Locus Equations As an Index of Coarticulation for Place of Articulation Distinctions in Children Locus equations were investigated as a phonetic index for children’ s production of stop + vowel tokens. Locus equations are straight-line regression fits to data points formed by plotting onsets of F2 transitions along the ordinate and their corresponding midvowel nuclei along the abscissa. Such functions for adult speech have ... Research Article
Research Article  |   August 01, 1992
Locus Equations As an Index of Coarticulation for Place of Articulation Distinctions in Children
 
Author Affiliations & Notes
  • Harvey M. Sussman
    University of Texas at Austin
  • Katherine A. Hoemeke
    University of Texas at Austin
  • Helen A. McCaffrey
    University of Texas at Austin
Article Information
Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   August 01, 1992
Locus Equations As an Index of Coarticulation for Place of Articulation Distinctions in Children
Journal of Speech, Language, and Hearing Research, August 1992, Vol. 35, 769-781. doi:10.1044/jshr.3504.769
History: Received July 18, 1991 , Accepted December 30, 1991
 
Journal of Speech, Language, and Hearing Research, August 1992, Vol. 35, 769-781. doi:10.1044/jshr.3504.769
History: Received July 18, 1991; Accepted December 30, 1991

Locus equations were investigated as a phonetic index for children’ s production of stop + vowel tokens. Locus equations are straight-line regression fits to data points formed by plotting onsets of F2 transitions along the ordinate and their corresponding midvowel nuclei along the abscissa. Such functions for adult speech have been found to be extremely linear with slope and y-intercept values contrastively distinctive across place of articulation. Sixteen children, aged 3–5 years, produced /bVt/, /dVt/, and /gVt/ tokens embedded in a carder phrase and repeated in randomized order a minimum of three times. Six medial vowel contexts were used [i, I, ae, ٨ , a, u]. Both individual and group mean scatterplots were extremely linear and highly remniscent of adult prototypes. While labial and velar slopes exhibited some degree of overlap, labial versus alveolar and alveolar versus velar slopes were significantly different. All y-intercepts as a function of place of articulation were significantly different. Compared to adult norms, intersubject variability of slope and y-intercept ranges were greater for children. Locus equations can provide a phonetic descriptor for a child’ s attainment of stop place categories seeking to achieve the adult standard of a balance between coarticulatory adjustments and contrastive distinctiveness.

Acknowledgments
This research was supported by grant BNS-8919221 from the National Science Foundation to the first author. We would like to extend our sincere appreciation to the staff at the Open Door Preschool, Austin, Texas, and to Sooki Kaul and all her friends who took the time to leave the playground and talk to us. The editorial comments of Barbara Davis and Richard Meier during the preparation and revision of the manuscript are also greatly appreciated. We also thank Seung Jae Moon for his assistance with some of the graphics.
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