Life is a little like going for a walk in the rain. Sooner or later you’re going to get wet – be that in the form of bad health, unrequited love or job redundancy. It’s remarkable that we ever venture out. We do so sheltered under the umbrella of “unrealistic optimism”. Depressed people aside, the rest of us underestimate the likelihood that bad things will happen to us and overestimate the likelihood of good outcomes. Asked to imagine positive scenarios, we do so with greater vividness and more immediacy than when asked to picture negative occurrences – our images of those are hazy and distant.

Now Tali Sharot (author of the forthcoming book The Optimism Bias) and her colleagues have investigated the brain mechanisms underlying this rosy outlook. Sharot had participants estimate their likelihood of experiencing 80 adverse life events from developing Alzheimer’s to being robbed. After they gave each estimate, the participants were given the correct average probability for a person in their socio-economic circumstances. In a subsequent testing session, participants had a second chance to forecast their risk of experiencing the same 80 misfortunes. Throughout this process, Sharot scanned the activity of the participants’ brains.

One key finding is that the participants showed a bias in the way that they updated their estimates, being much more likely to revise an original estimate that was overly pessimistic than to revise an original estimate that was unduly optimistic (79 per cent of participants showed this pattern). The researchers checked and this difference wasn’t to do with the positive feedback being remembered better, but purely to do with it being taken account of more than negative feedback.

There were some intriguing neural insights. Discovering that an initial estimate was unduly pessimistic was associated with increased activity across the frontal lobes, in left inferior frontal gyrus, left and right medial frontal cortex/superior frontal gyrus, and also in the right cerebellum – and this increased activity correlated with the participants’ subsequent updating of their estimate in the second round of predictions. By contrast, discovering that they’d been overly optimistic was associated with reduced activity in the inferior frontal gyrus extending into precentral gyrus and insula, and again this activity change was related to the likelihood that the participants would revise their estimate in the second round of predictions.

The researchers also compared the brain activity between the most and least optimistic participants. High scorers in trait optimism showed less of the activity drop in inferior frontal gyrus when they discovered they’d been overly optimistic. That is, their brains seemed to ignore information educating them about the depressing reality of their chances of experiencing adversity later in life. In contrast, the brains of the high and low optimists responded to desirable feedback (in which they learned they’d been unduly pessimistic) in exactly the same way.

“Our findings offer a mechanistic account of how unrealistic optimism persists in the face of challenging information,” said Sharot and her team. “We found that optimism was related to diminished coding of undesirable information about the future in a region of the frontal cortex (right inferior frontal gyrus) that has been identified as being sensitive to negative estimation errors.”

The researchers also reflected on the wider implications of their research. They said that unrealistic optimism likely evolved to enhance exploratory behaviour and has the benefit of reducing stress and anxiety. However, they said that this rosy view comes at a cost. “For example,” they said, “unrealistic assessment of financial risk is widely seen as a contributing factor in the 2008 global economic collapse.”

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Sharot, T., Korn, C., and Dolan, R. (2011). How unrealistic optimism is maintained in the face of reality. Nature Neuroscience, 14 (11), 1475-1479 DOI: 10.1038/nn.2949

Post written by Christian Jarrett for the BPS Research Digest.