Aptitude-treatment interaction in L2 learning: A research synthesis

Abstract

Aptitude treatment interaction research relies on learner characteristics to adapt instructional methods in systematic and productive ways. In the field of second language acquisition, there is agreement that individual differences affect attainment in various ways and many instructed second language acquisition studies have included an individual difference. However, the primary focus has usually been on the instructional treatment itself rather than on any interactions between the effectiveness of the treatment and the individual difference factor. In other words, the effect of individual differences has been examined post hoc, instead of proposing treatments that will enhance learning for a subset of learners with a particular characteristic identified a priori, before treatment is delivered. This article reviews instructed second language acquisition studies that included a cognitive individual difference and an aptitude-treatment-interaction component. Our objective was to examine the extent to which cognitive abilities in the domain of explicit cognitive processes were related to outcomes under explicit instructed conditions, while cognitive abilities in the domain of implicit cognitive processes were related to outcomes under implicit instructed conditions. The results of this research synthesis showed that when learning takes place under explicit instructed conditions, the relationship with explicit cognitive abilities is positive and moderate, whereas the relationship with implicit cognitive abilities is negative and weak. When learning takes place under implicit instructed conditions, the relationship with both implicit and explicit cognitive abilities is negative and moderately weak.