Vowel perception in children with and without language impairment.

Twenty-four children with language impairment (LI) and 22 children without language impairment (LN) participated in a study of discrimination, identification, and serial ordering of the highly dissimilar vowels/a/ versus /i/, and the highly similar vowels /epsilon/ versus /ae/. The vowel pairs were presented to the subjects in long- and short-duration sets. Both groups had greater difficulty in identifying /epsilon/ versus /ae/ than /a/ versus /i/. Neither group had greater difficulty with the short- than the long-duration vowel sets. The LI children were less efficient than the LN in identifying /a/ versus /i/, but could identify them accurately. They were significantly less accurate than the LN in identifying /epsilon/ versus /ae/. The majority of the children who could identify the /a/ and /i/ vowels were able to order them serially as well, although this second task appeared to be more difficult than identification. Fewer LI than LN children were able to proceed to the serial ordering task with /epsilon/ and /ae/. The children who could not identify the vowels within a set were almost always able to discriminate them. It was concluded that LI children have an auditory perceptual learning deficit and consequently a less robust central representation for steady state vowels than LN.