Optimism bias
Expecting good things to be more likely, and bad things less likely, for yourself than for others or than the evidence supports.
What drives it
Sustains motivation, risk-taking and mood. People update more on good news about themselves than on bad (Sharot), which keeps the rosy forecast in place.
How it shows
Work
Timelines that always slip. Founders sure they will beat the base rate. Hiring someone with known red flags because 'it will be different here'. Assuming a difficult colleague will settle down once the reorganisation is over.
Relationships
Expecting a partner to change after the wedding, the move or the baby. 'Divorce happens to other people.' Believing a parent will be different this Christmas.
Self
You hear the base rate and feel it does not apply to you. When judging people, you predict their future behaviour from your hopes rather than from their past.
What tells it apart
Illusion of control: Illusion of control credits your own actions for outcomes; optimism bias expects the good outcome even with no action, as in 'it'll work out'.
Manic defence: Manic defence is driven, excited optimism that wards off loss or depression and collapses when it fails; optimism bias is calm, everyday and sits alongside ordinary mood.
Hubris syndrome: Hubris syndrome develops with sustained power and includes contempt for others' advice; optimism bias is near-universal and needs neither power nor contempt.
A test
Compare the person's forecast with the base rate and with their own track record on similar forecasts; persistent overshoot after feedback confirms it.
Questions to carry
- Set against how similar plans have gone, for this person and for most others, where does this forecast land?
- Which of my plans assumes the usual odds don't apply to me, and what makes me think so?
How strong the research is
moderate. People reliably rate their own risks below average, but Harris and Hahn (2011) showed part of the group-level effect can arise from statistical artefacts, and unrealistic optimism in a particular individual is harder to establish.
Where it comes from
Neil Weinstein, 1980; Daniel Kahneman and Amos Tversky, 1979 (planning fallacy); Tali Sharot, 2011 (asymmetric updating)