I wonder if the study asked a question of WHY the people were meaner.... I mean if someone tries to do good, and they start to realize that everyone else appears to be self-centered "all for me, and screw our kids" mentality for the future, they may appear "mean" yet really may just be fed up with everything.
Then the willingness to share.... if a green person is spending 50-100% more for the items, why would they want to share? That's a lot of money they'd be shelling out in comparison. And then bringing in computers to see if someone would cheat... um... "cheat codes" show up more than not on games--people "cheat" all the time on computer-based things and think nothing of it as it is not real.
Not saying the results may not be valid (as I have seen similar things involving religion and such), just using computer games and something involving an envelope (without any real details), it is hard to tell. Not to mention, the researcher's appear to have made their minds up on what would happen, potentially influencing the outcome (even if it is valid).