714 ROGER T. DAVIS AND ARNOLD A. McDOWELL 



was other-animal-directed behavior. Visual survey and rapid-energy-expendi- 

 ture were more frequent in ours. The manipulation and visual regard of 

 inanimate objects were slightly more frequent in our study, but it dropped 

 to 24% of the total behavior during the second 5 days of the experiment, a 

 level almost identical to that attained in their study. 



Frequencies of activities are presented in Table II. The most frequently 

 occurring behaviors were highly reliable, and all correlations were significant 

 at or beyond the 5% confidence level. Looking at self, looking toward sounds, 

 orienting to sounds, and resting were so infrequent, they could not be 

 analyzed. 



Two changes were attributable to the effects of radiation. The A group 

 engaged in significantly more rapid energy expenditure after radiation than 

 before, t = 3.03, p < .05, and the AP group showed significantly more visual 

 survey after radiation than before, t = 3.90, p < .01. 



Two differences were characteristic of all four groups and were probably 

 effects of adaptation to the strange environment. There was a significant 

 decline in the number of times a cage was manipulated and the number of 

 times it was examined visually, p < .05 in both comparisons using the sign 

 test. 



Chronic Effects of Head Radiation 



Table III indicates the subjects that died during the year following irradia- 

 tion and identifies the focus of irradiation.Three monkeys in the A group died 

 between the first and second radiation. Approximately 2 weeks after the 

 experiment, one in the AP group died. During the next 150 days the rest of 

 the AP group, two in the A group, and two in the P group died. None in the 

 control group died during the year following the experiment. The clinical 

 pattern was severe, acute motor ataxia occurring approximately in the 48 

 hours before death. This pattern was followed without variation by the AP 

 group. 



Although the data are limited, they suggest an immediate cause of death 

 manifest during the 1st week following radiation and a delayed cause evident 

 at an average duration of 144 days after the second radiation. 



McDowell and Brown have followed up the original study with investiga- 

 tions of the behavior of subjects that survived. They studied discrimination 

 along a peripheral cue gradient ( 1960) , visual acuity ( 1960a), oddity reversal 

 and delayed response (McDowell et al., 1961), effects of repetitious work 

 (1960b), and response latency (1960b). Their findings are generally similar 

 to results obtained with surgically brain-damaged monkeys and contrary to 

 the results obtained with large doses of whole body radiation. 



