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

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.

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.

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.

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.