This chapter introduces personal investment theory to motivate research into the affective and conative dimensions of task-based language teaching (TBLT). Personal investment is defined as the meaningfulness that task content and outcomes have for learners in terms of their previous experiences and their physical, social or emotional needs in communicating. Following a discussion of personal investment theory in education and self-reference effects in cognitive psychology, personal investment is disambiguated from related constructs that have been discussed in the TBLT and SLA literature, and ways of operationalizing personal investment that have been proposed in the literature are discussed. Following this, recent empirical research on personal investment in second language (L2) task design and performance is summarized, focusing on research on the impact of learner-generated as opposed to teacher-generated content. Directions for future research are then pointed out. The chapter closes with questions for ongoing discussion as well as suggestions for further reading.