Then you murder the twin prior to the game of chicken, and fake his suicide. Or you intimidate the twin, using your advanced rational skills to determine how exactly to best fill them with fear and doubt.

But before murdering or risking an uncertain intimidation feint, there's another question you need to ask yourself. How certain are you that the twin is irrational? The Cold War was (probably) a perceptual error; neither side realized that they were in a prisoners dilemma, they both assumed that the other side preferred "unbalanced armament" over "mutual armament" over "mutual disarmament;" in reality, the last two should have been switched.

Worst case scenario? You die playing chicken, because the stakes were worth it. The Rational path isn't always nice.

(There are some ethical premises implicit in this argument, premises which I plan to argue are natural derivatives from Game Theory... but I'm still working on that article.)