Simulations of stuttered speech: numbers and types of dysfluencies

The purpose of this study was to assess whether stuttered speech could be simulated by normal-speaking individuals and to identify significant parameters used in the simulation process. The subjects were 24 normal-speaking graduate students in speech-language pathology. The subjects were assigned the task of simulating stuttered speech given specific levels of severity. Then they were asked to listen to the simulated samples and identify the number and types of dysfluencies presented. Analysis showed agreement among subjects on the number of dysfluencies, with the exception of samples simulating severe stuttering behavior. Judging the number of dysfluencies in the simulated samples of severe stuttering appeared to be a more difficult task. The types of dysfluencies noted by the listeners were restricted primarily to repetitions and prolongations. Simulated stuttered speech was therefore judged to be composed of fewer types of stuttering behavior than actual stuttered speech is reported to be.     

Perception of temporal order in speech: The role of vowel transitions.

Presented 32 undergraduates with tape loops consisting of 4 sounds. 3 types of stimuli were used to construct tape loops. These consisted of (a) consonant noise removed from consonant-vowel (cv) syllables, (b) cv syllables composed of consonant noise and the first 75 msec of vowel (including vowel transitions), and (c) transitionless cv syllables composed of consonant noise and 75 msec of steady-state vowel. Ss judged the order of the 4 sounds in each tape loop. Tape loops composed of consonant noise were most difficult to order correctly. Transitionless syllables were more difficult to order correctly than normal cv syllables of the same duration. This result suggests that vowel transitions aid in maintaining the temporal order of speech sounds in normal speech. (French summary) (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vowel-related differences in laryngeal articulatory and phonatory function

The purpose of this investigation was to study the interaction between the supralaryngeal and laryngeal components of the speech mechanism by examining vowel-related effects for a variety of vocal fold articulatory and phonatory measures. Secondary issues were to determine if vowel-related differences were influenced by the nature of the speaking task or gender. Between-vowel differences in estimated subglottal air pressure, peak oral air flow, mean phonatory air flow, air flow near the termination of the vowel, electroglottograph cycle width (EGGW), fundamental frequency, and voice onset time were examined for men and women during syllable repetitions and sentence productions. Significant vowel-related differences were found for all of the measures except mean phonatory air flow, and generally were not influenced by speaking task or gender. Vowel-related effects for estimated subglottal air pressure, peak oral air flow, fundamental frequency, and VOT were consistent with some earlier studies. New findings included vowel-related differences in EGGW and air flow near the termination of the vowel. We propose a model that includes the contribution of mechanical forces, reflexive neural activity, and learned neural activity to explain vowel-related effects. When vowel height is varied, changes in laryngeal cartilage positioning and vocal fold and vocal tract tension appear to influence laryngeal articulatory and phonatory function.     

Adaptation of stuttering frequency during repeated readings: associated changes in acoustic parameters of perceptually fluent speech

This study is part of a series investigating the hypothesis that stuttering adaptation is a result of motor learning. Previous investigations indicate that nonspeech motor learning typically is associated with an increase in speed of performance. Previous investigations of stuttering, on the other hand, indicate that improvements in fluency during most fluency-enhancing conditions or after stuttering treatment tend to be associated with decreased speech rate, increased duration of specific acoustic segments, and decreased vowel duration variability. The present acoustic findings, obtained from 8 individuals who stutter, reveal that speech adjustments occurring during adaptation differ from those reported for other fluency-enhancing conditions or stuttering treatment. Instead, the observed changes are consistent with those occurring during skill improvements for nonspeech motor tasks and, thus, with a motor learning hypothesis of stuttering adaptation. During the last of 6 repeated readings, a statistically significant increase in articulation rate was observed, together with a decrease in word duration, vowel duration, and consonant-vowel (CV) transition extent. Other adjustments showing relatively consistent trends across individual subjects included decreased CV transition rate and duration, and increased variability of both CV transition extent and vowel duration.     

Second formant transitions of selected consonant-vowel combinations in the speech of deaf and normal-hearing children

Although it is well known that the speech produced by the deaf is generally of low intelligibility, the sources of this low speech intelligibility have generally been ascribed either to aberrant articulation of phonemes or inappropriate prosody. This study was designed to determine to what extent a nonsegmental aspect of speech, formant transitions, may differ in the speech of the deaf and of the normal hearing. The initial second formant transitions of the vowels /i/ and /u/ after labial and alveolar consonants (/b, d, f/) were compared in the speech of six normal-hearing and six hearing-impaired adolescents. In the speech of the hearing-impaired subjects, the second formant transitions may be reduced both in time and in frequency. At its onset, the second formant may be nearer to its eventual target frequency than in the speech of the normal subjects. Since formant transitions are important acoustic cues for the adjacent consonants, reduced F2 transitions may be an important factor in the low intelligibility of the speech of the deaf.     

The specific-word frequency effect: Implications for the representation of homophones in speech production.

