20 Weird Facts About Sex and Love

Scientists already knew that people tend to choose romantic partners with similar characteristics, such as age, race, religion, income, and upbringings. But a study published in the Proceedings of the National Academy of Science found that people also tend to marry others with similar DNA. When researchers studied the genetic material of 825 white American couples, they found fewer differences in the DNA between married people than between two randomly selected individuals within the same race. In fact, they calculated that the tendency to pair up with a genetically similar spouse is about one-third as strong as the tendency to do so with someone with a similar education.

Watching movies may be one key to marital bliss, says Matthew Johnson, PhD, director of the Marriage and Family Studies Laboratory at Binghamton University. In his study, couples attended counseling or watched relationship-themed movies and completed discussion guides together. Both strategies cut the groups' divorce rate in half after three years—but the movie-watching activity took 50% less time and took place almost entirely at home. "The key is to talk with your partner about your relationship in the context of a movie," says Johnson.

Your brain wiring may influence your number of sexual partners, according to a University of California Los Angeles study. Researchers performed brain scans of volunteers while they viewed images, some sexually suggestive, and also asked their sexual behaviors within the past year. Turns out those whose brains were most active when viewing the sexual images also tended to have had the most partners. Levels of "sexual motivation" do vary form one person to another, says Justin Garcia, PhD, assistant professor at the Kinsey Institute for Research in Sex, Gender, and Reproduction at Indiana University.

Along with damaging arteries and working the heart overtime, high cholesterol can also contribute to erectile dysfunction in men. In fact, ED may serve as a warning sign for cardiovascular disease. The good news? Men who take statins or other medications to lower their cholesterol are also likely to see an improvement in their sexual function, according to a 2014 study by researchers at Rutgers University's Robert Wood Johnson Medical School. Of course, stains should not be prescribed to treat ED on its own, say the researchers, since the condition can also be caused by other physical or emotional issues.

Arguments and aggression between husbands and wives can sometimes be the result of low blood glucose levels, say Ohio State University researchers. In a 2014 study, they asked 107 married couples to test their blood sugar each night and morning, and to stick pins into "voodoo dolls" that represented their spouses, based on how angry they were with them. The lower their blood sugar over the course of 21 days, the more pins they used. One possible reason? Low blood sugar can cause people to feel hungry—and therefore cranky and irritable. "It's simple advice but it works," says lead author Brad Bushman, PhD. "Before you have a difficult conversation with your spouse, make sure you're not hungry."

Here's a scary-sounding stat for you: More than two-thirds of healthy Americans adults are infected with one or more strains of human papillomavirus (HPV), a type of virus that is transmitted through sexual intercourse and oral sex. That's what NYU Langone Medical Center researchers found when they tested the DNA of 104 men and women in a 2014 study. The not-so-scary news, however, is that only four of those people tested were infected with the types of HPV that are known to cause cervical cancer, throat cancer, or genital warts. And even though the most high-risk strands, known as genotypes 16 and 18, can cause cancer, the good news is they usually don't. (Most of the time, the body eliminates HPV without special treatment.)

Having trouble getting a date? Appearing less pretentious may increase your chances, according to a published in the Journal of Positive Psychology. When volunteers were asked to read fake dating profiles and rate them on likability, friendliness, fun, and likelihood of going on a date, they rated humbler profiles more favorably. In a second study, volunteers who considered their significant others to be humble were more likely to forgive them for a transgression. "This suggests that humility in a relationship encourages relational repair in ongoing romantic couples," says Daryl Van Tongeren, assistant professor of psychology at Hope College in Holland, Mich.

A long car ride may sometimes seem like the worst place to hash out important issues with your significant other—after all, you're stuck in your seat for hours. But that's what makes it work, says Johnson. "Many couples find long car rides to be a good way to work on problems that need sustained attention," he says. Road trips can also be a good time to get to know your partner better, he adds. "Ask detailed questions about their hopes for the future, their wildest fantasies, or their childhood memories. Then, be a good listener and ask real follow-up questions that are meaningful to both of you."

In a 2014 study, Albright University researchers found that women were able to deliberately manipulate their voices—while counting from one to 10—to sound more attractive. But, sorry guys: When men tried to be sexier, they were actually rated as sounding worse! When a woman intentionally drops her voice to make it sound low and breathy, she's often perceived as more attractive—but not exactly for the reasons you might think. Men tend to prefer women with higher, more feminine voices, says co-author Susan Hughes, PhD, associate professor of psychology. But when a woman lowers her voice to "sound sexy," she's signaling her interest in a potential mate—a clue that men are able to pick up on.

