Society has long had a deep affinity for the color red, perhaps even before it bore a name — from the time blood first leaked from a person’s skin to the near infinite uses it sees today. In the world of film, the “lady in red” connotes sexuality — consider Scarlett O’Hara in Gone With the Wind — but science has only recently begun to concretize the rationale behind this behavior, with one growing body of evidence suggesting that women who wear red are most likely looking for a mate.

The Red Hypothesis

A collection of studies in recent years has helped shape the scientific theory that women wear red in order to appear more attractive to men, with the majority of cases taking place during ovulation. While the jury is still out regarding the behavior’s cause — though some say it has to do with a flushing of the face following sex — experts often appeal to biological influences, arguing men’s animalistic brains awaken when confronted with some deep primal force — in this case, the color red.

red study
Daniela Niesta's study examined red vs. blue clothing to determine which color men found more attractive on women. University of Rochester

"It's only recently that psychologists and researchers in other disciplines have been looking closely and systematically at the relationship between color and behavior,” said Andrew Elliot, professor of psychology at the University of Rochester. “Much is known about color physics and color physiology, but very little about color psychology. It's fascinating to find that something as ubiquitous as color can be having an effect on our behavior without our awareness."

Read more: Study Reveals How Women Wearing Red Lipstick Are Perceived To Look Younger

Elliot and co-researcher Daniela Niesta questioned male subjects in three separate experiments as to the attractiveness of a woman shown to them in a photo.

In the first study, the experimenters showed the men pictures of identical women but with either a red or white border. Other experiments used gray, green, and blue. The final study actually changed the woman’s shirt color, meaning participants saw her wearing either a red shirt or blue shirt. Overwhelmingly, subjects found the woman in red more attractive, despite both pictures depicting the same person.

Subjects were also asked in the final study to imagine they had $100 to spend on a date with the girl. "How much would they spend on her?" the researchers asked. Men reported a much greater willingness to spend more money on the woman in red.

"Our research demonstrates a parallel in the way that human and nonhuman male primates respond to red," concluded the authors. "In doing so, our findings confirm what many women have long suspected and claimed – that men act like animals in the sexual realm. As much as men might like to think that they respond to women in a thoughtful, sophisticated manner, it appears that at least to some degree, their preferences and predilections are, in a word, primitive."

Turning The Tables

And while this reflexive behavior in men is to prefer red, according to Elliot and Niesta’s study, that doesn’t say much for a woman’s choice of color. Perhaps men are more accustomed to seeing celebrities in red, so they equate the color with beauty. But what about women?

To test the phenomenon in the other direction, researchers Alec Beall and Jessica Tracy from the University of British Columbia in Canada recruited 100 American women and 24 Canadian women online. They had the women report the number of days since their last period and the color of the shirt they were wearing.

In both groups, a far greater percentage of women wearing pink or red were in the ovulation group.

Read more: Melissa Nelson, ‘Irresistible’ Employee Fired By Dentists For Being Too Attractive, Will Get Another Day In Court

“Women at high-conception risk were substantially more likely to be wearing a red/pink-colored shirt compared to women at low-conception risk; 40% vs. 7%,” the researchers wrote in their report. “We found that 76% of women in Sample A and 80% of women in Sample B who were wearing red/pink were at peak fertility, suggesting that red/pink-colored clothing is a strong indicator of ovulation.”

At a 76-80 percent likelihood that women in red/pink-colored shirts are ovulating, the study provides considerable fuel to the overall fire. It also has similar pitfalls as Elliot and Niesta’s study, as the women wearing red could be appealing to other variables, namely, high fashion or taste. In both cases, the degrees of freedom allow for social influences in a set of experiments that otherwise targets biology.

It’s for this reason that hard conclusions about human sexuality and biology come to be derided as “biotruths.” Critics of Beall and Tracy’s study may say, for instance, that self-reported data fails to adequately capture information that could be better found with hormonal tests, given the effects of birth control on mate preference and the slipperiness of social phenomena.

“Regardless of these issues,” Beall and Tracey concluded, “which highlight important directions for future research, the present results are the first to indicate that female ovulation, long assumed to be hidden, is in fact associated with a distinct, objectively observable behavioral display.”

Sources: Elliot A, Niesta D. Romantic red: Red enhances men’s attraction to women. Journal of Personality and Social Psychology. 2008.

Beall A, Tracy J. Women more likely to wear red or pink at peak fertility. Psychological Science. 2013.