I'd like to add a third kind of rationality that seems popular in these circles: ''recreational rationality''. This would include things like the Prisoner's Dilemma, Newcomb's Paradox, the Monty Hall Problem, the "rationality quotes"-series and so forth.

Even though they are seldom useful in real-world decision making, they are simply ''interesting'' for many people that visit LW, I suspect -- including myself.