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Concept: Phonetics

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The influence of speech production on speech perception is well established in adults. However, because adults have a long history of both perceiving and producing speech, the extent to which the perception-production linkage is due to experience is unknown. We addressed this issue by asking whether articulatory configurations can influence infants' speech perception performance. To eliminate influences from specific linguistic experience, we studied preverbal, 6-mo-old infants and tested the discrimination of a nonnative, and hence never-before-experienced, speech sound distinction. In three experimental studies, we used teething toys to control the position and movement of the tongue tip while the infants listened to the speech sounds. Using ultrasound imaging technology, we verified that the teething toys consistently and effectively constrained the movement and positioning of infants' tongues. With a looking-time procedure, we found that temporarily restraining infants' articulators impeded their discrimination of a nonnative consonant contrast but only when the relevant articulator was selectively restrained to prevent the movements associated with producing those sounds. Our results provide striking evidence that even before infants speak their first words and without specific listening experience, sensorimotor information from the articulators influences speech perception. These results transform theories of speech perception by suggesting that even at the initial stages of development, oral-motor movements influence speech sound discrimination. Moreover, an experimentally induced “impairment” in articulator movement can compromise speech perception performance, raising the question of whether long-term oral-motor impairments may impact perceptual development.

Concepts: Infant, Perception, Sense, Mind, Acoustics, Phonetics, Philosophy of perception, Tongue

169

The Lombard effect describes the automatic and involuntary increase in vocal intensity that speakers exhibit in a noisy environment. Previous studies of the Lombard effect have typically focused on the relationship between speaking and hearing. Automatic and involuntary increases in motor output have also been noted in studies of finger force production, an effect attributed to mechanisms of sensory attenuation. The present study tested the hypothesis that sensory attenuation mechanisms also underlie expression of the Lombard effect. Participants vocalized phonemes in time with a metronome, while auditory and visual feedback of their performance were manipulated or removed during the course of the trial. We demonstrate that providing a visual reference to calibrate somatosensory-based judgments of current vocal intensity resulted in reduced expression of the Lombard effect. Our results suggest that sensory attenuation effects typically seen in fingertip force production play an important role in the control of speech volume.

Concepts: Time, Auditory system, Sensory system, Human voice, Control theory, Phonetics, Audio feedback, Lombard effect

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Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.

Concepts: Acoustics, Human voice, Larynx, Phonation, Vocal folds, Phonetics, Fundamental frequency, Histology of the Vocal Folds

29

PROMPT (Prompts for Restructuring Oral Muscular Phonetic Targets) is a treatment approach for the improvement of speech sound disorders in children, which uses tactile cues to support and shape movements of the oral articulators. No research to date has systematically examined the efficacy of PROMPT for children with Childhood Apraxia of Speech (CAS). Methods Four children (3.6-4.8), all meeting the ASHA (2007) criteria for CAS were treated. All children received 8 weeks, 2×/week of treatment including at least 4 weeks of full PROMPT treatment, including tactile cues. During the first four weeks, two of the four children received treatment which included all PROMPT components except tactile information. This design permitted both between-subject and within-subject comparisons to evaluate the effect of tactile cues. Gains in treatment were measured by standardized tests and by criterion referenced measures based on the production of untreated probe words, reflecting change in speech movements and auditory perceptual accuracy.

Concepts: Psychometrics, Sense, Somatosensory system, Phonetics, Norm-referenced test, Standardized test, Criterion-referenced test, Apraxia

28

OBJECTIVE: A growing body of evidence suggests that individuals with dyslexia perceive speech using allophonic rather than phonemic units and are thus sensitive to phonetic variations that are actually irrelevant in the ambient language. This study investigated speech perception difficulties in adults with dyslexia using behavioural and neural measurements with stimuli along a place-of-articulation continuum with well-defined allophonic boundaries. Adults without dyslexia served as control participants. METHODS: Categorical perception of a /bə - də/ place-of-articulation continuum was evaluated using both identification and discrimination tasks. In addition to these behavioural measures, mismatch negativity (MMN) was recorded for stimuli that came from either similar or different phoneme categories. RESULTS: The adults with dyslexia exhibited less consistent labelling than controls, but no heightened sensitivity to allophonic contrasts was observed at the behavioural level. Neural measurements revealed that stimuli from different phoneme categories elicited MMNs in both the adults with dyslexia and controls, whereas stimuli from the same category elicited an MMN in the adults with dyslexia only. CONCLUSION: The finding that adults with dyslexia have heightened sensitivity to allophonic contrasts in the form of neural activation supports the allophonic explanation of dyslexia. SIGNIFICANCE: Sensitivity to allophonic contrasts may be a valuable marker for dyslexia.

