Children’s acquisition of language is an amazing feat. Children master the syntax, the sentence structure of their language, through exposure and interaction with caregivers and others but, notably, with no formal tuition. How children come to be in command of the syntax of their language has been a topic of vigorous debate since Chomsky argued against Skinner’s claim that language is ‘verbal behavior.’ Chomsky argued that knowledge of language cannot be learned through experience alone but is guided by a genetic component. This language component, known as ‘Universal Grammar,’ is composed of abstract linguistic knowledge and a computational system that is special to language. The computational mechanisms of Universal Grammar give even young children the capacity to form hierarchical syntactic representations for the sentences they hear and produce. The abstract knowledge of language guides children’s hypotheses as they interact with the language input in their environment, ensuring they progress toward the adult grammar. An alternative school of thought denies the existence of a dedicated language component, arguing that knowledge of syntax is learned entirely through interactions with speakers of the language. Such ‘usage-based’ linguistic theories assume that language learning employs the same learning mechanisms that are used by other cognitive systems. Usage-based accounts of language development view children’s earliest productions as rote-learned phrases that lack internal structure. Knowledge of linguistic structure emerges gradually and in a piecemeal fashion, with frequency playing a large role in the order of emergence for different syntactic structures.
Throughout the 20th century, structuralist and generative linguists have argued that the study of the language system (langue, competence) must be separated from the study of language use (parole, performance), but this view of language has been called into question by usage-based linguists who have argued that the structure and organization of a speaker’s linguistic knowledge is the product of language use or performance. On this account, language is seen as a dynamic system of fluid categories and flexible constraints that are constantly restructured and reorganized under the pressure of domain-general cognitive processes that are not only involved in the use of language but also in other cognitive phenomena such as vision and (joint) attention. The general goal of usage-based linguistics is to develop a framework for the analysis of the emergence of linguistic structure and meaning. In order to understand the dynamics of the language system, usage-based linguists study how languages evolve, both in history and language acquisition. One aspect that plays an important role in this approach is frequency of occurrence. As frequency strengthens the representation of linguistic elements in memory, it facilitates the activation and processing of words, categories, and constructions, which in turn can have long-lasting effects on the development and organization of the linguistic system. A second aspect that has been very prominent in the usage-based study of grammar concerns the relationship between lexical and structural knowledge. Since abstract representations of linguistic structure are derived from language users’ experience with concrete linguistic tokens, grammatical patterns are generally associated with particular lexical expressions.