Memory factors in vowel discrimination of normal and at-risk infants.

The role of memory factors in infant vowel discrimination was examined by studying the categorical versus continuous discrimination of very brief vowels and the effect on discrimination of the silent delay interval between the last familiar and the first novel stimulus. 8-week-old infants of normal and at-risk medical histories were presented in a nonnutritive sucking paradigm with either a between-category or a within-category vowel shift. The results revealed reliable between-category but not within-category discrimination. In addition, the magnitude of the recovery in the between-category shift was related inversely to the duration of the shift delay interval. Finally, differences were observed between normal and at-risk infants in their initial attention to, discrimination of, and memory for short vowels. These findings were discussed in terms of the relative contributions of auditory and phonetic short-term memory in infant and adult vowel perception.