Laboratoire de Sciences Cognitives et Psycholinguistique, Département d'Études Cognitives, Ecole Normale Supérieure, Ecole des Hautes Etudes en Sciences Sociales, CNRS, Paris Sciences et Lettres Research University, 75005 Paris, France.
Department of Linguistics, University of Maryland, College Park, MD 20742.
Proc Natl Acad Sci U S A. 2022 Sep 20;119(38):e2123230119. doi: 10.1073/pnas.2123230119. Epub 2022 Sep 12.
At birth, infants discriminate most of the sounds of the world's languages, but by age 1, infants become language-specific listeners. This has generally been taken as evidence that infants have learned which acoustic dimensions are contrastive, or useful for distinguishing among the sounds of their language(s), and have begun focusing primarily on those dimensions when perceiving speech. However, speech is highly variable, with different sounds overlapping substantially in their acoustics, and after decades of research, we still do not know what aspects of the speech signal allow infants to differentiate contrastive from noncontrastive dimensions. Here we show that infants could learn which acoustic dimensions of their language are contrastive, despite the high acoustic variability. Our account is based on the cross-linguistic fact that even sounds that overlap in their acoustics differ in the contexts they occur in. We predict that this should leave a signal that infants can pick up on and show that acoustic distributions indeed vary more by context along contrastive dimensions compared with noncontrastive dimensions. By establishing this difference, we provide a potential answer to how infants learn about sound contrasts, a question whose answer in natural learning environments has remained elusive.
出生时，婴儿能辨别世界上大多数语言的声音，但到 1 岁时，婴儿就成为了特定语言的听众。这通常被认为是婴儿已经学会了哪些声学维度是有区别的，或者对区分他们的语言（或多种语言）中的声音有用，并开始在感知语音时主要关注这些维度的证据。然而，语音是高度可变的，不同的声音在声学上有很大的重叠，经过几十年的研究，我们仍然不知道语音信号的哪些方面可以让婴儿区分对比和非对比维度。在这里，我们展示了尽管存在高度的声学可变性，但婴儿仍然可以学习他们的语言的哪些声学维度是有区别的。我们的解释基于跨语言的事实，即使在声学上重叠的声音，在它们出现的语境中也有所不同。我们预测，这应该会留下一个婴儿可以察觉的信号，并表明在对比维度上，声学分布确实比非对比维度更受语境的影响。通过建立这种差异，我们为婴儿如何学习声音对比提供了一个潜在的答案，而在自然学习环境中，这个问题的答案一直难以捉摸。
