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Fluent speech production is a complex task that spans multiple processes, from conceptual framing and lexical access, through phonological encoding, to articulatory control. For the most part, imaging studies portraying the neural correlates of speech fluency tend to examine clinical populations sustaining speech impairments and focus on either lexical access or articulatory control, but not both. Here, we evaluated the contribution of the cerebellar peduncles to speech fluency by measuring the different components of the process in a sample of 45 neurotypical adults. Participants underwent an unstructured interview to assess their natural speaking rate and articulation rate, and completed timed semantic and phonemic fluency tasks to assess their verbal fluency. Diffusion magnetic resonance imaging with probabilistic tractography was used to segment the bilateral cerebellar peduncles (CPs) and frontal aslant tract (FAT), previously associated with speech production in clinical populations. Our results demonstrate distinct patterns of white matter associations with different fluency components. Specifically, verbal fluency is associated with the right superior CP, whereas speaking rate is associated with the right middle CP and bilateral FAT. No association is found with articulation rate in these pathways, in contrast to previous findings in persons who stutter. Our findings support the contribution of the cerebellum to aspects of speech production that go beyond articulatory control, such as lexical access, pragmatic or syntactic generation. Further, we demonstrate that distinct cerebellar pathways dissociate different components of speech fluency in neurotypical speakers.

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OBJECTIVE: The objective of the present study was to investigate the effect of fast speaking on pause duration, breath group duration, and fundamental frequency (FO) in rote speech (counting). METHOD: Twenty-eight healthy women (age 18-39) who had no experience of voice training, repeated a counting task in both a habitual and fast speaking rate. Pause duration, breath group duration, and mean fundamental frequency were measured from audio recordings. Differences in the study variables between habitual and fast speaking rates were analyzed and tested for statistical significance. RESULTS: In fast speaking rate, mean pause duration was shorter and mean breath group duration longer as compared with habitual speaking rate, both with statistical significance at the group level. Surprisingly, mean fundamental frequency was significantly lower in the fast-speaking rate condition. CONCLUSION: The results overall supported the hypothesis that pause duration becomes shorter and breath group duration longer with a fast-speaking rate. This may have clinical relevance for voice therapy and supports the importance of speaking rate for the understanding and treatment of some hyperfunctional voice disorders. Notably, however, our findings indicated that counting as a speech task induces a specific pattern which may not be comparable to other speech tasks, nor representative of spontaneous speech in every-day-life.

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BACKGROUND: Slower speaking rates and higher pause rates are found in individuals with migraine or post-traumatic headache during headache compared to when headache-free. We aimed to determine whether headache intensity influences the speaking rate and pause rate of participants with migraine or acute post-traumatic headache (aPTH) following mild traumatic brain injury (mTBI). METHODS: Using a speech elicitation tool, participants with migraine, aPTH, and healthy controls (HC) submitted speech samples over a period of 3 months. Speaking and pause rates were calculated when participants were headache-free and when they had mild or moderate headache. In this observational study, speaking and pause rates in participants with migraine and aPTH were compared to HC, controlling for age, sex, and days since mTBI (participants with aPTH only). RESULTS: A total of 2902 longitudinal speech samples from 13 individuals with migraine (mean age = 33.5, SD = 6.6; 12 females/1 male), 43 individuals with aPTH (mean age = 44.4, SD = 13.5; 28 females/15 males), and 56 HC (mean age = 40.8, SD = 13.0; 36 females/20 males) were collected. There was no difference in speaking rate between HC and the combined headache cohort of participants (migraine and aPTH) when they had headache freedom or a mild headache. When participants had moderate intensity headache, their speaking rate was significantly slower compared to that of HC and compared to their speaking rate during mild headache intensity or headache freedom. For the combined headache cohort of participants, pause rates were significantly higher when they had headache freedom or had a headache of mild or moderate intensity relative to HC. Compared to participants' pause rate during headache freedom, their pause rate was significantly higher during mild and moderate headache intensity. Participants with aPTH had significantly slower speaking rates compared to participants with migraine during headache freedom, mild headache intensity, and moderate headache intensity. Participants with aPTH had significantly higher pause rates compared to participants with migraine when experiencing moderate headache intensity. DISCUSSION: For both aPTH and migraine, more severe headache pain was associated with higher pause rates and slower speaking rates, suggesting that speaking rate and pause rate could serve as objective biomarkers for headache-related pain. Slower speaking rate in participants with aPTH could reflect additional consequences of TBI-related effects on motor control and speech production.

