Dichotic speech perception: A comparison between stuttering and nonstuttering children

A stop consonant-vowel dichotic listening task was administered to 90 right- handed boys, 30 in each age group of 5, 7, and 9 yr. Half in each group were stutterers, half nonstutterers. Two and a half times as many stutterers as nonstutterers were found to display either a left-ear advantage (LEA) or no ear advantage (NEA). This finding suggested a greater tendency on the part of stutterers, as opposed to nonstutterers, for reversed or bilateral representation of the auditory speech areas of the brain. In addition, both stutterers and nonstutterers displayed significant developmental increases in the number of times they were able to identify both dichotic speech stimuli, thereby supporting the hypothesis of an age-related increase in children's total information processing capacity. The results are discussed in terms of the differences between stutterers and nonstutterers with respect to the issues of motor representation, cognitive modes, and higher-order linguistic processes.     

Perceptual comparisons of adolescent stutterers' and nonstutterers' fluent speech

Numerous investigators have reported that listeners are able to perceptually differentiate adult stutterers' and nonstutterers' fluent speech productions. However, findings from similar studies with children ranging in age from 3 to 9 yr have indicated that perceptual discrimination of child stutterers is difficult. A logical extension of this line of investigation would be to determine when during maturation from childhood to adulthood stutterers' fluent speech becomes perceptibly different than nonstutterers'. Therefore, in this study similar fluent speech samples from seven 12–16-yr-old adolescent male stutterers and seven matched nonstutterers were analyzed perceptually in a paired stimulus paradigm by 15 sophisticated listeners. Individual subject analyses using signal detection theory revealed that five of the seven stutterers were discriminated. When averaged for subject group comparison, these findings indicated that listeners successfully discriminated between the fluent speech of the two groups. Therefore, the perceptual difference in fluent speech production reported previously for adults appears to be present by adolescence.     

Timing and stiffness in speech motor control of stuttering and nonstuttering adults

Twelve stutterers and 12 nonstutterers were investigated in order to measure speech movements of the jaw. They spoke the nonsense word /papapas/ with stress on either the first or second syllable and with three speech rates (fast, moderate, and slow). During these trials, jaw movements were analyzed with a selspot-like optical tracking system. It was shown that stutters and nonstutterers applied the same strategies for realizing jaw movements of accented and unaccented syllables. The first strategy (stiffness variation) was used to achieve fast jaw movements while the second strategy (timing) was used in order to realize jaw movements for accented syllables. These results were taken as evidence for the assumption that, in general, stutterers and nonstutterers used the same control strategies when speaking fluently. However, it was also evident that stutterers produced lengthened jaw opening and closing durations as well as reduced peak velocities and maximal opening and closing displacements. This deviating movement pattern was supposed to reflect motor compensations necessary to achieve fluent speech rather than anomalies of the speech neuromotor system.     

Syntactic determinants of stuttering in the spontaneous speech of normally fluent and stuttering children

Conflicting findings have been reported concerning whether fluent children use more complex syntactic structures than stutterers and whether or not stutterers experience specific difficulty with complex syntactic structures. On critical examination, the first of these apparent discrepancies appears to be due to (a) differences in the methods employed for syntactic analysis in different studies, and (b) misleading impressions gained by looking at speakers within a single age range. Data were reanalyzed where one method of analysis had shown that fluent speakers and stutterers did not differ with regard to syntactic structures used but where they did show a propensity for stuttering to occur on complex syntactic structures. These data cover a range of age groups. When the second method of syntactic analysis was applied, a difference was found between fluent speakers and stutterers, with the stutterers initially using more simple structures and fewer complex ones. This difference decreased over age groups. However, a difference still remained with respect to which syntactic structures stutterers experience difficulty. An additional analysis, not formerly conducted on these data, showed that, as reported elsewhere, there was a higher probability of stuttering on clause-initial and. It was also shown that this tendency decreased with age group of the stutterers.     

