Jayanthi Sasisekaran

Language and motor abilities of preschool children who stutter: Evidence from behavioral and kinematic indices of nonword repetition performance

UNLABELLED Stuttering is a disorder of speech production that typically arises in the preschool years, and many accounts of its onset and development implicate language and motor processes as critical underlying factors. There have, however, been very few studies of speech motor control processes in preschool children who stutter. Hearing novel nonwords and reproducing them engages multiple neural networks, including those involved in phonological analysis and storage and speech motor programming and execution. We used this task to explore speech motor and language abilities of 31 children aged 4-5 years who were diagnosed as stuttering. We also used sensitive and specific standardized tests of speech and language abilities to determine which of the children who stutter had concomitant language and/or phonological disorders. Approximately half of our sample of stuttering children had language and/or phonological disorders. As previous investigations would suggest, the stuttering children with concomitant language or speech sound disorders produced significantly more errors on the nonword repetition task compared to typically developing children. In contrast, the children who were diagnosed as stuttering, but who had normal speech sound and language abilities, performed the nonword repetition task with equal accuracy compared to their normally fluent peers. Analyses of interarticulator motions during accurate and fluent productions of the nonwords revealed that the children who stutter (without concomitant disorders) showed higher variability in oral motor coordination indices. These results provide new evidence that preschool children diagnosed as stuttering lag their typically developing peers in maturation of speech motor control processes. EDUCATIONAL OBJECTIVES The reader will be able to: (a) discuss why performance on nonword repetition tasks has been investigated in children who stutter; (b) discuss why children who stutter in the current study had a higher incidence of concomitant language deficits compared to several other studies; (c) describe how performance differed on a nonword repetition test between children who stutter who do and do not have concomitant speech or language deficits; (d) make a general statement about speech motor control for nonword production in children who stutter compared to controls.

The Effects of Cognitive: Linguistic Variables and Language Experience on Behavioural and Kinematic Performances in Nonword Learning

The aim of the present study was to investigate the effects of cognitive-linguistic variables and language experience on behavioral and kinematic measures of nonword learning in young adults. Group 1 consisted of thirteen participants who spoke American English as the first and only language. Group 2 consisted of seven participants with varying levels of proficiency in a second language. Logistic regression of the percent of correct productions revealed short-term memory to be a significant contributor. The bilingual group showed better performance compared to the monolinguals. Linear regression of the kinematic data revealed that the short-term memory variable contributed significantly to movement coordination. Differences were not observed between the bilingual and the monolingual speakers in kinematic performance. Nonword properties including syllable length and complexity influenced both behavioral and kinematic performance. The findings supported the observation that nonword repetition is multiply determined in adults.

Nonword repetition and nonword reading abilities in adults who do and do not stutter

PURPOSE In the present study a nonword repetition and a nonword reading task were used to investigate the behavioral (speech accuracy) and speech kinematic (movement variability measured as lip aperture variability index; speech duration) profiles of groups of young adults who do (AWS) and do not stutter (control). METHOD Participants were 9 AWS (8 males, Mean age=32.2, SD=14.7) and 9 age- and sex-matched control participants (Mean age=31.8, SD=14.6). For the nonword repetition task, participants were administered the Nonword Repetition Test (Dollaghan & Campbell, 1998). For the reading task, participants were required to read out target nonwords varying in length (6 vs. 11 syllables). Repeated measures analyses of variance were conducted to compare the groups in percent speech accuracy for both tasks; only for the nonword reading task, the groups were compared in movement variability and speech duration. RESULTS The groups were comparable in percent accuracy in nonword repetition. Findings from nonword reading revealed a trend for the AWS to show a lower percent of accurate productions compared to the control group. AWS also showed significantly higher movement variability and longer speech durations compared to the control group in nonword reading. Some preliminary evidence for group differences in practice effect (seen as differences between the early vs. later 5 trials) was evident in speech duration. CONCLUSIONS Findings suggest differences between AWS and control groups in phonemic encoding and/or speech motor planning and production. Findings from nonword repetition vs. reading highlight the need for careful consideration of nonword properties. EDUCATIONAL OBJECTIVES At the end of this activity the reader will be able to: (a) summarize the literature on nonword repetition skills in adults who stutter, (b) describe processes underlying nonword repetition and nonword reading, (c) summarize whether or not adults who stutter differ from those who do not in the behavioral and kinematic markers of nonword reading performance, (d) discuss future directions for research.

