19th century psychologist  Herman Ebbinghaus demonstrated that we normally forget 40% of new material within the first twenty minutes, a phenomenon known as the forgetting curve.
Al segle 19, el psicòleg Herman Ebbinghaus va demostrar que normalment oblidem un 40% del material nou que aprenem al cap de vint minuts, un fenomen conegut  com a la corba de l'oblit.