I use experimental and corpus research designs to investigate (i) how first language (L1) background, and second language (L2) proficiency shape L2 grammatical development, especially at advanced stages of learning, and (ii) how theoretically-driven L2 acquisition research can inform language teaching. These lines of inquiry address fundamental questions about how we learn, process, and use language.

My work in L2 grammatical development in advanced French has examined the foundations of accepted approaches/theories, which has led me to challenge existing theories and work towards developing alternative accounts of L2 grammatical development (e.g., contra the Aspect Hypothesis by assigning a role to L1 background, McManus 2013, 2015). My recent co-authored monograph with Rosamond Mitchell and Nicole Tracy-Ventura (2017, Routledge) examined how social networking and interaction can drive grammatical development during study abroad. Here too, we counter long-held claims that study abroad does not benefit L2 grammatical development. Furthermore, our open-access longitudinal corpus of advanced-level L2 French and L2 Spanish (, now an international resource, is contributing to current and future research agendas in L2 grammatical development.

A second major research strand addresses L1 use in L2 teaching,which was funded by the British Academy (2013-2016). Grounded in my previous research on L1 effects in L2 learning, this work investigated the extent to which  L1 awareness can facilitate L2 grammatical development. A series of experimental interventions provided classroom learners with different types of explicit instruction and practice about  L1-L2 differences. Learners’ performance before, during, and after the intervention showed long-lasting benefits following explicit information and practice about L2 and L1, with few benefits  for instruction about L2 only. These findings have far-reaching implications both for L2 learning theories and foreign language education because: (i) there was no support that L1 use is detrimental to L2 learning and (ii) results indicated connections between online and offline processing.