The impact of threat and cognitive stress on speech motor control in people who stutter

PurposeIn the present study, an Emotional Stroop and Classical Stroop task were used to separate the effect of threat content and cognitive stress from the phonetic features of words on motor preparation and execution processes.MethodA group of 10 people who stutter (PWS) and 10 matched people who do not stutter (PNS) repeated colour names for threat content words and neutral words, as well as for traditional Stroop stimuli. Data collection included speech acoustics and movement data from upper lip and lower lip using 3D EMA.ResultsPWS in both tasks were slower to respond and showed smaller upper lip movement ranges than PNS. For the Emotional Stroop task only, PWS were found to show larger inter-lip phase differences compared to PNS. General threat words were executed with faster lower lip movements (larger range and shorter duration) in both groups, but only PWS showed a change in upper lip movements. For stutter specific threat words, both groups showed a more variable lip coordination pattern, but only PWS showed a delay in reaction time compared to neutral words. Individual stuttered words showed no effects. Both groups showed a classical Stroop interference effect in reaction time but no changes in motor variables.ConclusionThis study shows differential motor responses in PWS compared to controls for specific threat words. Cognitive stress was not found to affect stuttering individuals differently than controls or that its impact spreads to motor execution processes.Educational objectives: After reading this article, the reader will be able to: (1) discuss the importance of understanding how threat content influences speech motor control in people who stutter and non-stuttering speakers; (2) discuss the need to use tasks like the Emotional Stroop and Regular Stroop to separate phonetic (word-bound) based impact on fluency from other factors in people who stutter; and (3) describe the role of anxiety and cognitive stress on speech motor processes.     

Speech Motor Skill and Stuttering

The authors review converging lines of evidence from behavioral, kinematic, and neuroimaging data that point to limitations in speech motor skills in people who stutter (PWS). From their review, they conclude that PWS differ from those who do not in terms of their ability to improve with practice and retain practiced changes in the long term, and that they are less efficient and less flexible in their adaptation to lower (motor) and higher (cognitive–linguistic) order requirements that impact on speech motor functions. These findings in general provide empirical support for the position that PWS may occupy the low end of the speech motor skill continuum as argued in the Speech Motor Skills approach (Van Lieshout, Hulstijn, & Peters, 2004).     

Speech motor skill and stuttering

The authors review converging lines of evidence from behavioral, kinematic, and neuroimaging data that point to limitations in speech motor skills in people who stutter (PWS). From their review, they conclude that PWS differ from those who do not in terms of their ability to improve with practice and retain practiced changes in the long term, and that they are less efficient and less flexible in their adaptation to lower (motor) and higher (cognitive-linguistic) order requirements that impact on speech motor functions. These findings in general provide empirical support for the position that PWS may occupy the low end of the speech motor skill continuum as argued in the Speech Motor Skills approach (Van Lieshout, Hulstijn, & Peters, 2004).     

Phonological encoding in the silent speech of persons who stutter

The purpose of the present study was to investigate the role of phonological encoding in the silent speech of persons who stutter (PWS) and persons who do not stutter (PNS). Participants were 10 PWS (M=30.4 years, S.D.=7.8), matched in age, gender, and handedness with 11 PNS (M=30.1 years, S.D.=7.8). Each participant performed five tasks: a familiarization task, an overt picture naming task, a task of self-monitoring target phonemes during concurrent silent picture naming, a task of monitoring target pure tones in aurally presented tonal sequences, and a simple motor task requiring finger button clicks in response to an auditory tone. Results indicated that PWS were significantly slower in phoneme monitoring compared to PNS. No significant between-group differences were present for response speed during the auditory monitoring, picture naming or simple motor tasks, nor did the two groups differ for percent errors in any of the experimental tasks. The findings were interpreted to suggest a specific deficiency at the level of phonological monitoring, rather than a general monitoring, reaction time or auditory monitoring deficit in PWS. Educational objectives: As a result of this activity, the participant should: (1) identify and assess the literature on phonological encoding skills in PWS, (2) enumerate and evaluate some major psycholinguistic theories of stuttering, and (3) describe the mechanism by which defective phonological encoding can disrupt fluent speech production.     

