Our outlook for the future tends to be unrealistically positive. Most of us expect to live a longer, healthier and more successful life than evidence suggests is likely. This optimistic bias seems to be important to good health, as a pessimistic outlook has previously been linked to depression. Several brain regions have been implicated in negative emotions — could the brain also be responsible for generating our rose-tinted view of the future?

Tali Sharot, now a postdoc at University College London, didn't set out to answer this question. Brain-imaging data indicate that emotion and memory are neurologically intertwined, and Sharot wondered whether the same was true of emotion and future predictions. The results of a pilot study changed the direction of her work.

In the pilot — which Sharot conducted while a postdoc with Elizabeth Phelps in New York University's psychology department — she asked volunteers to rate each of 80 events as positive, negative or neutral. The volunteers overwhelmingly cast the best light on these hypothetical future events, even when the scenarios they considered weren't intended to elicit optimism.

For example, one participant rated 'going to a museum' as positive, because she imagined meeting a romantic partner there who presented her with flowers. And several rated 'the end of a relationship' as positive, saying that they expected their next romantic partner to be more satisfactory. “We had trouble getting people to imagine negative events,” says Sharot. “They made them neutral and even positive.” She hadn't anticipated that it would be so difficult to get people to think of their future in a negative way, and, she says, “that made me think of the positivity bias”.

The next step was to set up a study similar to the pilot but with an imaging component. Volunteers were asked to read descriptions of events on a computer screen while inside an MRI scanner. The events were labelled either 'past' or 'future' to indicate whether the volunteers should think of events in the past or imagine an event that might happen in the future. When they had formed a clear mental picture, the volunteers pressed a button — to capture their brain's activity — then labelled the event as positive, negative or neutral. After they emerged from the machine, volunteers were asked to describe the image and rate how vivid it was and how long ago or far into the future it took place.

The results were striking. “I could pretty much predict what their optimism scale was just from the MRI data, before they e-mailed me back the questionnaire,” Sharot says. Matching the questionnaires to the MRI images only confirmed her hunches (see page 102).

The images showed that the same parts of the brain that are involved in processing memory and emotion have a role in anticipating and rating the future. They also showed a neurological basis for optimism. “When behavioural data are that robust, there's usually a link to some observable neural mechanism,” Sharot says. “When we looked at the MRI data, it was clear that the activation was much stronger for the positive-rated events.”

Sharot says she enjoyed the research, and not just because the experiments went relatively smoothly and produced robust results. She enjoyed seeing volunteers' glass-half-full outlooks manifest themselves by means of brain imaging — basically imaging the hardiness of the human spirit. “I'm very optimistic myself,” Sharot says. “I can relate.”