Participants in the study played an online multiplayer game and researchers found that people generally behaved socially ‘well’. From the conclusion:

Negative actions are balanced to a large extent by good ones. Players with a high fraction of negative actions tend to have a significantly shorter life. This may be due to two reasons: First because they are hunted down by others and give up playing, second because they are unable to maintain a social life and quit the game because of loneliness or frustration. We interpret these findings as empirical evidence for self organization towards reciprocal, good conduct within a human society.

Sounds like evidence for a Millian social contract theory.