A behavioral economist and collaborator of Kahneman and Tversky’s. Thaler coined the different classifications of Econs and Humans, which draw a distinction between the way economists view people and the way psychologists view people. As a graduate student, Thaler discovered people’s behavior was often inconsistent with accepted economic theory, and was attracted by Kahneman and Tversky’s work on prospect theory to help explain some of those inconsistencies. Together, the three men explored different behavioral economics principles like the endowment effect and broad framing, significantly advancing and defining the field.