The impact of deictic gesture on vowel acoustics in childhood apraxia of speech

Abstract

A growing literature supports the notion that manual gestures and speech are entrained, with one movement modulating the spatiotemporal properties of the other. For instance, Krahmer and Swerts (2007) demonstrated that gestures elicited unintentional prosodic stress production in healthy adult speakers. Understanding this relationship in individuals with motor speech disorders could inform both the underlying neuromotor impairment and the design of efficacious interventions. For example, two of the hallmark characteristics of childhood apraxia of speech (CAS) are atypical prosody and vowel distortions (ASHA, 2007). Given the impact of prosodic stress on vowel formants (e.g., Hay et al., 2006), enhanced prosody elicited through gestures may improve vowel clarity and consistency. The current investigation was designed to explore the relationship between manual and speech gestures in CAS by evaluating the consequences of deictic (pointing) gestures on vowel acoustics. Participants included children with CAS and healthy controls (ages 6-12 years). Vowel formants (F1, F2) were extracted from utterances produced with and without targeted stress and gestures. Metrics of formant centralization, vowel distinctiveness, and consistency of production were compared across stress and gesture conditions and between speaker groups. Preliminary findings suggest the potential of manual gestures to facilitate vowel production in CAS.