1.2 A truly interdisciplinary subject Modern decision theory has developed since the middle of the 20th century through contributions from several academic disciplines. Although it is now clearly an academic subject of its own right, decision theory is typically pursued by researchers who identify themselves as economists, statisticians, psychologists, political and social scientists or philosophers. There is some division of labour between these disciplines. A political scientist is likely to study voting rules and other aspects of collective decision-making. A psychologist is likely to study the behaviour of individuals in decisions, and a philosopher the requirements for rationality in decisions. However, there is a large overlap, and the subject has gained from the variety of methods that researchers with different backgrounds have applied to the same or similar problems.