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OBJECTIVE: The purpose of this study was to examine a number of pause-and-speech-measurements in patients with unilateral vocal fold paralysis, before and after injection laryngoplasty. The non-invasive measurements were selected to investigate and explain the treatment effect on connected speech in these patients. STUDY DESIGN: Retrospective study with repeated measurements design. METHOD: Voice recordings of 24 patients with unilateral vocal fold paralysis from before and after injection laryngoplasty in local anesthesia were analyzed retrospectively with the computer program Praat. Measurements examined were number of pauses, average pause duration, pause ratio (expressing the amount of pausing during a reading-aloud task), number of breath groups, average duration of breath groups, articulation rate, speaking rate, maximum phonation time, and Voice Handicap Index. RESULTS: Injection laryngoplasty had a significant improving effect on the number of pauses, pause ratio, number of breath groups, average duration of breath groups, articulation rate, speaking rate, maximum phonation time, and Voice Handicap Index. Maximum phonation time before treatment correlated with several pause and speech measurements. CONCLUSION: The results showed that treatment with injection laryngoplasty had a clear effect on several pause and speech measurements and that these measurements correlated with maximum phonation time, but not with Voice Handicap Index.

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INTRODUCTION/AIMS: Many people living with amyotrophic lateral sclerosis (PALS) report restrictions in their day-to-day communication (communicative participation). However, little is known about which speech features contribute to these restrictions. This study evaluated the effects of common speech symptoms in PALS (reduced overall speaking rate, slowed articulation rate, and increased pausing) on communicative participation restrictions. METHODS: Participants completed surveys (the Communicative Participation Item Bank-short form; the self-entry version of the ALS Functional Rating Scale-Revised) and recorded themselves reading the Bamboo Passage aloud using a smartphone app. Rate and pause measures were extracted from the recordings. The association of various demographic, clinical, self-reported, and acoustic speech features with communicative participation was evaluated with bivariate correlations. The contribution of salient rate and pause measures to communicative participation was assessed using multiple linear regression. RESULTS: Fifty seven people living with ALS participated in the study (mean age = 61.1 years). Acoustic and self-report measures of speech and bulbar function were moderately to highly associated with communicative participation (Spearman rho coefficients ranged from rs = 0.48 to rs = 0.77). A regression model including participant age, sex, articulation rate, and percent pause time accounted for 57% of the variance of communicative participation ratings. DISCUSSION: Even though PALS with slowed articulation rate and increased pausing may convey their message clearly, these speech features predict communicative participation restrictions. The identification of quantitative speech features, such as articulation rate and percent pause time, is critical to facilitating early and targeted intervention and for monitoring bulbar decline in ALS.

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The relationship between speaking rate and speech motor variability was examined in three groups of neurotypical adults, n = 40; 15 young adults (18-30 years), 13 adults (31-40 years), and 12 middle-aged adults (41-50 years). Participants completed a connected speech task at three speaking rates (habitual, fast, and slow) where kinematic (lower lip movement) and acoustic data were obtained. Duration and variability were measured at each speaking rate. Findings revealed a complex relationship between speaking rate and variability. Adults from the middle age range (31-40 years) demonstrated shorter acoustic and kinematic durations compared with the oldest age group (41-50 years) during the habitual speaking rate condition. All adults demonstrated the greatest variability in the slow speaking rate condition, with no significant differences in variability between habitual and fast speaking rates. Interestingly, lip aperture variability was significantly lower in the youngest age group (18-30 years) compared with the two older groups during the fast speaking rate condition. Differences in measures of acoustic variability were not observed across the age levels. Strong negative correlations between kinematic/acoustic duration and lip aperture/acoustic variability in the youngest age group were revealed. Therefore, while a slow speaking rate does result in greater variability compared with habitual and fast speaking rates, longer durations of productions by the different age groups were not linked to higher spatiotemporal index (STI) values, suggesting that timing influences speech motor variability, but is not the sole contributor.

