The idea behind superrationality is that two logical thinkers analyzing the same problem will come up with the same, correct, answer. For example, if two persons are both good at arithmetic, and both have been given the same complicated sum to do, it can be predicted that both will get the same answer before the sum is known. In arithmetic, knowing that the two answers are going to be the same doesn't change the value of the sum, but in game theory, knowing that the answer will be the same might change the answer itself.

source: www.wikipedia.org