| The study has three foci: to investigate how Systemic-Theoretical Instruction (STI) based on the work of P. Gal'perin operates in second language teaching; to define L2 development from a Sociocultural perspective while proposing appropriate research tools for its study; to assess the extent to which this approach fosters L2 grammatical development.;STI emerges from Vygotsky's argument that properly organized learning leads development and is based on three main principles: the concept as the pedagogical unit of instruction; materialization of the object of study through didactic models and physical objects; and verbalization aimed at internalization. L2 development is defined as the appropriation, understanding and control of conceptual meanings---grammatical and otherwise---that change both in their quality and in their relationship to specific language features in L2 learning.;Twelve adult university students in an advanced Spanish grammar and composition class participated in the study. Multiple sets of developmental data were collected over a sixteen-week semester, including learners' definitions of grammatical concepts; spontaneous learner performance comprising several written and oral language diagnostics: verbalization consisting of student recordings explaining to themselves use of specific grammatical features.;The data are analyzed through three heuristics elaborated with the intent of capturing the complexity of L2 development as a conceptual process: Conceptual interrelated Feature Analysis (CFA) for definition analysis, Conceptual Grammatical Distribution (CGD) for discourse analysis, and Concept as Tools for Internalization (CTI) for verbalization analysis.;Findings confirm that STI fosters L2 development construed as the attainment of higher levels of awareness and control over the L2. STI leads to the internalization of more sophisticated semantic understandings of grammatical meanings and thereby promotes learners' ability to effectively and creatively use the relevant grammatical features in spontaneously produced written and oral discourse.;Thus, the central moment in L2 development is the use of the concept as a tool for learner understanding and therefore, all L2 pedagogical activities should emerge from this fundamental principle. An argument is developed for inclusion of Second Language Acquisition in Vygotsky's 'science of the person', which privileges the study of individual meaning creation and intentionality. |
