What is base rate neglect?

Base rate neglect is a concept in personal epistemology: Statistical base rates predict outcomes better than compelling individual stories. Your brain will fight this truth every time a vivid narrative competes with a dry statistic — and your brain will be wrong.

Example: A product manager reads a passionate customer email describing a catastrophic bug that destroyed a week of work. She feels the urgency viscerally and is ready to reprioritize the entire sprint around this bug. Then she checks the base rate: out of 40,000 active users, the bug has been reported by three people — a rate of 0.0075%. The monitoring dashboard shows the feature works correctly 99.97% of the time. The email was real, the suffering was real, but one vivid story nearly overrode the statistical reality that this bug affects almost nobody. She logs the report, schedules a low-priority fix, and keeps the sprint focused on the feature that analytics show 6,000 users are waiting for. The narrative pulled toward one direction. The base rate pointed somewhere else entirely. She followed the base rate.

This concept is part of Phase 8 (Perceptual Calibration) in the How to Think curriculum, which builds the epistemic infrastructure for perceptual calibration.