6.6 KiB
Premortem Principles
The Psychology of Overconfidence
Why We're Systematically Overconfident
The Planning Fallacy:
- We focus on best-case scenarios
- We ignore historical delays and failures
- We assume "our case is different"
- We underestimate Murphy's Law
Research:
- 90% of projects run over budget
- 70% of projects run late
- Yet 80% of project managers predict on-time completion
The fix: Premortem forces you to imagine failure has already happened.
Hindsight Bias
The "I Knew It All Along" Effect
What it is: After an outcome occurs, we believe we "always knew" it would happen.
Example:
- Before 2008 crash: "Housing is safe"
- After 2008 crash: "The signs were obvious"
Problem for forecasting: If we think outcomes were predictable in hindsight, we'll be overconfident going forward.
The premortem fix: By forcing yourself into "hindsight mode" BEFORE the outcome, you:
- Generate the warning signs you would have seen
- Realize how many ways things could go wrong
- Reduce overconfidence
The Power of Inversion
Solving Problems Backward
Charlie Munger:
"Invert, always invert. Many hard problems are best solved backward."
In forecasting:
- Hard: "Will this succeed?" (requires imagining all paths to success)
- Easier: "It failed - why?" (failure modes are more concrete)
Why this works:
- Failure modes are finite and enumerable
- Success paths are infinite and vague
- Humans are better at imagining concrete negatives than abstract positives
Research on Premortem Effectiveness
Gary Klein's Studies
Original research:
- Teams that did premortems identified 30% more risks
- Risks identified were more specific and actionable
- Teams adjusted plans proactively
Key finding:
"Prospective hindsight" (imagining an event has happened) improves recall by 30%
Kahneman's Endorsement
Daniel Kahneman:
"The premortem is the single best debiasing technique I know."
Why it works:
- Legitimizes doubt - In group settings, dissent is hard. Premortem makes it safe.
- Concrete > Abstract - "Identify risks" is vague. "Explain the failure" is concrete.
- Defeats groupthink - Forces even optimists to imagine failure.
Outcome Bias
Judging Decisions by Results, Not Process
What it is: We judge the quality of a decision based on its outcome, not the process.
Example:
- Drunk driver gets home safely → "It was fine"
- Sober driver has accident → "Bad decision to drive"
Reality: Quality of decision ≠ Quality of outcome (because of randomness)
For forecasting: A 90% prediction that fails doesn't mean the forecast was bad (10% events happen 10% of the time).
The premortem fix: By imagining failure BEFORE it happens, you evaluate the decision process independent of outcome.
When Premortems Work Best
High-Confidence Predictions
Use when:
- Your probability is >80% or <20%
- You feel very certain
- Confidence intervals are narrow
Why: These are the predictions most likely to be overconfident.
Team Forecasting
Use when:
- Multiple people are making predictions
- Groupthink is a risk
- Dissent is being suppressed
Why: Premortems legitimize expressing doubts without seeming disloyal.
Important Decisions
Use when:
- Stakes are high
- Irreversible commitments
- Significant resource allocation
Why: Worth the time investment to reduce overconfidence.
When Premortems Don't Help
Already Uncertain
Skip if:
- Your probability is ~50%
- Confidence intervals are already wide
- You're confused, not confident
Why: You don't need a premortem to tell you you're uncertain.
Trivial Predictions
Skip if:
- Low stakes
- Easily reversible
- Not worth the time
Why: Premortems take effort; save them for important forecasts.
The Premortem vs Other Techniques
Premortem vs Red Teaming
Red Teaming:
- Adversarial: Find flaws in the plan
- Focus: Attack the strategy
- Mindset: "How do we defeat this?"
Premortem:
- Temporal: Failure has occurred
- Focus: Understand what happened
- Mindset: "What led to this outcome?"
Use both: Red team attacks the plan, premortem explains the failure.
Premortem vs Scenario Planning
Scenario Planning:
- Multiple futures: Good, bad, likely
- Branching paths
- Strategies for each scenario
Premortem:
- Single future: Failure has occurred
- Backward path
- Identify risks to avoid
Use both: Scenario planning explores, premortem stress-tests.
Premortem vs Risk Register
Risk Register:
- List of identified risks
- Probability and impact scores
- Mitigation strategies
Premortem:
- Narrative of failure
- Causal chains
- Discover unknown unknowns
Use both: Premortem feeds into risk register.
Cognitive Mechanisms
Why Premortems Defeat Overconfidence
1. Prospective Hindsight Imagining an event has occurred improves memory access by 30%.
2. Permission to Doubt Social license to express skepticism without seeming negative.
3. Concrete Failure Modes Abstract "risks" become specific "this happened, then this, then this."
4. Temporal Distancing Viewing from the future reduces emotional attachment to current plan.
5. Narrative Construction Building a story forces causal reasoning, revealing gaps.
Common Objections
"This is too negative!"
Response: Pessimism during planning prevents failure during execution.
Reframe: Not negative - realistic. You're not hoping for failure, you're preparing for it.
"We don't have time for this."
Response:
- Premortem: 30 minutes
- Recovering from preventable failure: Months/years
Math: If premortem prevents 10% of failures, ROI is massive.
"Our case really is different!"
Response: Maybe. But the premortem will reveal HOW it's different, not just assert it.
Test: If the premortem reveals nothing new, you were right. If it reveals risks, you weren't.
Practical Takeaways
- Use for high-confidence predictions - When you feel certain
- Legitimate skepticism - Makes doubt socially acceptable
- Concrete failure modes - Forces specific risks, not vague worries
- Widen confidence intervals - Adjust based on plausibility of failure narrative
- Set kill criteria - Know what would change your mind
- Monitor signposts - Track early warning signals
The Rule:
If you can easily write a plausible failure narrative, your confidence is too high.
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