In this article we explore the use of Granger Causality as a method to shed light on causal relationships in studies on (second) language acquisition. Understanding such relationships remains a central challenge in longitudinal SLA research, where both learner variables and measures of linguistic development interact and evolve dynamically over time. We first explain the concept of Granger Causality and show how the method works, before providing an illustration using weekly measures of L2 development (C-Test performance and speech fluency) and individual difference variables (operation span, motivation and wellbeing) to explore their possible causal relationships in a longitudinal study with later-life language learners. The results reveal several asymmetric patterns. The findings are discussed in relation to the existing literature on later-life language learning and demonstrate that Granger causality is a valuable method for examining the directionality of relationships between variables in longitudinal data.

Complex Dynamic Systems Theory (CDST) approaches to second language (L2) development have stressed that subsystems of language are intertwined (De Bot et al., 2007, Larsen-Freeman, 1997). A key challenge is accurately attributing causal explanations and determining suitable statistical methods to study relationships between linguistic processes, features, and forms within the CDST framework. In this chapter, we propose Granger Causality to investigate causes of change. This method quantitatively assesses to what extent one time series is dragging the other along, suggesting that one is causally prior to the other. We explored how this method can be used to assess whether certain aspects of linguistic complexity can induce change in others, thus serving as precursors or supporters in the relationship.

Recent years have seen a marked increase in the use of time-intensive longitudinal designs in applied linguistics, particularly in second language acquisition (SLA) research, where individual developmental trajectories have become inferential targets in their own right. Generalized additive mixed-effects models (GAMMs) have emerged as a powerful tool for modeling betweenand within-person variation, for disentangling linear from nonlinear relationships, and for assessing the predictive power of (relatively) static (e.g., gender, educational attainment) alongside time-varying (e.g., socioaffect, cognition) predictors on developmental pathways. Setting our tutorial apart from other GAMM resources in computational linguistics, phonetics, and sociolinguistics, we present the first in-depth application of GAMMs to identify and explain periods of significant change (growth or decline) in longitudinal datasets with repeated measurements. We draw on a novel micro-development study comprising 43 older adult L2 learners who completed a battery of L2, socioaffective, and cognitive tasks in 30 consecutive waves across a period of two years (i.e., 30 measures per participant per task). Our contribution guides readers through the computational steps to identify periods of statistically significant change. We then illustrate how findings can be interpreted and supplemented with both qualitative introspective data and quantitative measures of individual learner differences. While our tutorial focuses on SLA research, the methods are applicable to any number of disciplines in the social and natural sciences where developmental patterns are of direct inferential interest.

This study contributes to the methodological debate regarding the development of innovative data collection methods such as immersive virtual reality ( VR) technology to investigate second-language ( L2) learners' acquisition of sociolinguistic variation. Questionnaire data were collected from 32 L2 German learners (first-language English) regarding their VR user experience. We home in on participants' subjective judgements of system usability, workload, VR sickness, spatial presence, and satisfaction. Quantitative analyses revealed that the VR tasks did not disadvantage learners in terms of their user experience as a function of individual differences in age, L2 varietal proficiency, or exposure. We conclude with potential ways to exploit the strengths of VR in the expanding field of variationist SLA.

The aim of this study is to investigate both quantitatively and qualitatively the impact of career-related major life events (MLEs) on patterns of reported linguistic change across the lifespan, with an emphasis on how individual differences relate to differential patterns of MLE-related change. The occupational significant life events scrutinized here include entry into the workforce, job/career change, unemployment, and retirement. We analyzed survey data from 154 German-speaking adults in Austria who experienced (at least) one of these career-related MLEs. Results from Bayesian modeling showed that individual differences in event experiences (e.g., how stressful an MLE is perceived, how damaging an MLE is for one’s social status) alongside social factors such as varietal proficiency affect the degree of perceived MLE-related change in the sociolinguistic repertoire. Qualitatively, the thematic analysis revealed that facets of the linguistic marketplace seemed responsible for occupational MLE-related linguistic change, but also socio-affective drivers such as dialect pride and career-resultant shifts in one’s social networks and contact with other dialects.

This study is the first to explore microdevelopment in sociolinguistic evaluative judgments of standard German and Austro-Bavarian dialect by adult second language learners of German by using dense time serial measurements. Intensive longitudinal data (10 observations per participant) were collected from four learners at approximately weekly intervals over 3 months. We employed generalized additive models with superimposed periods of significant change to identify rapid developmental phases in individual developmental trajectories. By triangulating these models with qualitative introspective and retrodictive interview data, we identified environmental and psychological stimuli for change. Learners evinced increasing and decreasing periods of significant change, independent of length of residence. Dynamic constellations of identity- and agency-related variables alongside more intensive social interaction with target-variety speakers contributed to significant changes. We discuss findings from a complexity perspective and advocate for microlongitudinal studies in variationist second language acquisition to better capture stimuli for change in learners’ emerging multivarietal repertoires.

