From planning to articulation in speech production: what differentiates a person who stutters from a person who does not stutter?

The main purpose of the present study was to differentiate between people who stutter and control speakers regarding their ability to assemble motor plans and to prepare (and execute) muscle commands. Adult males who stutter, matched for age, gender, and educational level with a group of control speakers, were tested on naming words and symbols. In addition, their ability to encode and retrieve memory representations of combinations of a symbol and a word, was tested in a recognition task, using manual reaction times and sensitivity scores, as defined in signal detection theory, as performance measures. Group differences in muscle command preparation were assessed from electromyographic recordings of upper lip and lower lip. Results indicated no interaction between group and word size effects in choice reaction times or a group effect in the ability to recognize previously learned symbol-word combinations. However, they were significantly different in the timing of peak amplitudes in the integrated electromyographic signals of upper lip and lower lip (IEMG peak latency). Findings question the claim that people who stutter have problems in creating abstract motor plans for speech. In addition, it is argued that the group differences in IEMG peak latency that were found in the present study might be better understood in terms of motor control strategies than in terms of motor control deficits.     

Children's working-memory processes: A response-timing analysis.

Recall response durations were used to clarify processing in working-memory tasks. Experiment 1 examined children's performance in reading span, a task in which sentences were processed and the final word of each sentence was retained for subsequent recall. Experiment 2 examined the development of listening-, counting-, and digit-span task performance. Responses were much longer in the reading- and listening-span tasks than in the other span tasks, suggesting that participants in sentence-based span tasks take time to retrieve the semantic or linguistic structure as cues to recall of the sentence-final words. Response durations in working-memory tasks helped to predict academic skills and achievement, largely separate from the contributions of the memory spans themselves. Response durations thus are important in the interpretation of span task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stuttering, language, and cognition: a review and a model of stuttering as suprasegmental sentence plan alignment (SPA)

Extant models of stuttering do not account for the emergence of stuttering at the onset of productive language use; the greater incidence of stuttering during spontaneous speech, on complex sentences, and at sentence-initial positions; the greater incidence of stuttering in bilinguals' 2nd language; the apparent deficiency of stutterers in expressive and receptive language skills; the prevalence of spontaneous recovery from stuttering; and the lack of chronic physiological or articulatory deficits in stuttering children's fluent speech. The author presents a model of stuttering as points of suprasegmental sentence plan alignment (SPA). Such alignment processes occur when, due to on-line sentence production processes, SPAs adopted prior to utterance initiation need to be aligned with revised SPAs. This model parsimoniously accounts for the findings reviewed in the article.     

What words are stuttered?

A number of studies on the properties of stuttered words are critically reviewed. The factors considered are initial sound, position of letters in words and of words in sentences, length, and grammatical class. The studies reviewed indicate that on the whole these factors each affect stuttering independently. They contribute in different amounts to stuttering, but together seem to account for most of stuttering dependent on words. The amount of information from all these factors, and an additional factor of articulatory complexities for the consonant-vowel effect, are discussed as possible underlying mechanisms. An analogy in underlying mechanisms is suggested between hesitation pauses in normal speech and stuttering. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stuttering as a function of the information value and sentence position of words.

24 stutterers read aloud a 95-word passage of banal prose, and the incidence of stuttering was determined for each word. The information value of each word was estimated by studying the extent to which each word could be predicted from knowledge of the preceeding words by 46 normal speakers. Results indicated that both position in the sentence and information value of words are significantly correlated with stuttering incidence. It is concluded that the positional phenomenon cannot be explained as a redundancy effect. Its nature is discussed briefly from the approach-avoidance conflict and operant viewpoints of stuttering. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Utterance rate and linguistic properties as determinants of lexical dysfluencies in children who stutter

Two important determinants of variation in stuttering frequency are utterance rate and the linguistic properties of the words being spoken. Little is known how these determinants interrelate. It is hypothesized that those linguistic factors that lead to change in word duration, alter utterance rate locally within an utterance that then gives rise to an increase in stuttering frequency. According to the hypothesis, utterance rate variation should occur locally within the linguistic segments in an utterance that is known to increase the likelihood of stuttering. The hypothesis is tested using length of tone unit as the linguistic factor. Three predictions are confirmed: Utterance rate varies locally within the tone units and this local variation affects stuttering frequency; stuttering frequency is positively related to the length of tone units; variations in utterance rate are correlated with tone unit length. Alternative theoretical formulations of these findings are considered.     

