Sex differences in spatial cognition are not caused by isolation housing

In mammals, males typically have better spatial ability than do females. However, most of the data come from laboratory tests and it is possible that factors impacting on the captive animal cause the observed sex differences in spatial cognition. A common influence on cognitive ability is stress, which may have its effect acutely, in the testing situation, or chronically, due to the housing conditions. We used a spatial working and reference memory task (the Morris water maze) to investigate if isolation housing had a differential impact on spatial cognition in male and female rats. Either as juveniles or as adults, rats were housed in pairs or in isolation. We also manipulated the duration of isolation housing. Regardless of housing condition, we found a sex difference in spatial ability only in the youngest rats. However, we found no evidence that isolated rats were spatially impaired relative to pair-housed rats. We also found no difference in body weight, food intake or bar biting behaviour (indicators of welfare in rodents) between pair and isolated rats. We conclude that isolation housing causes insufficient stress to cause sex differences in spatial cognition.