Our mood states and behaviors naturally vary over the course of the year. For example, some people experience Seasonal Affective Disorder, a form of depression that usually kicks in during the winter. Extreme psychological changes like this are relatively rare; however, smaller seasonal fluctuations are actually quite common, even among healthy people , and these changes can have noticeable implications for our sexual and romantic lives. Indeed, a recent study revealed that, at least among heterosexual men, their patterns of sexual attraction change with the seasons, and not in the way that you might expect .
In this experiment, 114 heterosexual men between the ages of 16 and 53 rated the attractiveness of several women every three months over the course of about one year. Specifically, once per season, each man was asked to rate two sets of photos that appeared in a random order: one showing only women’s faces, and the other showing women’s bodies. The body photos consisted of either women in revealing bathing suits or close-up shots of women’s breasts.
The researchers found that men’s attraction to women’s faces did not change during the course of the year; however, their attraction to women’s bodies did, such that men reported being more attracted to women’s bodies and breasts during the winter months compared to the summer months. Furthermore, men who were in the same romantic relationship over the course of the entire study reported similar fluctuations in how attracted they were to their partner. Specifically, guys tended to think that their partners were hotter in the winter than in the summer.
How do we explain this pattern of results? We can't say for sure, but one possibility is that there is a greater contrast effect in warmer weather. Because women tend to wear sexier and more revealing clothes in the summer months and bundle up in the winter, the standard of bodily comparison is much higher when it is warmer outside. Think of it this way: because everyone is showing a lot of skin during summer, the bar for what qualifies as "hot" is set higher; in the winter, skin is rarely seen, so it becomes more novel and arousing to look at. The fact that facial ratings didn’t change supports this idea. Given that people tend to see faces all year round, the standard of facial comparison is always pretty constant. An alternative possibility is that men’s hormone levels fluctuate seasonally, and perhaps this is what accounts for their differing patterns of attraction.
Are there any real world implications of these changes? Research has found that birth rates tend to peak in the third quarter of the year , which means that a higher than usual number of conceptions happens during the winter months. Not only that, but diagnoses of sexually transmitted infections tend to peak during the first quarter of the year , which is when the coldest weather typically occurs (at least in the northern hemisphere). Of course, we don't know whether these sexual health changes are a direct function of changes in men's patterns of attraction, but it does seem like quite a coincidence that merits further research.
More work is also needed to determine whether seasonal changes in attraction also apply to women and to persons of different sexualities. However, the existing research at least gives us reason to suspect that the weather isn't the only thing that changes with the seasons.
 Kasper, S., Wehr, T. A., Bartko, J. J., Gaist, P. A., & Rosenthal, N. E. (1989). Epidemiological findings of seasonal changes in mood and behavior: A telephone survey of Montgomery County, Maryland. Archives of General Psychiatry, 46, 823-833.
 Pawlowski, B., & Sorokowski, P. (2008). Men's attraction to women's bodies changes seasonally.Perception, 37, 1079-1085. doi: doi:10.1068/p5715
 Wellings, K., Macdowall, W., Catchpole, M., & Goodrich, J. (1999). Seasonal variations in sexual activity and their implications for sexual health promotion. Journal of the Royal Society of Medicine, 92, 60-64.
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