When we pass from the mere outward and organic description of his peculiarities, attempted above in the case of very young children, and aim to ascertain the mental peculiarity which accompanies it and carries on the type through the individual's maturer years, we see our way to its meaning.

The fact is that a peculiar kind of mental imagery tends to swell up in consciousness and monopolize the theatre of thought.

This is only another way of saying that the attention is more or less educated in the direction represented by this sort of imagery.

Every time a movement is thought of, in preference to a sound or a sight which is also available, the habit of giving the attention to the muscular equivalents of things becomes more firmly fixed.

This continues until the motor habit of attention becomes the only easy and normal way of attending; and then the person is fixed in his type for one, many, or all of his activities of thinking and action.
So now it is no longer difficult to see, I trust, why it is that the child or youth of this sort has the characteristics which he has.