ATTENTION. 425 



better than otherwise we could — both more successive 

 things and each thing more clearly. It also 

 (e) shortens 'reaction-time.' 



a and h. Most people would say that a sensation at- 

 tended to becomes stronger than it otherwise would be. 

 This point is, however, not quite plain, and has occasioned 

 some discussion. * From the strength or intensity of a 

 sensation must be distinguished its clearness ; and to in- 

 crease this is, for some j)«Jchologists, the utmost that 

 attention can do. When the facts are surveyed, however, 

 it must be admitted that to some extent the relative inten- 

 sity of two sensations may be changed when one of them is 

 attended to and the other not. Every artist knows how he 

 can make a scene before his eyes appear warmer or colder 

 in color, according to the way he sets his attention. If 

 for warm, he soon begins to see the red color start out of 

 everything; if for cold, the blue. Similarly in listening for 

 certain notes in a chord, or overtones in a miisical sound, 

 the one we attend to sounds probably a little more loud as 

 well as more emphatic than it did before. When we men- 

 tally break a series of monotonous strokes into a rhvthm, 

 by accentuating every second or third one, etc., the stroke 

 on which the stress of attention is laid seems to become 

 stronger as well as more emphatic. The increased visi- 

 bility of optical after-images and of double images, which 

 close attention brings about, can hardly be interpreted 

 otherwise than as a real strengthening of the retinal 

 sensations themselves. And this view is rendered par- 

 ticularly probable by the fact that an imagined visual 

 object may, if attention be concentrated upon it long 

 enough, acquire before the mind's eye almost the brill- 

 iancy of reality, and (in the case of certain exceptionally 

 gifted observers) leave a negative after-image of itself when 

 it passes away (see Chapter XVIII). Confident expectation 

 of a certain intensity or quality of impression will often 

 make us sensibly see or hear it in an object which really 



* See, e.g., Ulrici : Leib u. Seele, ii. 28; Lotze: Metaphysik, j; 273; 

 ?echner; Revision d. Psycbopbysik, xix ; G. E. Milller : Zur Theorie d. 

 sinnl. Aufmerksamkeit, § 1; Stumpf : Toupsychologie, i. 71. 



