ABSTRACT
Prior to the 1990s, explanation of second language acquisition (SLA) fell into two basic periods. The first period is marked by the use of behaviorism-a theory taken from psychology-to account for both first and second language acquisition and by structuralist approaches to the study of language. Subsequently, as empirical research on both first and second language acquisition demonstrated some major problems with the structuralist-behaviorist account of language learning, the field of SLA entered a period in which multiple theories emerged, attempting to account for SLA. There were many competing accounts and explanations of various aspects of SLA at that time (see the suggested readings for further information on these). Some of these have evolved and remain influential; others have faded from prominence. The dominant theory in this early period, however, is one that retains considerable influence today: the Monitor Theory of Stephen Krashen. In this chapter, we explore both the structuralist-behaviorist approach and Monitor Theory, both of which have had lasting impact on SLA, particularly for classroom instruction.
