Most of us have embraced the notion that we use only 10 percent of our brain. This dates back more than a century, but was never true.27 It nonetheless persists because deep down it serves our longings. Psychics want it to be true so that they can claim untapped powers of mind await us all. Teachers want it to be true so they can motivate their underperforming students. The rest of us want it to be true because it gives us hope for ourselves.