Acquisition, retention, and generalization of rhotics with and without ultrasound visual feedback

The purpose was to provide a preliminary within-participant comparison of speech therapy with and without exposure to ultrasound visual feedback for postvocalic rhotics (/r/- colored vowels). Effects of the two treatments on acquisition, retention, and generalization were explored. It was hypothesized that treatment with ultrasound would facilitate acquisition but hinder retention and generalization.

A single subject randomized block design was replicated across four American English-speaking participants ages 7-9 years. Each participant was trained on postvocalic /r/. Each week for seven weeks, one session with ultrasound visual feedback and one session with no ultrasound were randomly ordered. A Training Probe and Generalization Probe were used to measure acquisition within each session as well as retention and generalization between two consecutive sessions. Graphical displays of the data, effect size calculation, and statistical results from a randomization test were used to analyze the results.

Two participants showed essentially no evidence of acquisition, retention or generalization of rhotics (<5%). Of the two who showed evidence of acquisition, one participant showed a significant advantage and large effect size for ultrasound sessions over no ultrasound sessions in acquisition of rhotics. However, no participants showed differences between treatment conditions in generalization or retention of rhotics.

For some children, acquisition may be facilitated by ultrasound visual feedback. Ultrasound visual feedback neither inhibited nor facilitated retention or generalization of rhotics. As a whole, the 14 treatment sessions (7 with ultrasound and 7 without) were effective for 2 of the 4 participants when comparing pre/post generalization scores. Future studies should evaluate the effectiveness of ultrasound visual feedback given a larger dose and differing age groups.