Sleep learning

Sleep learning is a method in which a person attempts to learn a subject through listening to a recorded voice when they sleep.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Brainy attempted to use sleep learning to increase his education by having a magical voice spell recite the contents of various books borrowed from the Smurf House of Archives as well as from Papa Smurf's laboratory. Eventually he found that method to be useless for the sake of education.

Papa Smurf was given a sleep learning spell by his former mentor Paladore called the Nocturnal Illumine which allowed him to learn sorcery and magic spells while he was resting. This spell was later cast upon Brainy sometime before Papa Smurf's death so that Brainy could succeed as Papa Smurf's successor as a sorcerer.