Second language acquisition theory has traditionally focused on the cognitive and psycholinguistic processes involved in additional language (L2) learning. In addition, research on learner psychology has primarily centered on learners' cognitive abilities (e.g., aptitude and working memory) and internal traits or states (e.g., dispositions,…

In this Methods Showcase Article, we illustrate mixed-effects modeling with a multinomial dependent variable as a means of explaining complexities in language. We model data on future-time reference in second language Spanish, which consists of a nominal dependent variable that has three levels, measured over 73 participants. We offer step-by-step…

Additional language (L2/Ln) research largely focuses on learners whose first languages are spoken and who are learning additional spoken languages. In the past few decades, sign languages have become increasingly popular for hearing students in schools. These students must not only learn the vocabulary and grammar of sign languages but also manage…

The past decades have seen an explosion of research using electrophysiological or neuroimaging techniques for studying the neurocognitive underpinnings of second language (L2) processing. Although this field has a shorter history than does research on language learning more generally, important insights into the neurocognitive basis of L2…

This article addresses different ways scholars conceptualize the multilingual repertoire. Formal and functional approaches investigate crosslinguistic influence across clearly demarcated languages, while dynamic systems theory and translanguaging approaches question countability and boundedness of languages. Problems with both perspectives are…

Multisite research (MSR) offers the key advantages of greater statistical power and external validity via larger and more diverse participant pools. In second language acquisition (SLA) research, recent developments in meta-analysis have created a robust foundation for MSR. Although logistical and financial obstacles can complicate expansion…

Adequate reporting of quantitative research about language learning involves careful consideration of the logic, rationale, and actions underlying both study designs and the ways in which data are analyzed. These guidelines, commissioned and vetted by the board of directors of "Language Learning," outline the basic expectations for…

Although classical statistical techniques have been a valuable tool in second language (L2) research, L2 research questions have started to grow beyond those techniques' capabilities, and indeed are often limited by them. Questions about how complex constructs relate to each other or to constituent subskills, about longitudinal development in…

Second language acquisition researchers often face particular challenges when attempting to generalize study findings to the wider learner population. For example, language learners constitute a heterogeneous group, and it is not always clear how a study's findings may generalize to other individuals who may differ in terms of language background…

This paper presents a set of guidelines for reporting on five types of quantitative data issues: (1) Descriptive statistics, (2) Effect sizes and confidence intervals, (3) Instrument reliability, (4) Visual displays of data, and (5) Raw data. Our recommendations are derived mainly from various professional sources related to L2 research but…

In this article I make the point that there has been a continuous focus on second language development in second language acquisition research for over 40 years and that there is clear empirical evidence for generalizable developmental patterns. I will both summarize some of the core assumptions of Processability Theory (PT) as an approach to…

In this article I discuss the contributions to this Special Issue of "Language Learning" on orders and sequences in second language (L2) development. Using a list of questions, I attempt to characterize what I see as the strengths, limitations, and unresolved issues in the approaches to L2 development represented in this Special Issue. I…

In empirical applied linguistics research it is essential that the key variables are operationalized in a valid and reliable way, and that the scores are treated appropriately, allowing for a proper testing of the hypotheses under investigation. The current article addresses several theoretical and practical issues regarding the use of measurement…

This chapter introduces three applications of Bayesian inference to common and novel issues in second language research. After a review of the critiques of conventional hypothesis testing, our focus centers on ways Bayesian inference can be used for dealing with missing data, for testing theory-driven substantive hypotheses without a default null…

The goals of this article are to appraise second language acquisition's (SLA) disciplinary progress over the last 15 years and to reflect on transdisciplinary relevance as the field has completed 40 years of existence and moves forward into the 21st century. I first identify four trends that demonstrate vibrant disciplinary progress in SLA. I then…