Producing the vowel/a/ prior to speaking inhibits stuttering in adults in the English language.

This study investigated the effects of producing and listening to the vowel /a/ on the frequency of overt stuttering moments in eight people who stuttered. Stuttering frequency counts were made for the speech produced in the control condition, and after each of these four experimental conditions: (a) producing a vowel /a/ for 4 s; (b) producing a vowel /a/ for 4 s and waiting for 4 s; (c) listening to a recording of the vowel /a/ for 4 s; and (d) listening to a recording of the vowel /a/ for 4 s and waiting for 4 s. A significant reduction in the stuttering frequency was only observed following production of the vowel /a/ without a 4 s delay (P=0.02), suggesting that the vowel production prior to speech, serves as a temporary fluency enhancer. Its similarity to the occurrence of overt stuttering moments (e.g. discrete part-word repetitions and prolongation's) and its relationship to the fundamental nature of the pathology are discussed.

Hemispheric processing characteristics for lexical decisions in adults with reading disorders.

The present study measured unilateral tachistoscopic vocal reaction times and error responses of reading-disordered and normally reading adults to single words and nonwords in a series of lexical decision tasks at two linguistic levels (concrete and abstract words). Analysis of variance on reaction times indicated that main effects of stimulus type, visual field, and the interaction of these variables were not significant for the reading-disordered group, but visual field and an interaction of visual field and stimulus type were for the normally reading adults. Error rate showed a significant interaction of stimulus x visual field for the reading-disordered group but not for the normal reading group. Post hoc tests showed significant differences in error rates between visual fields for concrete lexicon but not for abstract or nonsense lexicon for the reading-disordered group. These findings suggest a deficit in interhemispheric lexical transfer occurs for reading-disordered samples and suggest use of a callosal relay model wherein the left hemisphere is allocated responsibility for performing central operations underlying lexical decisions by adults with reading disorders.

Stutter-free and stutter-filled speech signals and their role in stuttering amelioration for English speaking adults.

This study examined the power of an exogenously generated stuttered speech signal on stuttering frequency when compared to an exogenously generated normal speech signal. In addition, we examined the specific components of the second speech signal, which might be responsible for the inducement of fluency in people who stutter. Eight males and two females who stuttered participated in this study. Experiment I involved meaningful speech: normal continuous speech, normal interrupted speech, stuttered continuous speech, and stuttered interrupted speech, whereas Experiment II involved vowels and consonants: /a/, /a-i-u/, /s/, /s-sh-f/. The results indicated that stuttered and normal speech signals were equally effective in reducing stuttering frequency. Further, the vowels were more powerful than consonants in inducing fluency for people who stutter. It is suggested that acoustic manifestations of stuttering, rather than a problem, may be a natural compensatory mechanism to bypass or inhibit the 'involuntary block' at the neural level.

Stutterers' vocal reaction times to unilaterally presented high and low frequency verbs.

The current study investigated vocal reaction times of 11 stuttering participants to verbs with high and low frequencies of occurrence when these verbs were unilaterally visually presented. No significant main effects or interactions between stimuli and visual-half field were found. Reaction times were 16 msec. faster after right visual field presentations and the Pearson correlation coefficient between visual fields .71 (p=.02). These results were interpreted as suggesting that the left hemisphere was dominant for processing the current lexical items, findings which parallel those for normal speakers.

Inducement of fluent speech in persons who stutter via visual choral speech.

A novel phenomenon of fluency enhancement via visual gestures of speech in the absence of traditional auditory feedback is reported herein. The effect on visual choral speech on stuttering frequency was investigated. Ten participants who stuttered recited memorized text aloud under two conditions. In a visual choral speech (VCS) condition participants were instructed to focus their gaze on the face, lips and jaw of a research assistant who 'silently mouthed' the text in unison. In a control condition, participants recited memorized text to the research assistant who sat motionless. A statistically significant (P=0.0025) reduction of approximately 80% in stuttering frequency was observed in the VCS condition. As visual linguistic cues are sufficient to activate the auditory cortex, one may speculate that VCS induces fluency in a similar yet undetermined manner as altered auditory feedback does.

Effects of monitoring condition and frequency-altered feedback on stuttering frequency.

The purpose of the study was to examine stuttering frequency during speaking conditions that are believed to mitigate stuttering frequency both with normal nonaltered auditory feedback (NAF) and a known fluency-enhancing feedback. Specifically, stuttering frequency was examined as a function of three monitoring conditions under NAF and frequency-altered feedback (FAF): no monitoring (i.e., speaking alone, in the absence of audio and visual recording), audiovisual monitoring (i.e., speaking alone with audiovisual recording), and audiovisual monitoring with observers (i.e., speaking with audiovisual recording in the presence of two observers). Seven adults and one adolescent who stutter served as participants. Stuttering frequency was differentially affected across monitoring conditions under each auditory feedback condition (p = .027). Post hoc analyses revealed no significant difference in stuttering frequency between the two conditions in the absence of the observers (i.e., no monitoring vs. audiovisual monitoring) under NAF (p = .45). There was, however, a significant difference in stuttering frequency for the no-monitoring and audiovisual-monitoring conditions relative to the audiovisual-monitoring-with-observers condition (p = .0002). There was no statistically significant difference in stuttering frequency across monitoring conditions under FAF (p > .05). The findings are consistent with the notion that during NAF stuttering frequency varies as a function of hierarchical socio-environmental conditions in which inanimate monitoring conditions constitute one entity. Such a relationship does not exist during FAF.

