Economic Choices, Rationality & the Menstrual Cycle

We have heard it all, or have we?

To all the women out there and the men who are interested. Our menstrual cycle can play havoc with our daily routine, our relationships, our self-esteem and so much more. But very few of us (both women and men) consider if there may be an advantage to these different phases of our menstrual cycle, specifically rational and economic benefits.

As a woman myself I have always seen the menstrual cycle as a countdown to that one week of annoyance. I never once considered that there may be benefits to the menstrual cycle. This is partly due to being fed information that this ‘certain time’ can make us irrational, irritable and difficult to negotiate with, and that we women need to learn to manage this. Of course when we label the menstrual cycle this way why would we even consider the positive side.

This is why a study called The Impact of Menstrual Cycle Phase on Economic Choice and Rationality caught my eye. Dr. Stephanie Lazarro and her colleagues did what many studies have overlooked; they examined how all phases of the menstrual cycle affect how we rationalise choices and make decisions. They did this by testing women’s blood during the four different phases: menstruation, the mid-follicular phase (after menstruation), ovulation and the luteal phase.

As already mentioned, many of the studies done on the menstrual cycle have only looked at certain phases of the menstrual cycle rather than the cycle as a whole. This was likely done to save money on expensive long-term studies (or due to bad design). Nevertheless there is no better way to see a difference than comparing one thing to a comparable other. The study consisted of only female participants and any comparisons made to men were from previous findings that had examined men’s rationality and economic choices.

Cookies, Milk and Rationality

The first test was to see if the participants are consistently rational during all four phases of their menstrual cycle. This was done with a logic test involving milk and cookies. The participants were presented with goodie-bundles containing milk and cookies with each bundle having a larger or smaller quantity of milk and cookies than the previous bundle. The idea was that the participants would consistently choose the bundle that would be most beneficial to them. If they continuously chose the bundle that benefited them the most, the researchers could assume that the participants would always try and maximize their self-defined goal, in this case choosing the amount milk and cookies that they wanted. Yum! (By the way, the participants had the option to choose either vegan or non-vegan cookies and milk.)

Surprise surprise! The participants consistently made rational choices in all phases of their menstrual cycle. But more surprising was that the participants were just as rational as their male counterparts. In other words, women’s rationality is not in a state of flux, but remains the same no matter what phase of the menstrual cycle we’re in.

Money money money

The second test was gambling! The participants were given $20 to gamble with. The most they could win was another $20 and the most they could lose was $20. The participants were asked to make either a ‘safe choice’, which would gain them a bit of money, or a ‘risky choice’, which would either gain them more money or gain them no money at all. The question: Would potentially losing money impact their decision more than gaining the equivalent amount of money, i.e. loss aversion? And does this change depend on which menstrual phase these women are currently in?

It turned out that women’s choices tend to vary depending on which phase of the menstrual cycle they’re in. The participants were less competitive and less risky during the infertile part of the luteal phase than the other phases. But during ovulation (high fertility phase), the participants were more likely to take risks compared to men.  The researchers compared their participant’s behaviour to an agent on a mission to maximize the expected value of their choices.

What can we take away from this study?

Firstly, women may express different choice behaviour at different times, but the choice behaviour is rational nevertheless. Secondly, women’s rationality is consistent in all phases of their menstrual cycle – any irrationality is likely due to something else. Lastly, women’s economic preferences may change depending on the menstrual cycle phase, however these changes range from either making similar safe financial choices to men or that women can be a little more risky. Lastly, this riskier behaviour could be because women are more willing to tolerate a potential economic loss during their ovulation phase compared to men.

On a final note, this study was just on rationality and economic choices. Other factors, like our emotional well-being, were not tested and it is possible (more than likely) that our emotions can fluctuate during the different phases in our menstrual cycle. Either way, I’m excited about this research and will keep following it to discover what they’ll find out next.

Written by Alison Holland