 Now, the Business Edge Minute. Here's Mitch Graff. We all know that the world is built around people who are right-handed, with only about 10% of the population being left-handed. That's why you don't see left-handed scissors or left-handed desks at the preschool. But there are some very good reasons to use both hands from time to time. Our brains are cross-wired, meaning that the left hemisphere controls the right-handed side of the body and vice versa. So left-handers can't use both hands.