A Preliminary Study of Speech Rhythm Differences as Markers of Stuttering Persistence in Preschool-Age Children.

PURPOSE: The purpose of this study was twofold: (a) to determine whether there are speech rhythm differences between preschool-age children who stutter that were eventually diagnosed as persisting (CWS-Per) or recovered (CWS-Rec) and children who do not stutter (CWNS), using empirical spectral analysis and empirical mode decomposition of the speech amplitude envelope, and (b) to determine whether speech rhythm characteristics close to onset are predictive of later persistence. METHOD: Fifty children (3-4 years of age) participated in the study. Approximately 2-2.5 years after the experimental testing took place, children were assigned to the following groups: CWS-Per (nine boys, one girl), CWS-Rec (18 boys, two girls), and CWNS (18 boys, two girls). All children produced a narrative based on a text-free storybook. From the audio recordings of these narratives, fluent utterances were selected for each child from which seven envelope-based measures were extracted. Group-based differences on each measure as well as predictive analyses were conducted to identify measures that discriminate CWS-Per versus CWS-Rec. RESULTS: CWS-Per were found to have a relatively higher degree of power in suprasyllabic oscillations and greater variability in the timing of syllabic rhythms especially for longer utterances. A logistic regression model using two speech rhythm measures was able to discriminate the eventual outcome of recovery versus persistence, with 80% sensitivity and 75% specificity. CONCLUSION: Findings suggest that envelope-based speech rhythm measures are a promising approach to assess speech rhythm differences in developmental stuttering, and its potential for identification of children at risk of developing persistent stuttering should be investigated further.

Articulatory Performance in Dysarthria: Using a Data-Driven Approach to Estimate Articulatory Demands and Deficits.

This study pursued two goals: (1) to establish range of motion (ROM) demand tiers (i.e., low, moderate, high) specific to the jaw (J), lower lip (LL), posterior tongue (PT), and anterior tongue (AT) for multisyllabic words based on the articulatory performance of neurotypical talkers and (2) to identify demand- and disease-specific articulatory performance characteristics in talkers with amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). J, LL, PT, and AT movements of 12 talkers with ALS, 12 talkers with PD, and 12 controls were recorded using electromagnetic articulography. Vertical ROM, average speed, and movement duration were measured. Results showed that in talkers with PD, J and LL ROM were already significantly reduced at the lowest tier whereas PT and AT ROM were only significantly reduced at moderate and high tiers. In talkers with ALS, J ROM was significantly reduced at the moderate tier whereas LL, PT, and AT ROM were only significantly reduced at the highest tier. In both clinical groups, significantly reduced J and LL speeds could already be observed at the lowest tier whereas significantly reduced AT speeds could only be observed at the highest tier. PT speeds were already significantly reduced at the lowest tier in the ALS group but not until the moderate tier in the PD group. Finally, movement duration, but not ROM or speed performance, differentiated between ALS and PD even at the lowest tier. Results suggest that articulatory deficits vary with stimuli-specific motor demands across articulators and clinical groups.

Dysarthria Subgroups in Talkers with Huntington's Disease: Comparison of Two Data-Driven Classification Approaches.

Although researchers have recognized the need to better account for the heterogeneous perceptual speech characteristics among talkers with the same disease, guidance on how to best establish such dysarthria subgroups is currently lacking. Therefore, we compared subgroup decisions of two data-driven approaches based on a cohort of talkers with Huntington's disease (HD): (1) a statistical clustering approach (STATCLUSTER) based on perceptual speech characteristic profiles and (2) an auditory free classification approach (FREECLASS) based on listeners' similarity judgments. We determined the amount of overlap across the two subgrouping decisions and the perceptual speech characteristics driving the subgrouping decisions of each approach. The same speech samples produced by 48 talkers with HD were used for both grouping approaches. The STATCLUSTER approach had been conducted previously. The FREECLASS approach was conducted in the present study. Both approaches yielded four dysarthria subgroups, which overlapped between 50% to 78%. In both grouping approaches, overall bizarreness and speech rate characteristics accounted for the grouping decisions. In addition, voice abnormalities contributed to the grouping decisions in the FREECLASS approach. These findings suggest that apart from overall bizarreness ratings, indexing dysarthria severity, speech rate and voice characteristics may be important features to establish dysarthria subgroups in HD.

