THE METHOD OF TRIAL AND ERROR IN THE 

 BEHAVIOR OF LOWER ORGANISMS. 



A certain type of behavior in higher animals has been characterized 

 by Lloyd Morgan as the method of trial and error. The nature of such 

 behavior is well brought to mind by an example from Morgan (1894, 

 p. 257). His dog was required to bring a hooked walking stick 

 through a narrow gap in a fence. The dog did not pause to consider 

 that the stick would pass through the narrow opening only if taken 

 by one end and pulled lengthwise. On the contrary, he simply seized 

 the stick in the way that happened to be most convenient, near its 

 middle, and tried to carry it through the gap in the fence in that man- 

 ner. Of course, the stick would not pass, and after some effort the 

 dog was forced to drop it. Then he seized it again at random, and 

 made a new effort. Again the stick was stopped by the fence ; again 

 the dog dropped it, took a new hold, and tried again. After several 

 repetitions of this performance, the dog seized the stick by the hooked 

 end. This time it passed through the gap in the fence easily. 



The dog had "tried" all possible methods of pulling the stick 

 through the fence. Most of the attempts showed themselves to be 

 fc < error." Then the dog tried again, till he finally succeeded. Thus 

 he worked by the method of trial and error. 



This method of reaction has been found by Lloyd Morgan, Thorn- 

 dike (1898), and others, to play a large part in the development of 

 intelligence in higher animals. Intelligent action arises as follows: 

 The animal works by the method of trial and error till it has come 

 upon the proper method of performing an action. Thereafter it begins 

 with the proper way, not performing the trials anew each time. Thus 

 intelligent action has its basis in the method of " trial and error," but 

 does not abide indefinitely in that method. 



Behavior having the essential features of the method of " trial and 

 error" is widespread among the lower and lowest organisms, though 

 it does not pass in them so immediately to intelligent action. But like 

 the dog bringing the stick through the fence the first time, they try all 

 ways, till one shows itself practicable. 



This is the general plan of behavior among the lowest organisms 

 under the action of the stimuli which pour upon them from the sur- 

 roundings. On receiving a stimulus that induces a motor reaction, 

 they try going ahead in various directions. When the direction fol- 

 lowed leads to a new stimulus, they try another, till one is found which 

 does not lead to effective stimulation. 



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