Encyclopædia Britannica, Ninth Edition/Attention
ATTENTION, in Psychology, may be defined as the concentration of consciousness, or the direction of mental energy upon a definite object or objects. By means of it we either bring within the circle of our conscious life per ceptions and ideas which would not otherwise have risen from their obscurity, or render clearer and more distinct some of those already under notice. Its mode of operation and the effects produced by it may be compared with the concentration of visual activity on some definite part of the field of vision, and the clearer perception of the limited portion which is thereby attained. In both cases the result is brought about, not by effecting any change in the perceptions themselves, but simply by isolat ing them, and considering them to the exclusion of all other objects. Since all consciousness involves discrimina tion, i.e., isolation of one object from others, it involves attention, which might therefore be defined as the neces sary condition of consciousness. Such a definition is, however, too general, and throws no light upon the nature of the process whereby our mental energy is strengthened in particular cases. This increase of force, when conscious ness is directed to any one object to the exclusion of others, is partly to be explained by reference to the general law that, as the amount of intellectual energy at our disposal is limited, the greater the number of objects over which it is spread, the less will each receive, pluribus intentus, minor est ad singida sensus; and conversely, the greater the con centration, the fewer must be the objects attended to. In addition to this general law of limitation, there are special circumstances which determine the amount of consciousness we shall bestow on any object. In the first place, there are certain mechanical influences only partly subject to the will, such are the force or vividness of the impression, the interest attaching to an object, the trains of associated ideas excited, or the emotions roused by its contemplation. There is, secondly, an exercise of voli tion employed in fixing the mind upon some definite object ; this is a purely voluntary act, which can be strengthened by habit, is variable in different individuals, and to which, as being its highest stage, the name Atten tion is sometimes restricted. The general law of the limitation of conscious activity, pointed out above, throws considerable light on the nature of abstraction and its relation to Attention. It is clear that concentration of consciousness upon any one attribute or attrioutes of an object involves withdrawal of consciousness from all other attributes. This withdrawal is, logically and etymologically, Abstraction, which is thus the negative side of Attention, or, as Hamilton expresses it, the two processes form the negative and positive poles of the same mental act.