An ultrasound investigation of the speech motor skills of stuttering Italian children

ABSTRACT

This study aims at evaluating speech motor skills in the fluent speech of a cohort of stuttering Italian children. Stuttering is a neurodevelopmental disorder that may arise from an innate limitation of the speech motor control system, which fails to prepare and organize the movements required for fluent speech (Van Lieshout, Hulstijn, & Peters, 2004). Anticipatory coarticulation in CV sequences and stability of speech movements have been used as measures of the maturity of articulatory processes for fluent speech production. This study aims to assess if direct measures of speech dynamics can identify impaired mechanisms in stuttering speech during a phrase-repetition task. The Ultrasound Tongue Imaging data of eight school-aged children, half of whom stutter while the other half don’t, show different articulatory patterns between the two groups, for both motor aspects under investigation. Articulatory data show that the stuttering group presents a higher degree of intra-syllabic coarticulation compared to the control group and decreased stability (i.e. more variability) through multiple repetitions of the same alveolar and velar item. Outcomes of this study suggest that the speech motor control system of children who stutter is less mature in preparing and executing the speech gestures required for fluent speech. This study contributes to shedding light on the impaired articulatory patterns involved in stuttering speech and to identifying the diagnostic markers of the disorder by evaluating the speech of children close to the onset of stuttering.

KEYWORDS:

• Childhood stuttering
• ultrasound
• coarticulation
• locus equations
• token-to-token variability

Acknowledgements

We are grateful to the two anonymous reviewers for their helping feedback and, more importantly, to all children and parents without whom this research would not have been possible. We also thank Piero Pierotti and the A.I.BA.COM. Association for helping us to contact the families of the stuttering children.

Declaration of interest

This study was supported by Scuola Normale Superiore (Project: Dinamiche del parlato di bambini balbuzienti: studio acustico e articolatorio per una diagnosi differenziale fra balbuzie cronica e remissiva). The authors report no conflict of interest.

Notes

¹ These results corroborate Chang et al.’s (2002) acoustic findings on the speech of CWS (see above).

² Since several studies have associated the frontness of the body of the tongue in the vocal tract to F2, Iskarous et al. (2010) used Electromagnetic Midsagittal Articulografy (EMMA) to measure the horizontal position of the tongue body at the release of the consonant and in the middle of the vowel, in order to investigate the articulatory origins of LE. The authors found the same linear relations present in the acoustic domain.