The transition to increased automaticity during finger sequence learning in adult males who stutter

The present study compared the automaticity levels of persons who stutter (PWS) and persons who do not stutter (PNS) on a practiced finger sequencing task under dual task conditions. Automaticity was defined as the amount of attention required for task performance. Twelve PWS and 12 control subjects practiced finger tapping sequences under single and then dual task conditions. Control subjects performed the sequencing task significantly faster and less variably under single versus dual task conditions while PWS' performance was consistently slow and variable (comparable to the dual task performance of control subjects) under both conditions. Control subjects were significantly more accurate on a colour recognition distracter task than PWS under dual task conditions. These results suggested that control subjects transitioned to quick, accurate and increasingly automatic performance on the sequencing task after practice, while PWS did not. Because most stuttering treatment programs for adults include practice and automatization of new motor speech skills, findings of this finger sequencing study and future studies of speech sequence learning may have important implications for how to maximize stuttering treatment effectiveness. Educational objectives: As a result of this activity, the participant will be able to: (1) Define automaticity and explain the importance of dual task paradigms to investigate automaticity; (2) Relate the proposed relationship between motor learning and automaticity as stated by the authors; (3) Summarize the reviewed literature concerning the performance of PWS on dual tasks; and (4) Explain why the ability to transition to automaticity during motor learning may have important clinical implications for stuttering treatment effectiveness.     

Speech and nonspeech sequence skill learning in adults who stutter

Two studies compared the speech and nonspeech sequence skill learning of nine persons who stutter (PWS) and nine matched fluent speakers (PNS). Sequence skill learning was defined as a continuing process of stable improvement in speed and/or accuracy of sequencing performance over practice and was measured by comparing PWS's and PNS's performance curves of accuracy, reaction time, and sequence duration, as well as retention and transfer. In experiment one, participants completed a 30-trial finger tapping sequence and in experiment two, a 30-trial read-aloud sequence of nonsense syllables. Significant between-group differences were found in the speed of sequencing performance after practice, and on retention and transfer tests. These results partially supported the inference that PWS demonstrated differences in early stages of sequence skill learning compared to PNS. EDUCATIONAL OBJECTIVES: As a result of this activity the participant will be able to: (1) define skill learning and the important indicators of skill learning; (2) summarize the reviewed literature concerning the performance of PWS on speech and nonspeech sequencing tasks over practice; and (3) explain the implication of reaction time differences over practice between PWS and PNS.     

汉语口吃者在不出声言语中的语音编码

口吃者与非口吃者在不出声言语中语音编码的差异是口吃者语音加工异常的有力证据。通过三个实验,分别考察了口吃者与非口吃者监控汉语拼音中声母、韵母及声调的差异。结果表明,口吃者对声母的监控与非口吃者相比没有显著的差异,但在监控韵母及声调时,口吃者的反应显著慢于非口吃者。研究结果支持了关于口吃的“内在修正假说”,对研究汉语的语音编码有启发,对于口吃的诊断和治疗也有重要的启示     

Speeded verbal responding in adults who stutter: are there deficits in linguistic encoding?

