the motor side the child's judgments are enormously increased and are made more accurate. This is necessarily true because by the use of the motor side his opportunities for comparison and discrimination are multiplied. He is called upon, for instance, to form a judgment out of the ideas already in his possession. If now he stops with this judgment he has no new criteria with which to judge its correctness. On the other hand, if he can convert this judgment into motor terms a comparison is forthwith instituted and the judgment undergoes revision.
I have already spoken of the physical activity of youth as a marked characteristic, and have said that this activity is due to the discharge of energy into motor channels. It is a significant fact that the attention of the child can be held for a surprisingly long time provided he is so employed that this motor energy is expended in movement. Attention from the first is therefore closely related to the motor side. The reason seems to be that there are many groups of cells more or less isolated from each other, but each closely connected with the main branches of the nervous system. Each group has functions largely peculiar to itself; when the brain is fully developed these isolated groups of cells become more closely interrelated by means of filamentary outgrowths, called by some writers pathways of association and by others dynamic pathways, by which energy is more readily distributed to various groups. In other words, if I may use a bold metaphor, short circuits become at last established between the various centers, so that the energy is not discharged into the early isolated channels. If, therefore, we wish to hold the child's attention to any particular line of study, we must at the same time provide for the expenditure of the energy that is gathered in the other groups of cells whose connections of interrelation are not yet built up or established. If we do not provide for this, the natural discharge of the energy from the overfilled cells of those other groups swerves the child's attention from what we have in hand for him. Every mental act, it must be remembered, involves the complete arc of the sensory and the motor, and in the child the inherent stress is on the motor. Again I quote from Prof. Baldwin: "Just in as far as the motor ingredient of a mental content of any kind is large—that is, in so far as the sensory ingredient is intense—just to this degree also will the direction of attention be secured, and to this degree also will both the ingredients be intensified by this act of attention. Intensity draws attention, and attention increases intensity—the law of sensory-motor association—i. e., every mental state is a complex of sensory and motor elements, and any influence which strengthens the one tends to strengthen the other also."
I have spoken of how the use of the motor side adds new ave-
