From 1880 to 1885, Hermann Ebbinghaus ran a study about the memorisation of nonsense syllables, such as "WID" and "ZOF" by repeatedly testing himself after various time periods and recording the results. He plotted these results on a graph creating what is now known as the "forgetting curve".
Our brain forgets quickly newly learned information. Spaced repetitions are the most effective approach to internalize.
Explore more quotes
The speed of forgetting depends on a number of factors such as the difficulty of the learned material (e.g. how meaningful it is), its representation and physiological factors such as stress and sleep. Furthermore higher original learning also reduces forgetting. The rate differs little between individuals.