(Wall Street Journal) — For a small group of people—perhaps just 1% to 3% of the population—sleep is a waste of time. Natural “short sleepers,” as they’re officially known, are night owls and early birds simultaneously. They typically turn in well after midnight, then get up just a few hours later and barrel through the day without needing to take naps or load up on caffeine. They are also energetic, outgoing, optimistic and ambitious, according to the few researchers who have studied them. The pattern sometimes starts in childhood and often runs in families. While it’s unclear if all short sleepers are high achievers, they do have more time in the day to do things, and keep finding more interesting things to do than sleep, often doing several things at once. Nobody knows how many natural short sleepers are out there. “There aren’t nearly as many as there are people who think they’re short sleepers,” says Daniel J. Buysse, a psychiatrist at the University of Pittsburgh Medical Center and a past president of the American Academy of Sleep Medicine, a professional group.