"Are Smarter Groups More Cooperative? Evidence from Prisoner's Dilemma Experiments, 1959-2003", Jones 2008:

A meta-study of repeated prisoner's dilemma experiments run at numerous universities suggests that students cooperate 5% to 8% more often for every 100 point increase in the school's average SAT score.

Later: http://econlog.econlib.org/archives/2012/10/group_iq_one_so.html

This finding was the first of its kind: In prisoner's dilemmas, smarter groups really were more cooperative. Since then other researchers have found similar results, some of which I discuss in Section III of this article for the Asian Development Review. It looks like intelligence is a form of social intelligence...Does that happen in the real world? If it does, does it mean that there are negative political externalities to low-skill immigration? That's a topic for a later time. Another worthy question: Why would high IQ groups be more cooperative anyway? Isn't cynicism intelligent? Sure, sometimes, but the political entrepreneur who can find a way to sustain a truce can probably skim quite a lot of the resulting prosperity off for herself. And people who are better at solving the puzzles in an IQ test are probably better at solving the puzzles of human interaction.