Health psychology/Cognitive biases · Clinical reasoning

Representativeness

What it means

Judging probability by how closely a case matches a typical prototype, neglecting atypical presentations and base rates.

Worked example

Dismissing MI because the patient "doesn’t look like" a classic cardiac case.

In the exam

An elderly diabetic woman with nausea and fatigue but no chest pain is judged "not a heart attack" because she does not fit the textbook picture — and her atypical MI is missed.

What settles it

Representativeness over-relies on prototype fit. Base-rate neglect is specifically ignoring the underlying prevalence/prior probability.

Classically confused with

Base-rate neglect

Source: Tversky & Kahneman