638 HARRY F. HARLOW 



LD/50/30 produce a relatively persistent learning loss and that amount of 

 loss is related to particular developmental state and irradiation dose. 



The efTects of irradiation at varying times zn utero or in early neonatal 

 periods have not been measured for the monkey. However, techniques for 

 determining dated pregnancies have been established, and methods for 

 large scale breeding have been developed. Next year we should be in a posi- 

 tion at Wisconsin to initiate limited investigations in these areas. 



One of the most intriguing discoveries concerning the efTects of radiation 

 on behavior is the finding by Garcia et al. (1955) that rats developed a 

 conditioned avoidance to saccharin if they were induced to drink it in solu- 

 tion while being irradiated. Recently, they reported such behavioral changes 

 following fractionated radiation doses totaling less than 20 r. Garcia et al. 

 (1957) also demonstrated that conditioned spatial avoidance could be ob- 

 tained, in that after irradiation rats would spend less time in a chamber in 

 which they had been confined during a series of radiations than in a chamber 

 in which they had not been previously exposed to radiation. These general 

 results on radiation-conditioned spatial avoidance have been confirmed by 

 Overall et al. (1959) using a different apparatus and comparing the time 

 spent by the subjects in a chamber exposed to radiation with the time spent 

 in a lead-shielded chamber. 



Recently Garcia and Kimeldorf (1960), using localized x-radiation, 

 demonstrated that the abdomen is a region of special sensitivity in producing 

 saccharin aversion. Exposures of 54 r and 108 r delivered to the abdomen 

 produced a decrement in saccharin consumption, whereas radiation of the 

 head, thorax, or pelvis required a dose of 252 r to produce the same effect. 

 Garcia and Kimeldorf suggest that sensations triggered by gastric dys- 

 function may represent the stimuli through which radiation acts to condition 

 behavior in animals, but they recognize that this may not be the sole re- 

 ceptive mechanism, since saccharin avoidance can be produced by direct 

 head irradiation. 



During the last year, Sponholz, Bowman, project associate. Primate 

 Laboratory and I have investigated conditioned saccharin avoidance in 

 rats and monkeys. In 33 white male albino rats 40 to 50 days of age, 

 Holtzman strain, changes in preference between a saccharin solution and 

 tap water were tested after association of saccharin drinking with exposure 

 to several levels of x-irradiation. Sham radiation was carried out on 12 

 controls. 



The rats were given a choice of 0.5% saccharin solution or tap water from 

 bottles available in the home cages 24 hours a day except during the 24 

 hours before and 16 hours after irradiation. Preference levels for saccharin 

 and water were recorded 4 days preceding deprivation and 4 days following 