Practice and retention of nonwords in adults who stutter

PURPOSE We investigated short-term practice and retention of nonwords in 10 adults who stutter (Mean age=30.7 years, SD=15.1) and age and sex-matched 10 control participants (Mean age=30.8 years, SD=14.9). METHODS Participants were required to repeat nonwords varying in length (3, 4, and 6 syllables), phonotactic constraint (PC vs. NPC, on 3-syllable nonwords only), and complexity (simple, complex). They were tested twice with 1h gap between sessions. RESULTS Logistic mixed model of speech accuracy revealed that the AWS showed a significantly lower probability of correct responses with increasing length and complexity. Analysis of speech kinematics revealed practice effects within Session 1 in AWS seen as a reduction in movement variability for the 3-syllable nonwords; the control group was performing at ceiling at this length. For the 4-syllable nonwords, the control group showed a significant reduction in movement variability with practice, and retained this reduction in Session 2, while the AWS group did not show practice or retention. Group differences were not evident at the 6-syllable level. CONCLUSIONS Group differences in speech accuracy suggest differences in phonemic encoding and/or speech motor processes. Group differences in changes in movement variability within and between sessions suggest reduced practice and retention in AWS. Relevance of the combined use of both behavioral and kinematic measures to interpret the nature of the skill acquisition deficit in persons who stutter is discussed. EDUCATIONAL OBJECTIVES At the end of this activity the reader will be able to: (a) summarize the process of skill acquisition; (b) discuss the literature on skill acquisition deficits in adults who stutter, (c) summarize the differences between AWS and control participants in speech accuracy and speech kinematics with short-term practice and retention of nonwords, (d) discuss potential research directions in the area of skill acquisition in AWS.

Exploring the link between stuttering and phonology: a review and implications for treatment.

Three lines of research have been pursued in the literature to study the link between phonology and stuttering: (1) effects of phonological complexity on the location (loci) of stutter events; (2) outcomes of standardized test measures in children who do and do not stutter; and (3) studies of phonological encoding in children and adults who stutter. This review synthesizes findings from these three lines of research to address the purported link between phonology and stuttering and its potential implications for stuttering treatment. Results from the loci studies offer some support for the role of phonological complexity in the occurrence of stuttering. Studies of performance in standardized tests of phonology have not identified differences between children who do and do not stutter. Studies of phonological encoding have been equivocal in reporting differences between children and adults who stutter and those who do not stutter. Several cautions are raised in interpreting the findings from the discussed studies, and despite the mixed findings, some implications for treatments are considered.

A preliminary investigation of phonological encoding skills in children who stutter.

PURPOSE The present study investigated phonological encoding skills in children who stutter (CWS) and those who do not (CNS). Participants were 9 CWS (M=11.8 years, SD=1.5) and 9 age and sex matched CNS (M=11.8 years, SD=1.5). METHOD Participants monitored target phonemes located at syllable onsets and offsets of bisyllabic words. Performance in the phoneme monitoring task was compared to an auditory tone monitoring task. RESULTS Repeated measures analysis of the response time data revealed significant Group×Task×Position interaction with the CWS becoming progressively slower than the CNS in monitoring subsequent phonemes located within the bisyllabic words; differences were not observed in the auditory tone monitoring task. Repeated measures analysis of the error data indicated that the groups were comparable in the percent errors in phoneme vs. tone monitoring. The CWS group was also significantly slower in a picture naming task compared to the CNS. CONCLUSIONS Present findings suggest that CWS experience temporal asynchronies in one or more processes leading up to phoneme monitoring. The findings are interpreted within the scope of contemporary theories of stuttering. EDUCATIONAL OBJECTIVES At the end of this activity the reader will be able to: (a) discuss the literature on phonological encoding skills in children who stutter, (b) identify theories of phonological encoding in stuttering, (c) define the process of phonological encoding and its implications for fluent speech, (d) suggest future areas of research in the investigation of phonological encoding abilities in children who stutter.

