Department of Psychology, Concordia University, Montreal, QC, Canada H4B 1R6;
Department of Psychology, Concordia University, Montreal, QC, Canada H4B 1R6.
Proc Natl Acad Sci U S A. 2017 Aug 22;114(34):9032-9037. doi: 10.1073/pnas.1703220114. Epub 2017 Aug 7.
Infants growing up in bilingual homes learn two languages simultaneously without apparent confusion or delay. However, the mechanisms that support this remarkable achievement remain unclear. Here, we demonstrate that infants use language-control mechanisms to preferentially activate the currently heard language during listening. In a naturalistic eye-tracking procedure, bilingual infants were more accurate at recognizing objects labeled in same-language sentences ("Find the dog!") than in switched-language sentences ("Find the !"). Measurements of infants' pupil size over time indicated that this resulted from increased cognitive load during language switches. However, language switches did not always engender processing difficulties: the switch cost was reduced or eliminated when the switch was from the nondominant to the dominant language, and when it crossed a sentence boundary. Adults showed the same patterns of performance as infants, even though target words were simple and highly familiar. Our results provide striking evidence from infancy to adulthood that bilinguals monitor their languages for efficient comprehension. Everyday practice controlling two languages during listening is likely to explain previously observed bilingual cognitive advantages across the lifespan.
在双语家庭中成长的婴儿可以同时学习两种语言，而不会出现明显的混淆或延迟。然而，支持这一惊人成就的机制仍不清楚。在这里，我们证明婴儿使用语言控制机制，在倾听时优先激活当前听到的语言。在自然的眼动追踪过程中，双语婴儿在识别用同一种语言（“找到狗！”）标记的物体时比在转换语言（“找到！”）的句子中更准确。随着时间的推移，对婴儿瞳孔大小的测量表明，这是由于语言转换过程中认知负荷增加所致。然而，语言转换并不总是会导致处理困难：当从非主导语言转换为主导语言，并且跨越句子边界时，转换成本会降低或消除。成年人的表现模式与婴儿相同，即使目标词简单且非常熟悉。我们的研究结果从婴儿期到成年期都提供了引人注目的证据，证明双语者在倾听时会监控自己的语言以实现高效理解。在日常生活中，通过倾听来控制两种语言的练习可能解释了之前观察到的双语认知优势在整个生命周期中的存在。