In a series of experiments, the authors investigated whether naming latencies for homophones (e.g., /nΛn/) are a function of specific-word frequency (i.e., the frequency of nun) or a function of cumulative homophone frequency (i.e., the sum of the frequencies of nun and none). Specific-word but not cumulative-homophone frequency affected picture-naming latencies. This result was obtained in 2 languages (English and Chinese). An analogous finding was obtained in a translation task, where bilingual speakers produced the English names of visually presented Spanish words. Control experiments ruled out that these results are an artifact of orthographic or articulatory factors, or of visual recognition. The results argue against the hypothesis that homophones share a common word-form representation, and support instead a model in which homophones have fully independent representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived auditory continuity with alternately rising and falling frequency transitions

Conducted 6 experiments with 64 university students to investigate perceived auditory continuity with alternately rising and falling frequency glides, in which the glides were perceived as continuous when deleted portions were replaced by white noise bursts. The first 3 experiments showed that perceptual continuity could be obtained when the deleted portion came either in the middle of the glide, or at the top and bottom of the glides; continuity was actually better for the latter condition. Also, it was found that as glide duration increased, the threshold between perceived continuity and discontinuity increased; there was a similar increase as the difference between highest and lowest frequencies increased. In Exps IV-VI, when the peak was deleted and replaced with noise, there was no perceptual extrapolation of the incomplete glides; rather, there seemed to be considerable rounding off of the trajectory of the glide. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The activation of word class information during speech production.

In 5 picture-word interference experiments the activation of word class information was investigated. The first experiment, in which subjects used bare nouns to describe the pictures, failed to reveal any interference effect of noun distractor words as opposed to closed-class distractor words. In the next 4 experiments the pictures were named by using a definite determiner and the noun completing a sentence fragment. The data demonstrate that noun distractors interfere more strongly with picture naming than do non-noun distractors. This held for both visual and auditory presentation of the distractor words. The interference effect showed up in a time window where semantic interference can usually be observed, supporting the assumption that at an early stage of lexical access semantic and syntactic activation processes overlap. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Word frequency effects in speech production: Retrieval of syntactic information and of phonological form.

In 7 experiments the authors investigated the locus of word frequency effects in speech production. Exp 1 demonstrated a frequency effect in picture naming that was robust over repetitions. Exps 2, 3, and 7 excluded contributions from object identification and initiation of articulation. Exps 4 and 5 investigated whether the effect arises in accessing the syntactic word (lemma) by using a grammatical gender decision task. Although a frequency effect was found, it dissipated under repeated access to a word's gender. Exp 6 tested whether the robust frequency effect arises in accessing the phonological form (lexeme) by having Ss translate words that produced homophones. Low-frequent homophones behaved like high-frequent controls, inheriting the accessing speed of their high-frequent homophone twins. Because homophones share the lexeme, not the lemma, this suggests a lexeme-level origin of the robust effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Middle ear muscle activity during speech in stapedectomized and laryngectomized subjects

Middle ear muscle responses associated with speech production were observed in normal-hearing, stapedectomized, and laryngectomized subjects. Impedance changes associated with speech production were monitored by an electroacoustic impedance bridge simultaneously with vocal output. Results from stapedectomized subjects indicate that the tensor tympani muscle contracts prior to vocalization and is part of the neurological pattern of speech production. Data collected from laryngectomized subjects suggest that the presence of sensory fibers from the larynx is not a prerequisite for middle ear muscle activity during speech production.     

Conformational transitions in myosin cross-bridges during the mechanochemical act

The investigations of the molecular bases of muscle contraction posed the following question: in which part of the myosin cross-bridge, the head or the fibrillar part, the conformational changes occur that lead to the generation of force. The paper deals with experimental and theoretical data that are in some way related to the solution of this question. Based on the analysis of recent data, an alternative pattern of ATP hydrolysis-coupled structural alternations in the myosin bridge during the mechanochemical act is proposed.     

Eye movement of perceivers during audiovisual speech perception

Perceiver eye movements were recorded during audiovisual presentations of extended monologues. Monologues were presented at different image sizes and with different levels of acoustic masking noise. Two clear targets of gaze fixation were identified, the eyes and the mouth. Regardless of image size, perceivers of both Japanese and English gazed more at the mouth as masking noise levels increased. However, even at the highest noise levels and largest image sizes, subjects gazed at the mouth only about half the time. For the eye target, perceivers typically gazed at one eye more than the other, and the tendency became stronger at higher noise levels. English perceivers displayed more variety of gaze-sequence patterns (e.g., left eye to mouth to left eye to right eye) and persisted in using them at higher noise levels than did Japanese perceivers. No segment-level correlations were found between perceiver eye motions and phoneme identity of the stimuli.     

Irrelevant speech and irrelevant tones: The relative importance of speech to the irrelevant speech effect.

