The first characteristic which presents itself to us as an indication of intellectual development is related to _time_. The masses are so much alive to this primitive characteristic, that the popular expression "quick" is synonymous with intelligent. To be rapid in reacting to a stimulus, in the association of ideas, in the capacity of formulating a judgment--this is the most obvious external manifestation of intelligence. This "quickness" is certainly related to the capacity for receiving impressions from the environment, elaborating images, and externalizing the internal results. All these activities may be developed by means of an exercise comparable to a system of mental "gymnastics" to collect numerous sensations, to put them constantly in relation one with another, to deduce judgments therefrom, to acquire the habit of manifesting these freely, all this ought, as the psychologists would say, to render the conductive channels and the associative channels more and more permeable, and the "period of reaction" ever briefer. As in intelligent muscular movement, the repetition of the act not only renders it more perfect in itself, but more rapid in execution. An intelligent child at school is not only one who understands, but one who understands quickly. On the other hand, one who learns the same things, but who takes a longer time in so doing, say two years instead of one, is _slow_. Of a "quick" child, the people say that "nothing escapes him"; his attention is always on the alert, and he is ready to receive every kind of stimulus: as a sensitive scale will show the slightest variation in weight, so the sensitive brain will respond to the slightest appeal. It is Equally rapid in its associative processes: "He understands in a flash" is a familiar saying to indicate accurate conception. Now an exercise which "puts in motion" the intellectual mechanisms can only be an "auto-exercise." It is impossible that another person, exercising himself in our stead, should make us acquire skill.