This seminar is designed for MA and PhD students who are current or future researchers interested in individual differences (IDs) in second language acquisition (SLA). In addition to introducing students to relevant theoretical frameworks and approaches to studying major IDs-both classic, such as second-language (L2) aptitude, anxiety, and motivation, and more recent, such as L2 grit-the course will cover pertinent aspects of the study of L2 IDs such as: (a) conceptualization and measurement of latent vs. observed variables, (b) study design and instrumentation, (c) sampling and generalizability, and (e) validity andreliability. However, the focus of this seminar will be primarily substantive rather than methodological. The main assignment for the course will be a written research report of an empirical study with a focus on one (or more) IDs in SLA. MA and first-year PhD students are not required to conduct a full empirical study and have an option to do a proposal for the study instead.