Most of us hold unrealistically optimistic views of the future, research shows, downplaying the likelihood that we will have bad experiences. Now a study in Nature Neuroscience last October has found clues to the brain’s predilection for the positive, identifying regions that may fuel this “optimism bias” by preferentially responding to rosier information.

Tali Sharot, a University College London neurology researcher, and her colleagues asked 19 individuals between the ages of 19 and 27 to estimate their odds of experiencing 80 unfavorable events, such as contracting various diseases or being the victim of a crime. Participants were then told the actual average probability of each before repeating the exercise.

The participants revised most of their estimates the second time around, but 79 percent of those tested paid much more attention when their actual risk was lower than what they had initially guessed. After getting the good news, these subjects rated their risk for these events as significantly lower than they did earlier. In contrast, when they had underestimated their odds of meeting with a particular misfortune, they made less drastic revisions to their guess or none at all—clinging to their earlier belief that they would probably avoid the bad luck.

Using functional MRI, the resear­chers found areas in the prefrontal cortex, where conscious reasoning takes place, that were active when participants received infor­mation that was better than anticipated. The greater the difference between the subjects’ initial guess of their risk and the true probability, the more activity appeared in these regions, hinting that they contribute to positive error correction.

Activity in another part of the brain, the right inferior frontal gyrus, changed in response to discouraging information. There, however, activity did not correspond as closely with the magnitude of error in the participants’ initial risk estimates, matching the poorer correction later. That incon­sistent neural response was ob­served most clearly or most often in individuals who scored higher on standard tests for optimism as a personality trait.

This finding jibes with past studies that observed an optimism bias in about 80 percent of the population. Its absence can signal anxiety or depression. Yet being overly optimistic has consequences, too, Sharot says, preventing us from taking some precautions to avoid harm or misfortune. Realizing the brain’s partiality may be half the battle. “If you are aware of the optimism bias, you can commit to actions or rules that will help protect you,” Sharot notes.

This article was published in print as "Unflagging Optimism."