http://www.sciencemag.org/content/318/5847/107.abstract
They are actually smart enough to play the game right.
Likewise, you're not actually smart enough to understand that, for some people, revenge/spite has a nonzero utility.
Some of us are just in it for the lulz.
Dude, I agree with almost everything I've seen you write on this forum, but you have a really harsh way of displaying your opinions. Not everyone who disagrees with you is dumb. Tomcollins has proven he is intelligent and capable of putting forth some good arguments. Just sayin