Conversely, the more someone dreads or fears a potential outcome, the less likely they think it is to happen. In November 2007, economists in the Philadelphia Federal Reserve’s Survey of Professional Forecasters predicted just a 20 percent chance of “negative growth”—read: decline—in the U.S. economy any time in 2008, despite visible signals of an impending recession. There is, the economist Sergey Smirnov wrote in a review of economists’ botched predictions on the 2008 recession, “some deep inherent unwillingness to predict undesirable things.”

But people’s thinking isn’t as simplistic as “I wish it to happen, so it will” or, “I don’t want it to happen, so it won’t.” Self-interest influences our predictions in subtler ways.

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The Rutgers University psychologist Neil Weinstein discovered unrealistic optimism by accident. It was the late 1970s, and for no particular reason he had asked study subjects to rate their likelihood of experiencing certain negative future events, like getting divorced, fired, or mugged, from “below average risk” to “above average risk.” This was back when data were manually entered on yellow punch cards. So he was sitting at his punch-card machine punching people’s responses when he realized that “all the responses were on the below-average side of the scale.”

Unrealistic optimism is thinking that good things are more likely to happen to you than to other people, whereas bad things are less likely. It’s not outright denial of risk, says Weinstein. “People don’t say, ‘It can’t happen to me.’ It’s more like, ‘It could happen to me, but it’s not as likely [for me] as for other people around me.’” People predict that they’re less likely than others to experience illness, injury, divorce, death, and other adverse events—even when they’re exposed to the same risk factors. For instance, someone might think she’s less prone to diabetes than others, even if she weighs the same, eats the same, shares similar family history with, and has the same lifestyle as the people she's comparing herself to.

Take these Pew Research Center findings: In 2015, 65 percent of a representative sample of American workers predicted that automation would monopolize most of the work currently performed by humans within 50 years. But 80 percent of workers believed that their own jobs would remain intact. In essence, they admitted that automation posed a threat to workers but assumed they were less susceptible than average to its effects.

Anxiety affects people’s predictions subliminally. For example, they may unwittingly only gather and synthesize facts about their prediction that support the outcome they want. This process may even be biologically ingrained: Neuroscience research suggests that facts supporting a desired conclusion are more readily available in people’s memories than other equally relevant but less appealing information. Our predictions are often less imaginative than we think.