Sensorial perception, for example, certainly occurs with greater or less accuracy according to the degree of interest; it is constantly given other directions by the change of external stimuli and by ideas.
Hermann EbbinghausSeries of syllables which have been learned by heart, forgotten, and learned anew must be similar as to their inner conditions at the times when they can be recited.
Hermann EbbinghausNo matter how thoroughly a person may have learned the Greek alphabet, he will never be in a condition to repeat it backwards without further training.
Hermann EbbinghausOften, even after years, mental states once present in consciousness return to it with apparent spontaneity and without any act of the will; that is, they are reproduced involuntarily.
Hermann Ebbinghaus