Modelling category goodness judgments in children with residual sound errors

Abstract

This study investigates category goodness judgments of /r/ in adults and children with and without residual speech errors (RSEs) using natural speech stimuli. Thirty adults, 38 children with RSE (ages 7-16) and 35 age-matched typically developing (TD) children provided category goodness judgments on whole words, recorded from 27 child speakers, with /r/ in various phonetic environments. The salient acoustic property of /r/ - the lowered third formant (F3) - was normalized in two ways. A logistic mixed-effect model quantified the relationships between listeners' responses and the third formant frequency, vowel context and clinical group status. Goodness judgments from the adult group showed a statistically significant interaction with the F3 parameter when compared to both child groups (p < 0.001) using both normalization methods. The RSE group did not differ significantly from the TD group in judgments of /r/. All listeners were significantly more likely to judge /r/ as correct in a front-vowel context. Our results suggest that normalized /r/ F3 is a statistically significant predictor of category goodness judgments for both adults and children, but children do not appear to make adult-like judgments. Category goodness judgments do not have a clear relationship with /r/ production abilities in children with RSE. These findings may have implications for clinical activities that include category goodness judgments in natural speech, especially for recorded productions.

Keywords: Speech perception; speech acoustics; speech disorders.

Figures

Figure 1.

ROC curves for the acoustic parameters of both models using adult response data.

Figure 2.

Proportion of rejections of /r/ for adult listeners by each acoustic parameter. Pr(NO) indicates the probability that tokens in the quintile are judged incorrect. Left panel shows proportion of rejections using the model with the F3-F2 acoustic parameter and right panel shows the proportion of rejections using the F3 ratio acoustic parameter.

Figure 3.

Proportion of rejections of /r/ for all listeners by F3-F2 acoustic parameter. “TD” refers to typically developing children used as controls. “RSE” refers to children with residual sound errors. Pr (NO) refers to the probability of “no” (“not a correct /r/”) responses to stimuli falling within the quintile.

Figure 4.

Logistic curve depicting interaction effect of status and third formant parameter on the responses of adults (solid line), children with RSE (dashed line), and TD children (dotted line).