Linguistic encoding deficits in people who stutter (PWS, n=18) were investigated using auditory priming during picture naming and word vs. non-word comparisons during choice and simple verbal reaction time (RT) tasks. During picture naming, PWS did not differ significantly from normally fluent speakers (n=18) in the magnitude of inhibition of RT from semantically related primes and the magnitude of facilitation from phonologically related primes. PWS also did not differ from controls in the degree to which words were faster than non-words during choice RT, although PWS were slower overall than controls. Simple RT showed no difference between groups, or between words and non-words, suggesting differences in speech initiation time do not explain the choice RT results. The findings are consistent with PWS not being deficient in the time course of lexical activation and selection, phonological encoding, and phonetic encoding. Potential deficits underlying slow choice RTs outside of linguistic encoding are discussed. EDUCATIONAL OBJECTIVES: The reader will be able to (1) describe possible relationships between linguistic encoding processes and speech motor control difficulties in people who stutter; (2) explain the role of lexical priming tasks during speech production in evaluating the efficiency of linguistic encoding; (3) describe the different levels of processing that may be involved in slow verbal responding by people who stutter, and identify which levels could be involved based on the findings of the present study.     

图-词干扰范式下汉语口吃者的语义编码

采用图-词干扰范式, 通过2个实验考察了汉语口吃者的语义编码。实验1发现, 在基本水平命名中,口吃者与非口吃者均表现出语义干扰效应, 语义相关干扰词的命名时间显著长于语义无关干扰词的命名时间, 口吃者在语义相关干扰条件下所受到的干扰比非口吃者大; 在类别水平命名中, 口吃者与非口吃者的表现类似, 都表现出语义促进效应, 语义相关干扰词的命名时间显著短于语义无关干扰词的命名时间, 语义相关干扰词的命名错误率也显著低于语义无关干扰词的命名错误率。实验2发现, 在基本水平命名中, 当SOA为-200 ms、-100 ms和0 ms时, 语义相关干扰条件下的反应时显著长于在语义无关干扰条件下的反应时, 当SOA为-100 ms和0 ms时, 口吃者的语义干扰效应比非口吃者更加明显。整个研究表明, 口吃者的语义编码出现了延缓, 口吃者比非口吃者需要更多的时间来排除语义干扰词的干扰。研究结果在一定程度上支持了关于口吃的多因素模型。     

Anxiety and speaking in people who stutter: An investigation using the emotional Stroop task

People with anxiety disorders show an attentional bias towards threat or negative emotion words. This exploratory study examined whether people who stutter (PWS), who can be anxious when speaking, show similar bias and whether reactions to threat words also influence speech motor planning and execution. Comparisons were made between 31 PWS and 31 fluent controls in a modified emotional Stroop task where, depending on a visual cue, participants named the colour of threat and neutral words at either a normal or fast articulation rate. In a manual version of the same task participants pressed the corresponding colour button with either a long or short duration. PWS but not controls were slower to respond to threat words than neutral words, however, this emotionality effect was only evident for verbal responding. Emotionality did not interact with speech rate, but the size of the emotionality effect among PWS did correlate with frequency of stuttering. Results suggest PWS show an attentional bias to threat words similar to that found in people with anxiety disorder. In addition, this bias appears to be contingent on engaging the speech production system as a response modality. No evidence was found to indicate that emotional reactivity during the Stroop task constrains or destabilises, perhaps via arousal mechanisms, speech motor adjustment or execution for PWS.Educational objectives: The reader will be able to: (1) explain the importance of cognitive aspects of anxiety, such as attentional biases, in the possible cause and/or maintenance of anxiety in people who stutter, (2) explain how the emotional Stroop task can be used as a measure of attentional bias to threat information, and (3) evaluate the findings with respect to the relationship between attentional bias to threat information and speech production in people who stutter.     

Sequence skill learning in persons who stutter: implications for cortico-striato-thalamo-cortical dysfunction

The basal ganglia and cortico-striato-thalamo-cortical connections are known to play a critical role in sequence skill learning and increasing automaticity over practice. The current paper reviews four studies comparing the sequence skill learning and the transition to automaticity of persons who stutter (PWS) and fluent speakers (PNS) over practice. Studies One and Two found PWS to have poor finger tap sequencing skill and nonsense syllable sequencing skill after practice, and on retention and transfer tests relative to PNS. Studies Three and Four found PWS to be significantly less accurate and/or significantly slower after practice on dual tasks requiring concurrent sequencing and colour recognition over practice relative to PNS. Evidence of PWS’ deficits in sequence skill learning and automaticity development support the hypothesis that dysfunction in cortico-striato-thalamo-cortical connections may be one etiological component in the development and maintenance of stuttering.

