Bauhaus-Universität Weimar

Dictionary of philosophy and psychology including many of the principal conceptions of ethics, logics, aesthetics ... and giving a terminology in English, French, German and Italian, vol. 2 [lead-zwing]
Baldwin, James Mark
colour-curves are laid down (Fig. 12a): it is 
found that they do not coincide exactly with 
the curves of the two sorts of dichromates, the 
so-called red-blind and green-blind (Fig. 12 b). 
But would they have coincided if different 
independent variables had been chosen 1 The 
question is easily put to the test : it is a 
simple matter of mathematics (merely a 
B C 
Fig. 12 a. The proportions of the three trial ele¬ 
mentary colours required to match all the colours of 
the spectrum, for normal individuals. 
Fig. 12 b. W1} K, curves of sensation for two 
green-blind; W2, K, those for two red-blind indi¬ 
viduals ; S, curve showing the intensity of the grey 
sensation for the totally colour-blind. (König.) 
change in the triangle of reference) to find 
out if there are independent variables, that 
is, unit quantities of lights of particular wave¬ 
lengths, such that the entire spectrum as seen 
by the three different classes of individuals 
can be built up out of like amounts of two 
or three of the several constituents. In fact, 
it was only necessary to substitute for the 
colours first chosen others mixed out of them 
in this way, 
R-o-itjG + o-iB 
t= - 5 
to find that, with these new constituents, the 
warm-end curve of one sort of defective co¬ 
incided with the red curve, and that of 
the other sort of defective with the green 
curve of the normal individual. In Fig. 12a 
are represented the trial curves for König 
and Dieterici; in Fig. 13 the curves of co¬ 
incidence for normal and semi-defective indi¬ 
viduals. (In the dotted line of Fig. 12 a is 
given the green curve of a very small class of 
individuals, first noticed by Lord Bayleigh 
and by Donders, who differ markedly from 
the normal ; they require, to make a given 
yellow out of red and green, four times as 
much red to a given amount of green as the 
normal individual does.) Expressed in other 
words, this is the same as saying that all 
colour-matches formed by normal individuals 
Fig. 13. When A 470 (blue), A 505 (green), and a 
red a little less yellowish than the red of the spec¬ 
trum are taken as the elementary colours, the colour- 
mixture curves of the normal individual become co¬ 
incident respectively with those of the two sorts of 
partially colour-blind. 
are recognized to be such by both sorts of di¬ 
chromates \ but that colour-matches formed 
by the proteranope need to be distinctly 
changed before they are such for the deutera- 
nope. This means that the colour-systems of 
both sorts of dichromates are reduction- 
systems—all their sensations are accounted 
for by supposing that one certain element (not 
the same for both) is absent in their case. 
This is a very important result. It has quite 
lately been fully confirmed by v. Kries (‘ Ueber 
Farbensysteme,’ Zeitsch.f Psychol., xix, 1897). 
The theory of Hering fails to take account in 
any adequate way of the fact that the di¬ 
chromates are of two different sorts, and that 
nevertheless their colour-systems are both 
simply reduction-systems of normal colour- 
vision. On the other hand, the Young-Helm- 
holtz theory offers no explanation, of any 
degree of reasonableness, of the fact that the 
two classes of semi-defectives, instead of see¬ 
ing red and blue, and green and blue, respec- 
1 The converse of this proposition is, of course, not 
true : countless things which look alike to the semi¬ 
defective are of different colour to the normal eye. 


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