Abstract
This dissertation investigates the outcomes of two different types of instructional approaches on advanced second language (L2) learners and intermediate heritage language (HL) learners of Spanish. Two methodologically distinct pedagogical interventions were conducted: 1) MCE (Mindful Conceptual Engagement), derived from the principles set in Vygotsky’s sociocultural theory of mind (SCT); and 2) Grammar-Based Instruction, which is based upon more traditional methods of instruction involving the description and practice of grammatical content (e.g., fill-in-the blank exercises). Both interventions focused on usage of the subjunctive in variable contexts where the indicative was possible, but with a subsequent change in meaning (e.g., Busco un helado que no tiene/tenga azúcar). In MCE the concepts of [+/- EXPERIENCE] were presented to highlight the semantic contrast in the usage of indicative or subjunctive in adjectival clauses. Grammar-Based Instruction targeted adverbial clauses with aunque, cuando and hasta que. The study focused on four variables: 1) student sociodemographic profile (HL vs. L2); 2) instructional approach (MCE vs. GB); 3) task type (interpretative vs. productive); and 4) grammatical construction (adjectival vs. adverbial). Findings revealed that both groups improved in terms of productive and interpretive abilities as a result of both types of instruction. However, important statistical differences were observed between groups (L2 vs. HL) with regards to type of task (production and interpretation) and type of instruction (MCE and GB). Verbalization and definition data also indicated that participants who created more abstract and generalizable models showed more signs of conceptual development than other participants who did not.