The optimism bias

Tali Sharot, UCL neuroscientist and author of The Optimism Bias, presents the remarkable finding that about 80% of people are systematically, measurably, and predictably over-optimistic about their own futures — and that this bias, far from being a cognitive error to be corrected, appears to be a deeply adaptive feature of the human mind with significant benefits for health, motivation, and resilience.

Key Arguments

1. Optimism bias is universal and measurable. People consistently overestimate their chances of good outcomes and underestimate their chances of bad ones. This applies across cultures, ages, and domains — from predicting career success to health outcomes to relationship longevity. Optimism is not just a personality trait; it is a default cognitive stance.
2. The brain updates beliefs asymmetrically. When people receive better-than-expected information about their futures, they update their beliefs significantly toward optimism. When they receive worse-than-expected information, they update far less. This asymmetric belief updating, driven by the inferior frontal gyrus, is the neural mechanism of optimism bias.
3. Optimism is linked to better health outcomes. Optimists live longer, recover from surgery faster, have stronger immune systems, and are more likely to engage in health-protecting behaviors. The effect is partially mediated through reduced chronic stress and greater motivation to act on health information.
4. The dark side: we underestimate risks that affect us personally. While optimism bias produces resilience and motivation, it also makes people systematically underestimate their personal risk of cancer, divorce, and financial setbacks — even when they correctly assess average population risks. The challenge is to harness optimism without being blinded by it.

Evidence Context

Sharot’s research is among the most mechanistically precise in the psychology of belief and expectation. The asymmetric updating finding is well-controlled and neuroimaging-supported. The health benefits of optimism are drawn from a large epidemiological literature (including the famous nun study, the Mayo Clinic optimism-longevity study). The practical challenge she raises — calibrating optimism to maintain its benefits without ignoring genuine risks — is an active research area in decision science and behavioral economics.