Abstract
In the first years of life, children differ greatly from adults in the temporal organization of their speech gestures in fluent language production. However, dissent remains as to the maturational direction of such organization. The present study sheds new light on this process by tracking the development of anticipatory vowel-to-vowel coarticulation in a cross-sectional investigation of 62 German children (from 3.5 to 7 years of age) and 13 adults. It focuses on gestures of the tongue, a complex organ whose spatiotemporal control is indispensable for speech production. The goal of the study was threefold: 1) investigate whether children as well as adults initiate the articulation for a target vowel in advance of its acoustic onset, 2) test if the identity of the intervocalic consonant matters and finally, 3) describe age-related developments of these lingual coarticulatory patterns. To achieve this goal, ultrasound tongue imaging was used to record lingual movements and quantify changes in coarticulation degree as a function of consonantal context and age. Results from linear mixed effects models indicate that like adults, children initiate vowels’ lingual gestures well ahead of their acoustic onset. Second, while the identity of the intervocalic consonant affects the degree of vocalic anticipation in adults, it does not in children at any age. Finally, the degree of vowel-to-vowel coarticulation is significantly higher in all cohorts of children than in adults. However, among children, a developmental decrease of vocalic coarticulation is only found for sequences including the alveolar stop /d/ which requires finer spatiotemporal coordination of the tongue’s subparts compared to labial and velar stops. Altogether, results suggest greater gestural overlap in child than in adult speech and support the view of a non-uniform and protracted maturation of lingual coarticulation calling for thorough considerations of the articulatory intricacies from which subtle developmental differences may originate.
Highlights
IntroductionThe positioning and shaping of the tongue is determined by the segment currently under production but shows characteristics of neighboring speech segments at the same time
In spoken language, speech segments overlap with each other
This study was the first which addressed the maturation of lingual long-distance coarticulatory processes in a cross-sectional investigation of five age cohorts using articulatory measurements
Summary
The positioning and shaping of the tongue is determined by the segment currently under production but shows characteristics of neighboring speech segments at the same time. These gestural overlaps exist in heterorganic sequences employing different articulators for achieving the consonantal and vocalic gestures (e.g., /ba/ where the tongue body anticipates a low back position for /a/ during the production of /b/) as well as in homorganic sequences involving the same primary articulator for both gestures (e.g., the point of contact between the tongue body and the palate or velum for /g/ varies with the frontness of the following vowel) (e.g., [2]). Research on intersyllabic processes is crucial because it tackles a broader organization of speech production processes and addresses questions about the interplay between cognitive (e.g., phonological planning, gestural phasing) and motor domains (the physical implementation)
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