10 LIGHT AND THE BEHAVIOR OF ORGANISMS 



organisms must resemble those in man, and the Cartesian 

 doctrine must be wrong. 



The importance of this problem was at once recognized 

 and a number of able investigators undertook its solution. 

 Prominent among these may be mentioned Darwin, Paul 

 Bert, Graber, Romanes, Lubbock and Preyer. It should 

 be emphasized that these investigators were not primarily 

 interested in explaining behavior either mechanically or 

 otherwise. Their principal aim was to throw light on the 

 origin of mental phenomena in man. Do the lower animals 

 have sensations? Do they have memory? Do they rea- 

 son? were questions which shaped their investigations. 

 These questions they sought to answer by studying the 

 behavior of animals under various conditions. Their 

 results seemed to indicate that the psychic phenomena in 

 animals differ from those in man in quantity rather than 

 in quality. 



AVith reference to reactions to light they used what is 

 known as the preference method. Experimental condi- 

 tions were so arranged that the animals could get into 

 light of different intensities or different colors. The kind 

 of light in which they collected was supposed to be the kind 

 they preferred. The work was weak in that only end results 

 of the experiments were considered; it was never ascer- 

 tained precisely how the animals got into the region in 

 which they finally remained. Variation in the color or 

 in the intensity of light in the field was to these investi- 

 gators the controlling factor in the movement of animals. 

 They failed to consider the possible effects of the direction 

 of the rays, of variation in light intensity on the surface of 

 the animals, and of various internal factors. This led to 

 many erroneous conclusions. Still it must be said that 

 whatever one may think as to the point of view of these 

 investigators and the validity of their conclusions in general, 

 one cannot read with unprejudiced mind the account of 

 their work, especially that of Darwin, Lubbock, and 

 Romanes, without greatly admiring the keenness of their 



