[1][7] These games can also be effectively used in the study of third-party punishments with respect to distribution and cooperation norms with some modifications.
However, roughly 60% of the third party observers chose to punish dictators who donated less than half their endowment.
This suggests that third-party punishment may be motivated by a desire to both provide justice for those who have been wronged and to reprimand those who violate expected social norms.
The observer could then choose to spend from his endowment to punish the defectors who chose to put self-interest ahead of cooperation.
[1] Current evolutionary models state that human altruism evolved through the selective (cultural or biological) extinction of groups in inter-group conflicts.
[14] When subjects were examined with a PET scan while playing a second-party trust game with another player, it was shown that when they administered punishment, the dorsal striatum, an area of the brain associated with the processing of rewards as a result of goal-directed actions, was activated.
It was also shown that individuals with stronger activations of the dorsal striatum were willing to incur greater cost in order to punish the norm violator.
This suggests that the people that administrated punishment against norm violators derived satisfaction from the act.
The nucleus accumbens, a brain region associated with reward, had punishment-related activation for both the second-party and third-party punishment conditions.
There was, however, a large variance between societies as to how much of their endowment the observers were willing to pay in order to punish the dictator.
Adolescents integrated the outcome and the intention when making second- but not third-party punishment decisions.
However, it was found that punishment was qualitatively similar in all 4 conditions, which suggests that egalitarian sharing norms exist within-groups and also between-groups.
It was also found that the dictators expected much harsher punishments if third-party observers belonged to the same group as the victim.