One way to stop defections in a Prisoner’s Dilemma game is to change the mechanism to punish defections. Punishments enforce cooperation.

Our brains may be wired to punish cheaters. Men and women lose empathy for cheaters who are punished. Men, in particular, enjoy physically punishing someone who cheated. This may be our foundation of justice.

One thing neurologists discovered were mirror neurons which allow us to empathize with other individuals. We imagine what their emotions must be like. If someone is hurt, we feel for them by imagining what the pain must be like. This encourages cooperation.

This study helps solve the Prisoner’s Dilemma problem which discourages cooperation.

The game allows players to cooperate or double-cross one another, and so fosters camaraderie or enmity between players. Following the game, participants were placed inside an fMRI machine and then saw their fellow players zapped with electricity. The activity in their brain was recorded as they watched.

The scans revealed changes in activity as players who had cooperated got zapped, compared with those who had double-crossed them in the game….

Here are the results:

Both men and women also experienced slightly less activity in these areas when cheaters were given a shock, which suggests the feeling of empathy was dependent on social behaviour.

But tellingly, activity dropped much more in men when watching cheaters being buzzed. In addition, several other regions of male participants’ brains “lit up” instead – areas linked to the experience of reward known as the ventral striatum/nucleus accumbens and orbito-frontal cortex.

The results suggest that men not only feel less empathy for cheaters but experience pleasure when they are punished. ”

“Singer speculates that the disparity between men and women could mean men have evolved to have a key role in maintaining justice in human societies.”

In other words, if you cheat, a guy with a big stick will club you.

The evolution of cooperation is not based on empty-headed altruism since Nice Guys die first. I speculate that cooperation is born out of justice and retaliation. People cooperate because they fear the punishment and are enticed by the incentives.

If so, this is a biological version of “Tit for Tat” in the Prisoner’s Dilemma. If someone cooperates, you cooperate with them. If they cheat you, you retaliate and harm them until they start cooperating again.

I cannot comment on why men seem to enjoy punishment while women just turn off empathy for the punished. That could just be a statistical fluke from one study, or it could be something rooted in the biology where men were bred as enforcers in society. Many more studies are welcome.