Sex and Radiation as Factors in Peripheral Cue Discrimination Learning

Abstract

S>Tests were made on 84 rhesus monkeys, ranging in age from 40 to 52 months, which had been exposed to nuclear radiation (273-670 rem) at the Nevada Test Site approximates 28 months before the present study. This investigation sought to determine if monkeys with less training on direct response to the relevant cue, and younger than the subjects previously used, could resolve a peripheral cue, color discrimination problem. Secondly, in view of previously reported radiation and sex differences in scope of attention, the investigation sought to explore these two parameters with respect to this learning paradigm. All monkeys had previously experienced preliminary Wisconsin General Test Apparatus (WGTA) training, testing on reduced-cue discrimination and delayed response problems, and testing on a series of dot discrimination problems. All training was conducted in a modified version of the WGTA. The practice effect was significant indicating that rhesus monkeys, if given extended training, can learn color discrimination when the discriminanda are displaced in the horizontalparallel dimension for a distance of 7.875 in. from the site of reward. The radiation-groups-by-sex-by-practice interaction was significant: for the females, radiation exposure slowed the rate of improvement with practice; for the males, the converse was true. While the disparitymore » between these results and the earlier results cannot be adequately resolved in the context of the present experiment, such a disparity may reflect differences in the training histories of the subjects involved in the two studies. Thus, extensive training to respond directly in the contiguous cue-reward situation may reduce response tendencies to peripheral stimuli. The finding of a significant radiation-groups-bysex-by- practice interaction suggests that exposure to radiation affects the sexes differently; previous research, however, has shown that radiation exposure decreases the distractibility of the monkey with a consequent narrowing of attention and that female monkeys show greater focalization of attention than do male monkeys. In view of this previous research, the significant triple interaction can be interpreted as reflecting a radiation-induced narrowing of attention for both sexes. Because of the sex differences in attention in normal monkeys, however, the result of this induced narrowing of attention for the males may be proportionately greater exclusion of irrelevant (peripheral) stimuli whereas, for the females, the narrowing must involve, to a greater extent, the relevant (proximal) stimuli. (BBB)« less