30 L. W. SACKETT 



the hitch do He," but the ohactory stimulation and the fortuitous 

 success in opening the door, later a fixed motor response, seem 

 to offer a better explanation. Besides, this conforms with the 

 general policy of refusing an explanation involving higher men- 

 tal processes when one involving lower mental processes will 

 suffice. No. 4 opened the box 40 times the first day and would 

 have continued twice as long in all probability but, as yet, 

 neither the full measure of the appetite nor the endurance of 

 the porcupine had been appreciated by the experimenters. 



An incident the second day following is worthy of mention. 

 On the 152nd trial. No. 4 opened the box as usual, but, failing 

 to find his food, went back and pushed on the lever again, 

 though the door was open and the lever was down. After this 

 he found his food. The three following trials he pushed the 

 lever, turned, and although he could see and hear the door 

 open, he returned and gave the lever a second push before 

 looking for his food. After this he eliminated the second attack 

 on the lever, restoring his usual habit. The influence of that 

 one successful chance variation, however, came near throwing 

 the animal into a new method of procedure. Had it been as 

 simple as the former it might have persisted longer than it did. 



The writer is in full accord with the efforts of those recent 

 investigators who would eliminate the expression "trial and 

 error" from the studies of animal intelligence. It is fundamen- 

 tally wrong and can have little significance unless a definite 

 negative stimulus is imposed, throwing the emphasis on the 

 wrong rather than the right reaction. Normally, the animal 

 learns by "trial and success." Erroneous movements pass 

 without significance and tend to drop out and disappear. The 

 important factor, in all laboratory work at least, is the success- 

 ful movement. The same might also be said when the animal 

 is in the presence of its enemies. The individual which escapes 

 lives to engraph its success on the instincts of the species ; while 

 those which make the fatal error are exterminated and the 

 species profits little by their experience except in a negative 

 way. So long as No. 4 clawed at the door of the box, no prog- 

 ress was made; but as soon as the lever, or the end of the 

 box where the lever was located, or even a certain trip came 

 to be associated with the process of getting food, progress ensued 

 very rapidly. 



