Transcript auditory-acoustic

Auditory-acoustic
relations and effects on
language inventory
Carrie Niziolek [carrien]
24.922
5 may 2004
Introduction
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Quantal relations both acousticarticulatory and auditory-acoustic.
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How does the peripheral auditory system
shape responses to acoustics?
How does the central auditory system amplify
learned contrasts?
Purpose of report:
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to address feature constraints imposed by
the auditory system
to address perceptibility as a tool for
guiding feature constraints in a language
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Does perceptibility (and, by extension,
quantalness) affect survival in a language?
Categorical perception
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A continuous change in a variable is
perceived as instances of discrete
categories
Between-cat discrimination is better than
within-cat discrimination (enhanced
category boundaries)
CP is induced through category learning,
or merely acoustic exposure
Speech perception
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Motor theory: phonemes are processed by
special phonetic mechanisms of hearing
(learned internal lang-production model)
Preverbal infants and nonverbal animals
share categorical perception boundaries
What decoding processes do our auditory
systems have in common?
Feature constraints
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Auditory system needs 20 ms to perceive
temporal ordering (less than 20 ms = one
auditory event?)
Auditory-acoustic relations
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Eimas et al. (1971) used a bilabial VOT
continuum to show that English infants better
discriminate across-boundary stimuli
Eilers et al. (1979) showed that Spanish infants
also have greatest sensitivity across the English
boundary
Evidence for an auditorily-determined
boundary
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Do more languages have an English-like boundary
than not?
Non-speech aud-acoust relations
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Non-linear
acoustic to
auditory
mapping:
natural
auditory
sensitivities
Use sawtooth waves to test
perception: plucks or bows?
Non-speech aud-acoust relations
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Non-linear acoustic to
auditory mapping:
natural auditory
sensitivities
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Large-target regions:
small variations
Thresholds, regions of
instability (~40ms)
Range effects
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Input range affects perception: is boundary
merely at midpoint of range?
Perceptibility in Turkish
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Turkish [h] deletion
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Occurs in contexts where lower perceptibility
is predicted
Speech taking advantage of perceptual
constraints
Optimizing language contrasts
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Language evolution will tend to converge
on maximally distinct phonemes
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Maximize perceptual distance: vowel
dispersion
Maximize ease of articulation: find a stable
acoustic region that allows for a relatively
imprecise gesture
References
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Stevens K. On the quantal nature of speech. J. Phonetics (1989) 17, 3-45.
Harnad, S. Psychophysical and cognitive aspects of categorical perception: A critical
overview, in Harnad, Stevan, Eds. Categorical Perception: The Groundwork of
Cognition (1987), chapter 1, pages pp. 1-52. Cambridge University Press.
Howell, P. & Rosen, S. (1984) Natural auditory sensitivities as universal determiners of
phonemic contrasts. Linguistics 211: 205-235
Kuhl PK and Miller JD: Speech perception by the chinchilla. Science, 190: 69-72. 1975.
Mielke J. The interplay of speech perception and phonology: experimental evidence
from Turkish. Phonetica 2003 Jul-Sep;60(3):208-29.
Gao E, Suga N. Experience-dependent corticofugal adjustment of midbrain frequency
map in bat auditory system. Neurobiology 1998 Oct;95(21):12663-12670.
Neural measures of perception
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Lateral posterior STG
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Acoustic-phonetic processing: activation from
words, pseudowords, and reversed speech
Not critical for discrimination of non-speech
auditory stimuli (tones, noise)
Disputed: other human vocalizations?
(coughing)
Anterior STG
Inferior frontal cortex
Organization of speech circuits
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Model of functional circuits that are critical
for speech perception
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Functional subdivisions in left STG
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Anterior STG
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Posterior: phonological
Anterior: sentence processing
Posterior STG
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Anterior: acoustic-phonetic
Posterior: phonological
Temporoparietal junction: lexical-semantic
Organization of speech circuits
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Hierarchical organization
Acoustic-phonetic processing: local posterior
network
 Increasingly distributed networks as processing
becomes more complex
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Modular and distributed cortical circuits
Cortical perception
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Acoustic-phonetic processes localized to the
middle-posterior region of left STG
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Increased cortical distribution for higher-level
speech perception tasks
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Dissociation implies functional subdivisions,
hierarchical organization
Corticofugal pathways
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i.e., how the cortex affects processing in
lower auditory centers
Acoustic cues enhanced or suppressed
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Positive feedback to subcortical neurons
“matched” in tuning to an acoustic parameter
Lateral inhibition to “unmatched” neurons