This is a Lexicon entry: the mechanism, when it shows up, and the countermeasure. The full correction, with real-world cases and the audit prompt, hasn't been written yet.
Definition
Primary concept: Planning Fallacy. This entry examines a specific dimension; see Planning Fallacy for the broader mechanism.
When it shows up
Personal forecasts: how long your project will take, how your relationship will fare, how your health will hold up. Any prediction about your own future. Modern context: A founder building a second company after a failed first one accurately describes the base rate failure statistics for startups in their sector - and then explains in detail why their specific situation differs from all the failed cases. The explanation is coherent. The outcome distribution is not. High-stakes instance: New business formation - approximately 50% of new businesses fail within five years; surveys of founders at launch show the vast majority believe they will be in the surviving 50%, with modal estimate of personal failure probability below 20%. Failure mode: Self-directed forecasts systematically assume above-average outcomes, fewer obstacles and faster progress than base rates for similar situations. The forecaster has privileged access to reasons why their case is special; they do not have access to the symmetric reasons in other people's cases. Estimated cost: High - often irreversible where this bias dominates unchecked decisions.
Failure mode
Self-directed forecasts systematically assume above-average outcomes, fewer obstacles and faster progress than base rates for similar situations. The forecaster has privileged access to reasons why their case is special; they do not have access to the symmetric reasons in other people's cases.
Countermeasure
Forecast as if you were predicting a stranger's outcome with identical parameters. Use the stranger's base rate, not your felt confidence, as the estimate. When correction costs more than the bias: For motivation and entrepreneurial action: optimism bias is a precondition for attempting difficult things. Most ventures that succeeded would not have been attempted by a perfectly calibrated decision-maker. Correct optimism bias for planning and resource allocation; preserve it for the decision of whether to begin.
Related traps
Also connected in the map9 more, locked
Credit & first seen
DiscoveredKahneman, D., Lovallo, D.&Sibony, O. (2011).'Before You Make That Big Decision.'Harvard Business Review. Buehler, R. et al. (1994). Journal of Personality and Social Psychology 67(3) source ↗
Also revealed
Entry #70 of 631 in The Lexicon · see the full Lexicon