Retroflex versus bunched in treatment for rhotic misarticulation: evidence from ultrasound biofeedback intervention

Abstract

Purpose: To document the efficacy of ultrasound biofeedback treatment for misarticulation of the North American English rhotic in children. Because of limited progress in the first cohort, a series of two closely related studies was conducted in place of a single study. The studies differed primarily in the nature of tongue-shape targets (e.g., retroflex, bunched) cued during treatment.

Method: Eight participants received 8 weeks of individual ultrasound biofeedback treatment targeting rhotics. In Study 1, all 4 participants were cued to match a bunched tongue-shape target. In Study 2, participants received individualized cues aimed at eliciting the tongue shape most facilitative of perceptually correct rhotics.

Results: Participants in Study 1 showed only minimal treatment effects. In Study 2, all participants demonstrated improved production of rhotics in untreated words produced without biofeedback, with large to very large effect sizes.

Conclusions: The results of Study 2 indicate that with proper parameters of treatment, ultrasound biofeedback can be a highly effective intervention for children with persistent rhotic errors. In addition, qualitative comparison of Studies 1 and 2 suggests that treatment for the North American English rhotic should include opportunities to explore different tongue shapes, to find the most facilitative variant for each individual speaker.

Figures

Figure 1

Ultrasound images captured with the Interson SeeMore probe. The surface of the tongue appears as the white line. Images A and B are in sagittal section; the right side of the image is anterior. Image C is in coronal section. A: Typical adult speaker's bunched tongue shape for /ɝ/. B: Typical adult speaker's tongue shape for /u/, used in treatment to represent an undifferentiated (incorrect) tongue shape for rhotics. C: Typical adult speaker's tongue shape for /ɝ/ in coronal section, revealing midline groove and lateral bracing.

Figure 2

Word probe performance, Study 1. Y-axis represents percentage of tokens rated perceptually correct based on mode across three blinded clinician listeners. BL = baseline; TX = treatment; MN = maintenance.

Figure 3

Within-treatment performance, Study 1. Y-axis represents percent of tokens rated perceptually correct by a blinded listener. X-axis represents treatment session. Session numbers begin at 3 because no trials were elicited during instructional Sessions 1–2.

Figure 4

Word probe performance, Study 2. Y-axis represents percentage of tokens rated perceptually correct based on mode across three blinded clinician listeners.