Quantifying tongue tip shape in apical and laminal /s/: Contributions of palate shape

Maureen Stone, Arnold D. Gomez, Jiachen Zhuo, Ange Lydie Tchouaga, Jerry L. Prince

Research output: Contribution to journalArticle

Abstract

Purpose: Anterior tongue shape during /s/ production is often described as “tip-up” or apical, versus “tip-down” or laminal. Typically, this is determined by observing the shape of the anterior midline tongue. The purpose of this study was to identify methods of curvature calculation that quantify the observed shape differences and to examine whether the shape differences were affected by palate shape. Previous work shows that palate height has some effect (Grimm et al., 2017). Method: Four curvature-based measures were applied to a series of points selected along the tongue surface in midsagittal cine magnetic resonance images during speech. The measures were minimal curvature, averaged largest curvature (ALC), normalized ALC, and interpolated normalized ALC. These measures were compared to visual judgments of apical and laminal /s/. Anterior palate shape was measured from dental casts. Results: The apical /s/ contained a flat or concave region in the anterior tongue, while the laminal /s/ had a convex shape along the entire tongue. Thus, the laminal shape was less complex than the apical. The last 2 metrics, based on averages of multiple normalized curvatures, captured this complexity difference. Subjects with a more steeply sloped anterior palate tended to use laminal /s/. Conclusions: The tongue shape for the 2 /s/ types was best defined by complexity of the shape, rather than local anterior shape. Statistical quantities that measured curvature in multiple locations, and normalized across subjects, were best at distinguishing the 2 /s/ shapes. Interpolating additional points between the manually selected ones did not improve the method.

Original languageEnglish (US)
Pages (from-to)3149-3159
Number of pages11
JournalJournal of Speech, Language, and Hearing Research
Volume62
Issue number9
DOIs
StatePublished - Sep 2019

ASJC Scopus subject areas

  • Language and Linguistics
  • Linguistics and Language
  • Speech and Hearing

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