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M Studdert-Kennedy

Publications and source records attributed to M Studdert-Kennedy.

At least 19 recordsLinked to original sources
PubMed1989

Discovering phonetic coherence in acoustic patterns.

Despite spectral and temporal discontinuities in the speech signal, listeners normally report coherent phonetic patterns corresponding to the phonemes of a language that they know. What is the basis for the internal coherence of phonetic segments? According to one account, listeners achieve coherence by extracting and integrating discrete cues; according to another, coherence arises automatically from general principles of auditory form perception; according to a third, listeners perceive speech patterns as coherent because they are the acoustic consequences of coordinated articulatory gestures in a familiar language. We tested these accounts in three experiments by training listeners to hear a continuum of three-tone, modulated sine wave patterns, modeled after a minimal pair contrast between three-formant synthetic speech syllables, either as distorted speech signals carrying a phonetic contrast (speech listeners) or as distorted musical chords carrying a nonspeech auditory contrast (music listeners). The music listeners could neither integrate the sine wave patterns nor perceive their auditory coherence to arrive at consistent, categorical percepts, whereas the speech listeners judged the patterns as speech almost as reliably as the synthetic syllables on which they were modeled. The outcome is consistent with the hypothesis that listeners perceive the phonetic coherence of a speech signal by recognizing acoustic patterns that reflect the coordinated articulatory gestures from which they arose.

Adult↗
PubMed1989

The emergence of phonetic segments: evidence from the spectral structure of fricative-vowel syllables spoken by children and adults.

A variety of evidence, including the speech errors of normal and aphasic speakers, and the metalinguistic skills of literate individuals, demonstrates that speech has an underlying phonemic organization. However, we know little about how this organization develops in the child. The purpose of the present study was to test the hypothesis that phoneme-sized phonetic segments emerge as functional units of perceptuomotor control from the child's gradual reorganization of the gestures forming its early words or syllables. We investigated the acoustic structure of syllables produced by young children and adults. Fricative-vowel syllables spoken by 40 subjects (eight adults and eight children at each of the ages 3, 4, 5, and 7 years) were analyzed acoustically to determine how well different syllables-initial fricatives were contrasted and how strongly they were affected by vocalic context. Results indicated two independent developmental trends: The extent to which speakers differentiated between /integral of/ and /s/ increased with age, while the extent to which they coarticulated each fricative with its following vowel decreased. The results support the hypothesis that children initially organize their speech gestures over a domain at least the size of the syllable and only gradually differentiate the syllable into patterns of gestures more closely aligned with its perceived segmental components.

Adult↗
PubMed1987

The role of coarticulatory effects in the perception of fricatives by children and adults.

Adult listeners are sensitive to the acoustic variations that result from a speaker's coarticulation (or coproduction) of phonetic segments. The present study charted the development of such sensitivity in young children by examining their responses to coarticulatory effects in fricative-vowel syllables. Children, at each of the ages 3, 4, 5, and 7 years, and adults identified tokens from a synthetic /sh/-/s/ continuum followed by one of four natural vocalic portions: /i/ and /u/, produced with transitions appropriate for either /sh/ or /s/. Children demonstrated larger shifts in fricative phoneme boundaries as a function of vocalic transition than did adults, but relatively smaller shifts as a function of vowel quality. Responses were less consistent for children than for adults, and differences between children and adults decreased as children increased in age. Overall, these results indicate that perceptual sensitivity to certain coarticulatory effects is present at as young as 3 years of age. Moreover, the decrease in the sensitivity to vocalic transitions with age suggests that, contrary to a commonly held view, the perceptual organization of speech may become more rather than less segmental as the child develops.

Adult↗
PubMed1986

The stop-glide distinction: acoustic analysis and perceptual effect of variation in syllable amplitude envelope for initial /b/ and /w/.

Amplitude change at consonantal release has been proposed as an invariant acoustic property distinguishing between the classes of stops and glides [Mack and Blumstein, J. Acoust. Soc. Am. 73, 1739-1750 (1983)]. Following procedures of Mack and Blumstein, we measured the amplitude change in the vicinity of the consonantal release for two speakers. The results for one speaker matched those of Mack and Blumstein, while those for the second speaker showed some differences. In a subsequent experiment, we tested the hypothesis that a difference in amplitude change serves as an invariant perceptual cue for distinguishing between continuants and noncontinuants, and more specifically, as a critical cue for identifying stops and glides [Shinn and Blumstein, J. Acoust. Soc. Am. 75, 1243-1252 (1984)]. Interchanging the amplitude envelopes of natural /bV/ and /wV/ syllables containing the same vowel had little effect on perception: 97% of all syllables were identified as originally produced. Thus, although amplitude change in the vicinity of consonantal release may distinguish acoustically between stops and glides with some consistency, the change is not fully invariant, and certainly does not seem to be a critical perceptual cue in natural speech.

