Signatures of automaticity during practice:Explicit instruction about L1 processing routines can improve L2 grammatical processing.

This study examined the extent to which explicit instruction about first language (L1) and second language (L2) processing routines improved the accuracy, speed, and automaticity of learners' responses during sentence interpretation practice. Fifty-three English-speaking learners of L2 French were assigned to one of the following treatments: (a) a core treatment consisting of L2 explicit information (EI) with L2 interpretation practice (L2-only group); (b) the same L2 core+L1 practice with L1 EI (L2+L1 group); or (c) the same L2 core+L1 practice but without L1 EI (L2+L1prac group). Findings indicated that increasing amounts of practice led to more accurate and faster performance only for learners who received L1 EI (L2+L1 group). Coefficient of variation analyses (Segalowitz & Segalowitz, 1993) indicated knowledge restructuring early on that appeared to lead to gradual automatization over time (Solovyeva & DeKeyser, 2017; Suzuki, 2017). Our findings that EI and practice about L1 processing routines benefited the accuracy, speed, and automaticity of L2 performance have major implications for theories of L2 learning, the role of L1 EI in L2 grammar learning, and L2 pedagogy.