Research has found that people differ in how they view their intelligence. Some people believe that intelligence is fixed (an entity theory of intelligence) and others believe that intelligence is malleable and affected by training and effort (an incremental theory of intelligence). These different beliefs about intelligence lead to very different motivational frameworks and to differences in performance on intellectual tasks. Theories of intelligence may also affect intelligence in the longer term by changing people's reactions to opportunities for intellectual growth. This chapter discusses how different motivation-relevant beliefs, about intelligence, about stereotypes, and about one's belonging, change intellectual performance. The affective states of pleasure, enjoyment, and interest (that accompany and constitute intrinsic motivation for an activity) enhance intellectual performance, leading to higher grades and test scores. The research changes our understanding of intelligence and brings to light avenues through which motivation can enhance intellectual performance.