INTELLIGENCE IN LOWER VERTEBRATES 229 



In another set of experiments frogs were offered earth- 

 worms which had been dipped in chemicals. These worms 

 were frequently snapped at and swallowed. The diet pro- 

 duced in some cases symptoms of uneasiness and some of 

 the frogs would avoid eating earthworms for several days 

 afterward, although they would partake freely of other 

 kinds of food. 



An apparatus was arranged so that the frogs would re- 

 ceive an electric shock every time they snapped at a worm. 

 These frogs would avoid food altogether for a few days 

 after the shock. * Whether an association was formed hi 

 this case, or whether the result is due simply to the per- 

 sistance of the effect of the strong stimulus is uncertain. 

 That the frogs learn to avoid certain kinds of food more 

 quickly than they learn to follow a particular path may, 

 as Schaeffer suggests, be due to the fact that the discrim- 

 ination of food is so common an experience in the course 

 of a frog's daily life. The greater severity of the penalty 

 for error may be also a factor. 



What has been written on intelligence of reptiles is for 

 the most part in the form of scattered, casual observations. 

 We have several records of the taming of different reptiles, 

 of their following their keepers, their distinguishing between 

 different persons, and then* coming when called. Delboeuf 

 kept two lizards in captivity and in time they became quite 

 attached to their keeper. They would run to him from 

 across the room when called and crawl upon his body in the 

 hope of being fed. Each showed jealousy if any attention 

 were paid to the other. 



Gilbert White in his Natural History of Selbourne gives 

 an account of a tortoise which distinguished between dif- 

 ferent persons and became much attached to an old lady so 

 that "whenever the good old lady came in sight who had 