Research shows that when women take hormonal contraceptives, they show less of an attraction toward men with high testosterone levels and masculine physical characteristics. And one 2012 Scottish study found that women who met their partner while on the pill were less sexually attracted to their mates and less sexually satisfied during their relationship. At the same time, however, they tended to be more satisfied with their partner's financial status, and less likely to separate, than women who weren't on the Pill.

Women also tend to seek out masculine men during the most fertile times in their cycle, according to several studies. In one German report, women were asked to rate their desirability for soldiers returning home from war, some of which had trauma-related aggressive tendencies. Those in their most fertile times of the month were more likely to prefer the trauma-impacted soldiers as potential short-term mates, but not as long-term mates. Other research suggests that women may want more sex in general during ovulation, says Garcia.

"It's often assumed that people fake orgasms because they aren't enjoying themselves or they just want it to be over," say Garcia. But sometimes, putting on a big show is part of the enjoyment, he adds. "Sex is performative, and sometimes it's fun for both parties to get carried away."

Speaking of faking orgasms—did you know that men do it too? They can and often do, says Garcia, often for the same reasons women do. (Since sex involves a lot of fluids anyway, it's not always easy to tell whether he's ejaculated or not.)

Kissing, caressing, and affectionate talking after sex may be just as important to relationship satisfaction as intercourse itself, suggests a 2014 University of Toronto study. When researchers asked couples to spend more time cuddling together after sex, those who did reported higher levels of sexual and overall relationship satisfaction—especially those couples with kids. This may have to do with the release of oxytocin, says Johnson, which is released during sex and continues to be released with prolonged skin-to-skin contact. "Couples who augment their sex with cuddling—or other behaviors before, during or after sex—are probably reinforcing their bond," he says.

Sex can be a messy activity with lots of fluids and smells, but in the heat of the moment, none of that (usually) seems to matter. According to a study from the University of Groningen in the Netherlands, that's because sexual arousal overrides the body's natural "disgust response." When researchers asked women to watch either an erotic film, a sports video, or a "neutral" video of a train, and then perform a series of unpleasant acts (like drinking out of a cup with a bug in it), they found that those who'd watched the sexual acts rated the tasks as less disgusting—and were also able to complete more of them. Previous research has suggested that sexual arousal has a similar impact on men, as well.

There's a reason you can't stop thinking about that special new guy or girl in your life: MRI scans have shown that falling in love sends blood rushing to the "pleasure center" areas of the brain—the same areas that are responsible for obsessive-compulsive behaviors. Falling in love also lowers serotonin levels, which is common in people with obsessive-compulsive disorders, says Mary Lynn, DO, co-director of the Loyola Sexual Wellness Clinic at Loyola University in Chicago. "This may explain why we concentrate on little other than our partner during the early stages of a relationship," she says, and also why we tend to idealize new partners and turn a blind eye to their faults.

Marriage appears to strengthen men's skeletons, according to a University of California Los Angeles study, especially if they wait until after age 25 to tie the knot. Researchers aren't sure why, but they point out that it's not the first time marriage has been linked to health. Other studies, for example, have suggested that married people live longer, are more likely to survive cancer, and have a lower risk of cardiovascular disease.

Is he or she really "the one"? According to a 2013 study published in Science, deep down you probably know the answer. Researchers asked newlyweds—all of whom reported high levels of relationship satisfaction at the time—to look at images of their spouses paired with either negative or positive words, and rated their response times in distinguishing between them. Four years later, those who had quickly identified the negative words were more likely to report lower relationship satisfaction, suggesting that they'd had subconscious negative thoughts about their spouse all along.

Don't panic if you get red during sex: It's probably your body's natural response to increased blood flow and skin temperature, says Garcia. This so-called "sex flush" may appear on your cheeks, chest, genital area, or across your entire body.

"Some people get worried and think 'I must be allergic to something you're wearing, or maybe it's your beard scratching me,'" says Garcia. "But more often it's just a natural part of the sexual arousal process, and it should go away once things cool down and return to normal."

Getting busy between the sheets for an hour can blast as many calories as 30 minutes of jogging, according to a 2013 study from the University of Quebec. To crunch the numbers, researchers asked 21 couples, ages 18 to 35, to wear calorie-tracking armbands while they ran on a treadmill while they had sex once a week for a month. They found that men burned an average of 4.2 calories a minute during sex, while women burned about 3.1. Overall, men and women burned about 101 and 69 calories per session, respectively.

Sexual interest and sexual function do both decline with age—especially as adults begin to take more medications—but that doesn't mean that senior citizens aren't still getting it on. "Many people do continue to have sex into their old age, often until death," Garcia says. And they're not always careful: "Besides teenagers and young adults, the elderly is the biggest population for sexually-transmitted disease spikes," he adds. "They're not worried about getting pregnant, so they're not using condoms."