Why humans will always look on the bright side of life

Researchers identified an “optimism bias” in the brain that resists accurate information about the world.

This means people “update” their beliefs accurately only when things turn out to be better than expected, not when they are worse than expected, according to the study by University College London scientists.

But humans’ natural propensity to see the glass as half full may not always be helpful, they suggested, pointing out that an unrealistic assessment of risk may lie behind calamities such as the credit crunch.

The scientists reached their findings by presenting people with a list of adverse events, including getting Alzheimer’s disease and being robbed, and asking them to estimate how likely it was these things would happen to them.

After giving their answers the volunteers were provided with the actual probability of each event hitting them.

They then rated the likelihood of the same events again, in order to measure how information about actual probabilities changes people’s estimates of the likelihood of misfortunes befalling them.

The study, published in the journal Nature Neuroscience, found people were far more likely to change their estimates when the feedback indicated that in reality they were much less likely to suffer an adverse event than originally believed.

But when they were told that an adverse event was much more likely than they had originally thought, they still tended to give the original, incorrect estimate.

The scientists also tracked brain activity during the task and found that activity in frontal areas faithfully tracked inaccurate estimates when things were better than expected.

Meanwhile, tracking the estimation errors when things were worse than people originally thought was much weaker.

The study’s authors, Tali Sharot, Christoph Korn and Raymond Dolan, wrote: “Our findings offer a mechanistic account of how unrealistic optimism persists in the face of challenging information.”

Underestimating risks could help humans by making them more likely to explore and by reducing stress and anxiety, they suggested.

“However, any advantage is likely to come at a cost,” they warned. “For example, an unrealistic assessment of financial risk is widely seen as a contributing factor to the 2008 global economic collapse.

“Dismissing undesirable errors renders us susceptible to view the future through rose-coloured glasses.”