New Haven, CT 06511-6695

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