Читать книгу Lifespan Development - Tara L. Kuther - Страница 277

Newborn infants are primed to learn language. Recall from Chapter 4 that neonates naturally attend to speech and prefer to hear human speech sounds, especially their native language, as well as stories and sounds that they heard prenatally (May, Gervain, Carreiras, & Werker, 2018). Infants naturally notice the complex patterns of sounds around them and organize sounds into meaningful units. They recognize frequently heard words, such as their names. By 4½ months of age, infants will turn their heads to hear their own names but not to hear other names, even when the other names have a similar sound pattern (e.g., Annie and Johnny) (Mandel, Jusczyk, & Pisoni, 1995). At 6 months of age, infants pay particular attention to vowel sounds and, at 9 months, consonants (Kuhl, 2015).

Although infants can perceive and discriminate sounds that comprise all human languages at birth, their developing capacities and preferences are influenced by context (Hoff, 2015). For example, the Japanese language does not discriminate between the consonant sounds of “r” in rip and “l” in lip. Japanese adults who are learning English find it very difficult to discriminate between the English pronunciations of these “r” and “l” sounds, yet up until about 6 to 8 months of age, Japanese and U.S. infants are equally able to distinguish these sounds. By 10 to 12 months, however, discrimination of “r” and “l” improves for U.S. infants and declines for Japanese infants. This likely occurs because U.S. infants hear these sounds often, whereas Japanese infants do not (Kuhl et al., 2006). As they are exposed to their native language, they become more attuned to the sounds (and distinctions between sounds) that are meaningful in their own language and less able to distinguish speech sounds that are not used in that language (Werker, Yeung, & Yoshida, 2012). Native-language discrimination ability between 6 and 7 months predicts the rate of language growth between 11 and 30 months (Kuhl, 2015).

Infants’ speech discrimination abilities remain malleable in response to the social context (Kuhl, 2016). In one study, Kuhl and her colleagues exposed 9-month-old English-learning American infants to 12 live interaction sessions with an adult speaker of Mandarin Chinese over the course of 4 to 5 weeks (Kuhl, Tsao, & Liu, 2003). After the sessions, the infants were tested on a Mandarin phonetic contrast that does not occur in English. The infants discriminated the contrast as well as same-aged Mandarin-learning infants and retained the contrast for several days. The relevance of context is also illustrated by the infants’ loss of the ability to discriminate the Mandarin contrast several days after training, presumably in the absence of ongoing exposure to the Mandarin language (Fitneva & Matsui, 2015).

Social interaction is vital to language learning. In the study just described, the English-learning infants did not learn the Mandarin phonetic contrast when they were exposed to it only by audio or video. Live interaction may have increased infants’ motivation to learn by increasing their attention and arousal. Or perhaps live interaction provides specific information that fosters learning, like the speaker’s eye gaze and pointing coupled with interactive contingency (Kuhl et al., 2003).

In addition, social input, such as the quality of mother–infant interactions, plays a critical role in determining the timing of infants’ narrowing of speech sound discrimination. Specifically, infants who experience high-quality interactions with their mothers, characterized by frequent speech, show a narrowing earlier, as early as 6 months of age (Elsabbagh et al., 2013).