Cooperating = complying with social norms. Social norms are learned behavior. Many social norms are quite at odds with evolutionary psychology.
Adults have learned more than children; and children must learn before they are able to comply with social norms. You may find it diffucult to "cooperate" with adults who were exposed to greatly differing social norms; as may hapless sailors have discovered. Social dysfunctions aside, I really don't see it being any more complicated that this. Adam