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BACKGROUND: Speech contains neuromuscular, physiological and cognitive components, and so is a potential biomarker of mental disorders. Previous studies indicate that speaking rate and pausing are associated with major depressive disorder (MDD). However, results are inconclusive as many studies are small and underpowered and do not include clinical samples. These studies have also been unilingual and use speech collected in controlled settings. If speech markers are to help understand the onset and progress of MDD, we need to uncover markers that are robust to language and establish the strength of associations in real-world data. METHODS: We collected speech data in 585 participants with a history of MDD in the United Kingdom, Spain, and Netherlands as part of the RADAR-MDD study. Participants recorded their speech via smartphones every two weeks for 18 months. Linear mixed models were used to estimate the strength of specific markers of depression from a set of 28 speech features. RESULTS: Increased depressive symptoms were associated with speech rate, articulation rate and intensity of speech elicited from a scripted task. These features had consistently stronger effect sizes than pauses. LIMITATIONS: Our findings are derived at the cohort level so may have limited impact on identifying intra-individual speech changes associated with changes in symptom severity. The analysis of features averaged over the entire recording may have underestimated the importance of some features. CONCLUSIONS: Participants with more severe depressive symptoms spoke more slowly and quietly. Our findings are from a real-world, multilingual, clinical dataset so represent a step-change in the usefulness of speech as a digital phenotype of MDD.

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OBJECTIVE: Although speaking rate is central for many speech disorders, no consensus exists regarding the measurement of this feature. The purpose of this study was to examine the correlations between perceptual listener evaluations and various measures of speaking rate. Furthermore, the study investigated the relationship between speaking rate and articulation rate and how pauses in speech affect the perceived tempo. METHOD: Nine healthy females were selected to produce stimuli representing three habitual speech tempi during semi-spontaneous speech: slow (n = 3), neutral (n = 3) and fast (n = 3). Speaking rate was analyzed both by manual calculation and through automatic detection by a script to the computer-based program Praat. Thirty untrained male and female listeners evaluated the recordings with regard to speech tempo on visual analogue scales from very slow to very fast. RESULTS: Large, significant correlations (Pearson's r) were found between all objective measures of speaking rate and perceptual listener evaluations. Words/minute showed the largest correlation (.91), followed by syllables/second (.89), while articulation rate (pauses excluded) as automatically measured by the script, showed the smallest correlation (.69). Possible explanations for the findings are discussed. CONCLUSION: Untrained listeners' evaluation of speech tempo in normal subjects correlated strongly with objective measurements. The results both support the use of auditive-perceptual evaluation of tempo and the use of automatic script analysis for clinical use. Speaking rate (pauses included) showed better consistency with perceptual listener evaluations than articulation rate.

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Child-directed language can support language learning, but how? We addressed two questions: (1) how caregivers prosodically modulated their speech as a function of word familiarity (known or unknown to the child) and accessibility of referent (visually present or absent from the immediate environment); (2) whether such modulations affect children's unknown word learning and vocabulary development. We used data from 38 English-speaking caregivers (from the ECOLANG corpus) talking about toys (both known and unknown to their children aged 3-4 years) both when the toys are present and when absent. We analyzed prosodic dimensions (i.e., speaking rate, pitch and intensity) of caregivers' productions of 6529 toy labels. We found that unknown labels were spoken with significantly slower speaking rate, wider pitch and intensity range than known labels, especially in the first mentions, suggesting that caregivers adjust their prosody based on children's lexical knowledge. Moreover, caregivers used slower speaking rate and larger intensity range to mark the first mentions of toys that were physically absent. After the first mentions, they talked about the referents louder with higher mean pitch when toys were present than when toys were absent. Crucially, caregivers' mean pitch of unknown words and the degree of mean pitch modulation for unknown words relative to known words (pitch ratio) predicted children's immediate word learning and vocabulary size 1 year later. In conclusion, caregivers modify their prosody when the learning situation is more demanding for children, and these helpful modulations assist children in word learning. RESEARCH HIGHLIGHTS: In naturalistic interactions, caregivers use slower speaking rate, wider pitch and intensity range when introducing new labels to 3-4-year-old children, especially in first mentions. Compared to when toys are present, caregivers speak more slowly with larger intensity range to mark the first mentions of toys that are physically absent. Mean pitch to mark word familiarity predicts children's immediate word learning and future vocabulary size.

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The relationship between speaking rate and burst amplitude was investigated in plosives with differing oro-laryngeal timing: long-lag voice-onset time (VOT) (North American English) and short-lag VOT (Indian Tamil). Burst amplitude (reflecting both intraoral pressure and flow geometry of the oral channel) was hypothesized to decrease in pre-vocalic plosive syllables with the increase in speaking rate, which imposes temporal constraints on both intraoral pressure buildup behind the oral occlusion and respiratory air flow. The results showed that decreased vowel duration (which is associated with increased speaking rate) led to decreased burst amplitude in both short- and long-lag plosives. Aggregate models of bilabial and velar plosives (found in both languages) suggested lower burst amplitudes in short-lag stops. Place-of-articulation effects in both languages were consistent with models of stop consonant acoustics, and place interactions with vowel duration were most apparent with long-lag English stops. The results are discussed in terms of speaking rate and language-internal forces, contributing to burst amplitude variation and their implications for speech perception and potential to affect lenition phenomena.

