June 05, 2008
Low Serotonin Increases Desire To Punish Unfairness

University of Cambridge researchers have found that reducing brain serotonin increased the willingness of people to engage in altruistic punishment behaviors.

The researchers were able reduce brain serotonin levels in healthy volunteers for a short time by manipulating their diet. They used a situation known as the 'Ultimatum Game' to investigate how individuals with low serotonin react to what they perceive as unfair behaviour. In this game one player proposes a way to split a sum of money with a partner. If the partner accepts, both players are paid accordingly. But if he rejects the offer, neither player is paid.

Normally, people tend to reject about half of all offers less than 20-30% of the total stake, despite the fact that this means they receive nothing - but rejection rates increased to more than 80% after serotonin reductions. Other measures showed that the volunteers with serotonin depletion were not simply depressed or hypersensitive to lost rewards.

PhD student Molly Crockett, a Gates Scholar at the University of Cambridge Behavioural and Clinical Neuroscience Institute, said: "Our results suggest that serotonin plays a critical role in social decision-making by normally keeping aggressive social responses in check. Changes in diet and stress cause our serotonin levels to fluctuate naturally, so it's important to understand how this might affect our everyday decision-making."

The innate desire to punish those who are unfair is an essential instinct for maintaining a society. Rules for cooperation and fairness must be enforced or a society will decay. Our brains must feel internal rewarded for punishing others because the delivery of that punishment often delivers no external rewards.

See my previous posts Altruistic Punishment And Genetic Engineering Of The Mind and Brain Rewards For Carrying Out Altruistic Punishment.

Share |      Randall Parker, 2008 June 05 10:51 PM  Brain Altruism

Ken said at June 7, 2008 5:51 PM:

The primary problem with the desire to punish is that it isn't matched with any desire to investigate the facts first. It seems to be triggered by immediate perceptions, not judicious consideration. This desire is too easily misled and it underpins public and partisan support for all kinds of harsh acts, up to and including mass killing - because "they" deserve it , or even live within collateral damage range of someone who "deserves it". "They" can easily be people of the same nation, ethnicity, religion as particular "bad" people, balanced evidence of their "badness" not being required. The desire to punish is one that may have deep importance in a society, but a civil society ought to be preventing it's use outside of non-judicial settings first before applying it - hopefully with suitable safeguards and clear knowledge of it's defects.

Mirco said at June 8, 2008 7:39 AM:

The desire to punish others for their wrongdoing is needed and useful.
The problem is that this instinct was developed when the human groups were really smaller than now.
So it is not well suited to our developed societies.
What is need is others brain mechanisms that let people to delay the onset time of the punishments if the misdoing don't need an immediate response.
We also need to reduce the "fundamental attribution error" that so many people do when they analyze the behavior of others.

Randall Parker said at June 8, 2008 9:00 AM:


We need both greater intelligence as well as fewer cognitive biases.


People rationalize what is fair in order to help their own interests.

We need the desire to punish simply to get a person to testify in a case where they witnessed a crime committed against a total stranger. The desire to punish gets used in many situations on a daily basis.

Allan said at June 8, 2008 10:12 AM:

But who gets to decide what is "fair" and who determines the punishment?

Ken said at June 8, 2008 4:46 PM:

Randall, I just suspect it's a primary part of the mechanism by which harm done to others is justified - you don't suffer guilt and remorse for that attack on your neighbouring village, because, prior to that attack everyone was fired up by a fast talking ringleader who told you all about the horrible things they've done - ie they deserved to be punished and you can feel good about your brave warriors having burnt all their huts and whacking their boy kids on the head and stealing their girl kids. According to a previous post of yours, seeing people you believe deserve it get punished is actually accompanied by pleasure - this makes me highly suspicious of actions motivated by such urges unless restrained and constrained by judicial process.

Whilst the urge to punish has a part in everyday life, too many of the everyday uses of it are not benign or beneficial. This urge can be, and too often is, used to motivate people to actions - or to sanction actions - that other people (eg those on the receiving end) would similarly and rightly see as deserving of harsh punishment back. It can and does lead to cycles of retribution and revenge. As you say, people rationalise things to suit their own interests - and too often without real consideration of the real and ongoing consequences.

Jen said at January 28, 2011 3:47 PM:

Bullies creat bullies...that seems a strong enough realism to cause a man or woman to pause before "paying back" a suspected or actual wrong-doer for his/her wrong-doing.

Meaning that without judicial restraints a society is reduced to the "strongest wins"...which result may have nothing to do with truth.

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