Temporal Disruptions in the “Accurate” Speech of Articulatory Defective Speakers and Stutterers

Durational measures of vocalic steady states and transitions were made on phonetically accurate and fluently produced vowel-plosive, consonant-vowel bisyllables embedded in a carrier phrase. In the first experiment, these measures were taken from the speech of ten articulatory defective adult speakers and ten matched normal speakers. The second experiment analyzed durational measures in the speech of ten adult stutterers and ten matched nonstutterers. Using wideband spectrography, durational measurements were used to infer timing of articulatory movements during the subsegments of the VCV sequences. The results of both experiments suggest that the two groups of speech disordered subjects were able to produce transitional shifts appropriate to the phonetic environment but appeared to delay the initiation of coarticulatory movements. Aberrant speech timing may imply an involvement in the planning or integration of articulatory/coarticulatory movements rather than difficulty with movement execution per se.     

Variability in the initiation of articulatory movements in the speech of stutterers and normal speakers

This study was designed to investigate the differences between stutterers and normal speakers in phonatory and articulatory timing during the initiation of fluent utterances of monosyllabic words. Electromyographic recordings of four articulatory muscles and recordings of glottal vibrations were made of repetitive utterances of a series of monosyllabic words by 15 stutterers and 17 nonstutterers. These data were analyzed in terms of average interval times between voice onset and onset of EMG activity and between onset of EMG activity in each articulator and in terms of the intrasubject variability of these durational measures. Results showed that there were no significant differences between stutterers and nonstutterers in average interval times and that stutterers, in general, were significantly more variable in their speech onset timing. Findings are discussed in terms of recent hypotheses concerning the role of timing disturbances as the main source of speech disruption in stutterers.     

Acoustic evidence of aberrant velocities in stutterers' fluent speech

Movement rates of formant frequencies and the extents of articulatory change were spectrographically analyzed in the fLuent (VCV) utterances of 20 stutterers and nonstutterers. The velocities of articulator movement throughout the first vowel and velocities into the second vowel were not significantly different for the two groups. These mean rates of movement, although nonsignificant, were slower in stutterers and slightly more variable, and the extent of articulator movement was comparable. These results do not support the contentions that stutterers use coarticulatory movements that are too rapid or that stutterers have a poorer competence for rapid coordination of speech movements. The rationales of rate-control treatment methods to slow coarticulatory movements in stutterers need to be reexamined.     

Speech timing skills of normally fluent and stuttering children and adults

This study was designed to explore the speech timing skills of normally fluent and stuttering children and adults producing two sentences, ten consecutive times at basal and modified speaking rates. Spectrographic displays of subjects' utterances in both conditions were made in order to obtain consonant, vowel, pause, and utterance duration measures. Results showed that (1) the two groups of children produced speech durational values similar to those of the two adult groups and (3) there were no consistent between- and within-group differences in the basal and modified rate conditions. Findings are discussed in terms of methodological and sampling differences that exist between the present study and past research on stutterers' speech production abilities.     

Nasal consonant production in Broca's and Wernicke's aphasics: speech deficits and neuroanatomical correlates

The present study investigated the articulatory implementation deficits of Broca's and Wernicke's aphasics and their potential neuroanatomical correlates. Five Broca's aphasics, two Wernicke's aphasics, and four age-matched normal speakers produced consonant-vowel-(consonant) real word tokens consisting of [m, n] followed by [i, e, a, o, u]. Three acoustic measures were analyzed corresponding to different properties of articulatory implementation: murmur duration (a measure of timing), amplitude of the first harmonic at consonantal release (a measure of articulatory coordination), and murmur amplitude over time (a measure of laryngeal control). Results showed that Broca's aphasics displayed impairments in all of these parameters, whereas Wernicke's aphasics only exhibited greater variability in the production of two of the parameters. The lesion extent data showed that damage in either Broca's area or the insula cortex was not predictive of the severity of the speech output impairment. Instead, lesions in the upper and lower motor face areas and the supplementary motor area resulted in the most severe implementation impairments. For the Wernicke's aphasics, the posterior areas (superior marginal gyrus, parietal, and sensory) appear to be involved in the retrieval and encoding of lexical forms for speech production, resulting in increased variability in speech production.     

