Betty Tuller

Functionally specific articulatory cooperation following jaw perturbations during speech: Evidence for coordinative structures.

In three experiments we show that articulatory patterns in response to jaw perturbations are specific to the utterance produced. In Experiments 1 and 2, an unexpected constant force load (5.88 N) applied during upward jaw motion for final /b/ closure in the utterance /baeb/ revealed nearly immediate compensation in upper and lower lips, but not the tongue, on the first perturbation trial. The same perturbation applied during the utterance /baez/ evoked rapid and increased tongue-muscle activity for /z/ frication, but no active lip compensation. Although jaw perturbation represented a threat to both utterances, no perceptible distortion of speech occurred. In Experiment 3, the phase of the jaw perturbation was varied during the production of bilabial consonants. Remote reactions in the upper lip were observed only when the jaw was perturbed during the closing phase of motion. These findings provide evidence for flexibly assembled coordinative structures in speech production.

The nonlinear dynamics of speech categorization.

Little is known about the processes underlying the nonlinear relationship between acoustics and speech perception. In Experiment 1, we explored the effects of systematic variation of a single acoustic parameter (silent gap duration between a natural utterance of s and a synthetic vowel ay) on judgements of speech category. The resulting shifts in category boundary between say and stay showed rich dynamics, including hysteresis, contrast, and critical boundary effects. We propose a dynamical model to account for the observed patterns. Experiment 2 evaluated one prediction of the model, that changing the relative stability of the two percepts allows categorical switching. In agreement with the model; an increase in the number of stimulus repetitions maximized the frequency of judgments of category change near the boundary. Thus, a dynamical approach affords the rudiments for a theory of the effects of temporal context on speech categorization.

Reception of language in broca's aphasia

Abstract This experiment tests between two competing hypotheses about the source of failures in comprehension by Broca-type aphasics with agrammatic production. These are characterised as (1) the hypothesis that these aphasic individuals have sustained a partial loss in syntactic knowledge, and (2) the hypothesis that, despite intact structural knowledge, they suffer from an inability to put that knowledge to use in comprehension tasks such as object manipulation and sentence-picture matching. To decide between the hypotheses, this study compared the speed and accuracy of Broca-type aphasics with a control group of normal subjects using an on-line grammaticality judgement task in which the anomaly involved closed-class vocabulary items. The results are in accord with the view that the source of agrammatic performance is not a loss of syntactic knowledge, as the responses of the aphasic group closely mirror those of the control group (e.g. word position effects were found for both groups). The results are ...

A Dynamical Basis for Action Systems

Students of the neural basis of cognition might weil take as their dictum the first phrase in the gospel according to St. John: “In the beginning was the word.” In this chapter, we beg to differ and side instead with Goethe’s Faust who, not satisfied with the accuracy of the biblical statement, proposed a rather different solution: “Im Anfang war die Tat”—“In the beginning was the act.”1 Certainly, if there is a lesson to be learned from the fie1d of neuroembryology, it is that motility precedes reactivity; there is a chronological primacy of the motor over the sensory. 2 Although one of our main premises is that any distinction between sensory and motor is an artificiaI one (cf. Kelso, 1979), this brief sojoum into developmental embryology affords what we take to be a main contrast between the topic of concem in this chapter—the control and coordination of movement—and the subject matter of the rest of this book.

A “Dynamic Pattern” Perspective on the Control and Coordination of Movement

That speech is the most highly developed motor skill possessed by all of us is a truism; but how is this truism to be understood? Although the investigation of speech production and that of motor behavior have proceeded largely independently of each other, they share certain conceptions of how skilled movements are organized. Thus, regardless of whether one refers to movement in general or to speech as a particular instance, it is assumed that for coordination to occur, appropriate sets of muscles must be activated in proper relationships to others, and correct amounts of facilitation and inhibition have to be delivered to specified muscles. That the production of even the simplest movement involves a multiplicity of neuromuscular events overlapping in time has suggested the need for some type of organizing principle. By far the most favored candidates have been the closed-loop servomechanism accounts provided by cybernetics and its allied disciplines, and the formal machine metaphor of central programs. The evidence for these rival views seems to undergo continuous updating (e.g., Adams, 1977; Keele, 1981) and so will not be of major concern to us here. It is sufficient to point out the current consensus on the issue, namely, that complex sequences of movement may be carried out in the absence of peripheral feedback, but that feedback can be used for monitoring small errors as well as to facilitate corrections in the program itself (e.g., Keele, 1981; Miles & Evarts, 1979).

