The Influence of L1 Grammatical Skills on Adult L2 Development in Two Learning Contexts

Accounting for variability in second language (L2) acquisition is an important aim of our field. Interestingly, a growing number of studies reveal variability (individual differences, IDs) in the native language (L1, e.g., Dąbrowska, 2019), and some evidence points to a positive relationship between IDs in L1 literacy and oral skills and L2 acquisition (e.g., Sparks, 2012). However, gaps remain regarding the role of L1 grammatical skills in L2 development among adult learners. The present study investigates the extent to which IDs in L1 grammatical knowledge and processing explain variability in L2 grammatical and overall proficiency development and whether this connection is moderated by the learning context. Data was gathered from 58 L1 English speakers enrolled in intermediate-level Spanish classes in their home country, the AH group (n = 44), or in Alicante (Spain), the SA group (n = 14). A pre-posttest design was used to capture development of L2 grammatical knowledge (grammaticality judgement task), grammatical processing (picture selection task that captures grammar-based predictive processing), and overall proficiency (DELE and an Elicited Imitation Task). Individual differences in L1 grammatical knowledge were assessed through two subtests of the Test of Adolescent Language-3 battery (TOAL-3, Hammill, 1994) and the Modern Language Aptitude Test, part-IV (Carroll, 1990). In addition, three processing mechanisms involved in moment-to-moment computations of grammatical structure were assessed, namely, syntactic integration, adaptation, and depth of processing through a word monitoring (Hopp, 2015), picture description (Kaan & Chun, 2018), and picture selection task (Dąbrowska, 2019), respectively. Results revealed variability in L1 grammatical skills, as well as significant improvement of L2 grammatical knowledge and oral proficiency after a semester of study for both groups. Regression analyses suggested that the oral/aural engagement of L1 grammatical knowledge (TOAL-3) and L1 syntactic integration ability (Word Monitoring task) significantly explained variability in L2 predictive processing development. Although, the latter connection was moderated by the learning context, with a more positive role for the SA setting. This pattern of results extends previous evidence of linguistic interdependence to L1 grammatical skills among adult learners and highlights the need to explore the relationship between learner-internal and external factors in tandem.