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INTRODUCTION: As a key control variable, duration has been long suspected to mediate the organization of speech motor control strategies, which has management implications for neuromotor speech disorders. This study aimed to experimentally delineate the role of duration in organizing speech motor control in neurologically healthy and impaired speakers using a voluntary speaking rate manipulation paradigm. METHODS: Thirteen individuals with amyotrophic lateral sclerosis (ALS) and 10 healthy controls performed a sentence reading task three times, first at their habitual rate, then at a slower rate. A multimodal approach combining surface electromyography, kinematic, and acoustic technologies was used to record jaw muscle activities, jaw kinematics, and speech acoustics. Six muscular-kinematic features were extracted and factor-analyzed to characterize the organization of the mandibular control hierarchy. Five acoustic features were extracted, measuring the spectrotemporal properties of the diphthong /ɑɪ/ and the plosives /t/ and /k/. RESULTS: The muscular-kinematic features converged into two interpretable latent factors, reflecting the level and cohesiveness/flexibility of mandibular control, respectively. Voluntary rate reduction led to a trend toward (1) finer, less cohesive, and more flexible mandibular control, and (2) increased range and decreased transition slope of the diphthong formants, across neurologically healthy and impaired groups. Differential correlations were found between the rate-elicited changes in mandibular control and acoustic performance for neurologically healthy and impaired speakers. CONCLUSIONS: The results provided empirical evidence for the long-suspected but previously unsubstantiated role of duration in (re)organizing speech motor control strategies. The rate-elicited reorganization of muscular-kinematic control contributed to the acoustic performance of healthy speakers, in ways consistent with theoretical predictions. Such contributions were less consistent in impaired speakers, implying the complex nature of speaking rate reduction in ALS, possibly reflecting an interplay of disease-related constraints and volitional duration control. This information may help to stratify and identify candidates for the rate manipulation therapy.

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Prosodic patterning is known to affect the impression that speakers make on their listeners. This study explores prosodic phrasing in good public speakers of American English and Czech. Czech is a West Slavic language whose intonation is reported to be flatter and prosodic phrases longer than in English. We analyzed prosodic characteristics of 10 speakers of Czech and American English who appeared in TED Talks, assuming such appearance to be a mark of a "good speaker." Our objective was to see whether prosodic phrasing will be more similar in these public speeches between the two languages. We measured the length of prosodic phrases, speech rate in each phrase, and pitch range and melodic variability in the entire phrase, as well as in its pre-nuclear and nuclear portion. The number of syllables per phrase was higher in Czech than in English, although phrases were generally very short in both languages. The melodic indicators confirm smaller melodic variability in Czech even in publicly performed TED Talks. Overall, our results show that there are differences between Czech and English prosodic phrasing in good public speakers but that the genre also affects phrasing. Prosodic rendition-especially prosodic phrase length and melodic variability-is therefore a vital, albeit somewhat language-specific aspect of speech performance which public speakers should pay close attention to, both in their native language and in foreign languages.

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Evidence from acoustic and articulatory phonetics suggests that children coarticulate more than adults, but previous work has focused on the instantiation of coarticulation with phonology in a typologically homogeneous sample. The interplay of coarticulation with children's speaking rate has also been ignored. How do coarticulation and speaking rate (duration) interact over the course of development, and does the interaction manifest differently across distinct morphological environments? To answer this, the current study measured the speech patterns of bilingual Quechua-Spanish children (5-10 years) and adults. Coarticulation and duration were measured in two word environments, within morphemes and across morpheme boundaries. Unsurprisingly, adults consistently coarticulated more in shorter duration sequences, in both morphological environments. The children's coarticulation-duration patterns, however, varied by morphological environment. Additionally, the children's speech patterns, but not the adults', were sensitive to prosodic length: children produced increasingly shorter phones in words with more syllables. It is suggested that the differences between adults and children are attributable to adults' faster speaking rate and increased dominance in Quechua.

