The human brain is capable of impressive feats such as storing millions of memories, effortlessly processing complex visual scenes, and seamlessly integrating perception, thought, and action. At the same time, performance on many complex cognitive activities is highly limited. Individuals make well-known errors in scientific reasoning and decision making, have trouble comprehending difficult texts and diagrams, and can only store about 3-4 simple items in short-term memory. Our goal is to understand the nature of limitations in the performance of complex cognitive tasks and ultimately how these limitations may be overcome. We focus primarily on tasks relevant to school and other everyday contexts.