A person beaming with positivity all the time could be less inclined to take preventive actions against disasters, a British study says.

Previously, a separate British study revealed a link between the gene 5-HTT and individual satisfaction. People with the long version of the gene are more likely to be cheerful, while those with the short version tend to be the opposite, the study showed.

This time a study, published in Nature Neuroscience, concludes that seeing the light at the end of the tunnel all the time could result in failure to see an oncoming train.

In its story, The New Zealand Herald warned a penchant for wearing rose-tinted glasses may mean a failure to store risk awareness in a key part of the brain.

Tali Sharot, a professor at University College London, wanted to find out why so many people remain stubbornly, even pathologically, optimistic even on very gloomy occasions.

Nineteen volunteers participated in the study, during which Sharot and colleagues monitored subjects in a functional magnetic resonance imaging scanner as they were confronted with life situation scenarios, ranging from unpleasant to catastrophic.

Having their car stolen, getting fired from their job, developing Parkinson's disease or cancer were among 80 scenarios evoked, the Herald reported.

After each hypothetical disaster, the volunteers were asked to estimate the odds of the misfortune hitting them personally. Researchers would then tell the subjects the true average probability of the risk while they were still in the scanner.

After some time, the volunteers were asked again to guess the odds for experiencing each scenario, and this part showed that the volunteers updated their initial estimates when the revealed true figures were less gloomy.

For example, if a volunteer had initially guessed a 50 per cent chance of contracting cancer but the average likelihood turned out to be 30 per cent, the volunteers would sharply reduce their initial risk prediction the second time around.

On the other hand, if the odds were worse than original guess, the volunteers simply ignored the true statistics.

"Our study suggests that we pick and choose the information that we listen to," said Sharot, adding, "The more optimistic we are, the less likely we are to be influenced by negative information about the future," said Sharot.

In the brain scans, all participants showed increased activity in their frontal lobes - the brain part strongly associated with emotional control - whenever the real numbers were better than expected. This implied that the new information was being processed and stored.

But when the news was worse than the first guess, respondents who had rated highest for "optimism" showed the least activity in their frontal lobe when being informed of the true statistics.

All the participants took a personality test ahead of the brain scans to determine their optimism levels.

Sharot said their study showed those who rated highest for optimism seemed to simply refuse to perceive risks.

"Seeing the glass as half full rather than half empty can be a positive thing - it can lower stress and anxiety, and be good for our health and well-being," she said.

"But it can also mean that we are less likely to take precautionary action, such as practising safe sex or saving up for retirement," she further explained.

Sharot went as far as saying that many experts believed that the financial crisis that began in the fall of 2008 was in large part caused by wishful thinking about rising property values and the ability to downplay or dismiss levels of debt.