My research group is currently writing up the results for a study where we experimentally studied cooperation that took place over an entire month. We found the very interesting result that cooperation was basically maintained at a high level instead of declining over the course of a 1-hour lab session, as predicted by much previous work.<p>On a related point, this experiment is a little worrisome because each player only had &quot;9 rounds&quot; to interact with others due to the concern of extended reputation effects. In my experience running this type of experiment, that is not even enough to understand the rules within which people play. (In our case, we had people play 400 ten-round games, 4000 rounds total, and a steady state was reached after about 60-80 games.)<p>While not completely an &quot;organized society&quot;, it does address the generalization limitations of behavioral labs in one important way: the time and span of participation. As you mentioned, this is one fundamental respect where society differs from experiments.