Optimizing post-critical-period language learning

This chapter reports on a new language aptitude test, the High-level Language Aptitude Battery (Hi-LAB), whose development was motivated by the need for an aptitude measure for more advanced L2 speakers. Since many language learners begin as adults, critical-period constraints work against the desired outcome. All may not be lost, however, given that some individuals attain high-level, if not native, proficiency, despite a late start. We hypothesize that they possess language aptitude comprising inherent cognitive and perceptual abilities that compensate, at least in part, for the typical post-critical-period degradation in language-learning capacity. While tests currently in use were designed to predict early rate of learning in instructed settings, Hi-LAB is conceptualized to predict successful ultimate attainment. Aptitude is a measurable ceiling on language learning, holding equal all other factors. We discuss constructs and measures, reliability and validity evidence, and uses of Hi-LAB for selecting learners for language training and in aptitude-by-treatment interaction studies.