The effects of simulated stuttering and prolonged speech on the neural activation patterns of stuttering and nonstuttering adults

Functional magnetic resonance imaging was used to investigate the neural correlates of passive listening, habitual speech and two modified speech patterns (simulated stuttering and prolonged speech) in stuttering and nonstuttering adults. Within-group comparisons revealed increased right hemisphere biased activation of speech-related regions during the simulated stuttered and prolonged speech tasks, relative to the habitual speech task, in the stuttering group. No significant activation differences were observed within the nonstuttering participants during these speech conditions. Between-group comparisons revealed less left superior temporal gyrus activation in stutterers during habitual speech and increased right inferior frontal gyrus activation during simulated stuttering relative to nonstutterers. Stutterers were also found to have increased activation in the left middle and superior temporal gyri and right insula, primary motor cortex and supplementary motor cortex during the passive listening condition relative to nonstutterers. The results provide further evidence for the presence of functional deficiencies underlying auditory processing, motor planning and execution in people who stutter, with these differences being affected by speech manner.     

The effect of syntactic structure upon speech initiation times of stuttering and nonstuttering speakers

Past research has shown that adults who stutter tend to be slower than adults who do not stutter at initiating various speech-like movements, nonsense syllables, words, short phrases, and simple sentences. The present study sought to extend this research by examining the effect that syntactic structure has upon stutterers' and nonstutterers' ability to initiate sentences. Eleven persons who stutter (mean age=22.2 years) and 11 nonstuttering controls (mean age=23.3 years) read, rehearsed, and then reproduced a series of 96 sentences within a simple reaction time paradigm. The sentences were presented in four blocks of 24 sentences, and each block contained one version of each of the 24 base sentences. Versions of the base sentences varied, from simple to complex, along four levels of syntactic complexity. Results indicated that speech initiation times (SITs) were significantly longer for participants who stutter than they were for nonstuttering controls for three of the four sentence types. There was no significant difference in SITs across the four sentence types for either group. Among the stuttering participants, there was no significant correlation between stuttering severity and overall initiation time for the sentences. Consistent with other studies, the present findings suggest that persons who stutter are slower than persons who do not stutter at planning and/or initiating motor movements associated with speech production. EDUCATIONAL OBJECTIVES: The reader will be able to (1). describe how persons who stutter typically perform during various reaction time tasks, (2). explain the rationale for examining the effect of syntactic complexity upon speech initiation time, (3). discuss how the speech initiation times of persons who stutter compare to those of persons who do not stutter during the production of various types of sentences, (4). identify future research needs in this area.     

Perceptual evaluation of the speech before and after fluency shaping stuttering therapy

An often-cited criterion for assessing the effect of a stuttering therapy is the ability of the stutterers to produce normally fluent speech. Many modern stuttering therapies use special techniques that may produce stutter-free speech that does not sound completely normal. The present study investigates this problem in the framework of the Dutch adaptation of the Precision Fluency Shaping Program.

Pre-, post-, and -year follow-up therapy speech samples of 32 severe stutterers who were treated in a four-week intensive therapy are compared with comparable samples of 20 nonstutterers. For that aim the samples were rated on 14 bipolar scales by groups of about 20 listeners. The results show that the speech of the stutterers in all three conditions differs significantly from the speech of the nonstutterers. The pretherapy speech takes an extreme position on a Distorted Speech dimension, due to the large proportion of disfluencies. The posttherapy speech has extremely low scores on a Dynamics/Prosody dimension, a‘1 while the follow-up therapy speech differs from the normal speech on both dimensions, but now the distances are smaller. These results are discussed in relation to the severity of the stuttering problem in the group of treated stutterers. Finally, implications for future research on therapy evaluation are discussed.     

Voice reaction time of stuttering and nonstuttering children and adults

The voice reaction time (VRT) of 5-yr old, 9-yr old, and adult stutterers and nonstutterers was investigated. Subjects initiated the sound / Λ / in response to fifty-five 1000-Hz tones of 1 sec duration. The tones were presented in five equal sets of 11 tones each with the silent intervals between the tones randomly selected to be 3, 4, 5, or 6 sec. Data analysis was based on responses 2–11 for each set. The VRTs for both the stutterers and the nonstutterers decreased significantly as an inverse function of age, with the largest decrease in reaction time occuring between 5 and 9 yr. The VRTs for the stutterers, however, were significantly slower than those of the nonstutterers at each of the three age levels. The results suggest that observed disruption in the laryngeal behavior for at least some stutterers may not result from the development of stuttering with age, but may contribute to early difficulty in the child's ability to produce fluent speech. Consideration of central factors are discussed.     