Some Characteristics of Nonfluency in Normal Speakers and Stutterers.

The 1st study investigated the relationship between nonfluency and information value in the oral reading of normal Ss, controlling for the known relationship between nonfluency and sentence position of the words. As expected from studies of stuttering, a positive nonfluency-information relationship was found. The 2nd study investigated the same relationship in the spontaneous speech of normal Ss, again controlling for sentence position. Contrary to expectation, nonfluency tended to occur more often on lower information words. Further analysis showed that nonfluency was strongly related to sentence position of words as anticipated. The 3rd study failed to demonstrate a relationship between nonfluency and information value in the spontaneous speech of stutterers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What's new in speech perception? The research and ideas of William Chandler Bagley, 1874–1946.

Describes W. C. Bagley's (1900, 1901) research on the relation between sound and meaning in human speech perception. Using phonograph cylinders, Bagley presented Ss with spoken words, either individually or in sentences, that had been pronounced with a missing consonant sound. Ss, who were instructed to report only what they had heard, often restored words to their original form (i.e., heard the words as if they had been spoken correctly). Restorations were determined by the position of the missing sound in the word and the position of the word in the sentence. The pattern of results observed by Bagley and his conclusions about human speech perception find remarkable parallels in contemporary psycholinguistics. For example, Bagley explained his results in terms of the critical role of context in speech perception and the sequential use of sound in spoken-word recognition. Some of the main results of Bagley's research are compared to those obtained in more recent experiments. It is concluded that many of the most important insights about spoken-word recognition were first offered by Bagley. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nonfluency, information, and word length.

Investigated whether previously reported relationships between nonfluency and information value in 8 undergraduate stutterers' spontaneous speech were mediated by other more basic relationships. Information value was found to be strongly related to word length, but not to sentence position, initial sound, or occurrence of nonfluency. Also, word length was related to nonfluency, suggesting that previous relationships between stuttering and information might have been an artifact of the relationship of both variables to word length. Reexamination of previous data suggests somewhat similar conclusions for stutterers when reading, but not for nonstutterers either reading or speaking. Thus, the properties of nonfluency in stutterers may be somewhat different from those in normals, suggesting that stuttering is not simply a pathological exaggeration of normal nonfluency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in oral asymmetries during wordrepetition

During speech production the right side of the mouth is opened to a larger degree in most people. This facial asymmetry is thought to be related to a left hemisphere dominance in language processing and/or motor programming. We investigated asymmetrical lip separations during discrete or serial word productions in right handed persons. The results revealed a right sided lip separation bias in both genders during discrete word production in which the words had to be uttered once. As soon as the words had to be produced continuously, however, a clear sex difference appeared with males having the usual right bias but females now showing no clear asymmetry, with a tendency for larger lip separations on the left side. These results suggest the existence of two separate neural systems from which one controls the discrete task and which is left hemisphere dominant in both genders. The other is probably involved in serial word productions and shows a sex difference with regard to its asymmetry pattern.     