The timing of articulatory gestures: Evidence for relational invariants

In this article, we examine the effects of changing speaking rate and syllable stress on the space-time structure of articulatory gestures. Lip and jaw movements of four subjects were monitored during production of selected bisyllabic utterances in which stress and rate were orthogonally varied. Analysis of the relative timing of articulatory movements revealed that the time of onset of gestures specific to consonant articulation was tightly linked to the timing of gestures specific to the flanking vowels. The observed temporal stability was independent of large variations in displacement, duration, and velocity of individual gestures. The kinematic results are in close agreement with our previously reported EMG findings [B. Tuller et al., J. Exp. Psychol. 8, 460-472 (1982)] and together provide evidence for relational invariants in articulation.

Toward a theory of apractic syndromes.

Abstract Theoretical development on human motor behavior has occurred largely independently of data on pathological movement disorders. This paper represents an initial attempt to interface findings from studies of apraxia and those of normal motor behavior with a view to formulating a common theoretical framework. Such an integration may ultimately aid in understanding the nature of skill acquisition and provide insights into the organization of motor systems. Three putative theoretical models of movement control are discussed with reference to apractic syndromes. The most commonly accepted view—the hierarchy—possesses properties such as linear transitivity and unidirectionality of information flow that render it inadequate in explaining functional plasticity in the central nervous system. The heterarchy, which incorporates reciprocity of function and circular transitivity, is a more likely candidate but suffers from an inability to regulate the degrees of freedom of the system. Our favored candidate is the coalition model which embodies heterarchical principles, but in addition, offers a solution to the problems of degrees of freedom and context for motor systems. Evidence is reviewed from apraxia of speech and limbs in terms of a coalitional style of control and an experimental approach, consonant with coalitional organization, is developed. We promote the claim that an understanding of apractic behavior—and perhaps motor systems in general—will benefit when clinicians and experimenters embrace a theory of context and constraints rather than a theory of commands as is currently in vogue.

Patterns of interarticulator phasing and their relation to linguistic structure

Work by Tuller and Kelso [J. Acoust. Soc. Am. 76, 1030-1036 (1984)] and Kelso et al. [J. Phon. 14, 29-59 (1986)] has demonstrated stable relations between jaw and lip movements in (bV#CVb) utterances across rate and stress conditions. Specifically, the onset of lip movement toward the intervocalic consonant was found to be constant with respect to the vowel-to-vowel jaw cycle in both time and relative phasing. An attempt was made to replicate and extend this work by investigating interarticulator phase relations for utterances having a broader range of linguistic organization: In addition to rate and stress, syllable structure (open versus closed syllables) and identity of the intervocalic consonant (/p/ vs /m/) were manipulated. Results showed that the upper lips lowering onset varied systematically with respect to the jaw vowel cycle as a function of both rate and stress. In addition, syllable structure and consonant identity influenced the relation of lip and jaw gestures. There was a general tendency for any condition that shortened the first vowel to produce earlier onsets of the upper lip relative to the jaw. However, the within-condition jaw cycle duration variability did not correlate with the within-condition variability in phase. Thus it seems that stable interarticulator phase relations maintain not only the integrity of phonological structure, as suggested by Kelso et al., but structural integrity at other levels of linguistic organization as well.

Phase transitions in speech production and their perceptual consequences

Previous work shows that the relative phasing of articulatory events varies little across two levels of speaking rate and stress. But, one may ask, varies little with respect to what? A methodology is required that differentiates articulatory patterns as they evolve in time. With this aim, subjects were instructed to say /ip/ or /pi/ repetitively, at increasing speaking rates, while monitoring their glottal and lip movements. For /pi/, the observed interarticulatory phase relationships did not depend on speaking rate. For /ip/, relative phasing often changed markedly, suggesting that loss of stability underlies articulatory change (a phase transition). In two follow‐up perceptual experiments, listeners appeared to judge the consonants syllable affiliation on the basis of interarticulator relative phase, and did so in a “categorical” manner. These findings, interpreted in light of a theoretical model based on synergetics [Kelso et al., Physics Scripta 35, 79–87 (1987)], may help resolve controversies conc...

Prosodic influences on the resolution of temporary ambiguity during on-line sentence processing

We present three experiments designed to investigate the role of prosody during sentence processing. The first investigated the question of whether an utterances prosodic contour influences its comprehension on-line. We spliced the beginning and end portions of direct object and embedded clause sentences and observed the consequent effects on comprehension using a dual-task procedure to measure processing load. Our second experiment sought to determine-whether the constituent structure of these sentences could be reliably predicted using prosodic information. We found that the duration and F0 contour associated with the main-clause verb and the following NP reliably distinguished between the direct object and embedded clause constructions. In the final experiment, we manipulated the duration of the main-clause verb and found that subjects used this information to guide their initial parse during on-line sentence comprehension. The need for a model of sentence processing that addresses the use of prosodic information is discussed.