A mind for optimism

Brains are unabashedly optimistic, lapping up good news and virtually ignoring the bad, scientists report online October 9 in Nature Neuroscience. The findings could help explain why people overestimate their life span, underestimate their chances of getting a divorce, and scoff at the thought of bankruptcy.

The rosy results touch on a deep, systematic feature of human cognition that helps guide everyday behavior, says computational neuroscientist Read Montague of Virginia Tech in Blacksburg, who was not involved in the research. “This is an excellent paper,” he says.

In the study, Tali Sharot of University College London and colleagues examined what happens when reality doesn’t align with expectations. The team documented people’s predictions for 80 unpleasant events, including getting a cancer diagnosis, losing data through a computer crash, missing a flight or having a limb amputated.

While in a functional MRI brain scanner, the 19 study participants estimated their personal chances of experiencing each of the events. After the responses were registered, the scientists revealed the actual average risk of each event, then asked the participants to guess their own risk again.

When the news was better than expected, participants readily adjusted their answers. For instance, one participant estimated the risk of getting cancer to be 40 percent, but the average risk was only 30 percent. The second time around, the participant learned from that and lowered the personal estimate to 31 percent.

But when the news about risk was unexpectedly grim, most participants stuck closer to their original answers, the team found. The difference wasn’t simply due to people forgetting the bad news: In additional tests, subjects remembered the bad news just as well as the good news. “That was quite surprising,” Sharot says.

The brain appears to send a “Hey, you got it wrong” message when people got either good or bad news. For bad news in particular, fMRI scans generally revealed changes in activity on the right side of the brain in a region called the inferior prefrontal gyrus. However, when people who were separately classified as the most optimistic of the group got worse-than-expected news, the inferior prefrontal gyrus didn’t register the mistake. Those results suggest that brains with sunny outlooks are particularly immune to undesirable information.

Unbridled optimism could get people into trouble. Ignoring reality and expecting the best might make someone less likely to, say, buy health insurance or to keep the front door locked. But a positive outlook brings big benefits, too. “The fact that the brain is not showing this computation is because it’s adaptive at the end of the day. It’s actually better for us,” Sharot says, adding that some studies suggest optimists tend to live longer and be healthier.

To Montague, the most interesting question is why the brain would selectively update good news and ignore the bad. This asymmetry might have been helpful for some aspect of survival. For instance, a bias toward positive information might help an animal learn how to get food quickly, he says.