Tongue- and Jaw-Specific Articulatory Changes and Their Acoustic Consequences in Talkers With Dysarthria due to Amyotrophic Lateral Sclerosis: Effects of Loud, Clear, and Slow Speech.

Purpose This study aimed to determine how tongue and jaw displacement changes impact acoustic vowel contrast in talkers with amyotrophic lateral sclerosis (ALS) and controls. Method Ten talkers with ALS and 14 controls participated in this study. Loud, clear, and slow speech cues were used to elicit tongue and jaw kinematic as well as acoustic changes. Speech kinematics was recorded using three-dimensional articulography. Independent tongue and jaw displacements were extracted during the diphthong /ai/ in kite. Acoustic distance between diphthong onset and offset in Formant 1-Formant 2 vowel space indexed acoustic vowel contrast. Results In both groups, all three speech modifications elicited increases in jaw displacement (typical < slow < loud < clear). By contrast, only slow speech elicited significantly increased independent tongue displacement in the ALS group (typical = loud = clear < slow), whereas all three speech modifications elicited significantly increased independent tongue displacement in controls (typical < loud < clear = slow). Furthermore, acoustic vowel contrast significantly increased in response to clear and slow speech in the ALS group, whereas all three speech modifications elicited significant increases in acoustic vowel contrast in controls (typical < loud < slow < clear). Finally, only jaw displacements accounted for acoustic vowel contrast gains in the ALS group. In controls, however, independent tongue displacements accounted for increases in vowel acoustic contrast during loud and slow speech, whereas jaw and independent tongue displacements accounted equally for acoustic vowel contrast change during clear speech. Conclusion Kinematic findings suggest that slow speech may be better suited to target independent tongue displacements in talkers with ALS than clear and loud speech. However, given that gains in acoustic vowel contrast were comparable for slow and clear speech cues in these talkers, future research is needed to determine potential differential impacts of slow and clear speech on perceptual measures, such as intelligibility. Finally, findings suggest that acoustic vowel contrast gains are predominantly jaw driven in talkers with ALS. Therefore, the acoustic and perceptual consequences of direct instructions of enhanced jaw movements should be compared to cued speech modification, such as clear and slow speech in these talkers.

Detection of Articulatory Deficits in Parkinson's Disease: Can Systematic Manipulations of Phonetic Complexity Help?

Purpose This study sought to determine the feasibility of using phonetic complexity manipulations as a way to systematically assess articulatory deficits in talkers with progressive dysarthria due to Parkinson's disease (PD). Method Articulatory kinematics were recorded using three-dimensional electromagnetic articulography from 15 talkers with PD (58-84 years old) and 15 healthy controls (55-80 years old) while they produced target words embedded in a carrier phrase. Majority of the talkers with PD exhibited a relatively mild dysarthria. For stimuli selection, phonetic complexity was calculated for a variety of words using the framework proposed by Kent (1992), and six words representative of low, medium, and high phonetic complexity were selected as targets. Jaw, posterior tongue, and anterior tongue kinematic measures that were used to test for phonetic complexity effects included movement speed, cumulative path distance, movement range, movement duration, and spatiotemporal variability. Results Significantly smaller movements and slower movement speeds were evident in talkers with PD, predominantly for words with high phonetic complexity. The effect sizes of between-groups differences were larger for several jaw kinematic measures than those of the tongue. Discussion and Conclusion Findings suggest that systematic manipulations of phonetic complexity can support the detection of articulatory deficits in talkers with PD. Phonetic complexity should therefore be leveraged for the assessment of articulatory performance in talkers with progressive dysarthria. Future work will be directed toward linking speech kinematic and auditory-perceptual measures to determine the clinical significance of the current findings.

Auditory event-related potentials index faster processing of natural speech but not synthetic speech over nonspeech analogs in children.

Given the crucial role of speech sounds in human language, it may be beneficial for speech to be supported by more efficient auditory and attentional neural processing mechanisms compared to nonspeech sounds. However, previous event-related potential (ERP) studies have found either no differences or slower auditory processing of speech than nonspeech, as well as inconsistent attentional processing. We hypothesized that this may be due to the use of synthetic stimuli in past experiments. The present study measured ERP responses during passive listening to both synthetic and natural speech and complexity-matched nonspeech analog sounds in 22 8-11-year-old children. We found that although children were more likely to show immature auditory ERP responses to the more complex natural stimuli, ERP latencies were significantly faster to natural speech compared to cow vocalizations, but were significantly slower to synthetic speech compared to tones. The attentional results indicated a P3a orienting response only to the cow sound, and we discuss potential methodological reasons for this. We conclude that our results support more efficient auditory processing of natural speech sounds in children, though more research with a wider array of stimuli will be necessary to confirm these results. Our results also highlight the importance of using natural stimuli in research investigating the neurobiology of language.

