The bright-side bias

30 September 2012
Posted by Ginny Smith.

The brain basis of the human tendency to always look on the bright side has been revealed by new research.Scientists have known for some time that volunteers will take on board new information that has a positive message much more readily than negative information, which they tend to ignore. Human_brain_imageSome speculate that this "good news / bad news effect", as it's known, might underlie financial bubbles, and psychologists also suspect that it accounts for natural optimism, over-confidence and poor judgements made during critical medical or health situations.The reason for this has been a mystery. But now, UCL scientist Ray Dolan and his colleagues have used a technique called TMS -that's transcranial magnetic stimulation - to temporarily deactivate a brain region called the inferior frontal gyrus (IFG), making the effect disappear.The inferior frontal gyrus has previously been linked to self-inhibition and also to updating what we believe about ourselves and the world around us. Publishing in PNAS this week, the UCL team asked a group of volunteers to estimate the likelihoods of their suffering 40 different adverse events ranging from developing Alzheimer's to being robbed. The subjects were then presented with data showing the true frequency of each event in their representative populations. While they were reviewing this data, TMS was applied to the subjects' brains to switch off either their right or left inferior frontal gyrus, or an unrelated "control" part of the brain. They were then asked to re-estimate their risks for each of the adverse life events they had considered previously.The researchers found that inhibiting the right IFG, or a control brain region, had no effect. Just as before, the subjects revised their estimations in response to good news - when they found out they were less likely to suffer one of these events than they had thought - but they buried the bad news. Inhibiting the left IFG, though, produced a radical rethink on the part of the subjects, with 60% of them ceasing to ignore the bad news as they had done before.( Examining the data confirmed that the effect wasn't because subjects were less good than they had been previously at incorporating good news, rather their ability to take on board the bad had improved. )As the researchers point out in their paper, there are positive benefits to regarding the metaphorical glass as half full rather than half empty, because emphasising the pros and ignoring the cons "increases exploratory behaviour and reduces stress and anxiety, a factor that has links with physical and mental well-being..."In other words, it has probably evolved to help us to avoid depression and anxiety, and so be better able to function in the world...

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