Reduced sensitivity to linguistic context in schizophrenic thought disorder: evidence from on-line monitoring for words in linguistically anomalous sentences

The use of linguistic context in positively thought-disordered (TD) schizophrenics was investigated through examination of their performance on an on-line word-monitoring task. Controls and non-TD schizophrenics took longer to recognize words preceded by linguistic anomalies compared with words in normal sentences. Compared with both other groups, TD schizophrenics showed significantly smaller differences in reaction time, suggesting that they were relatively insensitive to linguistic violations. TD schizophrenics were also less sensitive to linguistic violations in an off-line version of the task, in which they judged whether the sentences "made sense." Finally, these participants produced more errors on a verbal fluency task than did non-TD schizophrenics or normal controls. These findings are consistent with the theory that schizophrenic thought disorder arises from a deficit in the use of linguistic context to process and produce speech.     

Verb retrieval and sentence production in aphasia

This paper presents a subject with a selective verb retrieval deficit. Nouns were produced more successfully than verbs in spontaneous speech, picture naming and when naming to definition. The word class effect was not observed in comprehension tasks, reading aloud or writing. This indicated that it was due to a specific problem in accessing verbs' phonological representations from semantics. The second part of the paper explores the implications of the verb deficit for sentence production. Analyses of narrative speech revealed a typically agrammatic profile, with minimal verb argument structure and few function words and inflections. Two investigations suggested that the sentence deficit was at least partly contingent upon the verb deficit. In the first, the subject was asked to produce a sentence with the aid of a provided noun or verb. The noun cues were not effective in eliciting sentences, whereas verb cues were. The second investigation explored the effects of therapy aiming to improve verb retrieval. This therapy resulted in better verb retrieval and improved sentence production with those verbs. These findings suggest that an inability to access verbs' phonological representations can severely impair sentence formulation. Implications for models of sentence production are considered.     

A perceptual-economy account for the inverted-optimal viewing position effect.

In reading, fixation durations are longer when the eyes fall near the center of words than when fixation occurs toward the words' ends-the inverted-optimal viewing position (I-OVP) effect. This study assessed whether the I-OVP effect was based on the fixation position in the word or the fixation position in the visual stimulus. In Experiments 1-3, words were presented at variable locations within longer strings of symbols. On trials with short fixation durations, there were effects of fixation position in the string. When long fixations were made, there were effects of fixation position in the word. In Experiment 4, an I-OVP effect was found for meaningless number strings, and its strength depended on the task's processing demands. The findings show that (a) the I-OVP effect is unrelated to orthographic informativeness and (b) the eyes are not constrained to spend more time at the center of visual stimuli. These results support a perceptual-economy account: Fixations are held longer when the eyes are estimated to be at locations in words/stimuli in which greater amounts of information are anticipated. Implications for eye movements in reading are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition deficits, list context, and word-class interactions in the RSVP of words in sentences.

Reports a failure to find a repetition deficit in recall following the rapid serial visual presentation (RSVP) of words within sentences, using adjectives rather than nouns as the critical items. In a series of experiments that ruled out participant and procedural differences as the source of the failure, both word class and list context were found to moderate the repetition deficit, but grammatical necessity did not. The presence in the list of sentences in which the repeated adjectives were separated by more than three words not only eliminated the repetition deficit for the recall of those sentences but also for the recall of sentences in which the repeated adjectives were separated by three or fewer words. However, although substantially reduced, a repetition deficit with noun-based materials was still found in this list context. Matching the adjective-based sentences with the noun-based sentences in sentence length and position of the critical items revealed that the moderating effect of word-class on the repetition deficit was mediated by the biases in sentence structure that using different word classes tend to induce. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Locus of interpretive and inference processes during text comprehension: A comparison of gaze durations and word reading times.

Investigated the locus of interpretive and inference processes during text comprehension. Two positions were contrasted: the buffer-integrate-purge position, which assumes that text-level interpretive and inference processes operate at sentence or clause boundaries, and the immediacy position, which assumes that interpretive and inference processes operate as soon as possible. Two methods of collecting word reading times were contrasted: gaze durations and self-paced word reading times. In simple narrative passages, there was an increase in word reading times for end-of-clause words when self-paced reading times were collected, but there was a decrease when gaze durations were measured with eye tracking equipment. The data indicate that interpretive and inference processes operate immediately and that buffering is to some extent an artifact of the self-paced moving window method. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Pictures in sentences: Understanding without words.

