10% Myth, 1% Fact?

In the comments to my post yesterday about Nanoarchaeum equitans, an ancient parasite, the discussion took an interesting turn. Web Webster wrote: "So in a way, N. equitans is both 'smarter' in that it uses more of its total capabilities (versus humans and the old '10% of the brain thing') and 'more efficient' in the way it works." To which Brent M. Krupp responded: "That 'old "10% of the brain thing' is complete and utter rubbish. Not a grain of truth to it, nor was there ever. Sorry to go off on this pet peeve of mine, but it's unclear if you were serious in your reference to that myth." I can't remember the first time I heard the claim that we only use 10% of our brain's full potential. It always sounded dicey to me, maybe because I didn't trust the people who pushed it. They'd always add that ...