Psychology has a long past, but only a short history.

A poem is learned by heart and then not again repeated. We will suppose that after a half year it has been forgotten: no effort of recollection is able to call it back again into consciousness.

Humans 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.

The amount of detailed information which an individual has at his command and his theoretical elaborations of the same are mutually dependent; they grow in and through each other.

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.

What is true [in psychology] is alas not new, the new not true.

Mental states of every kind, - sensations, feelings, ideas, - which were at one time present in consciousness and then have disappeared from it, have not with their disappearance absolutely ceased to exist.