The effects of language experience on the perception of affricate and fricative consonants in English-speaking and Mandarin-speaking adults and young infants

Previous studies have shown that the adult speakers experience difficulty in discriminating nonnative phonetic contrasts that are not phonemic in their native language but newborn infants are able to discriminate phonetic contrasts in any language. Reduced sensitivity to nonnative contrasts has been shown in 10- to 12-month-old infants, and is interpreted as reflecting the age of onset of language-specific processing. However, generalization of this finding is limited by the fact that few phonetic contrasts have been tested and a lack of evidence showing that sensitivity to native contrasts improve over age.; Five experiments were designed to assess the effects of language experience on adults (Experiments 1--3) and infants (Experiments 4--5). Experiment 1 showed that perceptual sensitivity of English-speaking adults was lower than Mandarin-speaking adults on the discrimination of a Mandarin alveolo-palatal affricate-fricative distinction. Experiment 2 showed that language experience affects the phonetic category organization of English- and Mandarin-speaking adults for Mandarin affricate and fricative consonants. In Experiment 2, Kuhl's perceptual magnet effect (PME), in which perceptual distances are shrunk near good exemplars of phonetic categories but extended near poor exemplars, was evident for native-language but not foreign-language perception of Mandarin tokens. Experiment 3 showed that the PME was demonstrated in English adults when perceiving English affricate and fricative consonants. Experiment 4 examined the sensitivity change between English- and Mandarin-leaning infants between 6 and 12 months of age on perceiving a Mandarin affricate-fricative contrast. The results demonstrated that infants improved their sensitivity to the native contrast with age while reducing their sensitivity to the nonnative contrast. Finally, the finding that English-learning infants aged 10--12 months were able to discriminate native affricative-fricative distinction ruled out the possibility that perceptual decline in Experiment 4 was due to infants' inability to detect differences in affricate and fricative contrasts. The results clearly demonstrate that the infants are born with language-general processing to perceive speech sounds and tune into language-specific strategies by the time they reach their first birthday. The developmental mechanisms of phonetic perception were discussed in the framework of the Native Language Magnet model.