Sleep-learning (also known as sleep-teaching, hypnopædia, or hypnopedia) is an attempt to convey information to a sleeping person, typically by playing a sound recording to them while they sleep. Research on this has been inconclusive. Some early studies tended to discredit the technique's effectiveness,[1][2] while others have found that the brain indeed reacts to stimuli and processes them while we are asleep.[3][4]