Applied rationality? EY developed this rationality stuff as part of his work on AI. In terms of rational behavior, there's a general question of how do we change behavior to what we think is rational and the specific question of what is rational for whatever it is we're dealing with. Now that I write that I realize that different areas might have different best ways to change behaviors (diet changes versus exercise perhaps). I think that looking at more specific applied cases--what is a 'rational' diet and how to rationally adopt that diet--might be a good way to both test and develop x-rationality? Versus more abstract decision theory (Prisoner's dilemma).