Radiation-Conditioned Behavior 



Donald J. Kimeldorf 



U. S. Naval Radiological Defense Laboratory, 

 San Francisco, California 



Radiation-conditioned behavior was detected initially in studies of physio- 

 logic responses during exposure to low dose rate gamma radiation (Table I) . 

 The consumption of food and water by rats decreased progressively during 

 successive weekly periods of irradiation, while consumption between exposures 

 was not reduced (Garcia et al., 1956a). This puzzling observation was not 

 consistent with accepted concepts concerning cumulative effects of radiation 

 exposure. However, the behavior did suggest a learning curve in which the 

 animal was conditioned to avoid food and water during irradiation. The 

 experimental research necessary to test the hypothesis that radiation is a 

 stimulus for conditioning behavior has occupied the attention of John 

 Garcia, E. L. Hunt, and myself for the past few years. 



It was reasoned that if the progressive reduction in food and water con- 

 sumption during exposure was a learned behavior, then the manipulations 

 involved in a sham irradiation test should likewise evoke the conditioned 

 (learned) response in previously irradiated animals (Garcia et al., 1956b; 

 Kimeldorf et al., 1955). Table H illustrates the previous exposure history 



TABLE I 

 Food and Water Consumption during Exposure to Gamma Radiation * 



Exposure conditions Consumption during Consumption for 10 hrs. 



successive exposures after each exposure 



Radiation + food and water declines normal 



Sham irradiation + food and water normal normal 



Radiation only — normal 



" Exposure pattern: 1-8 weekly exposures, 75 r per exposure at 9.4 r per hr. 



* The opinions and assertions contained herein are the private ones of the author 

 and are not to be construed as official views of the Navy Department. This study was 

 supported through funds provided by the Bureau of Medicine and Surgery, USN. 



683 



