18 L. W. SACKETT 



lefthanded with only one variation in 600 tests. No. 10 made 

 six variations in the first 30 but no more in 470 tests. In the 

 case of Nos. 12 and 16 the experimenter used the right hand, 

 and each became righthanded with only a few errors at first. 

 Nos. 13, 14 and 15 were each fed from the experimenter's left 

 hand and all responded with their left hand after a few irregular 

 reactions. No. 15 showed less tendency to settle down to the 

 use of one hand than any of the others in the later experiments. 

 This may be due to her extreme age and long experience estab- 

 lishing the bilateral habit. Personally the writer has tested 10 

 animals and No. 6 is the only one which failed to react with 

 the hand corresponding to the' one with which the food was 

 presented. One would suppose that if No. 6 had had anything 

 like the struggle which No. 3 experienced, he might have formed 

 a different habit. Some other factor seemed to have deter- 

 mined No. 6's reaction. An assistant was allowed to take four 

 newly captured animals and check the work under the same 

 precautions which had been observed. In all 14 animals have 

 been tested. In seven cases feeding was done with the experi- 

 menter's right hand and in six of them the animals became 

 righthanded. Of the seven instances in which food was pre- 

 sented with the left hand, six developed lefthandedness. The 

 two odd cases out of the 14 may well be treated as exceptions. 



Individual differences in the animal's progress were not very 

 great under any given set of conditions. Nos. 4 and 5 belong 

 to the earlier tests and conform more closely to No. 3 as shown 

 in tables I and II. This is attributed, not so much to the fact 

 that these animals were slower, but rather to the fact that the 

 experimenters were so fearful of getting their fingers bitten that 

 they did not keep the conditions constant. Considerable dex- 

 terity was required to place the food in the animal's hand so 

 that he would not drop it and lose the reward after he had 

 made his reaction. The effort on the experimenter's part was 

 .to make every reaction a successful one for the animal. As 

 this skill of the experimenter operated wholly after the porcu- 

 pine had reacted, it is considered an environmental condition 

 merely distracting, if not controlled, but of no consequence as 

 a cue to the animal previous to his reaction. 



As to the bearing of all these results on the general question 

 of bilateral symmetry and its noteworthy exception in man's 



