Young infants' perception of liquid coarticulatory influences on following stop consonants

Phonetic segments are coarticulated in speech. Accordingly, the articulatory and acoustic properties of the speech signal during the time frame traditionally identified with a given phoneme are highly context-sensitive. For example, due to carryover coarticulation, the front tongue-tip position for /1/ results in more fronted tongue-body contact for a /g/ preceded by /1/ than for a /g/ preceded by /r/. Perception by mature listeners shows a complementary sensitivity--when a synthetic /da/-/ga/ continuum is preceded by either /al/ or /ar/, adults hear more /g/s following /l/ rather than /r/. That is, some of the fronting information in the temporal domain of the stop is perceptually attributed to /l/ (Mann, 1980). We replicated this finding and extended it to a signal-detection test of discrimination with adults, using triads of disyllables. Three equidistant items from a /da/-/ga/ continuum were used preceded by /al/ and /ar/. In the identification test, adults had identified item ga5 as "ga,' and dal as "da,' following both /al/ and /ar/, whereas they identified the crucial item d/ga3 predominantly as "ga' after /al/ but as "da' after /ar/. In the discrimination test, they discriminated d/ga3 from da1 preceded by /al/ but not /ar/; compatibly, they discriminated d/ga3 readily from ga5 preceded by /ar/ but poorly preceded by /al/. We obtained similar results with 4-month-old infants. Following habituation to either ald/ga3 or ard/ga3, infants heard either the corresponding ga5 or da1 disyllable. As predicted, the infants discriminated d/ga3 from da1 following /al/ but not /ar/; conversely, they discriminated d/ga3 from ga5 following /ar/ but not /al/. The results suggest that prelinguistic infants disentangle consonant-consonant coarticulatory influences in speech in an adult-like fashion.