48 research outputs found
Interarticulator speech coordination (Masapollo & Nittrouer, 2023)
No full textPurpose: In skilled speech production, sets of articulators, such as the jaw, tongue, and lips, work cooperatively to achieve task-specific movement goals, despite rampant contextual variation. Efforts to understand these functional units, termed coordinative structures, have focused on identifying the essential control parameters responsible for allowing articulators to achieve these goals, with some research focusing on temporal parameters (relative timing of movements) and other research focusing on spatiotemporal parameters (phase angle of movement onset for one articulator, relative to another). Here, both types of parameters were investigated and compared in detail.
Method: Ten talkers recorded nonsense, disyllabic /tV#Cat/ utterances using electromagnetic articulography, with alternative V (/ɑ/−/ɛ/) and C (/t/−/d/), across variation in rate (fast–slow) and stress (first syllable stressed–unstressed). Two measures were obtained: (a) the timing of tongue-tip raising onset for medial C, relative to jaw opening–closing cycles and (b) the angle of tongue-tip raising onset, relative to the jaw phase plane.
Results: Results showed that any manipulation that shortened the jaw opening-closing cycle reduced both the relative timing and phase angle of the tongue-tip movement onset, but relative timing of tongue-tip movement onset scaled more consistently with jaw opening-closing across rate and stress variation.
Conclusion: These findings suggest the existence of an intrinsic timing mechanism (or “central clock”) that is the primary control parameter for coordinative structures, with online compensation then allowing these structures to achieve their goals spatially.
S1. Summary of token means of JVC durations, TT movement onset latencies and TT phase angles for each talker and each utterance.
S2. Main effect of production rate on maximum jaw displacement
S3. Main effect of production rate on jaw vowel-cycle duration
S4. Main effect of stress pattern on maximum jaw displacement
S5. Main effect of stress pattern on jaw vowel-cycle duration
S6. Main effect of vowel quality on maximum jaw displacement
S7. Main effect of vowel quality on jaw vowel-cycle duration
S8. Main effect of medial consonant on maximum jaw displacement
S9. Main effect of medial consonant on jaw vowel-cycle duration
S10. ANOVA results for JVC Duration
S11. ANOVA results for Maximum Jaw Displacements
S12. ANOVA results for TT Movement Onset Latencies
S13. ANOVA results for TT Phase Angles
Masapollo, M., & Nittrouer, S. (2023). Interarticulator speech coordination: Timing is of the essence. Journal of Speech, Language, and Hearing Research. Advance online publication. https://doi.org/10.1044/2022_JSLHR-22-00594
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Somatosensory influence on visual vowel perception (Masapollo & Guenther, 2019)
No full textPurpose: This study aimed to test whether (and how) somatosensory feedback signals from the vocal tract affect concurrent unimodal visual speech perception.Method: Participants discriminated pairs of silent visual utterances of vowels under 3 experimental conditions: (a) normal (baseline) and while holding either (b) a bite block or (c) a lip tube in their mouths. To test the specificity of somatosensory–visual interactions during perception, we assessed discrimination of vowel contrasts optically distinguished based on their mandibular (English /ɛ/–/æ/) or labial (English /u/–French /u/) postures. In addition, we assessed perception of each contrast using dynamically articulating videos and static (single-frame) images of each gesture (at vowel midpoint).Results: Engaging the jaw selectively facilitated perception of the dynamic gestures optically distinct in terms of jaw height, whereas engaging the lips selectively facilitated perception of the dynamic gestures optically distinct in terms of their degree of lip compression and protrusion. Thus, participants perceived visible speech movements in relation to the configuration and shape of their own vocal tract (and possibly their ability to produce covert vowel production–like movements). In contrast, engaging the articulators had no effect when the speaking faces did not move, suggesting that the somatosensory inputs affected perception of time-varying kinematic information rather than changes in target (movement end point) mouth shapes.Conclusions: These findings suggest that orofacial somatosensory inputs associated with speech production prime premotor and somatosensory brain regions involved in the sensorimotor control of speech, thereby facilitating perception of concordant visible speech movements. Supplemental Material S1. Analyses of stimulus order effects. Masapollo, M., & Guenther, F. H. (2019). Engaging the articulators enhances perception of concordant visible speech movements. Journal of Speech, Language, and Hearing Research, 62, 3679–3688. https://doi.org/10.1044/2019_JSLHR-S-19-0167</div
Asymmetries in visual vowel perception: The roles of oral-facial kinematics, orientation and configuration
No full textMasapollo, Polka, and Ménard (2017) recently reported a robust directional asymmetry in unimodal visual vowel perception: Adult perceivers discriminate a change from an English /u/ viseme to a French /u/ viseme significantly better than a change in the reverse direction. This asymmetry replicates a frequent pattern found in unimodal auditory vowel perception that points to a universal bias favoring more extreme vocalic articulations, which lead to acoustic signals with increased formant convergence. In the present article, the authors report 5 experiments designed to investigate whether this asymmetry in the visual realm reflects a speech-specific or general processing bias. They successfully replicated the directional effect using Masapollo et al.’s dynamically articulating faces but failed to replicate the effect when the faces were shown under static conditions. Asymmetries also emerged during discrimination of canonically oriented point-light stimuli that retained the kinematics and configuration of the articulating mouth. In contrast, no asymmetries emerged during discrimination of rotated point-light stimuli or Lissajou patterns that retained the kinematics, but not the canonical orientation or spatial configuration, of the labial gestures (...
