Speech perception in early infancy: discrimination of fricative consonants

Recent data strongly suggest that six‐month‐olds perceive a similarity between vowels produced by different sized vocal tracts [P. K. Kuhl, J. Acoust. Soc. Am. 61, S39(A) (1977)]. This study investigates the extent to which infants recognize phonetic similarity for a fricative consonant when it occurs in different vowel environments and is spoken by different talkers. Six‐month‐olds were tested in a discrimination task in which fricative contrasts (/f/ versus /θ/;/s/ versus /∫/) were examined in both the initial and final positions of naturally produced monosyllables. Infants were tested in a task in which a head turn was reinforced with a visual stimulus in the presence of an exemplar from one consonant category but not in the presence of an exemplar from the second consonant category. Infants were initially trained to differentiate a single exemplar from each of the two categories; then, the number of exemplars in each of the two categories was systematically increased until each category contained 12 d...