Lucie Ménard

The Perception for Action Control Theory (PACT): a perceptuo-motor theory of speech perception

It is an old-standing debate in the field of speech communication to determine whether speech perception involves auditory or multisensory representations and processing, independently on any procedural knowledge about the production of speech units or on the contrary if it is based on a recoding of the sensory input in terms of articulatory gestures, as posited in the Motor Theory of Speech Perception. The discovery of mirror neurons in the last 15 years has strongly renewed the interest for motor theories. However, while these neurophysiological data clearly reinforce the plausibility of the role of motor properties in perception, it could lead in our view to incorrectly de-emphasise the role of perceptual shaping, crucial in speech communication. The so-called Perception-for-Action-Control Theory (PACT) aims at defining a theoretical framework connecting in a principled way perceptual shaping and motor procedural knowledge in speech multisensory processing in the human brain. In this paper, the theory is presented in details. It is described how this theory fits with behavioural and linguistic data, concerning firstly vowel systems in human languages, and secondly the perceptual organization of the speech scene. Finally a neuro-computational framework is presented in connection with recent data on the possible functional role of the motor system in speech perception.

Auditory normalization of French vowels synthesized by an articulatory model simulating growth from birth to adulthood

The present article aims at exploring the invariant parameters involved in the perceptual normalization of French vowels. A set of 490 stimuli, including the ten French vowels /i y u e ø o E oe (inverted c) a/ produced by an articulatory model, simulating seven growth stages and seven fundamental frequency values, has been submitted as a perceptual identification test to 43 subjects. The results confirm the important effect of the tonality distance between F1 and f0 in perceived height. It does not seem, however, that height perception involves a binary organization determined by the 3-3.5-Bark critical distance. Regarding place of articulation, the tonotopic distance between F1 and F2 appears to be the best predictor of the perceived front-back dimension. Nevertheless, the role of the difference between F2 and F3 remains important. Roundedness is also examined and correlated to the effective second formant, involving spectral integration of higher formants within the 3.5-Bark critical distance. The results shed light on the issue of perceptual invariance, and can be interpreted as perceptual constraints imposed on speech production.

Measuring Tongue Shapes and Positions with Ultrasound Imaging: A Validation Experiment Using an Articulatory Model

Objective: The goal of this paper is to assess the validity of various metrics developed to characterize tongue shapes and positions collected through ultrasound imaging in experimental setups where the probe is not constrained relative to the subject’s head. Patients and Methods: Midsagittal contours were generated using an articulatory-acoustic model of the vocal tract. Sections of the tongue were extracted to simulate ultrasound imaging. Various transformations were applied to the tongue contours in order to simulate ultrasound probe displacements: vertical displacement, horizontal displacement, and rotation. The proposed data analysis method reshapes tongue contours into triangles and then extracts measures of angles, x and y coordinates of the highest point of the tongue, curvature degree, and curvature position. Results: Parameters related to the absolute tongue position (tongue height and front/back position) are more sensitive to horizontal and vertical displacements of the probe, whereas parameters related to tongue curvature are less sensitive to such displacements. Conclusion: Because of their robustness to probe displacements, parameters related to tongue shape (especially curvature) are particularly well suited to cases where the transducer is not constrained relative to the head (studies with clinical populations or children).

Production and perception of French vowels by congenitally blind adults and sighted adults

The goal of this study is to investigate the production and perception of French vowels by blind and sighted speakers. 12 blind adults and 12 sighted adults served as subjects. The auditory-perceptual abilities of each subject were evaluated by discrimination tests (AXB). At the production level, ten repetitions of the ten French oral vowels were recorded. Formant values and fundamental frequency values were extracted from the acoustic signal. Measures of contrasts between vowel categories were computed and compared for each feature (height, place of articulation, roundedness) and group (blind, sighted). The results reveal a significant effect of group (blind vs sighted) on production, with sighted speakers producing vowels that are spaced further apart in the vowel space than those of blind speakers. A group effect emerged for a subset of the perceptual contrasts examined, with blind speakers having higher peak discrimination scores than sighted speakers. Results suggest an important role of visual input in determining speech goals.

Articulatory–acoustic relationships during vocal tract growth for French vowels: Analysis of real data and simulations with an articulatory model

Abstract This paper reports on the articulatory–acoustic relationships involved during vocal tract growth. Data were taken from a database of ten French vowels uttered by 15 speakers ranging in age from 3 years old to adulthood. Despite the important acoustic variation encountered, one feature is displayed by all the speakers: the production of extreme focal vowels /i/, /u/, /a/, and /y/, realized with a strong concentration of spectral energy related to the proximity of two formant peaks. This feature represents an acoustic goal guiding the speakers task. Our simulations using an articulatory model demonstrate that the realization of the focalization feature may require different articulatory gestures for young children compared to adults, consisting of adaptive articulatory strategies exploited to compensate for the small pharynx of the former. Perceptual tests show that achieving focalization results in a lower intelligibility for the children than for the adults. Due to the relatively shorter pharyngeal cavity of the child compared to the adult, focalization cannot be achieved together with the perceptual objective related to rounded vowels /y/ in French. Results are discussed in light of the dispersion-focalization theory and the perception for action control theory (PACT).

