Decision theory is the theory of rational decision making. This is an interdisciplinary field to which philosophers, economists, psychologists, computer scientists and statisticians contribute their expertise. It is common to distinguish between normative and descriptive decision theory. Normative decision theory seeks to yield prescriptions about what decision makers are rationally required–or ought–to do. Descriptive decision theories seek to explain and predict how people actually make decisions. Descriptive decision theory is thus an empirical discipline, which has its roots in experimental psychology. Descriptive and normative decision theory are, thus, two separate fields of inquiry, which may or may not be studied independently of each other.