What is inattentional blindness?

Inattentional blindness is a concept in personal epistemology: The most important information is often in what you habitually ignore.

Example: A senior engineer reviews a deployment dashboard and sees all services reporting healthy. Everything looks green. But she pauses and asks: 'Where are the logs from the payment service?' There are none — not errors, not warnings, not even info-level output. The service isn't healthy. It never started. The absence of data was the most important data on the screen, and every other engineer walked past it because they were scanning for red, not for missing green.

This concept is part of Phase 5 (Observation Without Judgment) in the How to Think curriculum, which builds the epistemic infrastructure for observation without judgment.