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TRAP #049 ·VOL I The Individual · Judgment & Evaluation ErrorsLEXICON ENTRY

The Streetlight Effect

Searching Where It Is Easy, Not Where the Answer Is We look for answers where the light is good, not where we lost the keys. *(Evidence: Strong)* The tendency to focus research, analysis or investigation on areas that are easily accessible, measurable or familiar rather than on areas most likely to contain the answer. Named after the old joke about the drunk searching for his keys under the streetlight. Applies to science (studying what's measurable), business (optimising what's tracked) and personal reflection (examining comfortable truths).
Category: BiasEvidence: ReplicatedTier 2Type: Patternⓘ what these mean

This is a Lexicon entry: the mechanism, when it shows up, and the countermeasure. The full correction, with real-world cases and the audit prompt, hasn't been written yet.

When it shows up

KPI dashboards that measure what's easy to count rather than what matters. Research programs that study convenient populations. Startups optimising acquisition metrics while ignoring retention. Police focusing on well-lit, high-patrol areas.

Failure mode

Entire fields develop blind spots because the hard-to-measure domain never gets studied. Organisations make confident decisions using available but irrelevant data while the real drivers go unexamined.

Countermeasure

Ask: "Am I looking here because this is where the answer is or because this is where I can see?" Actively map the dark zones. Budget time for the hard measurement even if precision is lower.

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Related traps

Also connected in the map5 more, locked

Also revealed

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This entry has the mechanism and countermeasure. The full write-up - real cases, sources, the audit prompt - comes later.

Entry #49 of 631 in The Lexicon · see the full Lexicon