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.     

Language task effects A comparison of stuttering and nonstuttering children

This study examined the effects of language-elicitation tasks and syntactic complexity on disfluencies of stuttering and nonstuttering children. The total disfluencies occurring on the production of imitated and modeled sentences of varying syntactic complexity was compared for the two groups. Results indicated a significant task effect, but nonsignificant complexity and group effects. Results are discussed within the framework of the “Demands and Capacities” model.     

Traits attributed to stuttering and nonstuttering children by their mothers

Traits attributed to 34 stuttering and 34 nonstuttering male children by their mothers using an adjective checklist were studied. Mothers of school-aged male stutterers were found to perceive their children as being more insecure, sensitive, anxious, withdrawn, fearful, and introverted than did mothers of nonstutterers. It was concluded that although research has not demonstrated a characteristic stuttering personality, stutterers continue to be perceived as having characteristic personality patterns.     

Voice initiation and termination time in stuttering and nonstuttering children

Voice initiation time (VIT) and voice termination time (VTT) was measured in seven stuttering and eight nonstuttering children ranging in age from 4 yr, 6 mo to 6 yr, 10 mo. The experimental task was the production of /a/ in response to a 1000-Hz pure tone. Voice initiation time was defined as the period of time elapsing between the onset of the auditory stimulus and the onset of the subject's response of /a/, as displayed on an oscilloscope. Voice termination time was defined as the latency between termination of the stimulus tone and the point at which the oscilloscopic signal decreased by 90%. No statistically significant differences were found between the two groups with respect to either VIT or VTT. In addition, no apparent relationships were present among VIT, VTT, or stuttering severity.     

Communicative behavior of mothers of stuttering and nonstuttering high-risk children prior to the onset of stuttering

This portion of a multiyear prospective study was designed to investigate the communicative style, speaking rate, and language complexity of 93 mothers of preschool children with a parental history of stuttering. At the initial session none of the children sampled was regarded as being a stutterer. One year later, 26 of the children were classified as stutterers. Statistical analyses revealed that prior to the onset of stuttering the mothers of these children did not differ from the mothers of the children who continued to be seen as nonstutterers with respect to either communicative style or speaking rate. The only significant difference between the two groups of mothers was the complexity of their language. The pre-onset mean lengths of utterance (MLUs) of the mothers of children who later came to be regarded as stutterers were significantly shorter than those of the mothers whose children continued to be viewed as being fluent. These findings suggest that the communicative behavior of mothers of normally fluent children do not contribute to the development of stuttering.     

A tachistoscopic study of hemispheric processing in stuttering and nonstuttering children

Hemispheric processing, expressed as mean reaction time to various visual stimuli presented to the left and right visual fields, was investigated in eighteen stuttering and nonstuttering children. Tachistoscopic procedures were used to present linguistic stimuli (words and nonwords) as well as nonlinguistic stimuli (familiar and unfamiliar geometric figures) to the visual fields. Subjects responded by pressing a telegraph key when they perceived a real word or a familiar geometric figure. They were to make no response when they perceived nonwords or unfamiliar geometric figures. Faster reaction times were taken as an index of the most efficient or dominant hemisphere for a given task. No significant differences were found in mean reaction times for groups, visual fields, type of task, nor any of their interactions. Likewise, the data on accuracy also did not suggest that a larger proportion of stutters responded more accurately when linguistic stimuli were presented to the right hemisphere. Based on mean reaction times and on accuracy data, the stuttering and nonstuttering children performed with similar efficiencies and processing patterns.     

