Event-related potentials (ERPs) have become widespread in second language acquisition (SLA) research and a growing body of literature has been produced in recent years. We surveyed 61 SLA papers that use ERPs to study L2 sentence processing in healthy late learners. Our main aim was to provide a critical summary of findings from the decade…

The present systematic review examines what factors determine when, how and to what extent previous linguistic experience (from the first language, second language or both languages) affects the initial stages and beyond of adult third language (L3) acquisition. In doing so, we address what a bird's eye view of the data tells us regarding…

This commentary discusses Westergaard's (2021) keynote article, which presents a comprehensive model of first language (L1), second language (L2), and third language (L3) acquisition. The commentary presents evidence from a previous study of L3 learners that provides support for Westergaard's property-by-property transfer proposal. The commentary…

A number of longitudinal studies of L2 production have reported frequency effects wherein learners' produce more frequent words as a function of time. The current study investigated the spoken output of English L2 learners over a four-month period of time using both native and non-native English speaker frequency norms for both word types and word…

We present a proof-of-concept study that sketches the use of compression algorithms to assess Kolmogorov complexity, which is a text-based, quantitative, holistic, and global measure of structural surface redundancy. Kolmogorov complexity has been used to explore cross-linguistic complexity variation in linguistic typology research, but we are the…

Many people speak more than two languages. How do languages acquired earlier affect the learnability of additional languages? We show that linguistic distances between speakers' first (L1) and second (L2) languages and their third (L3) language play a role. Larger distances from the L1 to the L3 and from the L2 to the L3 correlate with lower…

In bilinguals and second language learners, the native (L1) and nonnative (L2) languages coexist and interact. The L1 influences L2 production via forward transfer, as is seen with foreign accents. However, language transfer is bidirectional: even brief experience with an L2 can affect L1 production, via backward transfer. Here, we review the…

Researching the longitudinal development of second language (L2) learners is essential to understanding influences on their success. This 7-year study of oral skills in adult immigrant learners of English as a second language evaluated comprehensibility, fluency, and accentedness in first-language (L1) Mandarin and Slavic language speakers. The…

Given that this special issue is devoted to the acquisition and processing of inflectional morphology by second language (L2) learners, the question in the title may appear redundant. However, recent research on first language (L1) and L2 morphological processing has challenged basic assumptions about the status of inflectional morphology in…

One central question in the formal linguistic study of adult multilingual morphosyntax (i.e., L3/Ln acquisition) involves determining the role(s) the L1 and/or the L2 play(s) at the L3 initial state (e.g., Bardel & Falk, Second Language Research 23: 459-484, 2007; Falk & Bardel, Second Language Research: forthcoming; Flynn et al., The…