Mental Models as Lens Switching
Borrow another vantage point instead of auditing yourself for bias
- Difficulty
- Moderate
- Time to result
- ~months to results
- Steps
- 6
- Confidence
- 87%
Parrish's mechanism starts from a diagnosis: the root of cognitive bias is the assumption that what we see is all there is. His physics image is the ball carried on a moving train — stationary relative to you, moving at sixty miles an hour to the observer outside. Bias checklists fail against this because they are applied after the decision, and the smarter you are, the better the story you tell about why the bias does not apply. Lens switching attacks the geometry instead of the psychology. You deliberately occupy another vantage point: a specific person ('how would Tim Ferriss think about this?'), a different discipline such as biology, or a structured question like 'and then what?', inversion, or the stoic pre-mortem. Each pass slightly shrinks the blind spot rather than justifying the existing view.
Origin
While writing his early blog, Parrish tried to reconcile how Kahneman derived cognitive biases with the fact that Buffett and Munger rarely discussed biases yet seemed to avoid them. He concluded that biases diagnose the past but do not prevent the future, and that perspective-shifting tools do. The work later became the Great Mental Models book series.
Core principles
- 01The source of all bad decisions is blind spots.
- 02Cognitive biases explain past mistakes well and prevent future ones badly.
- 03Every bias traces back to believing what you see is all there is.
- 04A model does not tell you the answer; it changes what you can see.
- 05Adopting a specific person's perspective is more usable than a generic checklist.
How to run it
- 1
Write down your current view
Capture the problem exactly as you see it now, so you have a baseline to compare each later lens against.
- 2
Adopt a named persona
Pick a specific person whose thinking you know and genuinely reason through the problem as them, using what you know of their priorities and constraints.
Pro tip Named people beat abstract archetypes because you can predict their actual objections.
Watch out This only works if you know the person's thinking well enough to be surprised by it.
- 3
Invert
Flip from 'how do I get what I want' to 'what outcomes must I avoid', then work backwards from avoiding them.
- 4
Run a pre-mortem
Assume the decision has already failed and write the account of why. The stoics have used this device for millennia.
- 5
Extend forward with 'and then what?'
Take your preferred answer and describe the state it lands you in, to catch consequences the current frame hides.
- 6
Compare what each lens revealed
Set the lenses side by side and note the specific facts each one surfaced that the original framing did not contain.
Pro tip The value is in the delta between lenses, not in any single lens being right.
Watch out Collecting models without applying them is cognitive indigestion, not judgment.
In the wild
Parrish uses a grade-nine physics setup to locate the root of bias. You stand on a train moving at sixty miles an hour holding a ball. Relative to you, the ball is not moving. To someone watching the train pass, the ball is travelling at sixty miles an hour. Both observations are correct and neither is available from the other position. Every cognitive bias, he argues, is a version of only ever occupying the position on the train.
→ Reframes bias as a problem of vantage point, which is fixable by moving, rather than a problem of discipline.
Ferriss points to Edward de Bono's Lateral Thinking and Six Thinking Hats as an early formalisation of the same mechanic: a practice that forces you to examine one situation through a deliberately different lens, a different set of questions, and a different perspective on each pass. The specific hats matter less than the enforced rotation.
→ A repeatable practice for producing multiple views of a single situation.
Common mistakes
Auditing yourself against a bias checklist
You reach for the list after deciding, so you use confirmation bias to clear yourself of every other bias.
Collecting models instead of applying them
Force-feeding yourself rules and biases produces cognitive indigestion, where you fail from too much information rather than too little.
Using vague personas
'What would a smart person do?' returns your own view in a costume; only a specific, well-understood person generates genuinely new objections.
Is it for you?
Best for
Analytical people who have read the behavioural-economics canon and still keep making the same category of mistake.
Not ideal for
Fast, low-stakes, reversible calls where the deliberation costs more than the error.
From the transcript
“the source of all bad decisions is blind spots mental models allow you to see a problem through a different lens”
“cognitive biases are really good at explaining why you made a mistake in the past but the really poor preventing you from making mistakes in…”
“the smarter you are the the better the stories get and the more believable they get”
From the episode
#695: Shane Parrish on Wisdom from Warren Buffett, Rules for Better Thinking, How to Reduce Blind Spots, The Dangers of Mental Models, and More