What is blood sugar brain function?

Blood sugar brain function is a concept in personal epistemology: Basic physiological states measurably alter what you perceive and how you evaluate it.

Example: A product manager schedules a critical prioritization meeting for 11:45 a.m. — fifteen minutes before lunch. She has not eaten since 7 a.m. By the time she sits down to evaluate three competing feature proposals, her blood glucose has dropped into the low-normal range. She does not feel impaired. She feels impatient. The proposals that require complex tradeoff analysis — weighing long-term infrastructure investment against short-term revenue — feel tedious. The proposal that offers a quick win with a clear metric feels obvious. She votes for the quick win. After lunch, reviewing her notes, she realizes the infrastructure proposal was clearly the better strategic choice. The tradeoff analysis was not actually difficult — her metabolic state made it feel difficult. She mistook a physiological signal for an evaluative judgment. Her hunger did not change the facts. It changed her perception of the facts.

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