Irrelevant auditory stimuli disrupt immediate serial recall. In the equipotentiality hypothesis, D. M. Jones and W. J. Macken (see record 1993-20312-001) made the controversial prediction that speech and tones have an equivalent disruptive effect. In the present study, 5 experiments tested their hypothesis. Experiments 1–4 showed that meaningful speech disrupts recall more than do tones. Experiments 3 and 4 provided some evidence that meaningful speech disrupts recall more than does meaningless speech, and Experiment 4 showed that even meaningless speech disrupts recall more than do tones. Using slightly different experimental procedures, Experiment 5 showed that letters disrupt recall more than do tones. Implications of these results for a number of theories of primary memory and the irrelevant speech effect are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The mismatch negativity to frequency deviant stimuli during natural sleep

Eight subjects spent a single night in the sleep laboratory. Event-related potentials (ERPs) were recorded during the presentation of two auditory "oddball' stimulus conditions in which tonal frequency was manipulated. In the first condition, 1000 Hz "standard' and 2000 Hz "deviant' tones were presented. In the second condition, the deviant tone was reduced to 1050 Hz. In both conditions, deviant probability was 0.2. Stimuli were presented every 600 ms during wakefulness and stages 2, 4, and REM of sleep. A distinctive N1 wave was visible in both stimulus conditions when the subject was awake. The deviant stimuli elicited a "mismatch negativity' (MMN) that inverted in polarity at the mastoid. In REM sleep, an N1 and a MMN were also elicited in both conditions. In the large deviance condition, the MMN had a slightly attenuated amplitude and was shorter in duration while in the small deviant condition, its peak latency was unusually early. Neither the N1 nor the MMN could be recorded in non-REM sleep.     

Microstructural transitions during containerless processing of undercooled Fe-Ni alloys

The microstructural development associated with solidification in undercooled Fe-Ni alloys has been reported in different studies to follow various pathways, with apparent dissimilarities existing as a function of sample size and processing conditions. In order to identify the possible hierarchy of microstructural pathways and transitions, a systematic evaluation of the microstructural evolution in undercooled Fe-Ni alloys was performed on uniformly processed samples covering seven orders of magnitude in volume. At appropriate undercooling levels, alternate solidification pathways become thermodynamically possible and metastable product structures can result from the operation of competitive solidification kinetics. For thermal history evaluation, a heat flow analysis was applied and tested with large Fe-Ni alloy particles (1 to 3 mm) to assess undercooling potential. Alloy powders (10 to 150 μm), with large liquid undercoolings, were studied under the same composition and processing conditions to evaluate the solidification kinetics and microstructural evolution, including face-centered cubic (fcc)/body centered cubic (bcc) phase selection and the thermal stability of a retained metastable bcc phase. The identification of microstructural transitions with controlled variations in sample size and composition during containerless solidification processing was used to develop a microstructure map which delineates regimes of structural evolutions and provides a unified analysis of experimental observations in the Fe-Ni system.     

The perception of speech gestures

Two experiments examined the effects of temporal overlap of speech gestures on the perception of stop consonant clusters. Sequences of stop consonant gestures that exhibit temporal overlap extreme enough to potentially eliminate the acoustic evidence of (at least) one of the consonants were obtained from x-ray microbeam data. Subjects were given a consonant monitoring task using stimuli containing stop sequences as well as those containing single stops. Results showed that (1) the initial consonant in the stop sequences was detected significantly less often than in the single stops; (2) bilabial gestures were considerably more effective at obscuring a preceding alveolar than the reverse; and (3) the detection rate correlated with an index of overlap between lip and tongue tip gestures. Experiment 2 employed stimuli that were truncated during the closure for the critical stop or stop sequence, so as to eliminate any information occurring in the acoustic signal at the stop release. This experiment showed that removing release information decreased detectability of the consonants generally. However, consistent with the observed gestural patterns, removing the release did not decrease detection of the alveolar stop when it was the first consonant of a sequence, indicating that there was no information about the alveolar stop present in acoustic realization of the second stop release. These experiments show that certain gestural patterns actually produced by English speakers may not be completely recoverable by listeners, and further, that it is possible to relate recoverability to particular metric properties of the gestural pattern.     

Effect of biofeedback-based relaxation on stuttering during reading and spontaneous speech.

Conducted 3 studies to develop methodology for using biofeedback to reduce stuttering by teaching relaxation of speech-related muscles. A total of 19 stutterers (mean ages 22.1–24.6 yrs) participated in 8–25 1-hr sessions. In Study 1, 7 Ss learned voluntary relaxation of the masseter muscles, and stuttering was essentially eliminated while reading units of 1–4 syllables. Study 2 attempted to enhance the generalization of fluency by training 6 Ss to develop their own internal cues for relaxation. Fluency generalized well to periods of no feedback, but relaxation generalized much less well. In Study 3, which specifically attempted to enhance the generalization of relaxation, 6 Ss were successfully trained to generalize both relaxation and fluency skills to spontaneous speech periods of up to 4-word units involving no feedback. (PsycINFO Database Record (c) 2010 APA, all rights reserved)