NaGEL, Color-Sense of a Child. 219 



correctly name? Or, in other words, what serial arrangement, 

 according to this method, will he give? Since I confined my tests 

 to a short period of time (two weeks), in order to minimize the 

 effects of "training," I could get no such complete answer to this 

 question as Preyer; yet I feel that I had here, again, a certain 

 advantage in the already mentioned principle of showing the 

 colors in various degrees of brightness, which enabled me to deter- 

 mine with greater certainty than Preyer whether the child, in the 

 given case, discriminated colors or merely differences in bright- 

 ness. 



The child investigated, my older son Gerhard, was two years 

 and four months old when the experiments began. He was 

 physically and, so far as one may conclude, at that age also men- 

 tally, well developed. To judge from Preyer's statements, I 

 should say that, especially in physique, but also mentally he was 

 somewhat in advance of Preyer's child, perhaps from three to 

 six months. 



In the mother's family (the mother being especially concerned 

 in the hereditary transmission of color blindness) anomalies in 

 color vision are not to be found. Both grandfathers of the child 

 have normal trichromatic color vision; I, his father, as well as one 

 of my two brothers, am deuteranopic (green color blind), the other 

 brother is normal. Two cousins (male), on the father's side, are 

 "anomale" trichromates, and, according to the designation of 

 V. Kries, "Rotanomale."^ 



I began the systematic investigation of the child in November, 

 1905. Similar tests had not previously been made; he had been 

 merely occasionally told that such an object was red, such an one 

 blue, etc. 



The boy often played with a so-called "game of mosaics," that 

 is, with a system of cubes on which single portions of differently 

 colored pictures were respectively represented. Some of these 

 parts contained a vivid red. One day I showed the child a red 

 spot and said to him, "that is red," which phrase he at once re- 



'"We may, indeed, represent the protanopic (red-blind) and the deuteranopic (green-blind) 

 •visual organs as originating in a lack of the red and green components (of Helmholtz's theory) 

 respectively, and the Rotanomale and the Griinanomale in a variation in the nature of the red or the 

 green component'' (Nagel's Handbuch der Physiologic des Menschen, Braunschweig, 1904, 

 III Band, S. 279). 