Educational objectives: As a result of this activity, the reader will: (1) be able to articulate the research regarding the basal ganglia system relating to sequence skill learning; (2) be able to summarize the research on stuttering with indications of sequence skill learning deficits; and (3) be able to discuss basal ganglia mechanisms with relevance for theory of stuttering.     

The nature and treatment of stuttering as revealed by fMRI A within- and between-group comparison

This article reviews some of our recent functional magnetic resonance imaging (fMRI) studies of stuttering. Using event-related fMRI experiments, we investigated brain activation during speech production. Results of three studies comparing persons who stutter (PWS) and persons who do not stutter (PWNS) are outlined. Their findings point to a region in the right frontal operculum (RFO) that was consistently implicated in stuttering. During overt reading and before fluency shaping therapy, PWS showed higher and more distributed neuronal activation than PWNS. Immediately after therapy differential activations were even more distributed and left sided. They extended to frontal, temporal, and parietal regions, anterior cingulate, insula, and putamen. These over-activations were slightly reduced and again more right sided two years after therapy. Left frontal deactivations remained stable over two years of observation, and therefore possibly indicate a dysfunction. After therapy, we noted higher activations in persons who stutter moderately than in those who stutter severely. These activations might reflect patterns of compensation. We discuss why these findings suggest that fluency-inducing techniques might synchronize a disturbed signal transmission between auditory, speech motor planning, and motor areas.

Educational objectives: The reader will learn about and be able to: (1) identify regions of brain activations and deactivations specific for PWS; (2) describe brain activation changes induced by fluency shaping therapy; and (3) discuss the correlation between stuttering severity and brain activation.     

Gestural overlap in consonant clusters: effects on the fluent speech of stuttering and non-stuttering subjects

This study was designed to investigate if persons who stutter differ from persons who do not stutter in the coproduction of different types of consonant clusters, as measured in the number of dysfluencies and incorrect speech productions, in speech reaction times and in word durations. Based on the Gestural Phonology Model of Browman and Goldstein, two types of consonant clusters were formed: homorganic and heterorganic clusters, both intra-syllabic (CVCC) and inter-syllabic (CVC#CVC). Overall, the results indicated that homorganic clusters elicited more incorrect speech productions and longer reaction times than the heterorganic clusters, but there was no difference between the homorganic and the heterorganic clusters in the word duration data. Persons who stutter showed a higher percentage dysfluencies and a higher percentage incorrect speech productions than PWNS but there were no main group effects in reaction times and word durations. However, there was a significant three-way interaction effect between group, cluster type and cluster place: homorganic clusters elicited longer reaction times than heterorganic clusters, but only in the inter-syllabic condition and only for persons who stutter. These results suggest that the production of two consonants with the same place of articulation across a syllable boundary puts higher demands on motor planning and/or initiation than producing the same cluster at the end of a syllable, in particular for PWS. The findings are discussed in light of current theories on speech motor control in stuttering. EDUCATIONAL OBJECTIVES: The reader will be able to describe: (1) the effect of gestural overlap between consonant clusters on speech reaction time and word duration of people who do and do not stutter and be able to (2) identify the literature in the field of gestural overlap between consonant clusters.     

