EFFECTS OF RADIATION ON CNS AND ON BEHAVIOR 



631 



ing after receivdng 650 r and 6 after receiving 1,000 r. They have been given 

 two 6-trial discrimination problems each day and four 6-trial oddity prob- 

 lems. We were interested in the outside possibility that the 3.5 month delay 

 would re\'eal differences between the two groups, although data such as 

 those of Davis et al. (1958) indicated that this interval was probably too 

 short, even if the phenomenon of delayed CNS necrosis following x-irradia- 

 tion exists. We also wanted to explore the feasibility and practicality of using 

 a skeletonized test program. 



Figure 2 shows comparable data for oddity learning for a group of normal 

 monkeys tested only on eight oddity problems a day, and for our radiated 

 monkeys trained on the skeletonized test program. The performance of the 

 noiTual monkeys, is, of course, superior, since they were not being run simul- 

 taneously on interfering problems. However, the important point is the effi- 

 cient, orderly, and reliable learning of the irradiated monkeys. We are 

 pleased with the consistency of the data obtained by this abbreviated test 

 program and plan to develop and extend the test techniques in future re- 

 searches; for if one wishes to trace behavior and behavioral changes over 

 long periods, the practical problems are overwhelming unless some efficient, 

 skeletonized behavioral test program can be established. 



Oddity learning curves for the two groups of irradiated monkeys, the 

 group trained after receiving 650 r and the group trained after 1,000 r, are 

 presented in Fig. 3. No significant differences were found, and it appears 

 obvious that neither the additional 350 r nor the 3.5 month delay was of any 

 importance. The learning set data are given in Fig. 4, and there is no reason 

 to believe that any significant difference between the groups will appear. The 

 females showed a significant early superiority on the oddity test, whereas the 

 differences for learning set favor the males (Figs. 5 and 6). 



50 - 



V 



/ • •MOON- HARLOW 



/'' O O RADIATED GROUP 



1-64 65-128 129-192 



PROBLEMS 



193-256 



Fig. 2. Oddity performance by normal monkeys and irradiated monkeys on skeleton- 

 ized test program. 



