150 COLOUR VISION 



differences, however, between the Todas on the one hand and the 

 Sholagas and Uralis and Egyptians on the other are very slight and 

 within the limits of the probable error. 



More important is the difference between the Todas and the Papuans 

 of Torres Straits. There is no great difference between the thresholds 

 for yellow of the two communities, but the thresholds for red differ 

 greatly, the difference, 14 '5, being considerably more than three times 

 the probable error of the difference 1 , which is 2'8. 



This difference is probably connected with the fact that among the 

 Papuans red-green blindness does not occur, while among the Todas it 

 reaches the highest frequency recorded in any community. The 

 difference seems to show that even in those Todas who were able to pass 

 the tests for colour-blindness, there was some deficiency in the sensibility 

 for red as compared with the Torres Straits islanders. 



For blue the Todas have a very distinctly higher threshold than the 

 English observers, though lower than the other savage or barbarous 

 races tested. The difference between the figures for the English and 

 the Toda observers is enormously greater than the probable error of the 

 difference, which is only 2 '8. The Todas confirm the conclusion pre- 

 viously reached by Rivers, that the defective nomenclature for blue 

 which is so generally found among races of low culture is associated 

 with a certain degree of defective sensibility for this colour. 



Rivers made observations on the colour fields of the Papuans and 

 the Todas. The former showed colour fields of considerable size, and 

 differences in the limits for different colours were clearly demonstrated. 

 The Todas had very small colour fields, so small that it was impossible 

 to detect any difference in size. Only in one man did the field for blue 

 seem larger than those for other colours. Since the Todas were more 

 intelligent than the Murray Islanders it is probable that the small fields 

 point to a definite sensory defect. 



McDougall 2 suggests that the colour names of the Homeric Greeks 

 and uncultured peoples may be explained by environment. The superior 

 power of red to strike the attention may be due to the fact that red 

 objects in nature are rare, while blue and green are constantly spread 

 out in large tracts of sky and sea and foliage. Further, while many 

 of the rare red objects (blood, fruits, animals, ironstone) are of practical 

 importance, and while the abundant green objects are presented in 



1 I.e., i^^ + 'Zy 2 where 2 X and S (/ are the probable errors of the two figures to be 

 Compared, 



2 Brit. Jl. of Psychol. n. 349, 1908. 



