Research into second language acquisition (SLA) has shown that individual difference (ID) variables can be strong predictors of language achievement (e.g., Dornyei, 2003; Skehan, 2003). Traditionally, this research conceptualized ID variables as static and monolithic variables (e.g., Dornyei, 2010). More recently scholars have questioned this…

Foreign language enrollments in U.S. higher education are falling at an unprecedented rate since the 1980s. This mixed methods case study sought to investigate this phenomenon by examining the motivational and attitudinal profiles of 89 beginning-level learners of foreign languages (Spanish, French, Arabic, Japanese) and the contextual factors…

Guided by Dynamic Systems Theory (DST) and multidimensional perspectives on individual differences (IDs) in instructed second language (L2) learning (e.g., Larsen-Freeman, 2014; Sun & Zhang, 2020), this longitudinal mixed-methods study focuses on three conceptually different categories of L2 learners' IDs: working memory (WM), motivation, and…

This dissertation investigates the longitudinal development of Chinese language proficiency among students in a Chinese as a Foreign Language (CFL) Flagship Program at an American public university from 2014 to 2024. Using Bayesian multilevel regression models, this study assesses the trajectories of listening, speaking, and reading proficiency…