I once read an acquisition paper built around a 22-page deck and a slide titled "Our Next Gatorade". The target had younger buyers and a bit of momentum, so the resemblance was doing all the heavy lifting. Lower margins and weaker retailer loyalty were pushed aside as if they were clerical details. The category itself rewarded novelty more than habit, which should have made the comparison wobble. The room wanted the costume, not the denominator. That is representativeness bias.
The real error is probabilistic. A case looks typical, so people stop asking what usually happens or which local conditions would have to hold for the comparison to mean anything at all. Sample size goes missing soon after. Nobody in the room asks how often the lookalike cases actually paid off.
Roger Estall and I wrote Deciding after watching boards do this with a straight face. A neat analogy saves time and spares the sponsor harder questions. In my experience, that is why the room likes it so much.
Representativeness bias is the habit of treating a past success as proof that the same approach will work again, without checking whether the conditions that made it work still hold.
How representativeness bias turns resemblance into probability
Daniel Kahneman and Amos Tversky named the mechanism in 1972. They showed that people judge likelihood by resemblance, then underweight base rates and sample size. Scientists did it too, which spoils the cosy story that this mistake belongs to amateurs. Expertise often just gives the pattern-match a nicer tie.
Among the usual types of cognitive bias, this one is especially dangerous because it sounds practical when spoken aloud. "It looks like the last one" passes for wisdom in many boardrooms. I hear guesswork wearing the badge of precedent.
When that line appears, I go back to the Universal Decision-Making Method and force the carry-over claim onto the page. What exactly is supposed to travel, and what local fact would make the comparison ridiculous? Once those questions are written down, the great precedent often shrinks into an anecdote that arrived overdressed.
Representativeness bias made Chile look exportable
Chile's pension reform gave ministers and advisers a very saleable story: here was a modern reform with a success halo, ready for export. In Kurt Weyland's account of Latin American pension reform, Chile became the model that dominated the agenda in the 1990s. Bolivia and Peru leaned heavily on Chilean advice, and one participant said about 90 per cent of one reform was taken directly from Chile.
That suited the people selling the model. A portable success story gives politicians instant legitimacy and gives advisers a franchise they can keep exporting. It is tidy nonsense that travels well. The citizens who have to live inside the copied system do not get the same convenience. Weyland notes that Peru's support for reform rested partly on promised macroeconomic benefits without firm empirical backing. I have seen the same move in corporate papers for years. A local win is relabelled as a general rule because the simplified version is easier to approve.
Representativeness bias hides inside the word fit
When investors say fit, they often mean the founder matches a picture already sitting in their heads. Dana Kanze and her co-authors looked at 392 ventures and then ran an experiment with 130 investors. Female-led ventures in male-dominated sectors were treated as worse fits than similar ventures in female-dominated sectors, while male-led ventures escaped that penalty.
Call it one of the psychological biases if you like. I care more about the move itself. The investor is not judging the venture cleanly; the investor is checking whether the founder matches a prototype already trusted. Then the word fit performs its usual little trick and turns a private picture into professional judgement.
That is why I refuse to reduce representativeness bias to stereotyping. Stereotypes are one outlet for it, nothing more. The deeper mistake is letting resemblance sneak past probability and dress itself up as discernment.
Experience does not rescue the room from it
Experience often makes this bias harder to challenge, because it gives the comparison rank. Sjoerd Stolwijk and Barbara Vis tested elected Dutch local politicians and found conjunction errors in two of three scenarios, plus scope neglect in another. The main sample covered 211 elected officials from larger municipalities, some responsible for budgets around EUR600 million.
These were not undergraduates amusing a lab. They were elected adults making consequential judgements, and experience did not save them. In my experience, senior rooms can be worse. One vivid prior case strolls in, the veteran says "we've seen this before", half the table relaxes, and the denominator quietly leaves by the side door.
This is one reason I get impatient when people treat experience as a substitute for frequency or actual evidence. Memory is not a base rate. It is a highlight reel, and highlight reels are wonderful tools for selling things that do not travel.
What I ask when a case looks comfortingly familiar
A board chair once introduced me as Grant Purdy, the man who asks what is different before he asks what is similar. Fair enough. My first question is representative of what, exactly. My next question is what base rate or local fact would make this comparison look foolish.
Under the Universal Decision-Making Method, that sends us straight into Recognise assumptions and Sufficient certainty. If the decision depends on one case behaving like another, the transfer conditions need to be written down in plain English. The room then has to decide what evidence justifies treating this case as comparable, rather than merely comforting.
If the room still wants to proceed, Design monitoring should name the first signs that the supposed precedent was never a precedent at all. This mistake appears across the wider cognitive biases in decision making guide, but this bias has a particular smell. A case looks familiar, the room gets comfortable, and nobody checks whether the odds live here too. I do not trust the comfort. I trust the denominator.
You could chase your next Gatorade and miss the conditions that made it rare.
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Grant Purdy is the co-author, with Roger Estall, of Deciding (2020), and the architect of the Universal Decision-Making Method.