Auditory-acoustic relations and effects on language inventory Carrie Niziolek [carrien] may 2004

Introduction Quantal relations both acoustic- articulatory and auditory-acoustic. How does the peripheral auditory system shape responses to acoustics? How does the central auditory system amplify learned contrasts?

Purpose of report: to address feature constraints imposed by the auditory system to address perceptibility as a tool for guiding feature constraints in a language Does perceptibility (and, by extension, quantalness) affect survival in a language?

Categorical perception 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 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 Auditory system needs 20 ms to perceive temporal ordering (less than 20 ms = one auditory event?)

Auditory-acoustic relations 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 Do more languages have an English-like boundary than not?

Non-speech aud-acoust relations Non-linear acoustic to auditory mapping: natural auditory sensitivities Use sawtooth waves to test perception: plucks or bows?

Non-speech aud-acoust relations Non-linear acoustic to auditory mapping: natural auditory sensitivities Large-target regions: small variations Thresholds, regions of instability (~40ms)

Range effects Input range affects perception: is boundary merely at midpoint of range?

Perceptibility in Turkish Turkish [h] deletion Occurs in contexts where lower perceptibility is predicted Speech taking advantage of perceptual constraints

Mispronunciation detection Percent detection increases as number of features change How do subjects integrate these features?

Optimizing language contrasts Language evolution will tend to converge on maximally distinct phonemes Maximize perceptual distance: vowel dispersion Maximize ease of articulation: find a stable acoustic region that allows for a relatively imprecise gesture

Predicts the optimization of acoustic structure of vowel inventory: maximize inter-vowel contrast Vowel dispersion

References 1. Stevens K. On the quantal nature of speech. J. Phonetics (1989) 17, 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 Cambridge University Press. 3. Howell, P. & Rosen, S. (1984) Natural auditory sensitivities as universal determiners of phonemic contrasts. Linguistics 211: Kuhl PK and Miller JD: Speech perception by the chinchilla. Science, 190: Mielke J. The interplay of speech perception and phonology: experimental evidence from Turkish. Phonetica 2003 Jul-Sep;60(3): Gao E, Suga N. Experience-dependent corticofugal adjustment of midbrain frequency map in bat auditory system. Neurobiology 1998 Oct;95(21):

Neural measures of perception Lateral posterior STG 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 Model of functional circuits that are critical for speech perception Functional subdivisions in left STG Anterior STG Posterior: phonological Anterior: sentence processing Posterior STG Anterior: acoustic-phonetic Posterior: phonological Temporoparietal junction: lexical-semantic

Organization of speech circuits Hierarchical organization Acoustic-phonetic processing: local posterior network Increasingly distributed networks as processing becomes more complex Modular and distributed cortical circuits

Cortical perception Acoustic-phonetic processes localized to the middle-posterior region of left STG Increased cortical distribution for higher-level speech perception tasks Dissociation implies functional subdivisions, hierarchical organization

Corticofugal pathways i.e., how the cortex affects processing in lower auditory centers Acoustic cues enhanced or suppressed Positive feedback to subcortical neurons “matched” in tuning to an acoustic parameter Lateral inhibition to “unmatched” neurons