The present study takes a variationist perspective to explore the varietal repertoires of adult learners of German as a second language (L2), that is, their variable use of standard German, Austro-Bavarian dialect, and mixture varieties. Forty L2 learners completed a virtual reality task involving interactions with dialect-speaking and standard-German-speaking interlocutors. Using Bayesian multilevel modeling, the goal was to explore differential outcomes in the acquisition of sociolinguistic competence by determining whether participants adjusted their varietal behavior to match that of the interlocutor (i.e., varietal convergence). The results show that there were no interindividual addressee-dependent convergence tendencies. A holistic person-centered analysis of individual learners' intraspeaker variation revealed that only select L2 learners adjusted their usage patterns but did not entirely invert their usage of dialect and standard language as a function of the variety of the interlocutor. Introspective qualitative data speak to potential drivers behind the differential development of L2 (multi)varietal repertoires. image

This study is the first to explore microdevelopment in sociolinguistic evaluative judgments of standard German and Austro-Bavarian dialect by adult second language learners of German by using dense time serial measurements. Intensive longitudinal data (10 observations per participant) were collected from four learners at approximately weekly intervals over 3 months. We employed generalized additive models with superimposed periods of significant change to identify rapid developmental phases in individual developmental trajectories. By triangulating these models with qualitative introspective and retrodictive interview data, we identified environmental and psychological stimuli for change. Learners evinced increasing and decreasing periods of significant change, independent of length of residence. Dynamic constellations of identity- and agency-related variables alongside more intensive social interaction with target-variety speakers contributed to significant changes. We discuss findings from a complexity perspective and advocate for microlongitudinal studies in variationist second language acquisition to better capture stimuli for change in learners' emerging multivarietal repertoires.

The main goal of this paper is to suggest a combination of data analyses – notably generalized additive models, time-series clustering methodology, visual methods for significance testing and qualitative analyses – that relate to Complex Dynamic Systems Theory (CDST). To this end, we report on findings from a larger project conducted in a bilingual (pre)primary school in Switzerland, aiming to elucidate the complex ways that L2 English development emerges over time in 45 children who received German/English bilingual instruction over a period of eight years (age 5-12) in combination with emerging extracurricular exposure to English. The results reveal that increased extracurricular activities in English are particularly noticeable during periods of rapid development, but the effects seem temporally limited to the end stages of testing and strongly hinge on the cluster in question (i.e., learners with trajectorial similarities). We relate the findings to the “authenticity gap” between English inside and outside of school, as clusters who perceive a discrepancy between in- and out-of-school encounters with English also show rapid development that is characterized by increased English exposure during extracurricular activities. Methodological implications of adopting non-linear models, which can model complex dynamic relationships in order to better reconcile generalizability, variability, and individuality, are discussed.

Abstract This longitudinal study with time-serial data examines for the first time whether different types of intraindividual variation in second language (L2) performance and cognitive functioning are related, and how and when they influence L2 development longitudinally in older adulthood. We analyzed the L2 development of 26 German-speaking adults aged 62–79 who were taught L2 English for 2 × 90 minutes per week over 6 months. At each of the 15 measurements, the participants completed three L2 tasks and eight cognitive measures, and they answered open-ended questions about socioaffective variables such as L2 motivation. Results of generalized additive mixed models and qualitative content analyses showed, inter alia, that L2 variability—rather than inconsistency or dispersion—had a (nonlinear) effect on L2 growth, being especially large during periods of rapid development. The qualitative analyses revealed a blended operation of internal and external states being associated with periods of significant L2 growth.

This study is the first to investigate subject-level variability in sociolinguistic evaluative judgements by 30 adult L2 German learners and explore whether the observed variability is characterizable as a function of individual differences in proficiency, exposure, and motivation. Because group-level estimates did not paint an accurate picture of the individual, we propose methods capable of integrating population-level estimates with person- and ensemble-centered approaches so as to reconcile generalizability and individuality. Using random effects from Bayesian mixed-effects models, we found that global subject-level variability in evaluative judgements was not predicted by individual differences. By building homogeneous ensembles (i.e., subgroups of individuals with similar evaluative judgements), however, it was possible to assess whether ensembles were characteristic of certain levels of individual differences. This ensemble-centered approach presents an innovative way to address the group-to-individual generalizability issue in cross-sectional data and transcend individual variability in order to make tentative generalizations of individual cases to wider populations.

This cross-sectional study addresses for the first time the non/linear association between individual learner differences of social, proficiency-related, and socioaffective nature (length of residence [LoR], varietal proficiency, exposure, and socioaffect) and differential outcomes in L2 sociolinguistic repertoires against the backdrop of the Austro-Bavarian naturalistic context. Forty adult migrant L2 German learners participated in a virtual reality experiment involving interactions with dialect-speaking and standard German-speaking interlocutors. The goal was to explore differences in participants' interpersonal varietal behavior, that is, their addressee-relational variable use of standard German, Austro-Bavarian dialect, and mixture varieties. The results of Bayesian multinomial modeling indicated that LoR, dialect exposure, and proficiency, as well as reduced anxiety when speaking dialect, predicted differences in interpersonal varietal behavior. That said, a visual-quantitative analysis revealed critical thresholds concerning when, within these predictors, changes in sociolinguistic behavior manifested, indicating a rapid change in sociolinguistic development at the inter-individual level and ultimately facilitating initial insights as to how advanced one needs to be in order to engage in sociolinguistic variation in the Austro-Bavarian naturalistic context.