Spatial and temporal lingual coarticulation and motor control in preadolescents.

PURPOSE In this study, the authors compared coarticulation and lingual kinematics in preadolescents and adults in order to establish whether preadolescents had a greater degree of random variability in tongue posture and whether their patterns of lingual coarticulation differed from those of adults. METHOD High-speed ultrasound tongue contour data synchronized with the acoustic signal were recorded from 15 children (ages 10-12 years) and 15 adults. Tongue shape contours were analyzed at 9 normalized time points during the fricative phase of schwa-fricative-/a/ and schwa-fricative-/i/ sequences with the consonants /s/ and /ʃ/. RESULTS There was no significant age-related difference in random variability. Where a significant vowel effect occurred, the amount of coarticulation was similar in the 2 groups. However, the onset of the coarticulatory effect on preadolescent /ʃ/ was significantly later than on preadolescent /s/, and also later than on adult /s/ and /ʃ/. CONCLUSIONS Preadolescents have adult-like precision of tongue control and adult-like anticipatory lingual coarticulation with respect to spatial characteristics of tongue posture. However, there remains some immaturity in the motor programming of certain complex tongue movements.

Revisiting Bloodstein's Anticipatory Struggle Hypothesis from a psycholinguistic perspective: a Variable Release Threshold hypothesis of stuttering.

UNLABELLED: This paper reviews Bloodstein's (1975) Anticipatory Struggle Hypothesis of stuttering, identifies its weaknesses, and proposes modifications to bring it into line with recent advances in psycholinguistic theory. The review concludes that the Anticipatory Struggle Hypothesis provides a plausible explanation for the variation in the severity of stuttered disfluencies across speaking situations and conversation partners. However, it fails to explain the forms that stuttered disfluencies characteristically take or the subjective experience of loss of control that accompanies them. The paper then describes how the forms and subjective experiences of persistent stuttering can be accounted for by a threshold-based regulatory mechanism of the kind described in Howell's (2003) revision of the EXPLAN hypothesis. It then proposes that shortcomings of both the Anticipatory Struggle and EXPLAN hypotheses can be addressed by combining them together to create a 'Variable Release Threshold' hypothesis whereby the anticipation of upcoming difficulty leads to the setting of an excessively high threshold for the release of speech plans for motor execution. The paper also reconsiders the possibility that two stuttering subtypes exist: one related to formulation difficulty and other to difficulty initiating motor execution. It concludes that research findings that relate to the one may not necessarily apply to the other. LEARNING OUTCOMES: After reading this article, the reader will be able to: (1) summarize the key strengths and weaknesses of Bloodstein's Anticipatory Struggle Hypothesis; (2) describe two hypothesized mechanisms behind the production of stuttered disfluencies (tension and fragmentation & release threshold mechanisms); and (3) discuss why the notion of anticipation is relevant to current hypotheses of stuttering.

The influence of anticipation of word misrecognition on the likelihood of stuttering.

UNLABELLED: This study investigates whether the experience of stuttering can result from the speaker's anticipation of his words being misrecognized. Twelve adults who stutter (AWS) repeated single words into what appeared to be an automatic speech-recognition system. Following each iteration of each word, participants provided a self-rating of whether they stuttered on it and the computer then provided feedback implying its correct or incorrect recognition of it. Each word was repeated four times. Unbeknown to participants, 'Correct' and 'Incorrect' recognition of words by the system was pre-determined and bore no relation to the actual quality of participants' iterations of those words. For words uttered in the 'Correct recognition' condition, the likelihood of AWS self-reporting stuttering on a word diminished across iterations, whereas for words in the 'Incorrect recognition' condition it remained static. On the basis of the findings it is argued that: (a) in AWS, the anticipation that a word will be misrecognized increases the relative likelihood of stuttering on that word in the future; and (b) this effect is independent of the degree of difficulty inherent in the formulation and motor execution of the word itself, although it may interact with it. Mechanisms that can account for these findings and yet are also congruent with the wider range of evidence from psycholinguistic and speech motor control domains are discussed. It is concluded that stuttered disfluencies may best be explained as resulting from the inappropriate functioning of covert repair and/or variable release threshold mechanisms in response to the anticipation of communication failure. LEARNING OUTCOMES: This article informs readers about two different theoretical approaches to explaining developmental stuttering: (1) stuttering as an adaptation response to an underlying impairment; and (2) stuttering as an anticipatory struggle response. It describes how these approaches account for different symptoms of the disorder, and proposes that both theoretical approaches are needed in order to fully account for the range of symptoms and experimental findings associated with stuttering.

Judgment of disfluency in people who stutter and people who do not stutter: results from magnitude estimation.

Two experiments used a magnitude estimation paradigm to test whether perception of disfluency is a function of whether the speaker and the listener stutter or do not stutter. Utterances produced by people who stutter were judged as "less fluent," and, critically, this held for apparently fluent utterances as well as for utterances identified as containing disfluency. Additionally, people who stutter tended to perceive utterances as less fluent, independent of who produced these utterances. We argue that these findings are consistent with a view that articulatory differences between the speech of people who stutter and people who do not stutter lead to perceptually relevant vocal differences. We suggest that these differences are detected by the speech self-monitoring system (which uses speech perception) resulting in covert repairs. Our account therefore shares characteristics with the Covert Repair (Postma & Kolk, 1993) and Vicious Circle (Vasic & Wijnen, 2005) hypotheses. It differs from the Covert Repair hypothesis in that it no longer assumes an additional deficit at the phonological planning level. It differs from the Vicious Circle hypothesis in that it no longer attributes hypervigilant monitoring to unknown, external factors. Rather, the self-monitor becomes hypervigilant because the speaker is aware that his/her speech is habitually deviant, even when it is not, strictly speaking, disfluent.

Alignment of "phrase accent" lows in dutch falling rising questions: theoretical and methodological implications.

In the first part of this study, we measured the alignment (relative to segmental landmarks) of the low F0 turning points between the accentual fall and the final boundary rise in short Dutch falling-rising questions of the form Do you live in [place name]? produced as read speech in a laboratory setting. We found that the alignment of these turning points is affected by the location of a postaccentual secondary stressed syllable if one is present. This is consistent with the findings and analyses of Grice, Ladd, & Arvaniti, 2000 (Phonology 17, 143-185), suggesting that the low turning points are the phonetic reflex of a "phrase accent." In the second part of this study, we measured the low turning points in falling-rising questions produced in a task-oriented dialog setting and found that their alignment is affected in the same way as in the read speech data. This suggests that read speech experiments are a valid means of investigating the phonetic details of intonation contours.