THE PSYCHOLOGICAL BASIS 23 



familiar awakens a memory picture in our minds : "we see it through 

 memory-coloured spectacles." Thus we often see it quite different from 

 what it is, and our capacity to dissociate accidental colours from the 

 so-called real colours of objects is very highly developed. Thus, the 

 shadows on the surface of a body, which largely influence our perception 

 of its shape, relief and distance, we instinctively regard as an epiphe- 

 nomenon, and we think that we see the actual or real colours through 

 the darkness of the shadows. A shadow on white paper appears quite 

 different to us from a grey spot on the paper, even though both reflect 

 exactly the same amount of light. Similarly a patch of cigarette ash 

 on a black coat conveys a different impression from a patch of bright 

 sunlight. Indeed, the difference manifests itself in words ; the one we 

 usually call white or grey or black, the other bright or dark. 



Hering has devised some simple, but very instructive experiments 

 to illustrate these facts. One example will suffice. In a room lighted 

 by a window on one side, the opposite wall being white, standing with 

 the back to the window and holding up a grey sheet of paper, the paper 

 looks grey and the wall white. The wall however reflects only a portion 

 of the light into the eye and " is " therefore grey. By looking through 

 a tube it is possible to select a grey paper which exactly matches the 

 greyness of the wall ; yet directly the tube is removed the wall at once 

 appears white, whilst the paper still remains grey. If, however, the 

 edge of the paper is fixed with one eye only, the wall appears to be on 

 the same plane and of the same tint as the paper. In this case different 

 localisation produces different colour impressions, and the ultimate 

 perceptions depend, not upon differences of physical light intensity, 

 but upon other impressions which simultaneously enter into conscious- 

 ness and modify judgment. 



One does not generally pay special attention to the colours of objects, 

 but uses them merely as indicators, specially associated with the objects; 

 hence when the object is seen again the colour impression is immediately 

 revived. Some dresses look blue by daylight, bluish-green by electric 

 light, and the wearers often think it strange when in artificial light people 

 say that they are bluish-green. Such people may even correct themselves 

 and say that they are certainly blue, when they are told that they are 

 blue. 



Hering points out that these facts have nothing to do with simul- 

 taneous contrast (v. Section VI, Chap, n) as has sometimes been thought. 

 They are indeed examples of the association of ideas or sympsychosis. 

 They show, however, the necessity for eliminating as far as possible all 