Nonword repetition and phoneme elision skills in school-age children who do and do not stutter

Nonword repetition and phoneme elision represent the combined influence of several speech and language processes. In the present study we investigated nonword repetition and phoneme elision performance in school-age children who stutter (CWS) and children who do not stutter (CNS). Participants were 14 CWS (mean = 11.7 years, SD = 2.1 years) and age- and sex-matched CNS (mean = 11.8 years, SD = 2.0 years). Each talker group was further subdivided into two age groups: younger (N = 7; 8-11.5 years) and older (N = 7; 11.6-15 years). Repeated-measures analyses were conducted on the accuracy and response time (in seconds) data. In nonword repetition, the CWS showed a trend for lower per cent of correct phonemes at the two-syllable level compared with the CNS. In phoneme elision, the younger CWS showed a significantly lower accuracy rate than the older CWS at the two- and three-syllable nonword lengths, while similar differences were not evident between the younger versus older CNS at any of the nonword lengths. No accuracy difference in phoneme elision was noted between the two talker groups. Group differences in speech initiation times were also not evident in either of the tasks. Findings from nonword repetition offer tentative support for difficulties experienced by school-age CWS in phonemic encoding/working memory abilities. Findings from the phoneme elision task suggest a complex pattern of age-dependent performance by the CWS. Comparison of response accuracy and speech initiation times in both the tasks failed to show speed-accuracy trade-off strategies in either of the groups.

Cross-sectional study of phoneme and rhyme monitoring abilities in children between 7 and 13 years

We investigated phonemic competence in production in three age groups of children - 7 and 8 years, 10 and 11 years, 12 and 13 years-using rhyme and phoneme monitoring. Participants were required to name target pictures silently while monitoring covert speech for the presence or absence of a rhyme or phoneme match. Performance in the verbal tasks was compared to a nonverbal control task in which participants monitored tone sequence pairs for a pattern match. Repeated measures ANOVA revealed significant differences between the three age groups in phoneme monitoring while similar differences were limited to the younger age groups in rhyme monitoring. This finding supported early and on-going acquisition of rhyme- and later acquisition of segment-level units. In addition, the 7 and 8-year-olds were significantly slower in monitoring phonemes within consonant clusters compared to the 10 and 11-year-olds and in monitoring both singleton phonemes and phonemes within clusters compared to the 12 and 13-year-olds. Regression analysis revealed that age accounted for approximately 30% variance in the nonverbal and 60% variance in the verbal monitoring tasks. We attribute the observed differences to the emergence of cognitive processes such as segmentation skills that are critical to performing the verbal monitoring tasks.

A preliminary investigation of segmentation and rhyme abilities of children who stutter.

UNLABELLED The present study investigated segmentation and rhyme abilities, skills critical for phonological encoding, of children who stutter (CWS) and those who do not (CNS). Participants were 9 CWS (8 males and 1 female, mean age=11.1, SD=2.31) in the age range of 7 and 13 years and 9 age and sex matched CNS (mean age=11.2, SD=2.19). Participants performed two verbal monitoring tasks, phoneme and rhyme monitoring, in silent naming. Performances in the verbal monitoring tasks were compared to a neutral, nonverbal tone monitoring task. Additionally, the complexity of the phoneme monitoring task was varied such that participants had to monitor for singletons vs. consonant clusters. Repeated measures analysis of the response time data did not reveal significant differences between the groups in the three monitoring tasks. Analysis of the complexity data revealed a trend for slower monitoring of the consonant clusters in the CWS group compared to the CNS. Present findings do not support a deficit in segmentation and rhyme abilities in CWS, although there was some preliminary evidence of segmentation difficulties with increasing phonological complexity of the stimuli. EDUCATIONAL OBJECTIVES At the end of this activity the reader will be able to: (a) discuss the literature on phonological encoding skills in children who stutter, (b) describe skills underlying the phonological encoding process, (c) summarize whether or not children who stutter differ from those who do not in segmentation and rhyme abilities, (d) suggest future areas of research in the investigation of segmentation and rhyme monitoring abilities in children who stutter.

Effects of Delayed Auditory Feedback on Speech Kinematics in Fluent Speakers

The effects of delayed auditory feedback on behavioral responses and speech kinematics were investigated. Participants were 10 men (M age = 22.2 yr., SD = 3.7) and 10 women (M age = 20.5 yr., SD = 2.2). Participants were required to repeat shorter (6 syllables) and longer (11 syllables) non-words in a reading task. Speech errors, lip movement variability, and movement duration of labial trajectories under delayed feedback were compared to effects under gated speech feedback and a control or synchronous auditory feedback condition. Repeated-measures analysis indicated a lower percent of correct productions, higher variability, and slower duration of lip movements in the delayed feedback condition compared to the gated feedback and control conditions. Implications for auditory feedback of movement control in continuous speech and for theories of delayed auditory feedback that attribute a role to movements are discussed.