The relation of habit to interest and attention is treated in Chapter XXIV.
=Nature of Attention.=--In our study of the principles of general method, it was noted that the mind is able to set up and hold before itself as a problem any partially realized experience. From what has been said concerning nervous stimulation and the passing inward of sensuous impression, it might be thought that the mind is for the most part a somewhat passive recipient of conscious states as they chance to arise through the stimulations of the particular moment. Further consideration will show, however, that, at least after very early childhood, the mind usually exercises a strong selective control over what shall occupy consciousness at any particular time. In the case of a student striving to unravel the mazes of his mathematical problem, countless impressions of sight, sound, touch, etc., may be stimulating him from all sides, yet he refuses in a sense to attend to any of them. The singing of the maid, the chilliness of the room as the fire dies out, even the pain in the limb, all fail to make themselves known in consciousness, until such time as the successful solution causes the person to direct his attention from the work in hand. In like manner, the traveller at the busy station, when intent upon catching his train, is perhaps totally unconscious of the impressions being received from the passing throngs, the calling newsboys, the shunting engines, and the malodorous cattle cars. This ability of the mind to focus itself upon certain experiences to the exclusion of other possible experiences is known as _attention_.
=Degree of Attention.=--Mention has already been made of states of consciousness in which the mind seems in a passive state of reverie. Although the mind, even in such sub-conscious states, would seem to exercise some slight attention, it is yet evident that it does not exercise a definite selective control during such passive states of consciousness. Attention proper, on the other hand, may be described as a state in which the mind focuses itself upon some particular impression, and thus makes it stand out more clearly in consciousness as a definite experience. From this standpoint it may be assumed that, in a state of waking reverie, the attention is so scattered that no impression is made to stand out clearly in consciousness. On the other hand, as soon as the mind focuses itself on a certain impression, for example, the report of a gun, the relation of two angles, or the image of a centaur, this stands out so clearly that it occupies the whole foreground of consciousness, while all other impressions hide themselves in the background. This single focal state of consciousness is, therefore, pre-eminently a state of attention while the former state of reverie, on account of its diffuse character, may be said to be relatively devoid of attention.