Humans↗
PubMed1985

Extending formant transitions may not improve aphasics' perception of stop consonant place of articulation.

Synthetic speech stimuli were used to investigate whether aphasics' ability to perceive stop consonant place of articulation was enhanced by the extension of initial formant transitions in CV syllables. Phoneme identification and discrimination tests were administered to 12 aphasic patients, 5 fluent and 7 nonfluent. There were no significant differences in performance due to the extended transitions, and no systematic pattern of performance due to aphasia type. In both groups, discrimination was generally high and significantly better than identification, demonstrating that auditory capacity was retained, while phonetic perception was impaired; this result is consistent with repeated demonstrations that auditory and phonetic processes may be dissociated in normal listeners. Moreover, significant rank order correlations between performances on the Token Test and on both perceptual tasks suggest that impairment on these tests may reflect a general cognitive rather than a language-specific deficit.

Adult↗
PubMed1983

Infant intermodal speech perception is a left-hemisphere function.

Prelinguistic infants recognized structural correspondences in acoustic and optic properties of synchronized, naturally spoken disyllables, but did so only when they were looking to their right sides. This result suggests that intermodal speech perception is facilitated by rightward orientation of attention and subserved by the left hemisphere.

Attention↗
PubMed1983

Perception of static and dynamic acoustic cues to place of articulation in initial stop consonants.

Two recent accounts of the acoustic cues which specify place of articulation in syllable-initial stop consonants claim that they are located in the initial portions of the CV waveform and are context-free. Stevens and Blumstein [J. Acoust. Soc. Am. 64, 1358-1368 (1978)] have described the perceptually relevant spectral properties of these cues as static, while Kewley-Port [J. Acoust. Soc. Am. 73, 322-335 (1983)] describes these cues as dynamic. Three perceptual experiments were conducted to test predictions derived from these accounts. Experiment 1 confirmed that acoustic cues for place of articulation are located in the initial 20-40 ms of natural stop-vowel syllables. Next, short synthetic CV's modeled after natural syllables were generated using either a digital, parallel-resonance synthesizer in experiment 2 or linear prediction synthesis in experiment 3. One set of synthetic stimuli preserved the static spectral properties proposed by Stevens and Blumstein. Another set of synthetic stimuli preserved the dynamic properties suggested by Kewley-Port. Listeners in both experiments identified place of articulation significantly better from stimuli which preserved dynamic acoustic properties than from those based on static onset spectra. Evidently, the dynamic structure of the initial stop-vowel articulatory gesture can be preserved in context-free acoustic cues which listeners use to identify place of articulation.

Communication Devices for People with Disabilities↗
PubMed1983

On learning to speak.

Every language, spoken or signed, deploys a large lexicon, made possible by permutation and combination of a small set of linguistic elements. In speech, rapid interleaving of the gestures that form these elements (consonants and vowels) leads to a complex acoustic signal in which the boundaries between elements are lost. However, for the child learning to speak, the initial task is not to recover these elements, but simply to imitate the sound pattern that it hears. Studies of "lipreading" in adults and infants suggest that imitation is mediated by an amodal representation, closely related to the dynamics of articulation, and that a left-hemisphere perceptuo-motor mechanism specialized to make use of this representation develops during the first six months of life. By drawing on this specialized mechanism, the infant learns the recurrent patterns of acoustic structure and articulatory gesture from which linguistic segments must be presumed to emerge.

Dominance, Cerebral↗
PubMed1978

Selective anchoring and adaptation of phonetic and nonphonetic continua.

A series of four experiments compared the effects of unequal probability anchoring and selective adaptation on phonetic and nonphonetic judgments. The basic stimulus series was a synthetic stop consonant continuum ranging from /b/ to /d/. On this continuum were superimposed covariations in fundamental frequency, intensity or vowel. In each experiment subjects listened to identical test tapes under two judgment conditions: place of articulation, and pitch or loudness or vowel judgments. The two types of judgment were significantly dissociated under both anchoring and adaptation paradigms, thus demonstrating that the former may be no less selective than the latter. From this and other evidence, it was concluded that the two paradigms are, in principle, equivalent, and that the main factors in speech adaptation effects are peripheral fatigue and central auditory contrast. If the selective processes of fatigue and contrast are taken to reflect functional channels of analysis rather than the operation of feature detectors, the same broad processes can be seen at work in both speech and nonspeech adaptation.

Adult↗