The long-term objectives of this research are to develop our basic knowledge of how humans discriminate and recognize speech sounds, and to apply that knowledge toward the explanation of regularities in the sound patterns of languages. The proposed research will investigate a general claim about the phonetic realization of phonological feature distinctions. This claim, referred to as the auditory enhancement hypothesis, states that phonetic correlates of feature distinctions tend to have mutually enhancing effects which help to ensure the perceptual robustness of the distinctions. Phonological features typically have multiple individual phonetic correlates, but these correlates often can be grouped into coherent subsets based on relations of auditory commonality or enhancement. These subsets thus form """"""""integrated perceptual properties"""""""" intermediate between the levels of the individual correlates and distinctive features. The auditory enhancement hypothesis is not only important for understanding speech perceptual performance, it also helps to account for various phonetic regularities that have resisted explanation in term of the physics and physiology of speech production. During the current grant period, much of the research has focused on the role of auditory enhancement in the perception of the distinction between [+voice] and [-voice] consonants and the distinction between [+high] and [- high] vowels. Most of the proposed research will evaluate applications of the enhancement hypothesis to a much broader range of feature distinctions. The distinctions to be investigated will include [+/-high], [+/-back], and [+/-coronal] among vowels and [+/-voice], [+/-continuant], [+/-sonorant], and sibilant vs. nonsibilant (where sibilant corresponds to [+strident] and [+coronal]) among consonants. For each feature distinction, specific claims about corresponding integrated perceptual properties, and their auditory basis, will be tested. In the case of vowels, a series of studies will evaluate the possibility that the """"""""spectral center of gravity"""""""" effect provides a common auditory account of several different distinctions. In the case of consonants, the auditory hypotheses to be evaluated are generally specific to each feature distinction. Multiple converging operations will be used to test many of the particular hypotheses. These converging operations will include studies of speech production, listener identification and discrimination of speech stimuli and acoustically analogous nonspeech stimuli, and auditory modeling. Clear progress in understanding how speech is represented in normal auditory systems will contribute importantly to the development of models of speech perception in hearing impaired persons.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Sensory Disorders and Language Study Section (CMS)
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University of Texas Austin
Schools of Arts and Sciences
United States
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Lindblom, Björn; Diehl, Randy; Creeger, Carl (2009) Do 'Dominant Frequencies' explain the listener's response to formant and spectrum shape variations? Speech Commun 51:622-629
Garcia-Sierra, Adrian; Diehl, Randy L; Champlin, Craig (2009) Testing the double phonemic boundary in bilinguals. Speech Commun 51:369-378
Kingston, John; Diehl, Randy L; Kirk, Cecilia J et al. (2008) On the internal perceptual structure of distinctive features: The [voice] contrast. J Phon 36:28-54
Diehl, Randy L (2008) Acoustic and auditory phonetics: the adaptive design of speech sound systems. Philos Trans R Soc Lond B Biol Sci 363:965-78
Hay, Jessica S F; Diehl, Randy L (2007) Perception of rhythmic grouping: testing the iambic/trochaic law. Percept Psychophys 69:113-22
Hay, Jessica F; Sato, Momoko; Coren, Amy E et al. (2006) Enhanced contrast for vowels in utterance focus: a cross-language study. J Acoust Soc Am 119:3022-33
Molis, Michelle R (2005) Evaluating models of vowel perception. J Acoust Soc Am 118:1062-71
Holt, Lori L; Lotto, Andrew J; Diehl, Randy L (2004) Auditory discontinuities interact with categorization: implications for speech perception. J Acoust Soc Am 116:1763-73
Diehl, Randy L; Lotto, Andrew J; Holt, Lori L (2004) Speech perception. Annu Rev Psychol 55:149-79
Wong, Patrick C M; Parsons, Lawrence M; Martinez, Michael et al. (2004) The role of the insular cortex in pitch pattern perception: the effect of linguistic contexts. J Neurosci 24:9153-60

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