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HARRY F. HARLOW 



preference was determined at the end of each trial by amounts consumed. 

 The subject received two tests per week for 6 weeks. 



After the preradiation preference testing, the monkey was exposed to 30 r 

 per day, for 45 minutes, for 5 consecutive days. During the exposures, the 

 animal was restrained in the small rotating cage used during the preradiation 

 tests, with only the Kool-Aid available. 



After the total dose of 150 r had been administered during the five day 

 conditioning period, preference tests were repeated at the rate of two per 

 week for 5 weeks. Kool-Aid ingestion was extinguished by the end of the 

 radiation exposure period and was greatly depressed during the 5 post- 

 radiation weeks. 



Similar, though less striking, data were obtained with another monkey 

 (Fig. 15) using a preferred and a nonpreferred Kool-Aid solution. 



5 10 151 212345 



PRERADIATION DAYS RADIATION DAYS POSTRADIATION DAYS 



Fig. 15. Radiation-reversed Kool-Aid preference by a monkey. 



Since we were not satisfied with Kool-Aid as a stable and commonly ac- 

 cepted high preference fluid, we tested the same monkey for preference of 

 apple juice, grape juice, or tap water by presenting him with a choice 

 between pairs of these three fluids for 18 days. Each possible pair of fluids 

 was presented in random order, one pair per day, for 1 hour periods in the 

 home cage. The cage was moved into the radiation chamber for half the 

 trials and left in the home room for the remaining tests. After 18 days of 

 preradiation preference testing, he was irradiated at the rate of 50 r in 55 

 minutes each day for 3 consecutive days. Only the preferred apple juice was 

 available to the animal during these exposures. Following the three daily ir- 

 radiations, the preference test procedure which had preceded the irradiation 

 was repeated for an additional 18 days. The fluids ingested during preference 

 testing were the only liquids the monkeys received during these 39 days. 



A second control monkey was given the same program of preference 

 testing except he was subjected to sham radiation. Consumption of apple 

 juice was greatly depressed for the experimental subject during the 3 post- 



