Rhotic vowel accuracy and error patterns in young children with and without Speech Sound Disorders

Rhotic vowels are known to be difficult sounds for children to learn, but their acquisition has not been investigated in detail. This study examined rhotic vowel development, including accuracy and error patterns, in young children across age, diagnostic groups, and phonetic contexts. Participants included 34 children from 2 to 6 years of age with and without speech sound disorders (SSD). Data included 36 elicited single words containing stressed and unstressed rhotic monophthongs ([ɜ˞] and [ə˞]) and four rhotic diphthongs (/ɪ͡ə˞/, /ε͡ə˞/, /ɔ͡ə˞/, and /ɑ͡ə˞/). Additional words containing non-rhotic vowels and the consonant /ɹ/ were also included for comparison. A significant difference in rhotic vowel production accuracy was found between diagnostic groups (with vs. without SSD), but not across age groups or phonetic contexts. Yet, the accuracy scores for children without SSD were bimodally distributed, showing overlapping patterns with children with SSD. Error patterns were examined for all children with low rhotic vowel accuracy scores, regardless of age and diagnostic status. Results of this study highlight the variability in rhotic vowel development in young children and the importance of studying rhotic sounds using overall rhotic sound accuracy of each individual child regardless of their age or diagnostic status. Clinically, systematic within-speaker error patterns suggest the need for the detailed error pattern assessment of rhotic sounds.