Menstrual cycle synchronization

The observed synchronization of the menstrual cycles of women living together in an all-female institution is ascribed to the effect of a primer pheromone and led to several earlier studies (e.g. [149,150]). Later results supported the pheromonal explanation of synchrony [151]. In an evaluation of the research on menstrual synchrony between mothers and daughters against the background of the results of other investigations, Weller and Weller [152] concluded that there are indications that menstrual synchrony could be affected by both pheromonal and environmental influences, and the interaction between them. 

As an undergraduate at Wellesley College, Martha McClintock noted that her female dormmates tended to synchronize their menstrual cycles over time. When she pointed this out to a group of scientists at a pheromone conference, she was challenged to study the phenomenon scientifically if she wanted to be believed. She took up the challenge, recruited 135 women from her dorm, and collected the data on dates of onset of menstrual cycles. The data strongly supported her informal observations and she wrote up the results of her study as her senior thesis. 

Ever since McClintock (1971) described synchronized estrus cycles in 135 women who roomed together in a women s college dormitory, the search for possible olfactory cues, as occur in other mammals, has continued. The longer the women in McClintock s study spent time together during the academic year (October through March), the closer the times of onset of their menstrual cycles... 

The axillary odor of women, collected over 10 different 3-day sections of the menstrual cycle and applied to the upper lip of recipients, had a different effect. The cycles of the receiving women became more synchronized with the cycle of the donor female (Preti et al, 1986), measured as difference in menses onset in terms of days. Wilson (1987) and Weller and Weller (1993) have criticized these experiments but still they remain pioneering studies in an extremely difficult field. 

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