Vowel-learning and the vowel system of deaf children: age and feedback-related differences

A study comparing perceptual judgments of vowels produced by deaf children taught to speak by using a computer-based aid (experimental group, E) and by conventional techniques (control group, C) revealed feedback-related differences. These concerned the ability to reorganise articulatory performance, intelligibility of vowels after training, and the strength of the memory trace, which all showed an advantage for the E group. A phoneme-by-phoneme analysis indicated that the E group improved consistently on back and central vowels, whereas no consistent trend was found in the C group. The modifications observed were also age-dependent, more progress was found in the younger than in the older children's performance. An error analysis showed that asymmetric vowel confusions were predominant and that the major factor accounting for all errors was the small difference between second formant values. The findings are discussed in terms of the articulatory and perceptual variables intervening in the vowel intelligibility of deaf children.