See also http://lesswrong.com/lw/dtg/notes_on_the_psychology_of_power/ where my comment included fulltext.
I wonder if inducing a feeling of power/high status in people would change the cooperative nature of the immediate response. It seems like in a tribe, you cooperate unless you're sure you can get away with defecting.
The "intuitive" (fast) interaction heuristic is predisposed towards selfishness, while the "calculated" (slow) decision making process favors greedier behavior: review of game studies.
I suspect you meant "selflessness" instead of "selfishness."
If it's a game close to a true prisoner's dilemma between two players, should we expect cooperation to rise again when we let people think even longer due to TDT considerations?