When Thomas Edison hit a wall with his inventions, he would nap in an armchair while holding a steel ball. As he started to fall asleep and his muscles relaxed, the ball would strike the floor, waking him with insights into his problems. Or so the story goes.
Now, more than 100 years later, scientists have repeated the trick in a lab, revealing that the famous inventor was on to something. People following his recipe tripled their chances of solving a math problem. The trick was to wake up in the transition between sleep and wakefulness, just before deep sleep.
“It is a wonderful study,” says Ken Paller, a cognitive neuroscientist at Northwestern University who was not part of the research. Prior work has shown that passing through deep sleep stages helps with creativity, he notes, but this is the first to explore in detail the sleep-onset period and its role in problem-solving.