Infant-directed speech facilitates lexical learning in adults hearing Chinese: implications for language acquisition.

Experiments 1 and 2 examined the effects of infant-directed (ID) speech on adults' ability to learn an individual target word in sentences in an unfamiliar, non-Western language (Chinese). English-speaking adults heard pairs of sentences read by a female, native Chinese speaker in either ID or adult-directed (AD) speech. The pairs of sentences described slides of 10 common objects. The Chinese name for the object (the target word) was placed in an utterance-final position in experiment 1 (n = 61) and in a medial position in experiment 2 (n = 79). At test, each Chinese target word was presented in isolation in AD speech in a recognition task. Only subjects who heard ID speech with the target word in utterance-final position demonstrated learning of the target words. The results support assertions that ID speech, which tends to put target words in sentence-final position, may assist infants in segmenting and remembering portions of the linguistic stream. In experiment 3 (n = 23), subjects judged whether each of the ID and AD speech samples prepared for experiments 1 and 2 were directed to an adult or to an infant. Judgements were above chance for two types of sentence: ID speech with the target word in the final position and AD speech with the target word in a medial position. In addition to indirectly confirming the results of experiments 1 and 2, these findings suggest that at least some of the prosodic features which comprise ID speech in Chinese and English must overlap.