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.     

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.     

Adaptation effect in nonfluent speech behavior of controlled stutterers and nonstutterers

The adaptation effect in stuttering behavior has received considerable attention. Adaptation effect is defined as the reduction in the frequency of nonfluencies in the speech of subjects during successive readings of the same passage. The objective of this investigation was to assess the adaptation effect of nonfluent speech behavior of controlled stutterers and nonstutterers. The subjects included 35 controlled stutterers and 35 nonstutterers matched for factors of sex, grade level, and age. Results suggest a significant mean difference between the number of nonfluencies between trials of controlled stutterers with evidence of adaptation in the speech of nonstutterers. Nonstutterers demonstrate significant mean differences in nonfluencies among replicated testing occasions. Findings of this investigation suggest that both controlled stutterers and nonstutterers demonstrate similar adaptation regarding their nonfluent speech behavior. Issues and import for future research are offered.     

Attitude and personality characteristics of older stutterers

Attitude and personality characteristics of 29 stutterers (19 male, 10 female) aged 52–82 yr were assessed using five questionnaires. Results indicate that, while the older stutterers score approximately the same as young adult stutterers on scales assessing approach and performance behaviors, the large majority of older stutterers perceive their stuttering as less handicapping than when they were young adults. Self-perceived personality characteristics of the older stutterers were similar to a group of older nonstutterers. While a few of the subjects had experienced some degree of success as a result of treatment later in life, the majority of the subjects did not currently desire treatment.     

Pause and utterance durations and fundamental frequency characteristics of repeated oral readings by stutterers and nonstutterers

Effects of repeated oral readings on durational and fundamental frequency characteristics and number and kinds of reading errors were investigated in 11 stutterers and 11 sex- +and age-matched nonstutterers. Computer analysis of durational and fundamental frequency characteristics of the first and sixth readings demonstrated statistically significant differences in mean pause duration, speaking-time ratio, and total speaking time between the stutterers and the nonstutterers. In addition, there were significant differences in mean utterance duration and number of utterances (and pauses) between the first and sixth readings. Finally, correlational analyses indicated variable performance in the stutterers whereas the nonstutterers demonstrated highly consistent performance between the first and sixth readings. Results of reading error analysis showed more and different types of reading errors by the stutterers in comparison to the nonstutterers although both groups demonstrated a reduction in reading errors from the first to the sixth readings.     

Speech and bimanual hand organization in adult stutterers and nonstutterers

A multivariate approach was used to investigate the relationship between speech fluency and bimanual handwriting in right-handed male stutterers and nonstutterers. Handedness was determined by the Harris Test of Lateral Dominance. Subjects were required to write the numbers 1 through 12 simultaneously, as quickly as possible. Speech measures were derived from the Stuttering Severity Instrument and from a reading passage. Stutterers performed more poorly than nonstutterers on all speech measures. There were no differences in bimanual handwriting performance for the dominant hand. However, stutterers performed more poorly than nonstutterers in nondominant handwriting. There were no relationships between speech measures and bimanual handwriting for stutterers or nonstutterers. Some stutterers performed better on the handwriting task than did some nonstutterers. It is suggested that disorganization in interhemispheric integration functions may be a more fundamental problem in stuttering than is incomplete cerebral dominance.     

Effects of stimulus ear presentation on the voice reaction time of adult stutterers and nonstutterers

The initial and optimum voice reaction times (VRT) to auditory stimuli presented separately to the left and right ears of ten adult stutterers and ten nonstutterers was investigated. Subjects initiated the neutral vowel sound /Λ/ in response to one hundred 4000 Hz tones of 2.5 sec in duration. The silent intervals between the tones varied randomly. The stimulus cues were divided into five equal response sets of 20 tones each with 10 tones in each set being presented to the right ear and 10 tones to the left ear alternating back and forth. No significant differences were reported between the VRTs for cues presented to the left or right ears for either group. However, the stutterers exhibited voice reaction times which were significantly longer and more variable than those of the nonstutterers. The between- group differences were observed for what appeared to be the “optimum” level of voice initiation for the experimental task. These results lend to the speculative hypothesis that the observed difficulty for adult stutterers to promptly and consistently initiate vocalization may in part be attributable to inherent rather than learned factors.     