Voice onset time characteristics in apraxia of speech

In order to examine the timing control of laryngeal and supralaryngeal articulatory adjustments in apraxia of speech, voice onset time (VOT) data for stop consonants in monosyllables /de/, /te/, /ge/ and /ke/ were obtained from four apraxic subjects and compared with those of fluent aphasic and normal (both young and aged) speakers (Experiment 1). The results indicated that the VOT distribution patterns of the apraxic patients differed markedly from those of the other speakers. A second experiment was conducted to determine whether the VOT distribution patterns of these four apraxic patients and of two normal controls would change with a lapse of time (Experiment 2). The results of the second experiment demonstrated marked changes in the VOT distribution patterns over time in half of the apraxic patients examined, but essentially no change in the normal controls.     

Multistable syllables as enacted percepts: a source of an asymmetric bias in the verbal transformation effect

Perceptual changes are experienced during rapid and continuous repetition of a speech form, leading to an auditory illusion known as the verbal transformation effect. Although verbal transformations are considered to reflect mainly the perceptual organization and interpretation of speech, the present study was designed to test whether or not speech production constraints may participate in the emergence of verbal representations. With this goal in mind, we examined whether variations in the articulatory cohesion of repeated nonsense words--specifically, temporal relationships between articulatory events--could lead to perceptual asymmetries in verbal transformations. The first experiment displayed variations in timing relations between two consonantal gestures embedded in various nonsense syllables in a repetitive speech production task. In the second experiment, French participants repeatedly uttered these syllables while searching for verbal transformation. Syllable transformation frequencies followed the temporal clustering between consonantal gestures: The more synchronized the gestures, the more stable and attractive the syllable. In the third experiment, which involved a covert repetition mode, the pattern was maintained without external speech movements. However, when a purely perceptual condition was used in a fourth experiment, the previously observed perceptual asymmetries of verbal transformations disappeared. These experiments demonstrate the existence of an asymmetric bias in the verbal transformation effect linked to articulatory control constraints. The persistence of this effect from an overt to a covert repetition procedure provides evidence that articulatory stability constraints originating from the action system may be involved in auditory imagery. The absence of the asymmetric bias during a purely auditory procedure rules out perceptual mechanisms as a possible explanation of the observed asymmetries.     

Multitimescale dynamical interactions between speech rhythm and gesture

Temporal patterns in human movement, and in speech in particular, occur on multiple timescales. Regularities in such patterns have been observed between speech gestures, which are relatively quick movements of articulators (e.g., tongue fronting and lip protrusion), and also between rhythmic units (e.g., syllables and metrical feet), which occur more slowly. Previous work has shown that patterns in both domains can be usefully modeled with oscillatory dynamical systems. To investigate how rhythmic and gestural domains interact, an experiment was conducted in which speakers performed a phrase repetition task, and gestural kinematics were recorded using electromagnetic articulometry. Variance in relative timing of gestural movements was correlated with variance in rhythmic timing, indicating that gestural and rhythmic systems interact in the process of planning and producing speech. A model of rhythmic and gestural planning oscillators with multifrequency coupling is presented, which can simulate the observed covariability between rhythmic and gestural timing.     

Voice onsets and segment durations of normal speakers and beginning stutterers

Longer VOT and segment durations apparently characterize the contrived responses of school-age stutterers examined under laboratory conditions. Thus, these variables may reflect basic disparities between the speech production abilities of stutterers and normal speakers. To better explore this possibility, VOT and segment durations were assessed in five nonstutterers who were closely matched with five preschool stutterers who had been diagnosed and tested in the experiment within six months of parental concern about fluency development. Target words were measured in isolation, in elicited sentences, and conversation. Results revealed significantly slower VOT and longer segment durations in the young stuttering members of the pairs of speakers. The stutterers were also more variable in their management of these same two aspects of motor speech timing control.     

Utterance timing and childhood stuttering

Articulatory speaking rate and response time latency are believed by many to be important factors in determining whether stuttering will occur in a given utterance. Currently, however, there is little empirical evidence to suggest that these measures of utterance timing are directly related to stuttering. This study examined the relationship between articulatory speaking rate and response time latency in the conversational speech of 12 boys who stutter (mean age = 55.2 months; SD = 8.8 months) who participated in 30-min conversational interactions with their mothers. Discriminant function analyses were conducted on 75 utterances drawn from each child's speech sample to determine if the articulatory speaking rate or response time latency of a specific utterance was related to the likelihood that the child would stutter on that utterance. No significant relationships between these measures of utterance timing and stuttering were found for any of the 12 subjects, and there were no significant relationships between these two measures of utterance timing. Findings do not provide support for many current theories of stuttering and suggest that the role of these measures of utterance timing in predicting the occurrence of stuttering in conversational speech in these theories may need to be reexamined.     

