634 



HARRY F. HARLOW 



Laboratory, and I have designed and used several "nonlearning" tests on 

 our 50 r and 100 r groups. We established a visual curiosity test by placing 

 three modified Butler boxes (Fig. 7) in such position that the monkeys 

 could view each other when they opened the windows. Figure 8 presents 

 data from our 100 r group that show a lower amount of visual exploration 

 during the last 5 weeks preceding death in irradiated monkeys, as compared 

 with a control group, and a pronounced and obvious drop in exploratory 

 activity in the last week of life. A progressive reduction in visual exploration 

 from 600 r onward is apparent from Fig. 9, and the differences between 

 irradiated and control subjects are significant, even though both show a 

 similar downward trend. 



However, we are not satisfied with statistically significant group differ- 

 ences, since we hope to achieve tests capable of predicting death for indi- 

 vidual monkeys. Therefore, in an effort to gain better control and to improve 

 our apparatus, we built the boxes into a compact, enclosed unit and had the 

 monkeys of our 50 r group view a rabbit rather than other monkeys. We 



Fig. 8. Visual curiosity performance as lethal radiation dose is approached. 



IRRADIATES (N = I2) 

 O O CONTROLS (N = 4) 



400 600 800 1000 1200 



ACCUMULATED ROENTGEN DOSE 



Fig. 9. Behavior of irradiated and control monkeys on visual curiosity test. 



