Evolution of Sex Differences in Spatial Ability

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In both humans and laboratory animals, males typically perform better than females on tasks that involve spatial thinking. Previous work in this field has tried to explain how sex differences in spatial ability occur during the lifetimes of males and females by focusing on the relatively immediate effects of sex hormones, brain organization and differential experience. Until now, the evolutionary and developmental components of this difference have received little attention. Dr. Gaulin has developed the ingenious hypothesis that sex differences in spatial ability have been favored by the evolutionary process. Dr. Gaulin proposes that evolution fosters spatial ability more strongly for more mobile animals: To orient successfully, an animal with a large home range needs more spatial skill than does an animal with a smaller range. To test this imaginative idea, he has chosen several closely related species of wild rodents which differ primarily in range size, and in reproductive strategies. Some species are polygamous, others monogamous. He has found that polygamous species have larger home ranges than members of closely related, but monogamous, species. Dr. Gaulin predicts that in monogamous species, where males and females have similar range sizes, no differences in spatial abilities will be found. Conversely, in the polygamous species, where males have much larger range sizes than do females, he predicts that these males will perform better in his laboratory tasks than do the females. Dr. Gaulin is combining both field and laboratory work to address this important question. Home ranges of individual male and female voles are measured using radio-telemetry, by fitting individual animals with miniaturized radio transmitters and following their movements for several weeks. Following the field work, he recaptures these same animals and measures their maze- learning ability in the laboratory. The current grant support is allowing him to continue these studies, originally funded by NSF grant BNS 85-08436. The results of these ongoing studies will contribute information of fundamental importance to ecology and to learning theory, and may eventually enhance our knowledge of factors that influence learning ability in humans.