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Being unfair is bad for us

Unfair stress Being unfair -- or being treated unfairly -- causes us to experience mental stress, a new study using heart monitors has found.

The study is more evidence that emotions play a role in human economic decision making, says economist Dr Uwe Dulleck of Queensland University of Technology.

"We feel negative stress if we are unfair," he says. "We seem to be happier if we behave more fairly."

While some economic theories assumes that individuals only make selfish and rational decisions, numerous studies using a tool called the Ultimatum Bargaining Game have found otherwise.

In the game there are two people sharing a resource, such as money. One person (the proposer) makes an offer to give the other (the responder) a particular share of the resource. The responder either accepts what is offered or both parties get nothing if the offer is rejected.

If we assume everyone is completely selfish and rational, a proposer would offer almost nothing and a responder would accept any offer no matter how small -- after all, some money is better than none, says Dulleck.

But, he says, repeated studies have found that responders usually reject any share less than 30 per cent.

Other studies using brain scanners have found that when the share offerred is above 30 per cent the responder's rational brain is activated, but below 30 per cent, and the parts of the brain involved in emotion light up.

Dulleck and colleagues wanted to use a less intrusive method to study physiological changes that accompany economic decision-making. And they wanted to study what happened for the proposers as well as the responders.

In a study reported recently in the journal PLOS ONE, they used high-resolution heart rate monitors on participants in the Ultimatum Bargaining Game.

They attached the monitors to 600 people, each of whom were teamed up with an anonymous partner via a computer to play the game.

When the share offered fell below 50 per cent and approached 30 per cent, both responders and proposers developed a heart rate pattern that is an indication of mental stress, says Dulleck.

"When you get closer to this 30 per cent, people became more nervous."

"Emotional reactions actually happen on both sides when we make decisions."

This is despite the fact that proposers were choosing to make unfair offers.

Co-author Dr Markus Schaffner, also from QUT, says "guilt" felt by the proposer making a low offer was one possible explanation for the observed increase in stress.

"This can be seen as evidence that we empathise with people and put ourselves in their shoes in these sorts of situations," he says.

Dulleck and colleagues are also using the heart rate monitors to study people's responses to paying taxes.