Scientists have discovered that people who are very optimistic about the outcome of events could in fact have a "faulty" brain.

The study, which was published in Nature Neuroscience, suggests that the brain is very good at processing information, whereas some people ignore anything negative, leading them with a positive outlook.

This had lead scientists to believe that people who are continuously optimistic when reality challenges their beliefs is due to a 'faulty' function of the brain's frontal lobe.

"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," said Tali Sharot of the Wellcome Trust Centre for Neuroimaging at UCL (University College London).

"But it can also mean we are less likely to take precautionary action, such as practising safe sex or saving for retirement. So why don't we learn from cautionary information?" he asked.

In the study, volunteers were presented with a series of "bad events" - including car theft, divorce or Parkinson's disease, whilst lying in a functional magnetic resonance imaging (fMRI) scanner, which measures activity in the brain.

They were then asked to estimate the probability of such events happening to them in the future. All together they saw 80 events.

The volunteers were then told how likely these events were in reality. At the end of the session, the participants were asked to rate the probabilities again.

The research found that people updated their estimates based in the information given, but only if the information was better than expected.

"Our study suggests that we pick and choose the information that we listen to. The more optimistic we are, the less likely we are to be influenced by negative information about the future. This can have benefits for our mental health, but there are obvious downsides," Sharot adds.

"Many experts believe the financial crisis in 2008 was precipitated by analysts overestimating the performance of their assets even in the face of clear evidence to the contrary," said Sharot.

"Smoking kills messages don't work as people think their chances of cancer are low. The divorce rate is 50%, but people don't think it's the same for them. There is a very fundamental bias in the brain."