Asymmetries in vowel perception, in the context of the Dispersion–Focalisation Theory

In a recent paper in this journal, Polka and Bohn [Polka, L., Bohn, O.-S., 2003. Asymmetries in vowel perception. Speech Communication 41, 221–231] display a robust asymmetry effect in vowel discrimination, present in infants as well as adults. They interpret this effect as a preference for peripheral vowels, providing an anchor for comparison. We discuss their data in the framework of the Dispersion–Focalisation Theory of vowel systems. We show that focalisation, that is the convergence between two consecutive formants in a vowel spectrum, is likely to provide the ground for anchor vowels, by increasing their perceptual salience. This enables to explain why [y] is an anchor vowel, as well as [i], [a] or [u]. Furthermore, we relate the asymmetry data to an old experiment we had done on the discrimination of focal vs. non-focal vowels. Altogether, it appears that focal vowels, more salient in perception, provide both a stable percept and a reference for comparison and categorisation.

Developmental and cross-linguistic variation in the infant vowel space: The case of Canadian English and Canadian French

This article describes the results of two experiments. Experiment 1 was a cross-sectional study designed to explore developmental and cross-linguistic variation in the vowel space of 10- to 18-month-old infants, exposed to either Canadian English or Canadian French. Acoustic parameters of the infant vowel space were described (specifically the mean and standard deviation of the first and second formant frequencies) and then used to derive the grave, acute, compact, and diffuse features of the vowel space across age. A decline in mean F1 with age for French-learning infants and a decline in mean F2 with age for English-learning infants was observed. A developmental expansion of the vowel space into the high-front and high-back regions was also evident. In experiment 2, the Variable Linear Articulatory Model was used to model the infant vowel space taking into consideration vocal tract size and morphology. Two simulations were performed, one with full range of movement for all articulatory paramenters, and the other for movement of jaw and lip parameters only. These simulated vowel spaces were used to aid in the interpretation of the developmental changes and cross-linguistic influences on vowel production in experiment 1.

The development of motor synergies in children: Ultrasound and acoustic measurements

The present study focuses on differences in lingual coarticulation between French children and adults. The specific question pursued is whether 4-5 year old children have already acquired a synergy observed in adults in which the tongue back helps the tip in the formation of alveolar consonants. Locus equations, estimated from acoustic and ultrasound imaging data were used to compare coarticulation degree between adults and children and further investigate differences in motor synergy between the front and back parts of the tongue. Results show similar slope and intercept patterns for adults and children in both the acoustic and articulatory domains, with an effect of place of articulation in both groups between alveolar and non-alveolar consonants. These results suggest that 4-5 year old children (1) have learned the motor synergy investigated and (2) have developed a pattern of coarticulatory resistance depending on a consonant place of articulation. Also, results show that acoustic locus equations can be used to gauge the presence of motor synergies in children.

Articulatory bias in speech categorization: Evidence from use-induced motor plasticity

Challenging the classical proposal of separate neural/cognitive processes for speech perception and speech production, several neurobiological and psycholinguistic models of speech perception argue for a functional connection between sensory and motor systems (e.g., Liberman and Whalen, 2000; Wilson and Iacoboni, 2006; Skipper et al., 2007; Schwartz et al., in press). In these models, phonetic interpretation of sensory information is determined or constrained by some internal motor simulation based on articulatory procedural knowledge. However, despite accumulating evidence that speech motor regions are activated in processing speech sounds (e.g., Fadiga et al., 2002; Pulvermuller et al., 2006; Sato et al., 2010), the question of whether articulatory processes mediate speech perception is still vigorously debated (e.g., Lotto et al., 2009; Sato et al., 2009; Scott et al., 2009). Using a new technique based on use-induced motor plasticity, we here provide evidence that the motor system can bias perceptual performance in auditory speech recognition and plays a mediating role in phonetic decision/categorization process.

Compensation strategies for a lip-tube perturbation of French [u]: An acoustic and perceptual study of 4-year-old children

The relations between production and perception in 4-year-old children were examined in a study of compensation strategies for a lip-tube perturbation. Acoustic and perceptual analyses of the rounded vowel [u] produced by twelve 4-year-old French speakers were conducted under two conditions: normal and with a 15-mm-diam tube inserted between the lips. Recordings of isolated vowels were made in the normal condition before any perturbation (N1), immediately upon insertion of the tube and for the next 19 trials in this perturbed condition, with (P2) or without articulatory instructions (P1), and in the normal condition after the perturbed trials (N2). The results of the acoustic analyses reveal speaker-dependent alterations of F1, F2, and/or F0 in the perturbed conditions and after the removal of the tube. For some subjects, the presence of the tube resulted in very little change; for others, an increase in F2 was observed in P1, which was generally reduced in some of the 20 repetitions, but not systematically and not continuously. The use of articulatory instructions provided in the P2 condition was detrimental to the achievement of a good acoustic target. Perceptual data are used to determine optimal combinations of F0, F1, and F2 (in bark) related to these patterns. The data are compared to a previous study conducted with adults [Savariaux et al., J. Acoust. Soc. Am. 106, 381-393 (1999)].