The possible relation of the menstrual cycle to susceptibility to fear acquisition.

Biological changes due to the menstrual cycle may account for the fact that fears are not equally distributed between the sexes. In a differential, classical conditioning paradigm, women in premenstrual phase of their menstrual cycles were compared with a control group of women at other points in their cycles except within seven days before menstruation. Electric shock and pictures of natural scenes were used as UCS and CS respectively. Premenstrual women showed an enhanced susceptibility to the acquisition of a conditioned skin conductance response and to delayed extinction, while control women did not. The possible role of an altered physiological state during the premenstrual phase in the acquisition of fear responses is discussed.