Why do we need a linguistic theory to describe learners' behaviors?

Abstract

A number of studies have been carried out since around 2000 to find out the cause of the universality in the acquisition and use of grammatical morphemes and learners' errors in producing them, a topic that was actively studied from the 1970s to the 80s. Researchers' positions are, roughly speaking, divided into two: Second language acquisition is, like acquisition of other general knowledge, fundamentally based on "memory of a stimulus", and "habit formation", in which factors such as “saliency” and "frequency" are important (Goldschneider & DeKeyser, 2001, among others); and Second language acquisition is based on the same knowledge as native language acquisition, where the mental grammar (interlanguage) plays an extremely important role in use of grammatical morphemes (Wakabayashi, 1997, etc.). In this paper, after clarifying the psychological reality of the interlanguage (Selinker, 1972), it will be shown that interlanguage is itself a kind of “natural language”. Based on data from six studies, we discuss Japanese-speaking English learners' knowledge and use of 3rd person singular -s. It will be argued that second language learners' acquisition and use of grammatical morphemes are, though general factors such as memory are also concerned, clearly based on their interlanguage, and that empirical research based on precise designs rooted in linguistics serves as a key to the elucidation of learner knowledge.