Abstract
It has been demonstrated that exposure to men has the capacity to shorten the menstrual cycle in women. In the present study, the impact of the variables of sleeping arrangements and sexual activity were examined on both menstrual cycle length and the occurrence of ovulation as determined by basal body temperature charts. It was found that women who spent at least two or more nights with men during a forty day period exhibited a significantly higher rate of ovulation (p less than 0.05) than those spending no or one nights. Cycle length was not affected by sleeping arrangements. Furthermore, frequency of sexual intercourse was unrelated to either cycle length or likelihood of ovulation. The mechanism underlying this phenomenon is unknown but it is conjectured that it is pheromonal in nature.