The Role of Working Memory in Shaping Syntactic Dependency Structures

Dependency syntax holds that the goal of syntactic analysis is to establish all the binary relations between words in a sentence. This process is closely related to working memory. In a sentence, the words between two syntactically related words make for dependency distance, which is an index of sentence comprehension difficulty because, when the two syntactically related words are combined to each other in working memory, the first of them may suffer from memory decay or memory interference caused by the intervening words. Thus, working memory and the least effort principle may dictate a universal tendency for syntactic structures to be organized in such ways as to reduce dependency distance. This tendency has great shaping effect on the patterns of word order in human languages and is potentially able to account for many linguistic universals in language typology. As for the sporadic long dependency structures motivated by communicative needs, specific syntactic patterns may have evolved, utilizing some cognitive mechanisms to lessen the memory load of these long dependencies. Syntactic structures, therefore, are probably the result of self-adaption of a language system to certain external human constraints and motivations, among which working memory is a very important one.