Temporal organization of syllables in paced and unpaced speech in children and adolescents who stutter

PurposeSpeaking with an external rhythm has a tremendous fluency-enhancing effect in people who stutter. The aim of the present study is to examine whether syllabic timing related to articulatory timing (c-center) would differ between children and adolescents who stutter and a matched control group in an unpaced vs. a paced condition.MethodsWe recorded 48 German-speaking children and adolescents who stutter and a matched control group reading monosyllabic words with and without a metronome (unpaced and paced condition). Analyses were conducted on four minimal pairs that differed in onset complexity (simple vs. complex). The following acoustic correlates of a c-center effect were analyzed: vowel and consonant compression, acoustic intervals (time from c-center, left-edge, and right-edge to an anchor-point), and relative standard deviations of these intervals.ResultsBoth groups show acoustic correlates of a c-center effect (consonant compression, vowel compression, c-center organization, and more stable c-center intervals), independently of condition. However, the group who stutters had a more pronounced consonant compression effect. The metronome did not significantly affect syllabic organization but interval stability improved in the paced condition in both groups.ConclusionChildren and adolescents who stutter and matched controls have a similar syllable organization, related to articulatory timing, regardless of paced or unpaced speech. However, consonant onset timing differs between the group who stutters and the control group; this is a promising basis for conducting an articulatory study in which articulatory (gestural) timing can be examined in more detail.     

Dyslexia: the articulatory hypothesis revisited

Articulatory disorders have been associated with developmental phonological dyslexia in the literature. However, very few information is available about the articulatory movements involved in speech production in dyslexic children. This study uses aerodynamic/acoustic data to explore how dyslexic children produce bilabial stops in French (/b, p/) within a sentence where they occurred in two positions and in three vowel environments. Average durations of articulatory closure and release were calculated in 10 phonological dyslexic children and two groups of age-matched and reading age-matched controls. Moreover, deviation from a standard pronunciation of the same material was evaluated separately by blind examiners. Our results reveal differences in the timing of the articulatory movements between dyslexics and normal controls, as well as more deviations from the target consonant for the dyslexics than for the controls. These observations are consistent with recent findings pointing to a general deficit in fine motor control in dyslexia.     

Visual speech information for face recognition

Two experiments test whether isolated visible speech movements can be used for face matching. Visible speech information was isolated with a point-light methodology. Participants were asked to match articulating point-light faces to a fully illuminated articulating face in an XAB task. The first experiment tested single-frame static face stimuli as a control. The results revealed that the participants were significantly better at matching the dynamic face stimuli than the static ones. Experiment 2 tested whether the observed dynamic advantage was based on the movement itself or on the fact that the dynamic stimuli consisted of many more static and ordered frames. For this purpose, frame rate was reduced, and the frames were shown in a random order, a correct order with incorrect relative timing, or a correct order with correct relative timing. The results revealed better matching performance with the correctly ordered and timed frame stimuli, suggesting that matches were based on the actual movement itself. These findings suggest that speaker-specific visible articulatory style can provide information for face matching.     

Anticipatory coarticulation in a patient with apraxia of speech

Articulatory anticipation of vowel gestures was assessed in an apraxic patient, a dysarthric patient, and three normal speakers. The technique of assessment included perceptual identification of gated speech stimuli. The speech material consisted of /getVte/ utterances with the target vowels /i/, /y/, and /u/. In the case of the apraxic patient the gated vowels were identified at a later instant relative to the preceding plosion burst than in the normal speakers. This result was interpreted as reflecting a delayed onset of coarticulatory gestures, in particular lip rounding. The identification rates for the dysarthric's vowels rather reflected the general reduction of this patient's vowel space.     

Sequencing and Optimization Within an Embodied Task Dynamic Model

A model of gestural sequencing in speech is proposed that aspires to producing biologically plausible fluent and efficient movement in generating an utterance. We have previously proposed a modification of the well‐known task dynamic implementation of articulatory phonology such that any given articulatory movement can be associated with a quantification of effort ( Simko & Cummins, 2010 ). To this we add a quantitative cost that decreases as speech gestures become more precise, and hence intelligible, and a third cost component that places a premium on the duration of an utterance. Together, these three cost elements allow us to derive algorithmically optimal sequences of gestures and dynamical parameters for generating articulator movement. We show that the optimized movement displays many timing characteristics that are representative of real speech movement, capturing subtle details of relative timing between gestures. Optimal movement sequences also display invariances in timing that suggest syllable‐level coordination for CV sequences. We explore the behavior of the model as prosodic context is manipulated in two dimensions: clarity of articulation and speech rate. Smooth, fluid, and efficient movements result.     

