THE PSYCHOLOGICAL BASIS 25 



this aspect of the object becomes less and less vivid, until finally, when 

 the appropriation of it by the mental system becomes complete, it is 

 implicitly apprehended, or, in terms of conation, the stimulus applied 

 by this aspect of the object is responded to automatically, while some 

 other aspect occupies the focus of consciousness. 



If, however, bearing in mind the underlying complex factors, we 

 attempt to make a psychological analysis of visual qualities it will be 

 generally agreed that they can be divided into two groups of colour 

 sensations, the untoned and the toned. The untoned or colourless form 

 a continuous series from the blackest black through all gradations of 

 grey to the whitest white. The toned or coloured include four, red, 

 yellow, green and blue, together with all the gradations between them. 

 So far as the insecure foundations of psychological analysis go red, 

 yellow, green, and blue are simple or pure visual qualities. All other 

 hues are psychologically mixtures of these qualities. Thus, orange 

 obviously partakes of the nature of both red and yellow, purple of both 

 red and blue, and so on. Yet that psychological analysis is necessary 

 is shown by the acceptance of green as a simple colour sensation ; 

 for without analysis most people would say that green is a mixture of 

 yellow and blue. That such is the case is doubtless due to familiarity 

 with the behaviour of pigments, yet it may have a deeper significance, 

 since the distinction between green and blue is vague amongst many 

 primitive races and frequently amongst the uneducated classes. 



Moreover, there are difficulties associated with black and white and 

 two toned colours, brown and olive-green. " White '' is particularly 

 variable, chiefly owing to complexities arising from adaptation. Hering 

 regards diffuse sunlight as distinctly yellow, and the " whites " of sun- 

 light, arc light, incandescent gas light and so on, even when reflected 

 from a surface of compressed magnesium oxide, show gross variations 

 which are not submissible to psychological analysis. Opinion differs 

 as to whether "black" is the negation of all sensation, as generally 

 accepted by physicists, or an active sensation, as accepted by many 

 psychologists. It is certain that there is a blacker blackness than that 

 experienced when the eyes are carefully shaded from the light. Simi- 

 larly the sensation of brown cannot be elicited by merely reducing the 

 intensity of a yellowish-red or any other spectral light or mixture of 

 spectral lights, and the same applies to olive-green. Under these 

 circumstances the spectral colours approximate more and more nearly 

 to black. In order that a brown sensation may be experienced the 

 stimulus effect of the yellowish-red light must be ' ' blackened ' by 



