Researchers across many fields have called for greater attention to heterogeneity of treatment effects--shifting focus from the average effect to variation in effects between different treatments, studies, or subgroups. True heterogeneity is important, but many reports of heterogeneity have proved to be false, non-replicable, or exaggerated. In…

Item response tree (IRTree) models are a flexible framework to control self-reported trait measurements for response styles. To this end, IRTree models decompose the responses to rating items into sub-decisions, which are assumed to be made on the basis of either the trait being measured or a response style, whereby the effects of such person…

Aptitude-treatment interaction (ATI) research is of both theoretical and practical interest to second language (L2) learning, since it provides insights into the processes linking learner-internal individual difference factors and learner-external contextual variables including instructional approach--variables that jointly determine L2 outcomes.…