US scientists studying how the brain behaves during decision making have discovered that when people are confronted with moral decisions, they think about efficiency in one part of the brain, and equity in another part of the brain that deals with emotions, and the latter tends to win, suggesting that a sense of fairness is fundamental to human nature.

The study is the work of researchers at University of Illinois and the California Institute of Technology, and appears in the 8th May issue of Science.

What is the better decision: to give more food to a few hungry people (the efficient choice), or let some food go to waste so that everyone gets a fair share (the more equitable choice)?

This was the dilemma faced by participants in the study, whose brains were scanned by functional magnetic resonance imaging (fMRI) while they considered a series of tough decisions in a scenario involving allocating food to children in a Ugandan orphanage.

In setting up this study the researchers wanted firstly to explore whether equity or efficiency was stronger to our sense of justice, and secondly, they wanted to find out how big a role emotions played in resolving such questions.

These two questions have been at the heart of longstanding debates about “distributive justice”.

Co-principal investigator Ming Hsu, a fellow of the Beckman Institute for Advanced Science and Technology at the University of Illinois, said that what makes us moral, and how we make trade offs, the fundamentals of moral choices, is a question that interests many scientists.

Hsu said many of the subjects said afterwards that “This is the worst experiment I’ve ever been in. I never want to do anything like this again!”

The participants were given the following scenario.

Each child in the orphanage starts with a monetary equivalent of 24 meals, an actual gift from the researchers to the orphanage.

Then, a number of meals is to be cut from the children’s allotments. The number that is cut depends on choices the participant makes.

Each decision, where the participant has to choose one of two options, comprises a moral dilemma where one option is efficient, and the other option is equitable. For instance, one could choose to take 15 meals from one child (option 1) or 13 meals from one child and 5 meals from another child (option 2). In option 1 fewer meals are lost (more efficient), and in option 2 more meals are lost (less efficient) but the burden is more “fairly” distributed.

Hsu and colleagues said that this type of decision is a good example of a distributive justice dilemma, where each option is compelling, but you can’t have both, so you have to trade one off against the other.

The participants made their decisions by watching a computer animation where they were shown pictures of two choices at a time, each being a photograph of the children affected and a number showing the number of meals that would be lost if they chose that option. They chose their option by selecting a lever that changed the path of a ball that was slowly moving across the screen.

The results showed that participants overwhelmingly chose equity over efficiency.

“They were all quite inequity averse,” said Hsu, who explained that the findings support other research that suggests people are fairly intolerant of inequity.

While the participants watched the screen and made their selections, the researchers observed their brains with fMRI scanners. They were particularly interested in the brain activity at the time they made the decision.

Three regions of the brain, the insula, putamen and caudate, were involved in different ways, at different points in the decision process.

The insula was active when equity changes were being considered, while the putamen was active when efficiency changes were being considered. And the caudate appeared to integrate equity and efficiency when the decision was taken.

Hsu said that the involvement of the insula suggests that emotion is involved when a person is thinking about inequity.

Studies have shown that the insula, which is involved in awareness of bodily states and emotions, becomes active when people feel hungry, crave drugs, or have intense feelings like anger, fear, disgust and happiness. Other studies have also suggested it mediates fairness.

The authors said the putamen and the caudate regions of the brain become activate during reward-related learning.

Hsu described what they saw. At first “you’re seeing the signal in the insula and the putamen,” he said, but “when they hit the lever you see the insula activation. And when the ball gets to the end you see (activation of) the caudate,” he added.

Hsu explained that:

“The putamen is responding only to the chosen efficiency, which is how many meals get taken away from the kids or how many meals they end up with.”

“The insula, however, responded to how equitably the burden of lost meals was distributed,” said Hsu.

The authors wrote that the results showed how the brain “encodes two considerations central to the distributive justice calculus and shed light on the cognitivist/sentimentalist debate regarding the psychological underpinnings of distributive justice”.

They suggested the findings support the notion that “a sense of fairness is fundamental to distributive justice, but, as suggested by moral sentimentalists, is rooted in emotional processing”.

On a more general level they suggested that:

“Emotional responses related to norm violations may underlie individual differences in equity considerations and adherence to ethical rules.”

“The Right and the Good: Distributive Justice and Neural Encoding of Equity and Efficiency.”
Ming Hsu, Cédric Anen, and Steven R. Quartz.
Science.Published Online May 8, 2008.
DOI: 10.1126/science.1153651.

Click here for Abstract.

Sources: Science press release and study abstract.

Written by: Catharine Paddock, PhD