Production constraints on learning novel onset phonotactics

Three experiments addressed the hypothesis that production factors constrain phonotactic learning in adult English speakers, and that this constraint gives rise to a markedness effect on learning. In Experiment 1, an acoustic measure was used to assess consonant–consonant coarticulation in naturally produced nonwords, which were then used as stimuli in a phonotactic learning experiment. Results indicated that sonority-rising sequences were more coarticulated than -plateauing sequences, and that listeners learned novel-rising onsets more readily than novel-plateauing onsets. Experiments 2 and 3 addressed the specific questions of whether (1) the acoustic correlates of coarticulation or (2) the coarticulatory patterns of self-productions constrained learning. In Experiment 2, stimuli acoustics were altered to control for coarticulatory differences between sequence type, but a clear markedness effect was still observed. In Experiment 3, listeners’ self-productions were gathered and used to predict their treatment of novel-rising and -plateauing sequences. Results were that listeners’ coarticulatory patterns predicted their treatment of novel sequences. Overall, the findings suggest that the powerful effects of statistical learning are moderated by the perception–production loop in language.     

Hearing lips in a second language: visual articulatory information enables the perception of second language sounds

We investigated the effects of visual speech information (articulatory gestures) on the perception of second language (L2) sounds. Previous studies have demonstrated that listeners often fail to hear the difference between certain non-native phonemic contrasts, such as in the case of Spanish native speakers regarding the Catalan sounds /ɛ/ and /e/. Here, we tested whether adding visual information about the articulatory gestures (i.e., lip movements) could enhance this perceptual ability. We found that, for auditory-only presentations, Spanish-dominant bilinguals failed to show sensitivity to the /ɛ/–/e/ contrast, whereas Catalan-dominant bilinguals did. Yet, when the same speech events were presented audiovisually, Spanish-dominants (as well as Catalan-dominants) were sensitive to the phonemic contrast. Finally, when the stimuli were presented only visually (in the absence of sound), none of the two groups presented clear signs of discrimination. Our results suggest that visual speech gestures enhance second language perception at the level of phonological processing especially by way of multisensory integration.     

Learning phonetic categories by tracking movements

We explore in this study how infants may derive phonetic categories from adult input that are highly variable. Neural networks in the form of self-organizing maps (SOMs; ) were used to simulate unsupervised learning of Mandarin tones. In Simulation 1, we trained the SOMs with syllable-sized continuous F(0) contours, produced by multiple speakers in connected speech, and with the corresponding velocity profiles (D1). No attempt was made to reduce the large amount of variability in the input or to add to the input any abstract features such as height and slope of the F(0) contours. In the testing phase, reasonably high categorization rate was achieved with F(0) profiles, but D1 profiles yielded almost perfect categorization of the four tones. Close inspection of the learned prototypical D1 profile clusters revealed that they had effectively eliminated surface variability and directly reflected articulatory movements toward the underlying targets of the four tones as proposed by . Additional simulations indicated that a further learning step was possible through which D1 prototypes with one-to-one correspondence to the tones were derived from the prototype clusters learned in Simulation 1. Implications of these findings for theories of language acquisition, speech perception and speech production are discussed.     

Characterizing the Bilingual Disadvantage in Noun Phrase Production

Up to now, evidence on bilingual disadvantages in language production comes from tasks requiring single word retrieval. The present study aimed to assess whether there is a bilingual disadvantage in multiword utterances, and to determine the extent to which such effect is present in onset latencies, articulatory durations, or both. To do so, we tested two groups of Spanish speakers (monolinguals and early highly proficient bilinguals using their first and dominant language) each in two different production tasks: bare noun and noun phrase production. Onset latencies were longer for bilinguals relative to monolinguals in both production tasks. Regarding articulatory durations, we observed a clear bilingual disadvantage in noun phrase production and a strong tendency in bare noun production. These findings generalize the bilingual disadvantage in speech production to various performance measures (onset latency and articulatory duration of production) and beyond single words.     

Pitch and Manual Gestures

Gestures and speech parallel or complement each other semantically and pragmatically. Previous studies have postulated a similarly close correlation between intonation and gesture. This study microanalyzed the gestures of three subjects frame by frame and matched the movements with direction of pitch changes for each syllable in 90 intonation groups. The speech was analyzed using spectrographs. Coordinating direction of pitch and manual gesture movements is an option available to speakers, but it is not biologically mandated.