A dual-task investigation of young stutterers and nonstutterers

Twenty right-handed grade-school stutterers and nonstutterers matched for sex, handedness, and age were the subjects of this neuromotor investigation. They were required to tap a button as rapidly as possible in a single-task control condition, in three increasingly demanding dual-task conditions in which finger-tapping and speech occured concurrently, and in a dual-task condition in which the subjects finger-tapped and vocalized the sound of a siren. The conditions were randomized, and hand order was counterbalanced. The overall tapping rate of the nonstutterers was statistically faster than that of the stutterers for both the right and left hand. Relative to the single-task silent control condition, the tapping rates of both groups decreased as the dual-task speech conditions became more demanding. However, the tapping rate of the nonstutterers was significantly faster across the speech conditions. Neither the group by hand, group by condition, or group by hand by condition interaction was statistically significant. The stutterers responded like the nonstutterers, though more slowly, providing support for the current contentions that the neuromotor system of stutterers is less robust than that of nonstutterers and more affected by the demands of speech production.     

Attention and stuttering: Do stutterers think too much about speech?

In this investigation the ability of stutterers and nonstutterers to simultaneously perform speech and nonspeech tasks was compared. Subjects were 10 stutterers and 10 nonstutterers. Two experiments were conducted. In the first, subjects performed a non-attention-demanding gross-motor task while they read aloud. In the second, subjects performed an attention-demanding task (reading comprehension) during speech. Results indicated that there was no significant change in the disfluency values of stutterers during the motor activity or as a result of the reading comprehension task. However, stutterers were found to perform significantly poorer than nonstutterers on the reading comprehension task. This finding was taken as evidence that stutterers devote more attention to speech than do nonstutterers.     

Effects of subgrouping in stuttering research

The most frequently utilized research design in stuttering research compares stutterers to nonstutterers, with the assumption that stutterers represent a homogeneous group. The present study examines the effects of subgrouping stuttering subjects. Sample populations were randomly selected from a pool of stuttering children, successively increasing the stringency of selection criteria for group membership. The groups were contrasted across five dependent variables. The results indicated that the performance differences between the groups increased as the selection criteria became more stringent. The findings were interpreted as supporting the need to more closely examine the individual differences of stutterers, deviating from the traditional research paradigm.     

A perceptual comparison between paired stimulus and single stimulus methods of presentation of the fluent utterances of stutterers

This investigation compared tape recordings containing the fluent utterances of treated stutterers with those of normal speakers as paired stimuli and single stimuli as presented to 20 sophisticated judges. Fluent utterances were obtained from stutterers successfully treated in one of the following programs: (1) Van Riperian, (2) metronome-conditioning speech retraining, (3) delayed auditory feedback, (4) operant conditioning, (5) precision fluency shaping program, and (6) holistic therapy. In addition, a group of partially treated stutterers were included. The original tape recordings containing matched samples of the fluent utterances of a stutterer and normal speaker were presented as paired stimuli. These paired samples were then separated, randomized, and assembled individually on another tape recording and presented as single stimuli to the same judges. The results of the statistical analysis indicated that the fluent utterances of treated stutterers was perceptibly different from the fluent utterances of nonstutterers, regardless of the method of stimulus presentation.     

Word fragmentations and repetitions in the spontaneous speech of 2–6-yr-old children

Samples of spontaneous speech of 110 nursery school children, aged 2 yr, 1 mo to 6 yr, were written down. Two of the children were regarded as stutterers by the parents and the nursery school personnel. Instances of word and phrase repetitions and word fragmentations were marked. Fragmentation of a word before the whole word is pronounced was used as criterion of stuttering. The nonstutterers had an average frequency of word repetitions of 6.3%, while word fragmentations were virtually nonoccurrent. The frequency of word repetitions decreased with increasing age. Relating word repetitions to grammatical complexity of speech, it was found that the decrease was particularly large at a certain point of the grammatical development. The two stutterers had, in addition to normal frequencies of word repetitions, marked occurences of word fragmentations (2.8 and 4.1%).     

