But things are different when she is told that she guessed too low, and the chances of her getting cancer are forty percent. Then she will raise her idea of her own chances. But she will raise her estimate by only a small amount.

Now she might think that her chances are about thirty-two percent. But she would not estimate the real average of forty percent.

The study results show that people usually accept good news but reject bad news. They reject the bad news even when they are told the truth.

It seems we think we are above average when dealing with good things. And we think we are below average in suffering bad things that might happen to us.

BOB DOUGHTY: The machine used to examine the test subjects’ brains is called an FMRI, or functional magnetic resonance imaging scanner. When the people thought good thoughts about their future, activity in the frontal lobes, or areas, of their brains increased.

But when the volunteers thought about negative things, there was no increased activity in these frontal lobe brain areas. Scientists believe this means the human brain naturally ignores the chances for negative future events. But they do not yet know why this happens.

SHIRLEY GRIFFITH: So, as Bobby McFerrin advises:

“Don’t worry. Be happy”

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Remember that the “optimism bias” can cause problems.

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BOB DOUGHTY: A listener in Vietnam wrote to thank us for the recent program about how to become a doctor in the United States. Kim Anh Nguyen was wondering if we also could explain the process of becoming a pharmacist.