It's Not Your Choice To Be Polite - Our Brains Make Us Behave Around Others

A new study has pinpointed the region of the brain where this need to behave normally when around people comes from.

Shaking hands with an opponent after a game, holding the door open for someone behind you, and having good table manners when dining out are all social norms – accepted behaviour that keeps the peace in large groups.

Christian Ruff and his colleagues at the University of Zurich found that the right lateral prefrontal cortex – the right side of the front of the brain – is the region that contains the neurons that enforce social norms.

The study was published Oct. 3 in Science Express.

The experiment

Neurons in the lateral prefrontal cortex had previously been shown to play a role in determining the consequences of our actions and choosing behaviour in response. The researchers thought the same region could be responsible for our obedience to social norms.

They studied the region by monitoring the brain activity of 63 participants during a money exchange simulation.

Each participant was paired with a randomly assigned anonymous partner. The first player receives money, then decides how much to divvy out to the second player. The assumed social norm in this situation is that the first participant should split the money evenly between himself or herself and the other participant.

However, the scientists found that on average, the first player only gave around 10% to 25% of the total amount of their money to player two. In other rounds of the simulation, player two could punish unfair division of cash by reducing the money player one had.

The scientists found that under the threat of punishment, player one stuck much closer to the social norm of an even split: on average, they gave about 40% to 50% to player two.

Testing the role of the right lateral prefrontal cortex

Social norm experimentScience Express/Marc LatzelThe scientists used a low current that either stimulated or depressed the participants’ neurons during the simulation.

To tinker with this result the scientists used a low-level current to either excite or depress the right lateral prefrontal cortex of one group. When the brain was stimulated, player one gave almost 34% more to player two. When the brain cells were turned down, player one gave almost 23% less to player two.

Surprisingly, this was only the result when under the threat of punishment from their partner. Without the backlash, brain stimulation actually made player one give less money.

The scientists believe this result means that the neurons are only active when we are around other people and there are consequences for our actions. If we’re alone, this area of the brain won’t influence our behaviour.

Ruff and his colleagues think this research could help treat people with certain types of psychiatric and neurological conditions. And eventually, they could help develop treatments for criminals who have trouble obeying the law.

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