Inhibitory Control and First Language Flexibility in Second Language Learning: A Neurocognitive Study

In today's world, many adults find themselves in a situation in which it is beneficial or even necessary to learn a second language (L2). Yet, learning an L2 during adulthood is a complex and challenging endeavor that results in a great deal of variability in learning outcomes. Researchers who examine L2 learning are interested in exploring what role internal factors, i.e., factors that are directly related to the learner, play in successful adult L2 development with the goal of identifying the ways in which they contribute to the experience of adult L2 learning. This dissertation study investigates two factors that have emerged from recent bilingualism studies as potentially relevant to successful L2 learning, namely inhibitory control abilities and first language (L1) flexibility. The study aims to provide a multi-dimensional perspective on the relationships between these two factors and adult L2 proficiency outcomes by offering both behavioral and neurocognitive evidence. Specifically, the study does so by assessing L2 proficiency and inhibitory control abilities with multiple behavioral measures and L1 flexibility at the grammatical level using event-related potentials (ERPs), a brain-based technique that allows for the exploration of the human mind related to different cognitive processes, among intermediate L2 learners of Spanish. Our results evidence a relationship between inhibitory control abilities, specifically reactive control, and L1 grammatical flexibility, as both factors accounted for the variability found in L2 proficiency among our group of intermediate-level adult L2 learners. These results contribute to the existing body of knowledge about individual factors related to adult L2 development by providing critical new insight into the underlying cognitive and brain mechanisms related to successful adult L2 learning. Furthermore, the results of this study, using both theories and methods from cognitive psychology, bilingualism, and L2 learning have the potential to inform research in these fields by expanding previous literature about the ways in which the adult brain is able to accommodate and regulate the presence of a new language and the functional role that inhibitory control and L1 flexibility abilities may play in adult L2 learning as well as in the becoming bilingual experience as a whole.