Sociocultural Foundations of Second Language Acquisition: From Vygotskian Theory to Contemporary Pedagogical Practice
Muhayyo Umarova 
Abstract. Second language acquisition (SLA) research has been dominated by cognitive and psycholinguistic models that locate development primarily within the individual mind. Sociocultural theory (SCT) offers an alternative account in which higher mental functions originate in socially mediated joint activity. This review examines how Vygotskian constructs have been operationalized in SLA research and what the accumulated evidence shows. A systematic narrative review was conducted across ERIC, PsycINFO, Scopus, and Google Scholar for publications between 1978 and 2024. Of 1,247 records retrieved, 186 met the inclusion criteria and were coded for theoretical construct, context, methodology, and findings; 15% were double-coded (κ = 0.81). Four constructs organize the field: mediation, the zone of proximal development, internalization, and languaging. Expert–novice scaffolding accounted for 38.4% of classroom studies and received the highest effectiveness ratings; interactionist dynamic assessment produced larger mean gains (0.79 SD) than static assessment (0.34 SD). Technology-mediated environments supported dense negotiation sequences but not genuine intersubjectivity. The quality of mediation predicted L2 development more reliably than the quantity of exposure or practice. Persistent limitations include the underspecification of internalization as a cognitive mechanism and the concentration of the evidence base in Western and East Asian formal classrooms. Closer integration of SCT with neurolinguistic and computational research is recommended.
Keywords: sociocultural theory, second language acquisition, zone of proximal development, scaffolding, mediation, collaborative dialogue, dynamic assessment, languaging