KAO LIANG CHOW 



513 



task, the visual discrimination Icarning-sct problem, to assess the capacity 

 of the isolated temporal and visual areas. Two of the animals were trained 

 on this problem after the tirst operation, retested after the second opera- 

 tion, and again after the third operation. The other two animals were 

 given this problem only after the third operation. 



Table II 



POST-OPERATIVE LEARNING AND RETENTION OF VISUAL DISCRIMINATIONS. 

 NUMBER OF TRIALS TO CRITERION, EXCLUDING CRITERION TRIALS. C . S, 

 CIRCLE I', square; V.H, vertical U. HORIZONTAL STRIATIONS ; 

 FIRST OPERATION, SECTION OF THE LEFT OPTIC TRACT, THE CORPUS 

 CALLOSUM, AND ABLATION OF THE LEFT TEMPORAL CORTEX; SECOND 

 OPERATION, DECORTICATION OF THE RIGHT HEMISPHERE SPARING THE 

 TEMPORAL AND VISUAL AREAS; THIRD OPERATION, ABLATION OF THE 

 RIGHT TEMPORAL CORTEX 



The learning-set problem involves a series ot 467 two-choice, visual 

 object discriminations. The preliminary sixty-seven problems were pre- 

 sented either titty, or twenty-four, or six times per problem. Three trials 

 per problem were given for the last 400 problems. After such a long series 

 of problems a normal monkey would make a random choice on the first 

 trial, but learn to choose correctly on the second trial (Harlow, 1949). The 

 results of the four experimental animals are presented in Fig. 3. Both 

 monkeys lost the previously established learning-set after the second 

 operation. They reacquired the learning-set through re-training, but 

 reached a final level lower than that achieved previously. The third 

 operation which more or less left only one visual area intact, rendered all 

 four monkeys incapable of learning or reacquiring the learning-set 

 (Chow, 1954a). These animals, however, could still learn any one object 

 discrimination to criterion within ninety trials. 



