In what might seem an oddball experiment in the first instance, later revealing some very interesting scientific facts, a Kyoto University researcher asked 60 women participating in a study to look at a 9-photo grid (eight were of flowers, and another captioned a snake) and identify as quickly as possible the snake photo. Women who were in their premenstrual phase of their menstrual cycles scored the highest, suggesting they’re more responsive to threatning stimuli than otherwise.
Nobuo Masataka, a Kyoto University Primate Institute researcher, asked 60 healthy, naturally cycling women ages 29 to 30 to look at grids of nine photos and to touch the photo in each grid that contained a snake. Flowers are considered neutral, while snakes are considered scary. Of the correspondents, 20 were in their follicular phase of their cycle, or the fifth day after the start of the menstrual period, and other 20 were in their early follicular phase and the luteal phase, when ovulation begins, while the rest of 20 participated during the late follicular phase and the luteal phase.
Results showed that women in their luteal phase, or premenstrual portion of the menstrual cycle, were quicker at detecting photos of snakes than they are during the early and late follicular phase of the cycle. There was no difference in snake-detecting ability between the early and late follicular phases.
The study suggests that in this phase of their natural cycle, often associated with PMS, but also maximum fertility, women experience a heightened state of anxiety, naturally evolved, the researchers suggest, to keep pregnant or soon to be pregnant women safe from outside threats. It’s worth noting that the study is just preliminary, and the data collected was correlated with dates participants gave for their last periods, not on direct hormone measurements.
The findings were recently published in in the Nature journal Scientific Reports.