The effect of a choice alternative on sex differences in passive avoidance behavior.

A modified standard passive avoidance conditioning procedure was used to investigate whether or not "inferior" passive avoidance behavior of female Wistar rats could be attributed to memory deficits. Male and female Wistar rats were first adapted to two standard passive avoidance conditioning compartments, which were clearly different from one another. Both compartments were accessible from the same illuminated platform. Three learning trials in one compartment were alternated with three trials in the other compartment and unavoidable shock was presented on the last (6th) learning trial in one of the compartments. One hour after shock presentation, subjects were again placed on the platform. Significantly more females than males reentered one of the compartments. Of the subjects which reentered , significantly more females and males than would have been expected by chance, entered the compartment in which shock had not been presented. The data are interpreted to show that sexual dimorphism in passive avoidance behavior should not be attributed to differences in memory capacities of male and female rats. Therefore, it remains to be determined which variables associated with hormonal or genetic background of the subjects and which requirements of the experimental task, are responsible for the occurrence of the observed difference.