How do you get someone to do what you want? Psychologists have been researching this question for decades and have discovered that numerous factors can affect the odds of compliance.

Perhaps not surprisingly, the requestor’s appearance plays a big role, with physically attractive people being more successful at getting others to do their bidding.

But it’s not just looks that matter—what you’re wearing matters, too. And if you’re a woman, your shoes appear to make all the difference.

According to a new set of studies published in the Archives of Sexual Behavior, women are more likely to gain compliance and receive spontaneous offers of help from men to the extent that they’re wearing high heels—and the higher the heel, the better.

Four studies were presented in support of this idea, all of which took place in French cities. In the first two studies, young female research assistants approached random strangers as they were walking across town and asked them to complete a brief survey on the spot.

These women were always wearing the same thing, except for their shoes. Specifically, they wore one of three different pairs of black leather shoes that varied in heel length: no heel, two-inch heels, or 3.5-inch heels. In order to control for differences in overall looks, each assistant wore each of the three pairs of shoes for the same amount of time.

So what did they find? Men were far more eager to compete the survey when approached by a woman wearing high heels.

When the assistant was wearing flat shoes, 42 to 47 percent of men complied. This increased to 60 to 63 percent with medium heels, and 82 to 83 percent with high heels. Thus, shoes made a huge difference in compliance rates—nearly twice as many men were willing to take a survey from a woman in high heels.

By contrast, regardless of what shoes the assistant was wearing, roughly one-third of female pedestrians agreed to complete the survey. In other words, the assistants’ shoes made no difference to women on the street.

In another study, female research assistants “accidentally” dropped a glove in a public setting without seeming to notice. Each time this happened, everything was kept the same, except for the shoes the assistant was wearing. What the researchers were interested in was how heel size affected the number of strangers who notified the assistant about the lost item.

The results followed the same pattern as the other studies—while heel size made no difference to female pedestrians, it did for men. Again, men’s likelihood of offering help increased with the length of the assistant’s heel.

In the final study, a research assistant sat alone in a bar wearing one of three pairs of shoes in order to determine whether heel length affected the speed with which men approached her. It did.

Male patrons approached her nearly twice as fast when she was wearing high heels compared to flats: 7.5 minutes versus 13.5 minutes.

So why are men more inclined to approach and assist women in heels? The author of these studies, Nicolas Gueguen, puts forth a few possibilities. One is that high heels change the way that women walk in such a way that they become more attractive to men. Support for this idea comes from other research finding that women walking in heels are perceived as more feminine and that this increased femininity is what enhances their attractiveness.

Another possibility is that men have simply learned to associate high heels with sex appeal or sexual intent. In other words, based on the way that women tend to be portrayed in the popular media, perhaps men have learned to think that women in heels are sexier or are inherently more interested in sex.

An alternative explanation, which Gueguen did not consider, is that perhaps women behave differently when they’re wearing heels and that this is responsible for the observed changes in men’s behavior. That is, perhaps wearing heels changes women’s own feelings of attractiveness, which ultimately produces changes in the way they are viewed and treated by men.

Although the mechanism behind this effect is still unclear, the results of this research reveal that women’s footwear holds a surprising amount of power over men.

Justin Lehmiller, PhD is a sex educator and researcher at Ball State University and author of the blog Sex and Psychology. Follow him on Twitter @JustinLehmiller.