Quantitative electroencephalogram of posterior cortical areas of fluent and stuttering participants during reading with normal and altered auditory feedback.

In the left and right hemisphere, posterior quantitative electroencephalogram Beta band activity (13.5-25.5 Hz) of seven adult participants who stutter and seven age-matched normal controls was obtained while subjects read text under three experimental conditions of normal auditory feedback, delayed auditory feedback, and frequency-altered feedback. Data were obtained from surface electrodes affixed to the scalp using a commercial electrode cap. Electroencephalogram activity was amplified, band-pass analog-filtered, and then digitized. During nonaltered auditory feedback, stuttering participants displayed Beta band hyperreactivity, with the right temporal-parietal lobe region showing the greatest activity. Under conditions of delayed auditory feedback and frequency-altered auditory feedback, the stuttering participants displayed a decrease in stuttering behavior accompanied by a strong reduction in Beta activity for the posterior-temporal-parietal electrode sites, and the left hemisphere posterior sites evidenced a larger area of reactivity. Such findings suggest than an alteration in the electrical fields of the cortex occurred in the stuttering participants under both conditions, possibly reflecting changes in neurogenerator status or current dipole activity. Further, one could propose that stuttering reflects an anomaly of the sensory-linguistic motor integration wherein each hemisphere generates competing linguistic messages at hyperreactive amplitudes.

A latent trait approach to the development of persistent stuttering.

The premise that stuttering disorders develop according to the orthogenetic principle, preceding in a continuous, unilinear fashion from a state of relative lack of differentiation to a state of increasing differentiation and hierarchic integration, was examined. Responses to Woolf's Perceptions of Stuttering Inventory of 87 individuals who stutter were analyzed using a Rasch 1980 latent trait model for dichotomously scored data. Analyses of responses indicated struggle, avoidance, and expectation through the development of stuttering that became increasingly articulated, integrated, stable, and yet responsive to environmental changes. Four stages of development were noted: Stage I was characterized by the expectation of interruptions in the flow of speech, the addition of unnecessary sounds, and general body tension. Stage II was typified by distinctions between troublesome and not so troublesome words and sounds and between the speaker and various audiences and contexts for speaking. In Stage III, speech control decreased despite more focused and complex efforts to control the environment and the speech apparatus. Stage IV was characterized by automatic scanning of all speech, increasingly uncontrolled body movements, and attempts to produce fluent speech by way of comprehensive changes to sound, rhythm, and pitch. Follow-up of 29 respondents suggested the latent struggle was generally stable over time.

Effect of altered auditory feedback on people who stutter during scripted telephone conversations.

The effect of altered auditory feedback (AAF) conditions on stuttering during scripted telephone conversations was investigated. Nine adult participants made 15 scripted telephone calls to business in New York City. Alterations in the participants' auditory feedback signal were generated by a commercially available digital signal processor (Casa Futura Technologies Desktop Fluency System Model BTD-400) that shifted participants' speech one-half octave down in frequency, produced a 50-ms delay, or produced non-altered auditory feedback. The AAF effects produced by the digital signal processor were not perceived by the recipients of the telephone calls. The proportion of stuttering events per scripted telephone conversations were significantly reduced in the AAF conditions relative to the non-altered auditory feedback condition (p = .0004). Stuttering frequency was reduced by 55% and 60% for the FAF and DAF, respectively. These findings demonstrate the applicability of this technology to situations of daily living involving telephone use.

Effect of monaural and binaural altered auditory feedback on stuttering frequency.

The effect of monaural and binaural alterations in auditory feedback on stuttering frequency was investigated. Eleven participants who stutter read aloud under nonaltered auditory feedback (NAF) and monaural and binaural conditions of frequency altered feedback [(FAF), on-quarter octave shift upward] and delayed auditory feedback [(DAF), 50-ms delay] at a normal speech rate. Relative to the NAF condition, reductions in stuttering frequency of approximately 60%-75% were found with the altered auditory feedback conditions. Post hoc single-df comparisons revealed a reduction in stuttering frequency with altered auditory feedback versus NAF (p < 0.0001), a greater reduction in stuttering frequency for binaural compared to monaural altered auditory feedback (p = 0.028), and nonsignificant differences in stuttering frequencies for right versus left monaural conditions (p = 0.54) and DAF versus FAF (p = 0.70).

Effect of speaking into a passive resonator on stuttering frequency.

The effect on stuttering frequency of speaking into a passive resonator was investigated. Eight participants who stuttered read aloud with and without the benefit of the resonator. A statistically significant reduction of approximately 30% in stuttering frequency was observed while the participants spoke with the resonator. These and similar commercially available devices may be employed with individuals who stutter, particularly children, as a means of enhancing fluency.