Reaction time for voiced and whispered /a/ in stutterers and nonstutterers

Recent research reviewed in this article suggests that stutterers' inability to initiate phonation promptly could be a significant factor in the occurence of stuttering. Since stuttering is either completely absent or markedly reduced in frequency during whisper, the present study tested the hypothesis that stutterers do not significantly differ from nonstutterers in reaction time (RT) for the initiation of whispered/a/, whereas the two groups differ significantly in RT for the initiation of voiced /a/. Ten adult stutterers and an equal number of comparable nonstutterers produced prolonged versions of the vowel /a/ using voice and whisper in response to tone stimuli. The results showed that stutteres and nonstutterers did not differ in RT for either voiced or whispered /a/. The stutterers, however, exhibited significantly longer RT to produce voiced /a/ than whispered /a/.     

A shortened version of the Southern Illinois university speech situation checklist for the identification of speech-related anxiety

This study investigated the ability of the 51-item Southern Illinois University Speech Situation Checklist (SSC) to differentiate stutterers known to have high levels of speech-related anxiety from nonstutterers with normal levels of speech- related anxiety. Checklist responses of 65 randomly selected subjects (33 stutterers and 32 nonstutterers) were subjected to a stepwise discriminant analysis. The analysis identified a combination of 21 SSC items that had significant discriminative power. Subsequently, the derived discriminant equation achieved 93% accuracy in correctly classifying a hold-out sample of 29 subjects (14 stutterers and 15 nonstutterers). These results strongly suggest that the 21 items of the SSC identified by discriminant analysis may provide an effective screening device for identifying disfluent speakers who experience an abnormal amount of speech-related anxiety.     

Variability in the initiation of articulatory movements in the speech of stutterers and normal speakers

This study was designed to investigate the differences between stutterers and normal speakers in phonatory and articulatory timing during the initiation of fluent utterances of monosyllabic words. Electromyographic recordings of four articulatory muscles and recordings of glottal vibrations were made of repetitive utterances of a series of monosyllabic words by 15 stutterers and 17 nonstutterers. These data were analyzed in terms of average interval times between voice onset and onset of EMG activity and between onset of EMG activity in each articulator and in terms of the intrasubject variability of these durational measures. Results showed that there were no significant differences between stutterers and nonstutterers in average interval times and that stutterers, in general, were significantly more variable in their speech onset timing. Findings are discussed in terms of recent hypotheses concerning the role of timing disturbances as the main source of speech disruption in stutterers.     

Personal constructs of fluency: a study comparing stutterers and nonstutterers

The personal construct systems relating to fluency of a group of five stutterers and a group of five nonstutterers were examined using the repertory grid technique. The results support findings that stereotypical notions about stuttering were characteristic of both stutterers and nonstutterers and did not support Fransella's 1972 assumption that constructs relating to fluency differ in the communication subsystems of stutterers and nonstutterers.     

The mean fundamental frequency in stutterers and nonstutterers during reading and spontaneous speech

Corresponding to the higher tension of muscles involved in speech production, a higher mean fundamental frequency should be expected in stutterers as compared to nonstutterers. It could be shown by the change scores of the mean fundamental frequency from reading to free conversation that stutterers tend to have a higher fundamental frequency during spontaneous speech.     

Brain stem electrical responses of stutterers and normals by sex,ears, and recovery

Auditory brainstem electrical responses (BSER) of right and left ears of active stutterers, recovered stutterers, and nonstutterers, both male and female adults, were obtained at click rates of 11.1 and 71.1/sec. Latency intervals of waves I, III, and V were measured. The auditory systems of subjects were stressed using a rapid rate of 71.1 clicks/sec. The latency of wave V was used as the measure of the stress condition.Analysis of variance was used to determine statistical significances of main effects and interactions of mean BSER (waves I, III, V, and wave V in stress condition) of left and right ears of male stutterers (active and recovered), female stutterers (active and recovered), and male and female nonstutterers.With one exception, all main effects and all higher order interactions were nonsignificant. The one main effect that was significant was gender. Females have significantly faster rates of neural transmission than do males. The question was raised, does this finding contribute toward an explanation of the sex ratio in stuttering?