Department of Linguistics, University of California, Los Angeles, CA 90095;
Department of Linguistics, University of Maryland, College Park, MD 20742.
Proc Natl Acad Sci U S A. 2021 Oct 12;118(41). doi: 10.1073/pnas.2026469118.
The human ability to produce and understand an indefinite number of sentences is driven by syntax, a cognitive system that can combine a finite number of primitive linguistic elements to build arbitrarily complex expressions. The expressive power of syntax comes in part from its ability to encode potentially unbounded dependencies over abstract structural configurations. How does such a system develop in human minds? We show that 18-mo-old infants are capable of representing abstract nonlocal dependencies, suggesting that a core property of syntax emerges early in development. Our test case is English -questions, in which a fronted -phrase can act as the argument of a verb at a distance (e.g., ). Whereas prior work has focused on infants' interpretations of these questions, we introduce a test to probe their underlying syntactic representations, independent of meaning. We ask when infants know that an object -phrase and a local object of a verb cannot co-occur because they both express the same argument relation (e.g., * ). We find that 1) 18 mo olds demonstrate awareness of this complementary distribution pattern and thus represent the nonlocal grammatical dependency between the -phrase and the verb, but 2) younger infants do not. These results suggest that the second year of life is a period of active syntactic development, during which the computational capacities for representing nonlocal syntactic dependencies become evident.
人类能够生成和理解无数句子的能力是由语法驱动的，语法是一种认知系统，可以组合有限数量的基本语言元素来构建任意复杂的表达式。语法的表达能力部分来自于它能够对抽象结构配置进行潜在无限制的依赖关系进行编码。这样的系统是如何在人类思维中发展的？我们表明，18 个月大的婴儿能够表示抽象的非局部依赖关系，这表明语法的一个核心属性在发展早期就出现了。我们的测试案例是英语疑问句，其中前置短语可以作为动词的远距离参数（例如，）。虽然之前的研究集中在婴儿对这些问题的解释上，但我们引入了一个测试来探测他们潜在的句法表示，而不依赖于意义。我们问婴儿什么时候知道一个宾语短语和动词的局部宾语不能同时出现，因为它们都表达了相同的参数关系（例如，*）。我们发现，1）18 个月大的婴儿表现出对这种互补分布模式的意识，因此代表了 -phrase 和动词之间的非局部语法依赖关系，但 2）年幼的婴儿则没有。这些结果表明，第二年是积极发展语法的时期，在此期间，代表非局部句法依赖关系的计算能力变得明显。
