The current psychological doctrine of mental "types" rests upon a great mass of facts, drawn in the first instance from the different kinds of mental trouble, especially those which involve derangements of speech--the different kinds of Aphasia. The broadest generalization which is reached from these facts is that which marks the distinction, of which I have already said so much, between the motor and the sensory types. But besides this general distinction there are many finer ones; and in considering the persons of the sensory type, it is necessary to inquire into these finer distinctions. Not only do men and children differ in the matter of the sort of mental material which they find requisite, as to whether it is pictures of movements on the one hand, or pictures from the special senses on the other hand; but they differ also in the latter case with respect to which of the special senses it is, in this case or that, which gives the particular individual his necessary cue, and his most perfect function. So we find inside of the general group called "sensory" several relatively distinct cases, all of which the teacher is likely to come across in varying numbers in a class of pupils. Of these the "visual" and the "auditory" are most important.
There are certain aspects of the case which are so common to all the cases of sensory minds, whether they be visual, auditory, or other, that I may set them out before proceeding further.
First, in all these matters of type distinction, one of the essential things to observe is the behaviour of the Attention. We have already seen that the attention is implicated to a remarkable degree--in what I called "fluid attention" above--in the motor scholar. The same implication of the attention occurs in all the sensory cases, but presents very different aspects; and the common fact that the attention is directly involved affords us one of the best rules of judgment and distinction. We may say, generally, of the sensory children, that the attention is best, most facile, most interest-carrying for some one preferred sense, leading for this sense into preoccupation and ready distraction. This tendency manifests itself, as we saw above, in the motor persons also, taking effect in action, speed, vivacity, hasty generalization, etc.; but in the sensory one it takes on varying forms. This first aspect of our typical distinction of minds we may call "the relation of the 'favoured function' to the attention."