Matmail: I have heard that we humans only use 10 percent of our brains and that Einstein used 11 percent. Is this true, and where do they come up with these numbers? What would they mean by “use”? Would the number refer to conscious thinking or just the brain's overall activity? I personally am glad I don't have to use 100 percent of my brain, because regulating my heartbeat and chewing gum could be a fatal combination. — Ether775, the Net

The fog lifts in a small corner of Aliceland! Dawn breaks, and the light of truth reveals big moth holes in an urban legend. Congrats, Ether, for puzzling this out for yourself.

The mysterious ten percent applies to nothing, really. It’s true that not all of our brain mass is devoted to thinking, swatting mosquitoes, digesting burgers, and generally interacting with the outside world. Our billions of neurons are embedded in a big glob of glial cells that do all the cranial housekeeping and dog work to make sure the neurons are happy. Glial cells make up more than 50 percent of our brain matter, so if you discount their background activity, it’s true that we “use” some (unknown) amount less than half our brains.

What sets Einstein apart from you and me...well, from you... isn’t the percentage of his brain that he “used,” it’s how that percentage was wired up (and perhaps some intangibles like where and when he lived and what outside influences came along while he happened to be paying attention). In the process of learning, our neurons make new connections with one another and establish patterns of thinking and acting that become more firmly established the more we exercise those circuits. So once again we find that it’s not how much of it you have, it’s how you use it.

Sourcing an urban legend is always tricky. In the popular press, you’ll see this one attributed to William James or to Einstein himself, but no reliable neuroscientist has found the origin. More to the point, who perpetuates the idea? Mostly seminar gurus selling the cosmic alarm clock that will wake up our dozing gray cells and turn us into millionaire babe magnets. Isn’t that typical? Here we find out that all the good stuff is in the 90 percent of our brains we leave idling in the driveway. The 10 percent we actually use just has the channel surfing-Beanie Babies-Pamela Anderson circuits.