Brain Scan Predicts Difference Between Altruistic And Selfish People
Funded by the National Institutes of Health, the research was conducted at the Duke University Medical Centre in Durham, North Carolina, and will be published in the February 2007 print issue of Nature Neuroscience. An early online edition is now available.
Altruism is defined as a tendency for people to put the welfare of others above their own. And what this research suggests is that altruism stems from being able to tune into the intention and actions of others which then leads to thinking along the lines of "perhaps I had better treat them like I would want to be treated".
Until now scientists have been puzzled by altruism because on the face of it the act offers no survival advantage to the individual. But perhaps, the survival advantage comes from an ability to perceive the intention of others, and therefore to anticipate their actions.
The researchers invited 45 volunteers to play a computer game and also to watch the computer play the game. In some instances successful completion of the game resulted in them winning money for themselves, and in other instances it resulted in money being donated to a charity each person had chosen at the beginning of the experiment. During these activities the researchers took functional magnetic resonance imaging (fMRI) scans of the participants' brains.
fMRI is a harmless procedure that detects activity in nerve cells in the brain by measuring changes in oxygen levels using magnetic pulses.
The scientists were surprised by the results. They were expecting to see activity in the brain's reward centres. And for the results to show that people who perform altruistic acts do so because they feel good about it, hence the expected activity in the reward centres.
But what they found was that another part of the brain was also involved, and it was quite sensitive to the difference between doing something for personal gain and doing it for someone else's gain. This part of the brain is called the posterior superior temporal cortex (pSTC). The pSTC sits in the back of the brain and appears to help us tune into perceiving and giving meaning to the actions of others. It is not focused on reward.
In the next stage the scientists asked the participants questions about type and frequency of their altruistic or helping behaviours. They then analysed the responses to generate an estimate of a person's tendency to act altruistically and compared each person's level against their fMRI brain scan. The results showed that pSTC activity rose in proportion to a person's estimated level of altruism.
The researchers suggest that the study shows that altruistic behaviour may arise from how we view the world rather than how we act in it.
"We believe that the ability to perceive other people's actions as meaningful is critical for altruism," said one of the team.
It could be that understanding the parts of the brain that enable us to give meaning to what we observe around us could help us understand disorders like autism. This research team has already started another project looking at the early development of this part of the brain.
"Altruism is associated with an increased neural response to agency."
Dharol Tankersley, C Jill Stowe, and Scott A Huettel.
Nature Neuroscience Published online: 21 January 2007; doi:10.1038/nn1833
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