As H. Douglas Brown pointed out in his review (1980), the field of second language acquisition [SLA] has emerged as its own discipline in the 1980s. A somewhat eclectic discipline, research in SLA involves methodologies drawn from linguistics, sociolinguistics, education, and psychology. Theoretical models are equally diverse (McLaughlin 1987), but in general a distinction is possible between representational and processing approaches (Carroll in press). Representational approaches focus on the nature and organization of second-language knowledge and how this information is represented in the mind of the learner. Processing approaches focus on the integration of perceptual and cognitive Processes with the learner's second-languages knowledge. This distinction is used here for purposes of exposition, although it is recognized that some approaches combine both representational and processing features, as any truly adequate model of second-language learning must.