In 1981, students in the US were asked, "Are you a better driver than most people in this group?" More than 90% said yes.

But only half of a group can be above the middle! Many people think good things will happen to them and bad things will happen to others. This is called optimism bias. It helps us try new things, but it can also stop us from preparing for danger.

Optimism bias is the tendency to believe that we are luckier or more skillful than other people. In a 1981 study, more than 90% of American students said they drove better than the average person in their group, which is mathematically impossible. A large replication in 2023 found the same pattern.

In 1980, another study showed that students expected good events, like getting a good job, to happen to themselves more than to others, and bad events, like getting sick, to happen to themselves less. A 2011 brain study suggested one reason: people changed their beliefs a lot after good news but only a little after bad news. However, some researchers argue that this result may partly come from the way it was calculated.

Optimism bias refers to people's tendency to see themselves as luckier, safer or more capable than others. In a 1981 study of about 160 students, more than 90% of the Americans and roughly 70% of the Swedes rated their own driving skill as above the group median, an outcome that cannot be true for so many. Although the sample was small, a preregistered replication with around 1,200 participants published in 2023 reproduced the effect.

In 1980, a separate study found that students judged desirable events, such as owning a home, as more likely to happen to themselves than to their peers, and undesirable events, such as divorce or illness, as less likely. Why does such optimism persist? A 2011 neuroscience study reported that people revised their risk estimates substantially after favorable information but only slightly after unfavorable information.

However, in 2016 another team argued that the method used to calculate belief updating could generate this asymmetry even in the absence of any bias, and the original researchers have responded that the effect remains. The debate is unresolved. Optimism can motivate people to take on challenges, but it may also lead them to neglect seat belts, health checks or disaster preparation.