The constant flux and caprice of mental events do not admit of the establishment of stable experimental conditions.
Hermann EbbinghausHumans more easily remember or learn items when they are studied a few times over a long period of time (spaced presentation), rather than studied repeatedly in a short period of time.
Hermann EbbinghausOne 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
Hermann EbbinghausIdeas which have been developed simultaneously or in immediate succession in the same mind mutually reproduce each other, and do this with greater ease in the direction of the original succession and with a certainty proportional to the frequency with which they were together
Hermann Ebbinghaus