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OBJECTIVES: The objective of this study was to investigate the effects of speaking rate (habitual and fast) and speech task (reading and spontaneous speech) on seven dependent variables: Breath group size (in syllables), Breath group duration (in seconds), Lung volume at breath group initiation, Lung volume at breath group termination, Lung volume excursion for each breath group (in % vital capacity), Lung volume excursion per syllable (in % vital capacity) and mean speaking Fundamental frequency (fO). METHODS: Ten women and seven men were included as subjects. Lung volume and breathing behaviors were measured by respiratory inductance plethysmography and fO was measured from audio recordings by the Praat software. Statistical significance was tested by analysis of variance. RESULTS: For both reading and spontaneous speech, the group increased mean breath group size and breath group duration significantly in the fast speaking rate condition. The group significantly decreased lung volume excursion per syllable in fast speech. Females also showed a significant increase of fO in fast speech. The lung volume levels for initiation and termination of breath groups, as well as lung volume excursions in % vital capacity, showed great individual variations and no significant effects of rate. Significant effects of speech task were found for breath group size and lung volume excursion per syllable, where reading induced more syllables produced per breath group and less % VC spend per syllable as compared to spontaneous speech. Interaction effects showed that the increases in breath group size and breath group duration associated with fast rate were significantly larger in reading than in spontaneous speech. CONCLUSION: Our data from 17 vocally untrained, healthy subjects showed great individual variations but still significant group effects regarding increased speaking rate, where the subjects seemed to spend less air per syllable and inhaled less often as a consequence of greater breath group sizes in fast speech. Subjects showed greater changes in breath group patterns as a consequence of fast speech in reading than in spontaneous speech, indicating that effects of speaking rate are dependent on the speech task.

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INTRODUCTION: Vocal loading tasks (VLTs) help researchers gather acoustic measurements and understand how a healthy speaker adjusts their voice in response to challenges. There is a dearth of evidence measuring the impact of speaking rate in VLTs on acoustic voice parameters and vocal fatigue. OBJECTIVES: In the present study, the relationships between acoustic voice parameters and self-reported vocal fatigue were examined through an experimental VLT. METHODS: 38 students completed a 45-minute VLT which involved the recording of three randomized reading tasks. The tasks varied by the speed in which the words were presented (slow, medium, fast) on a computer monitor. Vocal fatigue ratings were measured subjectively using a Borg scale and negative adaptations to vocal loading were measured objectively using Sound Pressure Level (SPL, in dBA), fundamental frequency (fo, in semitones), and phonation time (Dt %). RESULTS: Analysis indicated that vocal fatigue increases with time, and the slope of this relationship is affected by the speaking rate. SPL and fo increased with speaking rate and the standard deviation of SPL and fo decreased with speaking rate. On average, the male participants' phonation time values were 7.8% lower than the female participants. The rate of increase of vocal fatigue with time during the experiment was higher in the fast speaking style compared to the slow and medium ones. CONCLUSION: The results provide support that the novel VLT altered multiple vocal parameters to induce measurable changes in vocal fatigue.

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Individuals typically produce auditory sequences, such as speech or music, at a consistent spontaneous rate or tempo. We addressed whether spontaneous rates would show patterns of convergence across the domains of music and language production when the same participants spoke sentences and performed melodic phrases on a piano. Although timing plays a critical role in both domains, different communicative and motor constraints apply in each case and so it is not clear whether music and speech would display similar timing mechanisms. We report the results of two experiments in which adult participants produced sequences from memory at a comfortable spontaneous (uncued) rate. In Experiment 1, monolingual pianists in Buffalo, New York engaged in three production tasks: speaking sentences from memory, performing short melodies from memory, and tapping isochronously. In Experiment 2, English-French bilingual pianists in Montréal, Canada produced melodies on a piano as in Experiment 1, and spoke short rhythmically-structured phrases repeatedly. Both experiments led to the same pattern of results. Participants exhibited consistent spontaneous rates within each task. People who produced one spoken phrase rapidly were likely to produce another spoken phrase rapidly. This consistency across stimuli was also found for performance of different musical melodies. In general, spontaneous rates across speech and music tasks were not correlated, whereas rates of tapping and music were correlated. Speech rates (for syllables) were faster than music rates (for tones) and speech showed a smaller range of spontaneous rates across individuals than did music or tapping rates. Taken together, these results suggest that spontaneous rate reflects cumulative influences of endogenous rhythms (in consistent self-generated rates within domain), peripheral motor constraints (in finger movements across tapping and music), and communicative goals based on the cultural transmission of auditory information (slower rates for to-be-synchronized music than for speech).

