Against Gluco-Determinism

David Kohn investigates the notion that blood sugar levels regulate self-control:

“We have three weeks of food in our kitchens,” [psychologist Michael] McCullough says. “But that’s not how we evolved. It doesn’t make sense that cognition is so fragile that two hours after your last meal, thinking goes haywire. I don’t think natural selection would have been kind to humans whose brains shut down whenever they got hungry.”

I asked him how he would explain my kids’ tendency to insurrection when they’re hungry. “I am perfectly willing to believe that hunger is linked to angry outbursts in your kids,” he said. “If a child or animal is running low on blood glucose, it will act differently.” But this, he points out, does not prove that glucose regulates self-control. The change in behavior could be a direct, perhaps unconscious, way to signal hunger. (If that’s true, the strategy works, at least in our house. Outbursts usually lead to a pre-dinner snack.) Or it may be a vestigial sign that the organism is sick of being hungry, and is getting ready go find some food on its own.

Update from a reader:

Ya, the brain goes haywire when it’s low on glucose. Our six-year-old daughter is a Type 1 diabetic. We watch her behavior for both high and low blood sugar tip offs. However, one of the dead give-aways that she is going low is that she becomes dreamy and illogical. Last night, in the tub, she said “Dad, do all liquids controls their containers? Like if I were water in a bucket, would I have a shoe?” Yep: Blood sugar of 48. And just as inexplicable, when she’s high (say 230 against a normal of 130), she is very hungry and very crabby.