Diagnose before elaborating

Check the common, simple explanation first before searching for rare or complex ones.

Why it works

Cognitive availability bias makes vivid, unusual explanations feel probable because they are memorable. But base rates favor common explanations: the classic medical aphorism 'when you hear hoofbeats, think horses not zebras' encodes the same logic. Occam’s Razor applied to diagnosis means starting with the most prevalent cause that fits the evidence, not the most interesting one.

How to do it

1. List the top two or three most common explanations for the symptoms or situation you observe.
2. Check whether the common explanation is definitively ruled out by evidence before escalating.
3. Add complexity only in proportion to the evidence that demands it.
4. Document what finding would make you upgrade to a more elaborate explanation.

Evidence

The heuristic 'common things are common' is taught explicitly in clinical medicine and is grounded in base-rate reasoning. Anchoring on rare diagnoses before excluding common ones is a recognized source of clinical error. (clinical)

In medicine, zebras do exist; the razor is a triage tool, not a reason to stop investigating when common explanations are genuinely ruled out.

Common mistake

Jumping to elaborate explanations because the problem feels important or complex — importance does not raise the probability of a rare cause.