Hermann Ebbinghaus — German Psychologist born on January 24, 1850, died on February 26, 1909

Hermann Ebbinghaus was a German psychologist who pioneered the experimental study of memory, and is known for his discovery of the forgetting curve and the spacing effect. He was also the first person to describe the learning curve. He was the father of the eminent neo-Kantian philosopher Julius Ebbinghaus... (wikipedia)

Meanwhile the fact that the connection with the activity of memory in ordinary life is for the moment lost is of less importance than the reverse, namely, that this connection with the complications and fluctuations of life is necessarily still a too close one.
Mental events, it is said, are not passive happenings but the acts of a subject.
On the basis of the familiar experience that that which is learned with difficulty is better retained, it would have been safe to prophesy such an effect from the greater number of repetitions.
One needs but to say that, in the case of an unfamiliar sequence of syllables, only about seven can be grasped in one act, but that with frequent repetition and gradually increasing familiarity with the series this capacity of consciousness may be increased.
The school-boy doesn't force himself to learn his vocabularies and rules altogether at night, but knows that be must impress them again in the morning.