If you like to take mid-day naps on warm afternoons, scientists might have an explanation as to why you do. In a new study published in the journal Current Biology, researchers at Northwestern studied fruit flies. They found a switch in the brains of these flies that makes them want to sleep when the weather reaches a certain temperature – specifically when the temperature rises above 77 degrees Fahrenheit. This is also the favorite napping temperature for humans as well. This brain circuit promotes sleep during the middle of the day, especially during the hottest parts of the afternoons.