Experimental studies on punishment have sometimes been over-interpreted not only for the reasons Guala lists, but also because of a frequent conflation of proximate and ultimate explanatory levels that Guala's review perpetuates. Moreover, for future analyses we may need a clearer classification of different kinds of punishment.

On a proximate level, altruism may well be a temporally extended pattern of behavior that often seems to be maintained without extrinsic rewards (we may find it just valuable to be an altruistic person). However, recent theory and experiments have uncovered significant and often nonobvious extrinsic rewards for “altruistic” behavioral patterns. Ultimately, these patterns may mostly lead to a net benefit.