Vowel use of phonologically disordered identical twin boys: a case study

Very little is known about the vowel systems of phonologically disordered children. This study provides longitudinal data regarding vowel use of identical twin boys between the ages of 3;5 and 4;9. The boys were identified as phonologically disordered; however, their parents chose not to enroll them in therapy. Vowel-use information was taken from spontaneous language samples. It was discovered that initially their phonological disorder also affected their vowel systems, but as their phonological skills increased so did correct use of vowels and their vowel use tended to follow normal developmental trends.