Categorization of stop and nasal consonants by young infants

Abstract

A visually reinforced head-turn procedure was used to test six-month-old infants on phonetic-categorization tasks involving stop and nasal consonants. In one experiment, infants were reinforced for head turns when a change occurred from a series of background syllables containing nasal consonants (/m, n, n/) to comparison stimuli containing stop consonants (/b, d, g/). Each stimulus was produced by one male and one female talker. In another experiment, a separate group of infants was reinforced for head turns when a change occurred from syllables containing an initial /m/ to syllables containing an initial /n/. The stimuli were produced by male and female talkers in three vowel contexts: /a/, /i/, and /u/. The performance of infants in both of these “phonetic” experiments was compared to the performance of control groups run in “non-phonetic” experiments. In these experiments, stimuli were assigned to reinforced and unreinforced classes in such a way that the categories could not be organized by phonetic characteristics. Infants in both of the phonetic groups performed substantially better than infants in the corresponding nonphonetic groups. This finding suggests that infants in the phonetic groups recognized the phonetic similarity of the stimuli in the categories and used this information to organize their responses. [Work supported by NIH.]