On the nature of the natural referent vowel bias
No full textThere is considerable debate in the phonetic sciences concerning the nature of the information that is critical for speech perception, and the nature of the processing mechanisms that map the relevant signal properties onto phonetic categories. In the domain of vowel perception, research has shown that the mapping between the speech signal and phonetic structure is non-uniform, in that perceivers (both adult and infant) are universally biased toward the extremes of articulatory/acoustic space (peripheral in F1/F2 space; Polka & Bohn, 2003, 2011). Much of the evidence for this bias comes from studies showing that perceivers consistently discriminate vowels in an asymmetric manner. More precisely, perceivers perform better at detecting a change from a relatively less (e.g., /e/) to a relatively more peripheral vowel (e.g., /i/), compared to the same change presented in the reverse direction. Although the existence of this perceptual phenomenon (i.e., the natural referent vowel [NRV] bias) is well established, the mechanisms and processes that underlie it are poorly understood. One account of the NRV bias, which derives from the Dispersion–Focalization Theory (Schwartz, Abry, Boë, Ménard, & Vallée, 2005), is that extreme vocalic articulations give rise to speech signals that exhibit increased spectral salience due to formant frequency convergence, or "focalization." This dissertation presents a series of experiments aimed at assessing whether adult perceivers are indeed sensitive to differences in formant proximity while discriminating vowel stimuli that fall within a given category, and, if so, whether that sensitivity is attributable to general properties of auditory processing, or to phonetic processes that extract articulatory information available across sensory modalities. In Experiment 1, English- and French-speaking perceivers showed directional asymmetries consistent with the focalization account as they attempted to discriminate synthetic /u/ variants that systematically differed in their peripherality and hence degree of formant proximity (between F1 and F2). In Experiment 2, similar directional effects were found when English perceivers attempted to discriminate natural /u/ productions that differed in their peripherality when only acoustic-phonetic or only visual-phonetic information was present. Experiment 3 investigated whether and how the integration of acoustic and visual speech cues influences the effects documented in Experiment 2. When acoustic and visual cues were phonetically-congruent, an NRV bias was observed. In contrast, when acoustic and visual cues were phonetically-incongruent, this bias was disrupted, confirming that both sensory channels shape this bias in bimodal auditory-visual vowel perception. Collectively, these findings advance our understanding of the sensory and cognitive processes that are fundamental to the mapping between the speech signal and vowel categories. In particular, they suggest that perceivers are universally biased to attend to extreme vocalic gestures specified optically, in terms of articulatory kinematic patterns, as well as acoustically, in terms of formant convergence patterns. A complete understanding of this bias is not only important to speech perception theories, but provides a critical basis for the study of phonetic development as well as the perceptual factors that may constrain vowel inventories across languages.Un débat considérable dans le domaine des sciences phonétiques entoure la nature de l'information pertinente à la perception de la parole et la nature des mécanismes de processus transformant les propriétés des signaux en catégories phonétiques. Dans le domaine de la perception des voyelles, les recherches démontrent que la relation entre le signal de parole et la structure phonétique est déformée, en ce sens que les auditeurs (les adultes comme les nourrissons) sont universellement biaisés à porter attention aux voyelles dotées de propriétés articulatoires / acoustiques extrêmes (en périphérie de l'espace F1/F2; Polka & Bohn, 2003, 2011). Une preuve importante de ce biais provient d'études qui démontrent que les auditeurs discriminent les voyelles de manière asymétrique. Plus précisément, les auditeurs réussissent mieux à détecter un changement d'une voyelle relativement moins périphérique (par exemple, /e/) à une voyelle relativement plus périphérique (par exemple, /i/), comparativement à la même variation dans le sens inverse. Bien que l'existence de ce phénomène perceptif (c.-à-d. le biais de la voyelle référent naturel [VNR]) soit bien établie, les mécanismes et les processus qui le régissent sont mal compris. Une explication du VNR, qui découle de la théorie de la dispersion-focalisation (Schwartz et al., 1997, 2005), est que les articulations vocaliques extrêmes - comme /i/, /a/ et /u/ - donnent naissance à des signaux de parole particulièrement saillant spectralement en raison de la fréquence de convergence des formants, ou «focalisation». Cette thèse présente une série d'études visant à évaluer si les auditeurs sont sensibles aux différences de proximité des formants tout en discriminant le stimulus vocalique qui relève de la même catégorie phonétique, et dans ce cas, si cette sensibilité est attribuable aux propriétés générales de traitement auditif, ou à des processus phonétiques qui opèrent en termes de propriétés articulatoires. Dans l'étude 1, les auditeurs anglophones et francophones ont démontré des asymétries directionnelles en accord avec les prédictions de la focalisation lorsqu'ils tentaient de discriminer des variantes synthétiques de /u/ qui étaient systématiquement différentes dans leur périphérie et, par conséquent, dans le degré