Perceptual and task factors in fluent braille

Hypotheses that fluent braille depends (i) on coding letters by global outline shape for all task and speed levels, or (ii) on lateral dot-gap density scanning in fast reading for meaning were tested with three groups of fluent braillists who differed in reading speeds. In experiment 1, 90 degrees-rotated (near to far) texts under vertical and horizontal finger orientation were used. Hypothesis (i) was not supported. Finger orientation interacted significantly with Speed and Task. Vertical finger orientation, which disrupts lateral scanning, slowed reading for comprehension more than for letter search, and differentially more for faster readers. Horizontal finger orientation, which instead disrupts the familiar finger-body relation, did not have differential effects. The findings support hypothesis (ii). In experiment 2, normal texts and texts containing a degraded dot in some letters were used. These are felt in searching for individual letter patterns, but would disrupt lateral scanning of expected dot-gap density patterns in reading for meaning. The results supported the predictions from hypothesis (ii), that degraded texts slow reading for meaning significantly more than for letter search, and more in the case of faster readers than for the slowest group. Findings were not consistent with hypothesis (i), which predicts that text degradation affects tasks equally, and affects the slowest rather than the fastest readers. The results suggest that perceptual coding in reading differs with task demands and speed.     

Reading ability and disfluency in stuttering and nonstuttering elementary school children

This study was aimed at comparing the reading abilities of elementary school children who stutter with their nonstuttering peers. Forty-four stuttering children from four grade levels were matched with a group of normally fluent controls on the basis of age, sex, and grade level. Reading ability was assessed by means of three Dutch standardized tests yielding a total of six scores. Disfluency scores during oral reading were also obtained for each subject. Results indicated significant differences between the two groups on reading rate and reading errors, but not on reading comprehension. Analysis of reading errors did not show qualitative differences among subjects: stuttering and nonstuttering children made the same kinds of reading errors. Similarly, the two groups did not differ with respect to performances at different grade levels. Among both groups of subjects performances became better with increasing grade on four of the six measures. Correlational analyses indicated that the measures of reading ability used in this study were significantly associated with frequency of disfluency for the nonstuttering children. In contrast, no significant relationship was found between reading ability and disfluency in the stuttering group, except for reading rate. Results are discussed with respect to the possible interaction between verbal performance and linguistic competence in reading ability measures, particularly for the stuttering child.     

Oral form perception skills of stuttering and nonstuttering children measured by stereognosis

It has been suggested that a primary causative factor in stuttering is a disordered feedback mechanism. Some researchers have explored the relationship between stuttering and the integrity of the feedback mechanism through studies of oral form perception. The studies on the relationship between stuttering and oral form perception have been carried out largely on adult populations. The results of those studies have been contradictory. The purpose of this study was to explore the relationship of stuttering to oral form perception in a school-age population. The results are in agreement with previous studies which have indicated that stutters do not do as well as non-stutters on tasks of oral form perception.     

Clinician's molar and molecular stuttering analyses of expanded and nonexpanded speech

Twenty speech pathologists measured total words and completed molar and molecular stuttering analyses from audio-recorded contrived samples of stuttered speech. Each subject completed a criterion referenced test prior to performing the experimental tasks. Analyses were performed under two conditions: Condition I consisted of samples presented at 100 wpm as recorded (nonexpanded); Condition II consisted of parallel samples recorded at 100 wpm as recorded (nonexpanded condition); Condition II consisted of parallel samples recorded at 100 wpm but presented at 59 wpm via a speech time expander. Results indicate that presentation of expanded samples (Condition II) significantly increased subject accuracy for the specific disfluency form-types word repetitions and part-word repetitions. Similar trends were noted for sound prolongations and hard contacts. Theoretical, experimental, and clinical implications are offered.     

A comparative study of the perception of freedom-in-leisure between stuttering and nonstuttering individuals

A central assumption, which served as the basis for this study, was that an individual who shared a social speech disfluency known as “stuttering” perceived less freedom in leisure experiences and was thought to be in a reduced position for deriving benefit from leisure than a nonstuttering person. Concomitant was the supposition that a stuttering person's functioning in leisure was adversely affected by possible transcendent manifestations of this stuttering. The population surveyed was the membership of the National Stuttering Project (NSP) comprised of both stuttering and nonstuttering persons.Results indicated that there was no significant difference in the current level of perceived freedom in leisure between stuttering and nonstuttering members of the NSP. Stuttering members, however, perceived barriers, prohibiting freedom in leisure, significantly different than nonstuttering members.No generalizations were made outside the NSP population surveyed.