Bias in the perception of phonetic detail in children’s speech: A comparison of categorical and continuous rating scales

Previous research has shown that continuous rating scales can be used to assess phonetic detail in children’s productions, and could potentially be used to detect covert contrasts. Two experiments examined whether continuous rating scales have the additional benefit of being less susceptible to task-related biasing than categorical phonetic transcriptions. In both experiments, judgments of children’s productions of /s/ and /θ/ were interleaved with two types of rating tasks designed to induce bias: continuous judgments of a parameter whose variation is itself relatively more continuous (gender typicality of their speech) in one biasing condition, and categorical judgments of a parameter that is relatively less-continuous (the vowel they produced) in the other biasing condition. One experiment elicited continuous judgments of /s/ and /θ/ productions, while the other elicited categorical judgments. The results of Experiment 1 showed that the influence of acoustic characteristics on continuous judgments of /s/ and /θ/ was stable across biasing conditions. In contrast, the results of Experiment 2 showed that the influence of acoustic characteristics on categorical judgments of /s/ and /θ/ differed systematically across biasing conditions. These results suggest that continuous judgments are psychometrically superior to categorical judgments, as they are more resistant to task-related bias

Measuring Speech-Sound Learning Using Visual Analog Scaling

The ultimate goal for speech-language pathologists is to align the linguistic behaviors of the clients whom we serve with those of the ambient language of the community. In light of this goal, it is critical that change in speech production is measured accurately. In this article, we review the use of visual analog scaling as a measure of change in children’s speech production. Following a discussion of this tool, the authors consider the clinical utility of this type of measurement.</jats:p

Effect of Speaker Age on Listener Perceptions of Word-Final /l/

Purpose: This study investigated an effect of speaker age on listeners' perception of word-final /l/ produced by child and adult speakers of Southern White Vernacular English, a dialect that shows higher rates of word-final /l/ vocalization than other dialects of English. Method: Stimuli included children and adults' word-final /l/ embedded in monosyllabic words in two vowel contexts (/i, ɪ/ and /ɔ, ɑ/). A total of 25 monolingual adult listeners listened to each word and were asked to judge the /l/-likeness using a visual analog scale. Average listener ratings and three acoustic measures (F2 transition rate [F2 TR] and F2-F1 [Hz] values at 20% and 80% time points along the vowel−/l/ duration) were analyzed. Results: Adult productions were rated more as correct /l/ than those of children in both vowel contexts, despite the similarity in their F2 TR and F2-F1 values at the 80% time point. Correlation between the acoustic measures and the average listener ratings were weak for all three measures for adults' productions. For children's productions, while the correlation with F2 TR values were weak, moderate significant correlations were found for F2-F1 values at the 20% and 80% time points. In terms of vowel context, word-final /l/ in the high front vowel context was rated more as /l/ than those in low back vowel context. Conclusions: Findings suggest that listeners are more likely to accept word-final /l/ as being correct when produced by adult speakers, regardless of their acoustic characteristics, but more likely to perceive an error when produced by a child and attend more to acoustic information for their perceptual judgment. This highlights the importance of considering children's dialectal background when judging word-final /l/, which is more likely to be vocalized in certain dialects and certain vowel contexts, and thus can be misjudged without such consideration. </jats:sec