Motor speech patterns in Huntington disease.

OBJECTIVE: Dysarthric speech of persons with Huntington disease (HD) is typically described as hyperkinetic; however, studies suggest that dysarthria can vary and resemble patterns in other neurologic conditions. To test the hypothesis that distinct motor speech subgroups can be identified within a larger cohort of patients with HD, we performed a cluster analysis on speech perceptual characteristics of patient audio recordings. METHODS: Audio recordings of 48 patients with mild to moderate dysarthria due to HD were presented to 6 trained raters. Raters provided scores for various speech features (e.g., voice, articulation, prosody) of audio recordings using the classic Mayo Clinic dysarthria rating scale. Scores were submitted to an unsupervised k-means cluster analysis to determine the most salient speech features of subgroups based on motor speech patterns. RESULTS: Four unique subgroups emerged from the cohort of patients with HD. Subgroup 1 was characterized by an abnormally fast speaking rate among other unique speech features, whereas subgroups 2 and 3 were defined by an abnormally slow speaking rate. Salient speech features for subgroup 2 overlapped with subgroup 3; however, the severity of dysarthria differed. Subgroup 4 was characterized by mild deviations of speech features with typical speech rate. Length of CAG repeats, Unified Huntington's Disease Rating Scale total motor score, and percent intelligibility were significantly different for pairwise comparisons of subgroups. CONCLUSION: This study supports the existence of distinct presentations of dysarthria in patients with HD, which may be due to divergent pathologic processes. The findings are discussed in relation to previous literature and clinical implications.

Tongue- and Jaw-Specific Articulatory Underpinnings of Reduced and Enhanced Acoustic Vowel Contrast in Talkers With Parkinson's Disease.

Purpose This study sought to identify the articulator-specific mechanisms that underlie reduced and enhanced acoustic vowel contrast in talkers with dysarthria due to Parkinson's disease (PD). Method Seventeen talkers with mild-moderate dysarthria due to PD and 17 controls completed a sentence repetition task using typical, slow, loud, and clear speech. Tongue and jaw articulatory movements were recorded using 3D electromagnetic articulography. Independent tongue displacements, jaw displacements, and acoustic vowel contrast were calculated for the diphthong /aɪ/ embedded in the word kite. Results During typical speech, independent tongue displacement, but not jaw displacement, contributed significantly to the intertalker variance in acoustic vowel contrast. Loudness-related acoustic vowel contrast gains were predominantly jaw driven in controls but driven by the tongue and jaw in talkers with PD. Further, in both groups, clarity-related acoustic vowel contrast gains were predominantly jaw driven. Finally, in both groups, rate-related acoustic vowel contrast gains were predominantly tongue driven; however, the jaw also contributed. These jaw contributions were greater in the PD group than in the control group. Conclusions Findings suggest that a tongue-specific articulatory impairment underlies acoustic vowel contrast deterioration in talkers with PD, at least during the early stages of speech decline. Findings further suggest that slow speech engages the impaired tongue more than loud and clear speech in talkers with PD. However, slow speech was also associated with an abnormally strong jaw response in these talkers, which suggests that a compensatory articulatory behavior may also be elicited.

Effects of speaking rate, loudness, and clarity modifications on kinematic endpoint variability.

It is virtually impossible for a speaker to produce identical articulatory movements across several repetitions of the same utterance. This study examined how kinematic endpoint variability, defined as the positional variability of an articulator at its positional extremum, changes in response to cued speech behavioral modifications. As a second step, this study examined the strength of association between articulator speed and kinematic endpoint variability. Seventeen speakers repeated the sentence "Buy Kaia a kite" 10 times under the following conditions: typical, loud, slow, and clear speech. Speech movements were recorded using 3D electromagnetic articulography. Endpoint variability was measured at the maximum jaw opening position during "buy" and at the maximum elevation of the tongue back during /k/ in "Kaia". Significant speech modification effects were found for the jaw but not for the tongue. Specifically, typical speech yielded significantly lower kinematic endpoint variability than slow and loud speech. Further, jaw peak speed was moderately correlated with kinematic endpoint variability (r = .43, p < .01). Findings for jaw movements suggest that speech modifications that elicit an increase in speed (i.e. loud speech) may negatively impact kinematic endpoint precision; however, other factors such as motor learning and lacking emphasis on spatial precision (i.e. slow speech) may also play a role.

