There are still crucial gaps in our knowledge about developmental paths taken by children to adult-like speech motor control. Mature control of articulators during speaking is manifested in the appropriate extent of coarticulation (the articulatory overlap of speech sounds). This study compared lingual coarticulatory properties of child and adult speech, using ultrasound tongue imaging. The participants were speakers of Standard Scottish English, ten adults and ten children aged 6-9 years. Consonant-vowel syllables were presented in a carrier phrase. Distances between tongue curves were used to quantify coarticulation. In both adults and children, vowel pairs /a/-/i/ and /a/-/u/ significantly affected the consonant, and the vowel pair /i/-/u/ did not. Extent of coarticulation was significantly greater in the children than in the adults, providing support for the notion that children's speech production operates with larger units than adults'. More within-speaker variability was found in the children than in the adults.

Abstract

The patterns of weighting that children give to different acoustic characteristics of speech (their cue weighting) appear to change with increased linguistic experience.Previous speech perception research has found a correlation between children's cue weighting strategies and their ability to consciously think about and manipulate segment-sized units (phonemic awareness). That research was not, however, able to determine whether the relationship is in any way causal, and if so whether it is phonemic awareness development that impacts on cue weighting strategies, or if changes in cue weighting allow for the later development of phonemic awareness. The aim of this study was to follow the development of these two processes longitudinally in order to determine which of the above two possibilities was more likely. Five-yearold children were tested 3 times in 7 months on their cue weighting strategies for a /so/-/ o/ contrast, in which the two cues being manipulated were the frequency of fricative spectrum and the frequency of vowel onset formant transitions. The children were also tested at the same time on their phoneme segmentation and phoneme blending skills. Results showed that phonemic awareness skills tended to improve before cue weighting changed, and that early phonemic awareness ability predicted later cue weighting strategies. These results suggest that the linguistic experience which has been suggested is the catalyst for cue weighting changes must include meta-phonemic development.2

This is a dense book. Seventy-five dollars is a not-at-all-unusual price for linguistics works these days; but in this case you will certainly at least get value for the money. Because this is a collection of papers by different authors, quality and style vary from chapter to chapter, but there are few wasted words, and hardly a sentence without a kernel idea worth taking the time to understand. On the other hand, it is a difficult and demanding book to read cover to cover, and most readers will probably prefer to focus on areas of particular personal interest rather than tackling the whole volume at one go. In the Introduction, the editors introduce the notion of coarticulation by referring to how the sounds of language are highly context-sensitive and influenced by neighboring segments. This is followed by an overview of the chapters. Mention is also made of the book's origin as an EU-funded project of ACCOR ("Articulatory-acoustic correlations in coarticulation processes: a cross-linguistic investigation"), conducted 1992-95. Part I, "Theories and models", attempts to provide general background and a foundation for the other chapters of the book. Chapter 1, entitled "The origin of coarticulation" (Barbara Kühnert and Francis Nolan), discusses what causes coarticulation, a history of the investigation of coarticulation, and how coarticulation develops in children's speech. The term "coarticulation" is said to date to the 1930s, while experimental techniques for studying coarticulation were developed by Bruecke and Bell in the mid-1800s. A series of coarticulatory models is reviewed, including Lindblom's "target undershoot" model of the 1960s (p. 16), Oehman's observation that two vowels interact with each other across intervening stops (p. 17), Wickelgren's idea that we store not phonemes in our brains but collections of context-sensitive allophones (p. 18), up to Keating's "window" model of the 1980s (p. 21), in which every feature of a segment is associated with a range of values rather than an absolute target. The chapter is inconclusive regarding child acquisition of coarticulation, and cites the need for further study. Chapter 2, "Coarticulation models in recent speech production theories" (Edda Farnetani and Daniel Recasens), expands on these and other theories of the past thirty years, including Lindblom's continuum of "hyperto hypo-speech" (p. 34), Pauli and Sundberg's proposal that V-to-C coarticulation results from a low-cost production strategy (p. 37), Daniloff and Hammarberg's "feature-spreading" theory (p. 40), and a hybrid model (p. 59).

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.