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Objective: The use of speech measures is becoming a common practice in the assessment of bulbar disease progression in amyotrophic lateral sclerosis (ALS). This study aimed to establish psychometric properties (e.g. reliability, validity, sensitivity, specificity) of speech and pause timing measures during a standardized passage. Methods: A large number of passage recordings (ALS N = 775; Neurotypical controls N = 323) was analyzed using a semi-automatic method (Speech and Pause Analysis, SPA). Results: The results revealed acceptable reliability of the speech and pause measures across repeated recording by the control participants. Strong construct validity was established via significant group differences between patients and controls and correlation statistics with clinical measures of overall ALS and bulbar disease severity. Speaking rate, pause events, and mean pause duration were able to detect ALS participants at the presymptomatic stage of bulbar disease with a good discrimination ability (AUC 0.81). Conclusions: Based on the current psychometric evaluation, performing passage recording and speech and pause timing analysis was deemed useful for detecting early and progressive changes associated with bulbar ALS.

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Purpose: This research aimed to automatically predict intelligible speaking rate for individuals with Amyotrophic Lateral Sclerosis (ALS) based on speech acoustic and articulatory samples. Method: Twelve participants with ALS and two normal subjects produced a total of 1831 phrases. NDI Wave system was used to collect tongue and lip movement and acoustic data synchronously. A machine learning algorithm (i.e. support vector machine) was used to predict intelligible speaking rate (speech intelligibility × speaking rate) from acoustic and articulatory features of the recorded samples. Result: Acoustic, lip movement, and tongue movement information separately, yielded a R2 of 0.652, 0.660, and 0.678 and a Root Mean Squared Error (RMSE) of 41.096, 41.166, and 39.855 words per minute (WPM) between the predicted and actual values, respectively. Combining acoustic, lip and tongue information we obtained the highest R2 (0.712) and the lowest RMSE (37.562 WPM). Conclusion: The results revealed that our proposed analyses predicted the intelligible speaking rate of the participant with reasonably high accuracy by extracting the acoustic and/or articulatory features from one short speech sample. With further development, the analyses may be well-suited for clinical applications that require automatic speech severity prediction.

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Recent work in the literature on prosody presents a puzzle: Some aspects of prosody can be primed in production (e.g., speech rate), but others cannot (e.g., intonational phrase boundaries, or IPBs). In three experiments we aimed to replicate these effects and identify the source of this dissociation. In Experiment 1 we investigated how speaking rate and the presence of an intonational boundary in a prime sentence presented auditorily affect the production of these aspects of prosody in a target sentence presented visually. Analyses of the targets revealed that participants' speaking rates, but not their production of boundaries, were affected by the priming manipulation. Experiment 2 verified whether speakers are more sensitive to IPBs when the boundaries provide disambiguating information, and in this different context replicated Experiment 1 in showing no IPB priming. Experiment 3 tested whether speakers are sensitive to another aspect of prosody-pitch accenting-in a similar paradigm. Again, we found no evidence that this manipulation affected pitch accenting in target sentences. These findings are consistent with earlier research and suggest that aspects of prosody that are paralinguistic (like speaking rate) may be more amenable to priming than are linguistic aspects of prosody (such as phrase boundaries and pitch accenting).

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PURPOSE: Although it is frequently presumed that bulbar muscle degeneration in Amyotrophic Lateral Sclerosis (ALS) is associated with progressive loss of speech motor control, empirical evidence is limited. Furthermore, because speaking rate slows with disease progression and rate manipulations are used to improve intelligibility in ALS, this study sought to (i) determine between and within-group differences in articulatory motor control as a result of speaking rate changes and (ii) identify the strength of association between articulatory motor control and speech impairment severity. METHOD: Ten talkers with ALS and 11 healthy controls repeated the target sentence at habitual, fast, and slow rates. The spatiotemporal variability index (STI) was calculated to determine tongue, lower lip, and jaw movement variability. RESULTS: During habitual speech, talkers with mild-moderate dysarthria displayed significantly lower tongue and lip movement variability whereas those with severe dysarthria showed greater variability compared to controls. Within-group rate effects were significant only for talkers with ALS. Specifically, lip and tongue movement variability significantly increased during slow speech relative to habitual and fast speech. Finally, preliminary associations between speech impairment severity and movement variability were moderate to strong in talkers with ALS. CONCLUSION: Between-group differences for habitual speech and within-group effects for slow speech replicated previous findings for lower lip and jaw movements. Preliminary findings of moderate to strong associations between speech impairment severity and STI suggest that articulatory variability may vary from pathologically low (possibly indicating articulatory compensation) to pathologically high variability (possibly indicating loss of control) with dysarthria progression in ALS.

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