i6o evolution: the ages and tomorrow 



Arnold Gesell thinks that the mind Hke the body has a 

 definite morphogenesis, that the beginnings of the hfe of 

 the mind are an extension of the embryonic growth which 

 created it— again the idea of organization as a principle of 

 order. One school of psychology describes learning purely 

 in terms of trial and error, a blind search for an accidental 

 solution. At the other extreme there are still a few psycholo- 

 gists who hold that it is innate insight that reveals relation- 

 ships to the mind. 



H. F. Harlow has summarized the experimental approach 

 to the learning problem in primates. Among other activities, 

 Harlow and his associates made a comparative study of both 

 rhesus monkeys and nursery-children, two to five years old. 

 In these experiments, of course, the psychologists controlled 

 the entire learning history of the animals they used, and they 

 set out to determine whether monkeys had the ability to 

 solve a problem by insight after a trial-and-error training. 

 The first experiments were simple discrimination tests. The 

 monkeys were placed before two objects which differed in 

 shape, size, and color. Picking up the right object meant a 

 reward of food placed under it. Each time the two objects 

 were placed before the subject the food reward was under 

 the same object, but they were shifted about at random in 

 different trials until the monkey learned to pick the right 

 one. The experiments were continued and varied by using 

 many pairs of objects. When first faced with this test, the 

 monkeys fumbled about entirely by trial-and-error; but as 

 they solved one after the other they began to get an insight 

 into the situation. Soon, if the monkey picked up the correct 

 object the first time, it would rarely make a mistake the 

 second time. It would shift its choice at once if it picked up 

 the wrong object the first time. Some of the subjects learned 

 to respond almost perfectly to this kind of test. From this 

 and similar tests Harlow concludes that trial and error and 

 insight are not different capacities but are different phases 



