This article presents a theoretical review of and methodological guidelines for the study of two key notions in second language acquisition research, complexity and difficulty. The term "complexity" has gained considerable currency over the past decades and has taken on a wide range of meanings. We argue for a more restricted…

This article responds to calls for greater inclusivity in second language acquisition research and, more specifically, to calls to explore further the impact of first language literacy on second language oracy (e.g., Tarone et al., 2009). We conducted a partial replication of Foster and Skehan's (1996) influential study of task complexity,…

This study examined the relationship of linguistic complexity, captured using a set of lexical richness, syntactic complexity, and discoursal complexity indices, to second language (L2) learners' perception of text difficulty, captured using L2 raters' comparative judgment on text comprehensibility and reading speed. Testing materials were 180…

Many connectives, such as "therefore" and "however," are used very frequently in the written modality. Their acquisition thus represents an important milestone in developing written language competences. In this article, we assess the development of competence with such connectives by native French speakers in a sentence-level…

Frequency is often the only variable considered when researchers or teachers develop vocabulary materials for second language (L2) learners. However, researchers have also found that many other variables affect vocabulary acquisition. In this study, we explored the relationship between L2 vocabulary acquisition and a variety of lexical…

Large-scale learner corpora collected from online language learning platforms, such as the EF-Cambridge Open Language Database (EFCAMDAT), provide opportunities to analyze learner data at an unprecedented scale. However, interpreting the learner language in such corpora requires a precise understanding of tasks: How does the prompt and input of a…

This study investigates semantic categorization of the meaning of placement verbs by Danish and Spanish native speakers and two groups of intermediate second language (L2) learners (Danish learners of L2 Spanish and Spanish learners of L2 Danish). Participants described 31 video clips picturing different types of placement events. Cluster analyses…

This study investigated whether task complexity influences second language (L2) writers' fluency, pausing, and revision behaviors and the cognitive processes underlying these behaviors; whether task complexity affects linguistic complexity of written output; and whether relationships between writing behaviors and linguistic complexity are…

This study investigated the effects of task complexity on child learners' second language (L2) gains, the relationship between aptitude and L2 development, and the extent to which task complexity influences this relationship when recasts are provided. Sixty child EFL learners were assigned to two experimental groups. During the treatment, one…

Taking a psycholinguistic orientation within task-based language teaching scholarship, this study investigated the effects of mode (oral vs. written) and task complexity on second language (L2) performance. The participants were 78 Catalan/Spanish learners of English as a foreign language. Half of the participants performed the simple and complex…