ABSTRACT
This chapter discusses psychometric considerations in the study of how individual differences in cognitive abilities, such as language aptitude or working memory, influence second language acquisition. Psychometrics, or test theory, describes procedures for developing tests and evaluating their suitability for an intended assessment purpose. Significant issues in test construction include item analysis, test scoring, reliability, and validity; these topics make up the main part of the chapter and they are discussed in the contexts of both classical test theory and item response theory. Importantly, it is pointed out that lack of attention to psychometric concerns may negatively impact knowledge production in the field of second language acquisition. The final parts of the chapter provide examples of how test theoretical problems have been treated in previous research on individual differences in second language acquisition, and suggestions are made for enhancing psychometric awareness in the research community.
