Universal Principles of Design, Updated and Expanded Third Edition
by William Lidwell, Kritina Holden, Jill Butler
177 Streetlight Effect
A bias to search for things where it is easiest.
The streetlight effect is the tendency to focus on problems, questions, and data for reasons of convenience or availability versus reasons of relevance or import. The effect borrows from a joke:
A police officer sees a drunk searching for something under a streetlight. “What have you lost?” the officer asks. “My keys”, the drunk replies. The officer agrees to help look. After a few minutes, the officer asks, “Are you sure you lost them here?” The drunk replies, “No, I lost them in the park”. Incredulous, the officer asks, “Why are we searching here then?!” The drunk replies, “It’s too dark over there. This is where the light is”.
The streetlight effect is related to the ...
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