A first investigation of tongue, lip, and jaw movements in persons with dysarthria due to multiple sclerosis.

BACKGROUND: Multiple sclerosis can affect the speech motor system and result in dysarthria. OBJECTIVES: This pilot study sought to identify tongue, lip, and jaw motor deficits in persons with dysarthria due to multiple sclerosis (PwDMS) to better understand the speech motor mechanisms that underlie their aberrant speech. METHODS: Tongue and jaw movements during "ai" and lower lip and jaw movements during "bob"were examined in eleven PwDMS and fourteen age- and sex-matched controls using three-dimensional electromagnetic articulography. Movement duration, maximum displacement, peak speed, stiffness (i.e., peak speed/displacement ratio), and jaw contribution to lower lip and tongue displacements were of particular interest. RESULTS: Whereas most kinematic measures yielded significant between-group differences for tongue and jaw motor performance during "ai", lower lip and jaw motor performance during "bob" were mostly comparable between groups. CONCLUSION: Findings suggest that speech movements of the tongue are differentially more impaired than those of the lower lip in PwDMS. Particularly the ability to move the tongue with adequate speed during speech was significantly impaired in PwDMS, which may explain, in part, their slowed speech rate. Aberrant jaw kinematics during "ai" may be a compensatory strategy to maximize speech clarity in the presence of the impaired tongue motor performance.

A comparative study: tongue muscle performance in weightlifters and runners.

Exercise mode (i.e., resistance training, endurance training) is known to yield mode-specific effects on strength and endurance of muscles that are directly targeted during the exercise. Such mode-specific effects can also be observed in indirectly involved (i.e., nontargeted) muscles. Mode-specific muscle performance changes of nontargeted muscles, however, have only been investigated within the skeletal system. Therefore, as a first step, this study aimed to determine if bulbar muscle performance (tongue strength [TS], tongue endurance [TE]) differs between weightlifters and runners and if group differences are tongue region-specific. The Iowa Oral Performance Instrument (IOPI) was used to measure TS and TE of the anterior and posterior tongue regions in 21 weightlifters and 23 runners. In weightlifters anterior TS was significantly greater than posterior TS (P = 0.008), whereas in runners anterior and posterior TS were comparable. Furthermore, weightlifters produced significantly greater anterior TS than runners (P = 0.001). Finally, TE was overall significantly greater in runners than in weightlifters (P = 0.001). Findings suggest that exercise mode may differentially impact performance patterns of nontargeted bulbar muscles. More research is warranted to better understand the mechanisms underlying tongue muscle performance differences between weightlifters and runners.

Tongue- and Jaw-Specific Contributions to Acoustic Vowel Contrast Changes in the Diphthong /ai/ in Response to Slow, Loud, and Clear Speech.

Purpose: This study sought to determine decoupled tongue and jaw displacement changes and their specific contributions to acoustic vowel contrast changes during slow, loud, and clear speech. Method: Twenty typical talkers repeated "see a kite again" 5 times in 4 speech conditions (typical, slow, loud, clear). Speech kinematics were recorded using 3-dimensional electromagnetic articulography. Tongue composite displacement, decoupled tongue displacement, and jaw displacement during /ai/, as well as the distance between /a/ and /i/ in the F1-F2 vowel space, were examined during the diphthong /ai/ in "kite." Results: Displacements significantly increased during all 3 speech modifications. However, jaw displacements increased significantly more during clear speech than during loud and slow speech, whereas decoupled tongue displacements increased significantly more during slow speech than during clear and loud speech. In addition, decoupled tongue displacements increased significantly more during clear speech than during loud speech. Increases in acoustic vowel contrast tended to be larger during slow speech than during clear speech and were predominantly tongue-driven, whereas those during clear speech were fairly equally accounted for by changes in decoupled tongue and jaw displacements. Increases in acoustic vowel contrast during loud speech were smallest and were predominantly tongue-driven, particularly in men. Conclusions: Findings suggest that task-specific patterns of decoupled tongue and jaw displacement change and task-specific patterns of decoupled tongue and jaw contributions to vowel acoustic change across these speech modifications. Clinical implications are discussed.

