This chapter addresses psychological individual differences that are upmost importance for second language teachers. It answers teachers’ everyday questions such as Why do some students never speak? and Why do some students give up so easily? The chapter begins by explaining some key information to understand learner psychology (e.g., trait-like vs. state-like) and argues that some psychological constructs are susceptible to instruction but some are not. The chapter then discusses multiple individual differences including L2 motivation, willingness to communicate, foreign language anxiety and enjoyment, metacognition, self-regulated learning, mindset, interaction mindset, and learner beliefs. Throughout the chapter, pedagogical recommendations for maximizing learner psychology for second language learning are shared. In addition to learner psychology, the chapter discusses teacher psychology (e.g., teacher cognition) and how it influences the success of second language teaching.

Chapter 10 outlines affective, cognitive, and social dimensions of individual differences in language learning and discusses language teachers’ insufficient expertise to match instruction to these differences. This outline is followed by a report on the findings from a small-scale study that explored teachers’ perceptions and use of individual learner differences in their classes.