Peter F. MacNeilage

Acquisition of serial complexity in speech production: a comparison of phonetic and phonological approaches to first word production.

Comparison was made between performance-based and competence-based approaches to the understanding of first word production. The performance-related frame/content approach is representative of the biological/functional perspective of phonetics in seeking explanations based on motor, perceptual and cognitive aspects of speech actions. From this perspective, intrasyllabic consonant-vowel (CV) co-occurrence patterns and intersyllabic sequence patterns are viewed as reflective of biomechanical constraints emerging from mandibular oscillation cycles. A labial-coronal sequence effect involved, in addition, the problem of interfacing the lexicon with the motor system, as well as the additional problem of initiation of movement complexes. Competence-based approaches to acquisition are within the generative phonological tradition; involving an initial assumption of innate, speech-specific mental structures. While various current phonological approaches to acquisition involve consideration of sequence effects and intrasyllabic patterns, they do not adequately establish the proposed mental entities in infants of this age, and are nonexplanatory in the sense of not considering the causes of the structures and constraints that they posit.

On the Motor Control of Coarticulation in CVC Monosyllables

This study was an attempt to account for the motor control of speech production by a model in which discrete phoneme commands are modified according to phonological context by three motor system mechanisms. The model was evaluated by consideration of high‐speed cinelluorograms, and electromyograms from nine articulatory locations, recorded while one subject produced 36 consonant‐vowel consonant monosyllables. The syllables were formed by every possible combination of initial and final consonants /b/, /d/, and /g/, and the syllable nuclei /i/, /u/, /ae/, and /ɔ/. In every possible case, some aspect of the motor control of a later syllable component was influenced by the identity of the previous one. Except in a few cases, some aspect of the motor control of an earlier syllable component was influenced by the identity of the following one. These latter influences were of greater magnitude and complexity, and more reflected in movement, in the initial consonant than in the vowel. Some of the context effects o...

Hemispheric specialization for speech production and perception in stutterers

Abstract A group of stutterers was tested on presumed indices of hemispheric specialization for speech production (pursuit auditory tracking) and speech perception (dichotic listening). Previous studies of normal subjects [18, 19] have revealed a significant right ear advantage (REA) for tracking with a speech articulator but not with manual tracking. Stutterers showed no significant REA in either tracking condition, but did show a significant REA, similar to that of normal speakers, in dichotic listening. Results were considered to differentiate this population of stutterers from normals in terms of hemispheric specialization for speech production but not for speech perception.

Acquisition of Speech Production: The Achievement of Segmental Independence

As a primate communicative event, the repetitive, rhythmic, open-close alternation of the mandible, accompanied by phonation, is observable in three forms; some variants of the lipsmack, which is widespread in other primates, the initial babbling of human infants, and the production of the syllables of adult speech. In the first two of these, successive cycles tend to be uniform but in the third there is a highly variegated pattern in successive cycles. Adult segmental serial ordering errors, (e.g. spoonerisms) the effects of which are strongly constrained in terms of syllable structure, suggest that variegation is achieved by placement of independently controlled “Content” elements in syllable “Frames”. This paper considers implications of the view that development of infant communicative vocalizations from initial reduplicated babbling to variegated babbling and then to speech, primarily involves a gradual functional differentiation of segmental and subsegmental content elements from a phylogenetically prior basis consisting of ‘pure’ syllable frames; that is, mandibular oscillations without internal articulatory modulation.

Postural asymmetries and language lateralization in humans (Homo sapiens).

Is hemispheric specialization for speech more closely related to left hemisphere specialization for manual skill and sequencing, as is usually supposed, or to control of asymmetries in whole body posture, as recent findings of right-handedness in nonhuman primates suggest? This question can be evaluated in the 10% of humans who have mixed handedness and footedness. Footedness entails postural asymmetry, and persons with mixed limb preferences often prefer the hand ipsilateral to the preferred foot in asymmetrical actions for which whole body postural adjustments are obligatory (e.g., throwing). The dichotic listening test , and indicator of language laterality, was administered to 4 groups of 48 persons with the 4 possible combinations of hand and foot preference. As in 2 past studies, language lateralization was somewhat more strongly related to postural asymmetries than to asymmetries in manual skill and sequencing.