Tongue strength and endurance: Comparison in active and non-active young and older adults.

PURPOSE: Tongue strength and endurance are important for swallowing and upper airway patency. Physical activity positively affects targeted and non-targeted skeletal muscles; however, little is known about the indirect effect of physical activity on tongue muscles. This study sought to determine if tongue muscle performance differs between highly active and non-active individuals and if such an effect varies with age. METHOD: Forty-eight healthy adults were divided into two age groups (24 young, 20.96 ± 3.22 years; 24 older, 65 ± 3.72 years) and further divided into highly active and non-active based on The General Practice Physical Activity Questionnaire. Tongue strength (TS) and tongue endurance (TE) were obtained using the Iowa Oral Performance Instrument. RESULT: A significant main effect of activity level on TS and TE was found. Although the main effect of age on TS and TE and age × activity level interactions were not significant, the effect of activity level on TS and TE was more pronounced in older adults than younger adults. CONCLUSION: Findings suggest physical activity may affect TS and TE, particularly in older adults. Future research is warranted to understand the underlying mechanisms contributing to these group differences. Clinical implications of these findings are discussed.

Associations between tongue movement pattern consistency and formant movement pattern consistency in response to speech behavioral modifications.

The degree of speech movement pattern consistency can provide information about speech motor control. Although tongue motor control is particularly important because of the tongue's primary contribution to the speech acoustic signal, capturing tongue movements during speech remains difficult and costly. This study sought to determine if formant movements could be used to estimate tongue movement pattern consistency indirectly. Two age groups (seven young adults and seven older adults) and six speech conditions (typical, slow, loud, clear, fast, bite block speech) were selected to elicit an age- and task-dependent performance range in tongue movement pattern consistency. Kinematic and acoustic spatiotemporal indexes (STI) were calculated based on sentence-length tongue movement and formant movement signals, respectively. Kinematic and acoustic STI values showed strong associations across talkers and moderate to strong associations for each talker across speech tasks; although, in cases where task-related tongue motor performance changes were relatively small, the acoustic STI values were poorly associated with kinematic STI values. These findings suggest that, depending on the sensitivity needs, formant movement pattern consistency could be used in lieu of direct kinematic analysis to indirectly examine speech motor control.

Assessing articulatory speed performance as a potential factor of slowed speech in older adults.

PURPOSE To improve our understanding about the underlying factors of aging-related speaking rate decline, the authors sought to determine if lip and jaw speeds are physiologically constrained in older adults. METHOD Thirty-six females-10 young adults (ages 22-27 years), 9 middle-aged adults (ages 45-55 years), 10 young-old adults (65-74 years), and 7 very old adults (ages 87-95 years)-completed metronome-paced syllable repetitions while moving the lower lip or jaw to a fixed target with each repetition. Metronome paces incrementally increased from 1.4 Hz to 6.7 Hz. Lip and jaw movements were tracked using a 3-dimensional motion capture system. RESULTS Older adults' maximum percent increase in lip and jaw peak speed was comparable to or tended to be even greater than that of middle-aged and young adults. By contrast, lip and jaw stiffness, indexed by peak speed-displacement ratios, tended to decrease with age during fast and very fast repetition rates and were associated with mildly prolonged movement durations. CONCLUSIONS The findings suggest that lip and jaw speeds are not constrained in older adults. The trend of reduced stiffness during fast rates, however, suggests that fine-force regulation becomes difficult for older adults. Thus, older adults may implement reduced habitual speaking rates as a behavioral strategy to compensate for diminished articulatory control.

Speaking rate effects on articulatory pattern consistency in talkers with mild ALS.

