When research on second language acquisition (SLA) began to prevail in the 1970s and 1980s, the SLA process was primarily deemed as the cognitive process which occurs in the mind. While acknowledging the importance of this traditional approach, due to the increasing awareness of the socially constructed nature of cognitive development, many researchers currently claim that cognition is not the sole SLA paradigm and consider the cognitive and sociocultural processes as two parallel constituents of SLA. Such a perspective has contributed to the emergence of various sociocultural theories in the area of applied linguistics, such as Vygotskian sociocultural theory, language socialization, situated learning, critical theory, identity approach, socio-constructionist genre theory, and so on. This paper delineates the historical background of the paradigm shift from the dominance of cognitivism to sociocultural perspectives of SLA, and discusses how to apply sociocultural theories in empirical SLA studies, focussing on the socio-constructionist genre theory, the concept of situated learning, and an identity approach to SLA.[誤植の訂正]本文,P.20 上から10行目 （誤）ポスト構築主義理論→（正）ポスト構造主義理論 【PDFは修正済です（2012.5.1）】