The influence of workplace discrimination and vigilance on job satisfaction with people who stutter

Purpose The purpose of the present study is to examine the association between workplace discrimination, vigilance, and job satisfaction in people who stutter and compare this with people who do not stutter. Method Seventy-two people who stutter (PWS) and 92 people who do not stutter (PWNS) participated in an online survey. Participants completed a survey assessing 6 different areas: (a) background information, (b) job satisfaction, (c) everyday discrimination, and (d) heightened vigilance. Mediation analyses were conducted to evaluate the relationship between the independent variables and dependent variable. Results There was a relationship between being a PWS and job satisfaction, discrimination, and vigilance. PWS were found to experience higher discrimination as well as be more vigilant. Discrimination and vigilance were found to mediate the relationship between stuttering and job satisfaction. Conclusion Results of this study indicate that the participants who stutter differ from PWNS in their job satisfaction, discrimination, and vigilance. Clinicians can prepare PWS with self-advocacy strategies, legal knowledge of what their rights are as an employee who identifies as a person who stutters with a disability, a legal understanding of workplace discrimination, and counseling on the impact of vigilance on workplace experiences.     

Phoneme monitoring in silent naming and perception in adults who stutter

The present study investigated phonological encoding skills in persons who stutter (PWS). Participants were 10 PWS (M = 31.8 years, S.D. = 5.9) matched for age, gender, and handedness with 12 persons who do not stutter (PNS) (M = 24.3 years, S.D. = 4.3). The groups were compared in a phoneme monitoring task performed during silent picture naming. The phonological complexity of the target items in the task was varied such that participants monitored either compound words or noun phrases. Performance in this task was compared to phoneme monitoring performed on aurally presented target words to investigate whether any differences observed in silent naming were also evident in perception. Analysis of the response time data, in milliseconds, indicated that PWS were significantly slower as compared to PNS in phoneme monitoring during silent naming; group differences were not obtained in the perception task. The groups were also comparable in the response time to phoneme monitoring within compound words and noun phrases in both silent naming and perception. The findings suggested that PWS were slower in the encoding of segmental, phonological units during silent naming. Furthermore, absence of such differences in perception ruled out a general monitoring deficit in PWS. Findings are interpreted within the context of the psycholinguistic theories of stuttering that postulate phonological encoding and/or monitoring as a causal variable in stuttering.

Educational objectives: As a result of this activity, the participant should: (1) describe relevant literature on phonological encoding skills in children and adults who stutter, (2) identify paradigms that can be used to investigate phonological processing in PWS, and (3) discuss the role of phonological encoding in speech production.     

Beliefs of teachers versus non-teachers about people who stutter

PurposeAlthough prior research has investigated teachers’ beliefs about people who stutter (PWS), this work has not indicated how these beliefs compare with those of the general public or taken into account key demographic variables that may be related to these beliefs. The main purpose of this study was to evaluate whether beliefs about PWS in teachers are different from those in the general public. The second purpose of this study was to examine whether gender is related to beliefs about PWS for teachers, who are more frequently women.MethodsAnalyses were based on questionnaire responses regarding beliefs about PWS from 269 teachers and 1388 non-teachers in the United States. Due to their potential link to beliefs about PWS, familiarity with PWS and sociodemographic variables were included in the statistical model for this study.ResultsTeachers’ beliefs about PWS are no different than those of people in non-teaching professions. Findings also indicated that, regardless of whether respondents were teachers, women had more accurate beliefs about PWS than men. The statistical model tested indicated that beliefs about PWS were more accurate when the respondents were older, had more education, and had familiarity with a PWS.ConclusionIn the first study to compare teachers’ beliefs about PWS to the general public, findings indicated that teachers are no more accurate than the public in their beliefs about PWS. Associations found between these beliefs and several variables may indicate some promising mechanisms for improving beliefs, such as increased familiarity with individuals who stutter.Educational Objectives: Readers should be able to: (a) describe stuttering's potential effects on children's participation in the school setting; (b) identify actions teachers can take to improve the school experience of their students who stutter; (c) summarize findings regarding teachers’ beliefs about people who stutter (PWS); (d) identify key variables that are associated with beliefs about PWS.     

