For decades educational psychologists have bemoaned the black box approach of much research on learning, that is, the focus on product rather than process, and the absence of fine-grained analysis of the learning process in the individual. One way that progress has been made on this point in the last couple of decades is through cognitive…

In this article, I describe studies conducted over 25 years with secondary and post-secondary L2 learners in the United States. The evidence from these studies shows that there are important connections between students' early L1 skills and their L2 aptitude and L2 proficiency and that individual differences in students' L1 skills in elementary…