In 5 experiments with a total of 120 Ss of college age, sentences were presented in which a pictured object replaced a word (rebus sentences). Sentences were shown using rapid serial visual presentation at a rate of 10 or 12 words/second. With one set of materials (Exp I and II), Ss took longer to judge the plausibility of rebus sentences than all-word sentences, although the accuracy of judgment and of recall were similar for the 2 formats. With 2 new sets of materials (Exps III and V), rebus and all-word sentences were virtually equivalent except in 1 circumstance: when a picture replaced the noun in a familiar phrase such as seedless grapes. In contrast, when the task required overt naming of the rebus picture in a sentence context, latency to name the picture was markedly longer than to name the corresponding word, and the appropriateness of the sentence context affected picture naming but not word naming (Exp IV). It is concluded that the results fail to support theories that place word meanings in a specialized lexical entry. Instead, the results suggest that the lexical representation of a noun or familiar noun phrase provides a pointer to a nonlinguistic conceptual system, and it is in that system that the meaning of a sentence is constructed. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kinematic analysis of articulatory movements in central motor disorders

The various components of the central motor system are expected to play a similar role in speech production and in upper limb control. Slowed articulatory performance, therefore, must be expected in disorders of the corticobulbar tracts, cerebellum, and basal ganglia. Using an optoelectronic device, the present study recorded lower lip trajectories during production of sentence utterances in patients with Parkinson's disease (PD), Huntington's disease (HD), cerebellar atrophy (CA), and pseudobulbar palsy (PB). The various subject groups showed a similar range of overall motor disability. Patients with CA and PB exhibited slowed movement execution in terms of a reduced ratio of peak velocity to maximum amplitude ("stiffness"). In contrast to upper limb motor control, the lip excursions showed an uncompromised shape of velocity profiles. Two different patterns emerged in HD. A single patient suffering from the akinetic-rigid Westphal variant of this disease had articulatory hypometria, whereas the remaining subjects showed significant bradykinesia under increased temporal demands, concomitant with normal movement amplitudes. The PD patients had unimpaired velocity-displacement relationships. Presumably, biomechanical constraints such as the rather small excursions of articulatory lower lip gestures or the scarce spindle supply of facial muscles account for the observed discrepancies between upper limb and speech motor control in PD.     

Selection mechanisms in reading lexically ambiguous words.

Readers' eye movements were monitored as they read sentences containing lexically ambiguous words. The ambiguous words were either biased (one strongly dominant interpretation) or nonbiased. Readers' gaze durations were longer on nonbiased than biased words when the disambiguating information followed the target word. In Experiment 1, reading times on the disambiguating word did not differ whether the disambiguation followed the target word immediately or occurred several words later. In Experiment 2, prior disambiguation eliminated the long gaze durations on nonbiased target words but resulted in long gaze durations on biased target words if the context demanded the subordinate meaning. The results indicate that successful integration of one meaning with prior context terminates the search for alternative meanings of that word. This results in selective (single meaning) access when integration of a dominant meaning is fast (due to a biasing context) and identification of a subordinate meaning is slow (a strongly biased ambiguity with low-frequency meaning). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Creation of prosody during sentence production

Phrase-final words tend to be lengthened and followed by a pause. The dominant view of prosodic production is that word lengthening and pausing reflect the syntax of a sentence. The author demonstrates that, instead, lengthening and pausing reflect a distinctly prosodic representation, in which phonological constituents are arranged in a hierarchical, nonrecursive structure. Prosodic structure is created without knowledge of words' phonemic content. As a result, within a single sentential position, greater word lengthening necessitates shorter pauses, but across positions, word and pause durations show a positive correlation. The author presents a model of prosodic production that describes the process of prosodic encoding and provides a quantitative specification of the relation between word lengthening and pausing. This model has implications for studies of language production, comprehension, and development.