The speech naturalness of people who stutter speaking under delayed auditory feedback as perceived by different groups of listeners

This study investigated listeners' perception of the speech naturalness of people who stutter (PWS) speaking under delayed auditory feedback (DAF) with particular attention for possible listener differences. Three panels of judges consisting of 14 stuttering individuals, 14 speech language pathologists, and 14 naive listeners rated the naturalness of speech samples of stuttering and non-stuttering individuals using a 9-point interval scale. Results clearly indicate that these three groups evaluate naturalness differently. Naive listeners appear to be more severe in their judgements than speech language pathologists and stuttering listeners, and speech language pathologists are apparently more severe than PWS. The three listener groups showed similar trends with respect to the relationship between speech naturalness and speech rate. Results of all three indicated that for PWS, the slower a speaker's rate was, the less natural speech was judged to sound. The three listener groups also showed similar trends with regard to naturalness of the stuttering versus the non-stuttering individuals. All three panels considered the speech of the non-stuttering participants more natural. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) discuss the speech naturalness of people who stutter speaking under delayed auditory feedback, (2) discuss listener differences about the naturalness of people who stutter speaking under delayed auditory feedback, and (3) discuss the importance of speech rate for the naturalness of speech.     

Systematic studies of modified vocalization: speech production changes during a variation of metronomic speech in persons who do and do not stutter

The most common way to induce fluency using rhythm requires persons who stutter to speak one syllable or one word to each beat of a metronome, but stuttering can also be eliminated when the stimulus is of a particular duration (e.g., 1 second [s]). The present study examined stuttering frequency, speech production changes, and speech naturalness during rhythmic speech that alternated 1 s of reading with 1 s of silence. A repeated-measures design was used to compare data obtained during a control reading condition and during rhythmic reading in 10 persons who stutter (PWS) and 10 normally fluent controls. Ratings for speech naturalness were also gathered from naïve listeners. Results showed that mean vowel duration increased significantly, and the percentage of short phonated intervals decreased significantly, for both groups from the control to the experimental condition. Mean phonated interval length increased significantly for the fluent controls. Mean speech naturalness ratings during the experimental condition were approximately “7” on a 1–9 scale (1 = highly natural; 9 = highly unnatural), and these ratings were significantly correlated with vowel duration and phonated intervals for PWS. The findings indicate that PWS may be altering vocal fold vibration duration to obtain fluency during this rhythmic speech style, and that vocal fold vibration duration may have an impact on speech naturalness during rhythmic speech. Future investigations should examine speech production changes and speech naturalness during variations of this rhythmic condition.Educational objectives: The reader will be able to: (1) describe changes (from a control reading condition) in speech production variables when alternating between 1 s of reading and 1 s of silence, (2) describe which rhythmic conditions have been found to sound and feel the most natural, (3) describe methodological issues for studies about alterations in speech production variables during fluency-inducing conditions, and (4) describe which fluency-inducing conditions have been shown to involve a reduction in short phonated intervals.     

Effects of stuttering severity and therapy involvement on attitudes towards people who stutter

The purpose of this study was to explore whether stuttering severity or therapy involvement had an effect on the attitudes that individuals who do not stutter reported towards people who stutter (PWS). Two hundred and sixty (260) university students participated in this study. Direct survey procedures consisting of a 25-item semantic differential scale were utilized. Comparisons of the effects of stuttering severity, level of therapy involvement, and the interaction of these variables were completed. Results suggested that both stuttering severity and therapy involvement had significant effects on participants' attitudes towards PWS. Findings of this study support past research studies that has found that individuals who stutter mildly are perceived more positively than those who are severe. Similarly, the data supported past research that has found that PWS that attend therapy are perceived more positively than those who do not attend therapy. Surprisingly, the interaction of these variables was not significant. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) explain the possible effects of listeners' attitudes toward stuttering on the lives of PWS; (2) discuss how different factors might alter listeners' attitudes towards stuttering; (3) delineate how stuttering severity and involvement in therapy might impact listeners' attitudes towards PWS.