Dormitory effect menstrual synchrony study

• Pheromones in humans may be present in bodily secretions such as urine, semen or vaginal secretions, breast milk and potentially also saliva and breath, yet most attention thus far has been directed toward axillary sweat.
• McClintock (1971) observed that the cycles among her dormitory friends at university became synchronised.
• After further research, she concluded that the cycles of 135 women (aged 17 - 22 years) became synchronised due to pheromones (“smell” chemicals that when secreted, cause specific reactions in other individuals)
• McClintock and Stern (1988) began a follow-up 10-year longitudinal study that involved 29 women between the ages of 29 and 35 with a history of irregular, spontaneous ovulation.
• They obtained samples of pheromones from 9 of the women at certain points in their cycles by placing cotton wool pads under their arms the women wore these pads for at least 8 hours! These pads were then treated with alcohol (to kill bacteria and disguise the smell) and then wiped under the noses (on the top lips) of the other 20 women on a daily basis.
• Results 68% of the women responded to the pheromones. Menstrual cycles became synchronised to that of the pheromone donor
• Conclusion: The pheromones acted as an exogenous zeitgeber and modified the women’s Infradian rhythm of menstruation.
• Pheromones are chemicals that animals and humans use to communicate. Our bodies release pheromones through sweat, urine, semen, breast milk, and vaginal fluid.