What is unconscious bias?

Unconscious bias is a concept in personal epistemology: Evaluations you make so often that you no longer notice them are the most dangerous.

Example: A senior engineer reviews a pull request from a junior colleague and immediately thinks 'this is overengineered.' She rejects the PR with terse feedback. Later, reviewing the same pattern from a principal engineer, she calls it 'thoughtful abstraction.' The evaluation was never about the code — it was a habitual judgment about who wrote it. She made the same assessment dozens of times before without noticing the pattern, because the judgment had become invisible through repetition.

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.