Motor Explanations of Babbling and Early Speech Patterns

From the onset of canonical babbling, human vocal output is dominated by the cyclical open-close alternation of the mandible. Mandibular cyclicity has a long evolutionary history in sucking, licking and chewing in mammals, and also appears communicatively in lipsmacks, tonguesmacks and teeth chatters in other primates. It is argued that many of the articulatory regularities in the sound patterns of babbling, and early speech, which closely resembles babbling, (including consonants, vowels, syllables, and many of their detailed attributes) can be attributed directly to properties of this basic mandibular cycle. In addition, some interarticulator synergies evolving with the cycle, plus developmental limitations in changing locus of control between and within articulators during utterances, seem responsible for most other regularities in babbling and early speech.

Prosodic Correlates of Stress in Babbling: An Acoustical Study

Prelinguistic babbling often seems remarkably speech-like, not because it has recognizable words but because it seems to have adult-like prosody. To quantify this impression, we compared disyllabic sequences from five infants and five adults in terms of the use of frequency, intensity, and duration to mark stress. Significantly larger values for the three acoustic variables were observed on stressed than on unstressed syllables independent of syllable position for both groups. Adults showed the correlates of utterance final syllables--lower f0, lower intensity, and longer duration; infants showed only decrease in intensity. Ratios for stressed to unstressed syllables and participation of the three variables in stress production in individual disyllables were highly similar in both groups. No bias toward the English lexical trochaic stress pattern was observed. We conclude that infants in English environments produce adult-like stress patterns before they produce lexical items, which specify stress. Acoustic and perceptual analyses are used to explore stress marking by prelinguistic infants in an English language environment. Results show that infants employ the three acoustic correlates of stress in individual syllables in a manner largely similar to that of adult speakers, although they do not show second-syllable declination effects or an English language trochaic stress bias.

Studies of hemispheric specialization for speech production.

Subjects matched a continuously varying pure tone presented to one ear with a second tone presented to the other ear and controlled by unidimensional movements of part of their motor system. Performance was significantly better when the tone controlled by a speech articulator (tongue, jaw) was presented to the right ear, rather than the left (REA), but not if the tone was hand-controlled. Results suggest the presence in the left hemisphere of a speech-related auditorysensorimotor integration mechanism. A group of stutterers showed no REA. Magnitude of REA in tracking was not related to magnitude of REA in dichotic listening studies of speech perception either in normal subjects or in stutterers.

An Embodiment Perspective on the Acquisition of Speech Perception

Understanding the potential relationships between perception and production is crucial to explanation of the nature of early speech acquisition. The ‘embodiment’ perspective suggests that mental activity in general cannot be understood outside of the context of body activities. Indeed, universal motor factors seem to be more responsible for the distribution of early production preferences regarding consonant place and manner, and use of the vowel space than the often considerable cross-language differences in input available to the perceptual system. However, there is evidence for a perceptual basis to the establishment of a language-appropriate balance of oral-to-nasal output by the beginning of babbling, illustrating the necessary contribution of ‘extrinsic’ perceptual information to acquisition. In terms of representations, at least one assumption that segmental units underlying either perception or production in early phases of acquisition may be inappropriate. Our work on production has shown that the dominant early organizational structure is a relatively unitary open-close ‘frame’ produced by mandibular oscillation. Consideration of the role of ‘intrinsic’ (self-produced) perceptual information suggests that this frame may be an important basis for perceptual as well as production organization.

Organization of babbling: a case study.

Speech is probably the most complex serially ordered behavior in living forms. However, no systematic investigation of the organization of speech-related output when it is presumably simplest, namely during the babbling stage, has been attempted. Transcriptions of 423 babbled utterances (1145 syllables) were obtained from one subject 7–12 months of age. Most results could be interpreted in terms of a basic mouth opening-closing alternation, responsible not only for the typical vowel-consonant alternation of babbling, but also for many prominent details including within-utterance variation in vowel height (often stress-related) and in degree of closure for consonants. The results suggest that a “frame” for babbling is provided by mandibular oscillation, perhaps reflected, when operating alone, in the common alternation between labial consonants and central vowels. Variation in the amplitude of this oscillation may be responsible for the within-utterance vowel height and consonant manner variation and much of the perceived stress variation. Further variation is attributed to fronting movements of the tongue, the effects of which often spread beyond single vowels and consonants.