Optimism bias
Also known as: Unrealistic optimism
We expect good things to befall us, and bad things to spare us, more than the odds allow.
What it means
Optimism bias is the systematic tendency to overestimate the likelihood of positive events and underestimate the likelihood of negative ones happening to oneself relative to others. The underlying mechanism appears to be asymmetric belief updating: people readily revise their estimates toward good news but discount or resist bad news, a pattern linked to differential activity in frontal brain regions. It is one of the most pervasive and persistent biases, found across cultures, ages, and domains from health to finance, and it is notably resistant to correction by mere information. A boundary condition is that the bias can shrink or reverse for people in depressed mood or under acute personal threat, and it is weaker when negative outcomes feel personally controllable. It matters because unrealistic optimism leads people to underprepare for real risks — skipping insurance, screening, or savings — even as a moderate dose supports resilience, motivation, and mental health.
Examples
Most smokers judge their own cancer risk as below that of the average smoker — a comparison that cannot be true for everyone at once.
Couples applying for a marriage licence guess the national divorce rate roughly right, then put their own chance of divorce at zero — a figure that cannot possibly be true of everyone in the queue.
Few households in a flood-prone town buy flood cover. Each pictures the water reaching the neighbours' door rather than their own, and the river declines to make that distinction.
First described in Neil Weinstein (1980); Tali Sharot.
Where this comes up
- Inside Squid Game: A Behavioral Scientist’s PerspectiveWhat makes Squid Game so compelling? Explore how optimism bias, loss aversion, social proof, and other behavioral scien…