Connectionism is an important theoretical framework for the study of human cognition and behavior. Also known as Parallel Distributed Processing (PDP) or Artificial Neural Networks (ANN), connectionism advocates that learning, representation, and processing of information in mind are parallel, distributed, and interactive in nature. It argues for the emergence of human cognition as the outcome of large networks of interactive processing units operating simultaneously. Inspired by findings from neural science and artificial intelligence, connectionism is a powerful computational tool, and it has had profound impact on many areas of research, including linguistics. Since the beginning of connectionism, many connectionist models have been developed to account for a wide range of important linguistic phenomena observed in monolingual research, such as speech perception, speech production, semantic representation, and early lexical development in children. Recently, the application of connectionism to bilingual research has also gathered momentum. Connectionist models are often precise in the specification of modeling parameters and flexible in the manipulation of relevant variables in the model to address relevant theoretical questions, therefore they can provide significant advantages in testing mechanisms underlying language processes.
Phenomena involving the displacement of syntactic units are widespread in human languages. The term displacement refers here to a dependency relation whereby a given syntactic constituent is interpreted simultaneously in two different positions. Only one position is pronounced, in general the hierarchically higher one in the syntactic structure. Consider a wh-question like (1) in English:
(1) Whom did you give the book to <whom>
The phrase containing the interrogative wh-word is located at the beginning of the clause, and this guarantees that the clause is interpreted as a question about this phrase; at the same time, whom is interpreted as part of the argument structure of the verb give (the copy, in <> brackets). In current terms, inspired by minimalist developments in generative syntax, the phrase whom is first merged as (one of) the complement(s) of give (External Merge) and then re-merged (Internal Merge, i.e., movement) in the appropriate position in the left periphery of the clause. This peripheral area of the clause hosts operator-type constituents, among which interrogative ones (yielding the relevant interpretation: for which x, you gave a book to x, for sentence 1). Scope-discourse phenomena—such as, e.g., the raising of a question as in (1), the focalization of one constituent as in TO JOHN I gave the book (not to Mary)—have the effect that an argument of the verb is fronted in the left periphery of the clause rather than filling its clause internal complement position, whence the term displacement. Displacement can be to a position relatively close to the one of first merge (the copy), or else it can be to a position farther away. In the latter case, the relevant dependency becomes more long-distance than in (1), as in (2)a and even more so (2)b:
a Whom did Mary expect [that you would give the book to<whom >]
b Whom do you think [that Mary expected [that you would give the book to <whom >]]
50 years or so of investigation on locality in formal generative syntax have shown that, despite its potentially very distant realization, syntactic displacement is in fact a local process. The audible position in which a moved constituent is pronounced and the position of its copy inside the clause can be far from each other. However, the long-distance dependency is split into steps through iterated applications of short movements, so that any dependency holding between two occurrences of the same constituent is in fact very local. Furthermore, there are syntactic domains that resist movement out of them, traditionally referred to as islands. Locality is a core concept of syntactic computations. Syntactic locality requires that syntactic computations apply within small domains (cyclic domains), possibly in the mentioned iterated way (successive cyclicity), currently rethought of in terms of Phase theory. Furthermore, in the Relativized Minimality tradition, syntactic locality requires that, given X . . . Z . . . Y, the dependency between the relevant constituent in its target position X and its first merge position Y should not be interrupted by any constituent Z which is similar to X in relevant formal features and thus intervenes, blocking the relation between X and Y. Intervention locality has also been shown to allow for an explicit characterization of aspects of children’s linguistic development in their capacity to compute complex object dependencies (also relevant in different impaired populations).
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.