This study investigated speaking rate effects on articulatory pattern consistency in talkers with mild amyotrophic lateral sclerosis (ALS) to better understand speech rate declines during the early stages of speech deterioration. Eight talkers with mild ALS and 11 controls repeated a sentence at their typical rate, an accelerated rate, and a reduced rate. Lip and jaw movements were captured using a 3-D motion capture system. Results showed that talkers with ALS produced more consistent articulatory patterns during typical speech than did controls. Further, rate reduction resulted in diminished pattern consistency in both groups. Fast speech also elicited less consistent articulatory patterns in talkers with ALS. Controls, by contrast, tended to produce more consistent patterns during fast speech. Relatively inconsistent patterns during fast speech suggest that ALS may negatively affect articulatory control when the speech motor system operates near its performance limit. Relatively consistent patterns during typical speech indicate a successful adaption to disease-related articulatory deficits. Rate reduction does not appear to benefit articulatory stability during early stages of speech decline.

Hydration in older adults: the contribution of bioelectrical impedance analysis.

The sensory and gastrointestinal changes that occur with ageing affect older adults' food and liquid intake. Any decreased liquid intake increases the risk for dehydration. This increased dehydration risk is compounded in older adults with dysphagia. The availability of a non-invasive and easily administered way to document hydration levels in older adults is critical, particularly for adults in residential care. This pilot study investigated the contribution of bioelectrical impedance analysis to measure hydration in 19 older women in residential care: 13 who viewed themselves as healthy and six with dysphagia. Mann-Whitney U analyses documented no significant between-group differences for Total Body Water (TBW), Fat Free Mass (FFM), Fat Mass (FM), and percentage Body Fat (%BF). However, when compared to previously published data for age-matched women, the TBW and FFM values of the two participant groups were notably less, and FM and %BF values were notably greater than expected. If results are confirmed through continued investigation, such findings may suggest that long-term care facilities are unique environments in which all older residents can be considered at-risk for dehydration and support the use of BIA as a non-invasive tool to assess and monitor their hydration status.

A novel fixed-target task to determine articulatory speed constraints in persons with amyotrophic lateral sclerosis.

PURPOSE: The goal of this study was to determine if talkers with ALS are limited in their ability to increase lower lip and jaw speed at an early stage of the disease when their speaking rate and intelligibility are only minimally or not affected. METHOD: A novel metronome paced fixed-target task was used to assess movement speed capacities during lower lip and jaw oscillations in seven talkers with ALS and seven age and gender matched controls. RESULTS: Lower lip peak speeds were significantly lower in talkers with mild ALS than in healthy talkers suggesting a lower lip speed constraint in talkers with mild ALS. Jaw peak speeds tended to be lower, but jaw displacements tended to be larger in talkers with mild ALS than in healthy talkers. Because greater speeds are typically expected for larger displacements, outcomes also suggest a jaw speed constraint in talkers with mild ALS. CONCLUSIONS: Lower lip and jaw peak speeds may be sensitive measures to identify bulbar motor performance decline at an early stage of the disease when speaking rate and intelligibility are only minimally affected. LEARNING OUTCOMES: The reader will be able to explain two different articulatory strategies to increase speaking rate and understand why fast speech tasks and diadochokinetic pseudo-speech tasks are not suited to assess articulatory speed capacity in healthy and impaired talkers. The reader will also be able to explain how orofacial movement speed capacity can be tested using a fixed-target task and how ALS affects lower lip and jaw speed capacities during the early stages of the disease.

Articulatory-to-acoustic relations in response to speaking rate and loudness manipulations.

PURPOSE: In this investigation, the authors determined the strength of association between tongue kinematic and speech acoustics changes in response to speaking rate and loudness manipulations. Performance changes in the kinematic and acoustic domains were measured using two aspects of speech production presumably affecting speech clarity: phonetic specification and variability. METHOD: Tongue movements for the vowels /ia/ were recorded in 10 healthy adults during habitual, fast, slow, and loud speech using three-dimensional electromagnetic articulography. To determine articulatory-to-acoustic relations for phonetic specification, the authors correlated changes in lingual displacement with changes in acoustic vowel distance. To determine articulatory-to-acoustic relations for phonetic variability, the authors correlated changes in lingual movement variability with changes in formant movement variability. RESULTS: A significant positive linear association was found for kinematic and acoustic specification but not for kinematic and acoustic variability. Several significant speaking task effects were also observed. CONCLUSION: Lingual displacement is a good predictor of acoustic vowel distance in healthy talkers. The weak association between kinematic and acoustic variability raises questions regarding the effects of articulatory variability on speech clarity and intelligibility, particularly in individuals with motor speech disorders.