CONCEPTUAL THOUGHT 163 



tried to corroborate the Kohler claim of sudden insight 

 without learning, but with no success. 



One of the most dramatic concept-formation studies ever 

 made at levels below the human was done by B. Weinstein. 

 He taught monkeys to recognize differences and similarities, 

 just as in some intelligence tests that are given to children. 

 In this training nine objects were placed before the monkey; 

 his problem was to pick out all that were identical with a 

 sample which was handed to him and to leave the rest on the 

 tray. After prolonged training some monkeys were able to 

 solve an even more difficult situation. In this case the animals 

 were taught to respond to a symbol and then to select all 

 objects of a given color. For instance, the monkey was 

 handed an unpainted triangle as a sign to select all red ob- 

 jects, or an unpainted circle as a sign to pick out all blue 

 objects. Monkeys and children alike find this difficult. 

 Weinstein had one monkey, a sort of rhesus genius, who 

 learned to respond almost perfectly. 



Harlow and others have also been able to show a capacity 

 to identify symbols with particular learning sets at levels be- 

 low man. They trained monkeys to respond to signs in the 

 form of differently colored trays holding three test objects, 

 for instance, a red U-shaped block, a green U-shaped block, 

 and a red cross-shaped block— two alike in form and two 

 alike in color. When these objects were shown on an orange- 

 colored tray, the monkeys had to choose the green block, 

 the odd color, to be rewarded. When the same objects were 

 shown on a cream-colored tray, the monkeys had to pick 

 the cross-shaped block, the odd form, in order to receive a 

 reward. The color cue of the tray was finally mastered by 

 these monkeys, some making the correct choice trial after 

 trial. Here, in a sense, is a response to a simple sign language. 



These monkeys, particularly the Weinstein genius, show 

 an amazing ability to conceptualize or categorize. The 

 Weinstein monkey could conceptualize red and blue to 

 stimuli which had no physical characteristic common to any 



