Incidence of non-rhotic vowel errors in children: data from the Memphis Vowel Project.

Attention to vowels in phonological development and disorders has increased in recent years, but the incidence of vowel errors in children with phonological disorders has not yet been determined. In the present study, percentage of non-rhotic vowels correct (PVC-NR) was measured in single word productions of 314 monolingual American English-speaking children, 165 with normal phonology (NP) and 149 with delayed/disordered phonology (DP). Three cutoffs (PVC-NR < 85, < 90 and < 95) were used to determine incidence of vowel errors. The percentage of younger NP children (18 to 35 months of age) exhibiting vowel errors was high (24 to 65%, depending on the cutoff used), but decreased with age. Incidence of vowel errors in older NP children (> or = 36 months) was minimal (0 to 4%). In the DP group (age range 30 to 81 months), 11 to 32% exhibited vowel errors. DP children with moderate to severe consonant errors were at greatest risk for concurrent vowel errors.