Journal · Method
The pre-mortem: assume it already failed
One of the few debiasing techniques that is cheap, fast, and supported by a specific measured effect. The trick is grammatical: past tense, not conditional.
What is a pre-mortem? A technique where a team imagines a plan has already failed and explains why, rather than assessing whether it might fail. Prospective hindsight of this kind increased correct identification of reasons by roughly 30% in the study the method derives from (Mitchell, Russo and Pennington, 1989).
The underlying result comes from work on prospective hindsight by Mitchell, Russo and Pennington, published in the Journal of Behavioral Decision Making in 1989. Asking people to explain a future event as though it had already occurred produced substantially more reasons than asking them to assess its likelihood, and the reasons were more concrete and more action-shaped rather than abstract. Klein later popularised the technique for teams as the pre-mortem.
Why the tense matters
"Could this fail?" invites a judgement, and the judgement is usually reassuring, especially about a plan you helped write. "It failed. Why?" is a different cognitive task: it presupposes the outcome and asks for an explanation, and explanation is something people are very good at generating.
Certainty is what does the work. Not pessimism.
Running one properly
- State the failure as fact. "It is twelve months from now. This was a clear failure." No hedging, no "if".
- Write before speaking. Two minutes silent. Otherwise the first person to talk sets the frame for everyone.
- Collect causes, do not debate them. Debate at this stage kills the ones that sound implausible, and implausible-sounding causes are exactly the point.
- Then rank by plausibility and cost, and turn the top two into something observable before the decision is locked.
Where it fails
When it is run after the decision is effectively made, it becomes a ritual and produces polite risks nobody intends to act on. And it does not work on someone who cannot say the failure sentence with a straight face. If the room cannot accept the premise for ten minutes, the exercise returns nothing.
Five Peers editorial note. Sources named in the text.
Pre-mortem is one of the twelve, and it is in the library because of the result, not the slide.
Compose my board