their noses. Men are actually more likely to fall in love at first sight, and neuroimaging of men in the early stages of romantic love show increased brain activity in the visual centers. Men are swayed by facial symmetry, glowing skin, and a particular waist-to-hip ratio. These help to signal that a woman is healthy and able to bear children.
When it comes to mating, women are influenced by scent. The sense of smell is the oldest and least mediated sense in our brains and processes information more quickly than the other sensory systems. Because the brain cells for smell are only one synapse away from the amygdala, our emotion center, we have no real control over liking or being repulsed by an odor. Women have a more sensitive sense of smell, and more brain space devoted to processing smells and pheromones, thanks to estrogen. Estrogen helps us to detect pheromones, the signature scent of a potential mate, more adroitly than men do, especially during ovulation, when estrogen levels are highest. For optimal mating, we need someone who’s in the Goldilocks zone of different but not too foreign: genetically similar and compatible, but not family. Pheromones from the male sweat glands allow us to make this determination. Women prefer the smell of a stranger’s armpit over that of family members, which is an ageless signal to prevent inbreeding.
When it comes to mate selection, so much happens unconsciously that we don’t really have much control over. Pheremones are a good example. When a patient tells me she has a new boyfriend, I usually ask her if she likes the way he smells. I don’t mean his cologne or deodorant, and I definitely don’t mean his stink when he walks off the basketball court, but rather his scent, his natural odor. “If you stuck your nose in his armpit, would you be happy?” You’d be surprised how often this question is met with a resounding yes. When I hear “I could live there!” then I know they’re a good match. How someone smells to you matters tremendously. This is one of the reasons I’m not a huge fan of online dating. Pheromones help us to pick ideal mates for ourselves, and this process is based primarily on genetics, not on Photoshopped selfies.
In 1995, Swiss researcher Claus Wedekind performed a study that has come to be known as the sweaty T-shirt experiment. He asked women to sniff T-shirts that men had been donning for three days without showering or using cologne. Wedekind found, and further research has confirmed, that most of the women were attracted to the scent of men whose major histocompatibility complex (MHC) was markedly different from their own. The MHC indicates a range of immunity to various disease-causing agents. When you’re mating, you want someone with different immunities than you have, so that your offspring can benefit from the variety. Optimally, children will have more disease-fighting capacity than either of their parents. Too-similar immune systems of potential parents can lead to complications in fertility and pregnancy. Also, if a woman partners with a man whose genetic makeup is too similar to hers, she’s more likely to cheat on him. The more genes they share, the more likely she’ll be attracted to other men.
Pheromones are typically processed unconsciously, but lately this issue has come to the fore, and there have been more sweaty T-shirt parties going on around the country, a riff on the Wedekind experiment. Male invitees are told to bring a T-shirt they’ve worn for twenty-four hours (including overnight). They are assigned a number and the shirt is placed in a Ziploc bag. Women smell the shirts, choose the one they like the best, and find their lucky date through his number. “Pheromone party” organizers say they have created lasting pairs in this way. Follow your nose to marital bliss. Being attracted to someone’s pheromones can help carry you through some significant bumps in the relationship. Taking in another’s scent helps with bonding. Primates are prosocial, and they solidify bonds in their community by grooming, which involves sitting close to each other and breathing in each other’s scent, never mind picking and eating bugs off each other’s fur. The next time you’re mad at him, smell your man’s armpits or T-shirts, and see if that doesn’t help you feel a bit better about who he is and what you have together. If and when you have them, smell your kids, too. There’s research on mother-infant bonding via pheromones as well.
Men rate not just a woman’s visible sexual attractiveness as highest when she’s midcycle; they like her scent more then, too. If she’s on the Pill and not ovulating, she doesn’t have the same “cyclical attractiveness of odors” that naturally cycling women do. A much bigger deal: being on the Pill affects the way women process pheromones in terms of these important genetic compatibility issues. Women on the Pill don’t seem to show the same responsiveness to male scent cues. They tend to pick mates who are more similar to them, and less “other.” Scottish researcher Tony Little found that women’s assessment of men as potential husband material shifted drastically if they were on oral contraceptives. In a replay of the sweaty T-shirt experiment, women who were using birth control pills chose men’s T-shirts randomly or, even worse, showed a preference for men with similar immunity to their own. One study remarked that a woman on the Pill might go off it only to realize she is with someone who is more like a brother than a lover.
The good news is that she will probably pick a dad and not a cad. Women on the Pill favor less masculine men, which could mean he will stick around for child rearing. But do you want him? Women who were on oral contraceptives when they chose their mates scored lower on measures of sexual satisfaction and partner attraction. If there was a separation in their relationship, they were more likely to have initiated it than the men were, and more likely to complain of increasing sexual dissatisfaction. But they were also happier with how their partners provided for them, and often ended up having longer relationships.
These days, I actually recommend to my patients who are on oral contraceptives that they go off them for three or four cycles to make sure the man they met when they were on the Pill is still the man they want to bed down year after year and create a family with when they’re off it. Once you’re already in a relationship, it gets mighty complicated to stop your birth control to reassess the man you’ve already chosen. Better to do your mate selecting while not under the influence of any other hormones besides your own, which means finding a nonhormonal form of birth control—such as condoms, an IUD, a diaphragm, or a cervical cap—while you’re on the lookout for the man of your dreams. I also recommend spending some time in his armpit to make sure he’s the one. I’m not kidding. The body, undisrupted, is powerfully intuitive and worth listening to.
Mating, MILFs, Monogamy, and Menopause
The way we’re wired, neurologically and hormonally, has a lot to do with how we think and feel—and when we think and feel it. But relationships exert their own powerful effects on the body and the mind. The first few months of attraction create a heady mix of neurotransmitters that no drug can adequately mimic. As a psychiatrist, I will say this: falling in love turns women into manic, obsessive, delusional junkies. At its most unromantic, falling in love is the neural mechanism of mate selection, evolved to ensure that we pine for, obsess over, and pursue the one person we believe will provide us with not only the fittest offspring but also the support to nurture that child through infancy. Falling in love with someone is an elaborate dance in the brain and body that motivates and focuses us on mating with this preferred