Formant frequency characteristics of elderly speakers in contextual speech.

The present study measured F1 and F2 formant frequency levels of elderly and young male and female speakers producing the /i/, /ae/, [symbol: see text], /u/, and /a/ vowels in two carrier phrases. Results of a series of ANOVAs showed significant interactions of speaker age x vowel for both F1 and F2 formant frequencies for the male and female speakers. Results suggested that while elderly male speakers exhibit significant alterations in vowel production during contextual speech, elderly female speakers generally maintain formant frequency integrity or appropriate articulatory posturing during contextual vowel productions.

Effect of instruction to sing on stuttering frequency at normal and fast rates.

Singing as a fluency-enhancing mechanism is well-established. The fluency derived by singing has been attributed to a reduced speech rate, memorized material, semantically reduced content, and an imposed rhythm. In this study, we attempted to address each of these explanations. 12 participants who stuttered were instructed to read or sing each of four different passages under the following conditions: reading at a normal rate, reading at a fast rate, singing at a normal rare, and singing at a fast rate. Participants exhibited a statistically significant increase in disfluencies while reading, i.e., participants displayed a 75% reduction in disfluency in the singing condition relative to the reading condition. There was no difference in stuttering frequency with rate conditions. Current findings suggest that stutterers are capable of internally generating fluent speech production by imposing idiosyncratic melodic structures or some derivation of melody when asked simply to sing. There is no claim that these participants were singing, as skills and capabilities varied tremendously, only that participants achieved dramatic enhancement of fluency after they were just asked to sing. Thus, the only intervening variable was the instruction to sing, which suggests the attempt to follow the instruction, no matter how futile, generated fluent speech. Since fluency was maintained in both the normal and fast rates of production, alternate central mechanisms must be held accountable for these findings.

Hemispheric picture-naming hierarchies in stuttering subjects.

The present study was done to investigate the linguistic organization of the right hemisphere of stuttering subjects and the interhemispheric interactions that underlie verbal output in this population. Naming reaction times of 14 stuttering adults were measured to unilaterally presented pictures corresponding to vocabulary levels of < 5.5, 9.5-10.5, and > 18.0 years of age. An analysis of variance of latencies showed a significant main effect for picture vocabulary-age. Post hoc tests were interpreted as suggesting that the right hemisphere of stuttering subjects was capable of differential picture-encoding operations in a manner similar to the left hemisphere of normal speakers. Also, naming latencies favored left visual-field stimulations by 34 msec. Taken with significant and high correlations between visual fields for each level of picture vocabulary score, the right hemispheres of the stuttering subjects appeared responsible for picture-encoding operations. Left-hemispheric stimulus processing was not predicted, suggesting differences may exist in interhemispheric interactions underlying picture-naming functions in stuttering populations.

Use of magnitude-estimation scaling for predicting hemispheric processing of lexical decisions.

The purpose of this study was to evaluate the usefulness and validity of magnitude-estimation scaling as an alternative to a traditional, somewhat more cumbersome reaction-time procedure in the assessment of hemispheric processing asymmetry. Lexical decision vocal reaction times and magnitude-estimation scaling values were obtained for 16 normal subjects to tachistoscopically presented concrete and abstract words. Analysis of variance showed identical interactions of field x stimuli for each dependent variable while all pair-wise correlations between these measures were significant. Magnitude-estimation scaling may be a sensitive measure of visual psychophysical differences in hemispheric processing and may circumvent problems with variance of latencies associated with disordered populations.

Hemispheric processing strategies for lexical decisions among elderly persons.

Lexical decision vocal reaction times were obtained in 1990 for 30 young adult and 18 elderly subjects to tachistoscopically presented concrete and abstract words by Rastatter and McGuire. The young adults' data suggested differential right-hemispheric processing, while the elderly subjects' data were interpreted as suggesting that the right hemisphere loses its processing function. Here we reinterpret the elderly subjects' data based on visual information-processing theory and suggest that variations in processing strategy account more completely for their data.

Fundamental frequency variability in elderly women during production of stressed and unstressed words.

The purpose of this investigation was to examine intrasubject and intersubject fundamental frequency (F0) variability in a group of young adult and elderly female speakers during the production of stressed and unstressed words. While both groups exhibited greater intersubject variability during stressed versus unstressed productions, stressed productions were more variable in the elderly women than in the young adults. Also, the elderly women exhibited greater intrasubject variability during stressed and unstressed productions relative to young adults. Implications of these findings were discussed.

Do the hemispheres interact during object naming? Evidence from tachistoscopic viewing and time-sharing paradigms.

Here we report an experiment in which 16 right-handed young adults named a series of unilaterally presented pictures during concurrent unimanual finger tapping with the right and left hands at separate times. A multivariate analysis of variance showed no significant differences in picture-naming reaction time between left versus right visual-field stimulations. Also the test for finger tapping was nonsignificant, with the magnitude of disruption being symmetrical for the right and left hands as a function of visual fields. It was proposed that the two cerebral hemispheres interact with each other at later processing stages when performing tasks requiring both left and right hemispheric processing resources.