Brain Rules

Introduction: The Brain's Performance Envelope

There are children with an IQ of fifty or below who can do things most of us never could. One can multiply 8,388,628 by 24 in his head in seconds. Another can tell you the exact time of day at any moment, even while fast asleep. A third can judge the dimensions of a room from twenty feet away with a tape measure's accuracy. A fourth, at age six, draws well enough to hang in a gallery. And yet not one of these children can tie his own shoes. John Medina opens Brain Rules with this puzzle because it embarrasses everything we think we know about intelligence, and because it points to the real subject of his book: we have almost no idea how the brain works, and most of what we do in schools and offices actively fights against it.

Medina is a developmental molecular biologist, and he holds himself to a strict standard. He calls it, with characteristic humor, the Medina Grump Factor. To make it into this book, a finding had to be published in a peer-reviewed journal and then successfully replicated. No Mozart effect. No left-brain, right-brain personality types. No prenatal language tapes piped into a pregnant belly. What survives that filter is twelve rules, and a single organizing idea behind all of them.

The idea is the performance envelope. Your brain was built to solve problems, related to surviving, in an unstable outdoor environment, while in nearly constant motion. Every one of the twelve rules traces back to that one sentence. We grew up walking miles a day across the savannah, dodging predators, reading the intentions of other humans, and improvising when the weather, the food, and the threats kept changing. The brain is a survival organ, not a thinking organ that happens to keep us alive.