de proximité des formants (entre F1 et F2). Dans l'étude 2, des effets directionnels similaires ont été observés lorsque les auditeurs ont tenté de discriminer les réalisations naturelles de /u/ qui diffèrent dans leur périphérie seulement lors que l'information acoustique ou visuelle de parole était présente. L'étude 3 a étudié comment l'intégration des indices acoustiques vocaux et visuels influencent les effets documentés dans l'étude 2. Lorsque des signaux acoustiques et visuels étaient phonétiquement conformes, un biais de VNR a été observé. En revanche, lorsque les repères visuels et acoustiques étaient phonétiquement incongrus, ce biais était perturbé, ce qui confirme que les deux voies sensorielles créent ce biais dans la perception audiovisuelle. De façon globale, ces résultats améliorent notre compréhension des processus sensoriels et cognitifs qui sont essentiels au lien entre les propriétés des signaux et les catégories phonétiques. En particulier, ils suggèrent que les auditeurs sont prédisposés à détecter des signes vocaliques extrêmes visuellement spécifiés, en termes de modèles articulatoires cinématiques, ainsi qu'acoustiques, en termes de convergence de formants. Une compréhension complète de ce biais est non seulement importante pour les théories de la perception de la parole, mais elle fournit également une base crucial pour l'étude du développement phonétique ainsi que pour les éléments perceptuels qui pourraient restreindre les inventaires de voyelles à travers les langues
Infant preference for infant speech (Polka et al., 2021)
No full textPurpose: Current models of speech development argue for an early link between speech production and perception in infants. Recent data show that young infants (at 4–6 months) preferentially attend to speech sounds (vowels) with infant vocal properties compared to those with adult vocal properties, suggesting the presence of special “memory banks” for one’s own nascent speech-like productions. This study investigated whether the vocal resonances (formants) of the infant vocal tract are sufficient to elicit this preference and whether this perceptual bias changes with age and emerging vocal production skills.Method: We selectively manipulated the fundamental frequency (f0) of vowels synthesized with formants specifying either an infant or adult vocal tract, and then tested the effects of those manipulations on the listening preferences of infants who were slightly older than those previously tested (at 6–8 months).Results: Unlike findings with younger infants (at 4–6 months), slightly older infants in Experiment 1 displayed a robust preference for vowels with infant formants over adult formants when f0 was matched. The strength of this preference was also positively correlated with age among infants between 4 and 8 months. In Experiment 2, this preference favoring infant over adult formants was maintained when f0 values were modulated.Conclusions: Infants between 6 and 8 months of age displayed a robust and distinct preference for speech with resonances specifying a vocal tract that is similar in size and length to their own. This finding, together with data indicating that this preference is not present in younger infants and appears to increase with age, suggests that nascent knowledge of the motor schema of the vocal tract may play a role in shaping this perceptual bias, lending support to current models of speech development.Supplemental Material S1. Detailed description of the VLAM synthesis.Polka, L., Masapollo, M., & Ménard, L. (2021). Setting the stage for speech production: Infants prefer listening to speech sounds with infant vocal resonances. Journal of Speech, Language, and Hearing Research. Advance online publication. https://doi.org/10.1044/2021_JSLHR-21-00412</div
Behavioral and neural correlates of speech motor sequence learning in stuttering and neurotypical speakers: an fMRI investigation
No full textStuttering is a neurodevelopmental disorder characterized by impaired execution of articulatory movements needed for fluent speech production. Existing theoretical models propose that these deficits reflect a malfunction in the cortico-basal-ganglia-thalamocortical (cortico-BG) loop that is responsible for selecting and initiating speech motor programs. However, the cortico-BG loop has also been hypothesized to play a role in speech motor learning. To distinguish motor execution impairments from motor learning impairments in stuttering, the authors examined the behavioral and neural correlates of learning to produce novel phoneme sequences in adults who stutter (AWS) and neurotypical controls. Participants intensively practiced producing pseudowords containing non-native consonant clusters over two days. Results showed that, behaviorally, both AWS and controls produced the words with increased speed and accuracy following motor practice, and the rate of improvement was comparable for the two groups. Using functional magnetic resonance imaging (fMRI), the authors compared brain activity during articulation of the practiced words and a set of novel pseudowords (matched in phonetic complexity). FMRI analyses revealed no differences between AWS and controls in cortical or subcortical regions; both groups showed comparable increases in activation in left-lateralized brain areas implicated in phonological working memory and speech motor planning during production of the novel sequences compared to the practiced sequences. Moreover, activation in left-lateralized basal ganglia sites was negatively correlated with stuttering severity in AWS. Collectively, these findings indicate that AWS exhibit no deficit in learning novel speech sequences but do show impaired execution of these sequences prior to and after learning
