Judging probability by stereotypical similarity — how closely a case matches the mental image of a category — rather than by base rates or the quality of the evidence. "This looks like what a state-sponsored intrusion looks like, therefore it is one."
In intelligence analysis
- Attribution by resemblance: tooling, target set or tradecraft that matches the profile is read as confirming the actor, without asking how many other actors would produce the same signature.
- The heuristic also produces the conjunction problem — a detailed story (sophisticated tooling, specific targeting, plausible motive) feels more likely than its own components, because detail makes a scenario feel representative rather than improbable.
- It is the engine of Base-Rate Neglect: the stereotype replaces the prior, and the case is judged in isolation.
- It hardens into templates: once a category has a well-known example, new activity is fitted to it and anomalies are discarded as noise.
Countermeasure
- Ask how many other actors would look like this, and what evidence would distinguish them — the ACH question in another form (Structured Analytic Techniques).
- Grade the evidence for the attribution (Admiralty Rating) rather than the plausibility of the story.
Related
- Cognitive Bias — the taxonomy this bias sits within
- Base-Rate Neglect — the prior the stereotype displaces
- Mirror Imaging — assuming the actor shares our reasoning
- Structured Analytic Techniques — ACH as the structural counter