As part of the Working Group "Cold War Rationality," Paul Erickson's work explores the development and spread of mathematical theories of rational choice—especially game theory—since the Second World War. Much work to date has focused on the role of state (especially military) patronage in this process, and indeed military funding played a significant role in the early development of game theory, the mathematics of optimization, decision theory, and social choice theory, to name a few examples. However, Paul Erickson was especially interested in understanding the subsequent function of these theories within scientific disciplines, in particular, their ability to forge linkages across intellectual boundaries in the social, behavioral, and biological sciences. Game theory and theories of rational choice more generally hold out the possibility of unifying these areas of science, but this unification is accomplished at the cost of adopting a distinctly narrow conception of rationality, choice, and behavior. By focusing especially on the transfer of theories of rational choice between psychology, conflict resolution, and evolutionary biology, Paul Erickson shed light on both the spread of mathematical theories of rational choice, and on patterns of interdisciplinary communication in the social, behavioral, and biological sciences during the postwar era.