Concepts: Psychology, Phonology, Phoneme, Perception, Sense, Phonetics, Speech perception, Categorical perception

28

PURPOSE: This study was conducted to evaluate the clinical utility of error variability for differentiating between apraxia of speech (AOS) and aphasia with phonemic paraphasia. METHOD: Participants were 32 individuals with aphasia after left cerebral injury. Diagnostic groups were formed based on operationalized measures of recognized articulatory and prosodic characteristics of AOS and phonemic paraphasia. Sequential repetitions of multisyllabic words were elicited as part of a motor speech evaluation and transcribed phonetically. Four metrics of variability at the syllable and word levels were derived from these transcripts. RESULTS: The measures yielded different magnitudes of variability. There were no group differences between participants who displayed speech profiles consistent with AOS and participants who displayed speech profiles indicative of aphasia with phonemic paraphasia. Rather, correlation coefficients and analyses of covariance showed that the variability metrics were significantly mediated by overall error rate. Additionally, variability scores for individuals with salient diagnoses of AOS and conduction aphasia were inconsistent with current diagnostic guidelines. CONCLUSIONS: The results do not support diagnostic validity of error variability for differentiating between AOS and aphasia with phonemic paraphasia. Future research using error variability metrics should account for overall error rate in the analysis and matching of participant groups.

Concepts: Participation, Mathematical analysis, Phonology, Phonetics, Neurological disorders, Aphasia, Paraphasia, Apraxia

27

In electroencephalogram (EEG) recordings, there is a characteristic P1-N1-P2 complex after the onset of a sound, and a related complex, called the Acoustic Change Complex (ACC), when there is a change within a sound (e.g., a formant transition between two vowels). In the present study, the ACC was measured for all possible pairs of eight sustained voiced and voiceless English fricatives, in EEG recordings from native speakers of British English. The magnitude of the ACC was used as a similarity measure for multidimensional scaling (MDS), producing a two-dimensional perceptual space that related to both voicing and place of articulation. The results thus demonstrate that this combination of ACC and MDS can be effective for mapping multidimensional phonetic spaces at relatively early levels of auditory processing, which may be useful for evaluating the effects of language experience in adults and infants.

Concepts: Vector space, Space, Acoustics, Phonation, Phonetics, Real number, English language, Vowel

25

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Numerous studies have revealed an asymmetry tied to the perception of coronal place of articulation: participants accept a labial mispronunciation of a coronal target, but not vice versa. Whether or not this asymmetry is based on language-general properties or arises from language-specific experience has been a matter of debate. The current study suggests a bias of the first type by documenting an early, cross-linguistic asymmetry related to coronal place of articulation. Japanese and Dutch 4- and 6-month-old infants showed evidence of discrimination if they were habituated to a labial and then tested on a coronal sequence, but not vice versa. This finding has important implications for both phonological theories and infant speech perception research.

Concepts: Infant, Matter, Infant mortality, Phonetics, The Current, Place of articulation, Speech perception, Labiodental consonant

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This is a study of final poststressed vowel devoicing following /s/ in Brazilian Portuguese. We contradict the literature describing it as deletion by arguing, first, that the vowel is not deleted, but overlapped and devoiced by the /s/, and, second, that gradient reduction with devoicing may lead to apocope diachronically. The following results support our view: (1) partially devoiced vowels are centralized; (2) centralization is inversely proportional to duration; (3) total devoicing is accompanied by lowering of the /s/ centroid; (4) the /s/ noise seems to be lengthened when the vowel is totally devoiced; (5) aerodynamic tests reveal that lengthened /s/ has a final vowel-like portion, too short to be voiced; (6) lengthened /s/ favors vowel recovery in perceptual tests. This seems to be a likely path from reduction to devoicing to listener-based apocope.

Concepts: English-language films, Phonology, International Phonetic Alphabet, Phonetics, English language, Brazil, Japanese language, Syllable nucleus