Now that you’re both attracted, the next big question is: How do you move from attraction to falling in love? This is the question that I initially set out to understand and the one that helped me connect all the pieces of love.
When I first began to ponder this question, I was on vacation visiting my family. My cousin has a PhD in biochemistry. I told him what I had discovered about what happens to you scientifically when you’re falling in love (I explain this in detail in Chapter 7). I explained to him that when you fall in love, some neurotransmitters drop while others rise. I also told him how certain parts of our brain shut down. Then I said, “I want to understand how we get there; how do we fall in love? I believe it’s a biochemical process.” He nodded in agreement. Excellent, I thought.
I then said, “I think that certain neurotransmitters may build up and reach a tipping point, and on the other side of that point, we fall in love.” Again, he nodded, with a facial expression that said “plausible.”
I was getting excited. Hopefully, by talking about it with him, I would get closer to figuring out the mechanism for falling in love. I started to pose my next comment, but before I could continue, my then ninety-five-year-old grandmother, who had been listening intently, spoke up. She said, “You youngsters don’t understand anything about falling in love.” I was stunned by her comment, but also curious.
So I responded, “I know; that’s what I’m trying to figure out, Granny.” (We all call her Granny.)
“Your problem is that you young girls jump into bed too quickly. You fall in love, but a boy doesn’t fall in love that way.” she said.
Surprised, I looked over her shoulder at my cousin. He rolled his eyes as if to say, “You started this.”
I decided to hear what she had to say, so I asked, “Okay, Granny, so then how does a boy fall in love?”
“Back in my day, a girl understood that if you wanted a boy to fall in love with you, you couldn’t have sex with him right away.”
Now I’ve heard this line of thinking before. In fact, there are many different theories along this line, such as “The Three-Date Rule,” which states that you shouldn’t have sex until the third date, and “The Ninety-Day Rule” from Steve Harvey’s book Act Like a Lady, Think Like a Man, where he tells women to wait ninety days before having sex with a man. But the question is, are these biologically plausible or are they just old wives’ tales? I looked back at my cousin with raised eyebrows as if to ask, “What do you think?”
His face was no longer saying “plausible.” I don’t think he was buying the postpone sex for a man to fall in love thing.
But since I had heard this before, I decided to ask Granny another question.
“If I want a guy to fall in love with me, Granny, how long should we wait to have sex?”
Her eyes twinkled, “Ah, yes, that really is the question now, isn’t it?”
She sat with a smug grin on her face as I waited in anticipation.
Then she said, “The secret to getting a guy to fall in love with you is you wait until he falls in love first.”
What? I felt a kick in my chest and a painful ringing in my ears. I felt like I had just climbed the mountain to reach the guru at the top who had the secret to life, but when I finally asked him, all he gave me was a circular riddle.
Over her shoulder, my cousin shook his head again, as if to say, “You asked.”
I was already in deep, so I decided to continue and ask one more question.
“Okay, Gran, how do I know when he falls in love?”
“Oh, that’s easy,” she said. “You know he has fallen in love when he commits.”
I looked over at my cousin. He drops his head and just shook “no.” Then he spoke up and said, “Okay, Granny, let’s take you back home.”
It was obvious that my cousin, the brilliant scientist, was not buying into my grandmother’s theory. So I returned home defeated but even more determined to figure how we fall in love.
FALLING IN LOVE
Many scientists believe that falling in love is a neurological process, but understanding the exact mechanism is tricky. To understand the science, experiments must be run.
As you can imagine, doing this type of experiment on people would be difficult. You’d have to get a group of people together that had just fallen in love and ask them to participate, saying something like, “We would like to inject you with a substance in the center of your brain to see what effect it has on your love life. Interested? It pays fifty dollars.”
If they said yes, the researchers would have to follow them and make observations, followed by conclusions: “Oh look, he just cheated; it looks like love was successfully blocked.” Just finding participants would be tough. Then, imagine the ethical and moral logistics involved.
When experiments have issues like these, we often turn to animal models for study. But what animals fall in love? Helen Fisher separates attraction from love when one person begins to take on special meaning.89 In most cases, that’s when people form couples, rejecting other suitors and choosing to date exclusively
We know of many bird species that tend to mate for life. However, to get close to human physiology, it’s best to choose a mammal. The majority of mammals are nonexclusive. Not too many animals live out the vow “until death do us part.” Many have harems, while others may mate with one partner but not form pairs like we do.90
Researchers found an unlikely model in the monogamous prairie vole (Microtus ochrogaster). Scientists found that once a prairie vole has mated for more than fourteen hours, both males and females will show a preference, choosing their partner over a new companion.91 Because they form exclusive bonds, these little creatures have given us valuable clues as to what happens to us when we fall in love.
WHAT WE LEARNED FROM THE VOLES
Scientists suspected for a long time that love involved neurotransmitters that were linked to sexual attraction and partner selection. The problem was, which neurotransmitters and how do you prove it? One of the first neurotransmitters researchers looked at was dopamine. This makes sense, because dopamine is a chemical released by the reward center of the brain. The pleasurable feelings produced by dopamine cause an individual to want to repeat the behavior that triggered its release.
Dopamine is critical to motivation and the pursuing of rewards. Some researchers believe its principal role is to signal the brain to seek something enjoyable. It’s released during gratifying experiences, such as taking drugs, smoking, eating, and having sex.92 Dopamine keeps us coming back to the things we love for more.
Researchers at Emory University found that when a female prairie vole mates with a male prairie vole, her dopamine increases by 51 percent. The researchers also found that mating caused an increase in dopamine in males.93 Of course, an increase in a substance doesn’t mean the substance caused the reaction, which in this case was bonding. To make sure that it was dopamine that was causing the attachment between the voles, the researchers then injected the voles with a substance that blocked the effect of dopamine to see what happened. When the dopamine was blocked, the lovebirds broke up. The researchers found that the dopamine antagonist blocked the mating-induced partner preference.94 After this study, it appeared that dopamine might be nature’s love potion.
However, this needed to be confirmed. The Emory team decided to run one final test. To make sure it was dopamine and not some other neurotransmitter that might’ve been produced by mating, they took several unpaired voles that had not mated and injected them with a substance that increased dopamine. If the voles then showed a partner preference without mating, but only by having an elevated dopamine, level this would confirm that dopamine caused the bonding.
I can only imagine how excited the team was when they came in the next morning to find the little fluffy voles playing house. The researchers had confirmed that dopamine facilitated partner preference without mating in both male and female voles.95 This was huge! It could mean that causing an increase in someone’s dopamine level could make him or her fall in love. So what causes an increase in dopamine?
THE DOPE ON DOPAMINE
In the 1950s, James Old and Peter Milner of McGill University pioneered a series of experiments that exposed the nature of dopamine to the world. They implanted tiny electrodes into a rat’s brain. Then they gave the rat access to a lever. If the rat pressed the lever, it received an electrical pulse. The researchers predicted that the rat would hit the lever once, identify the sensation as pain, and avoid depressing the lever again. But that’s not what happened. To the researchers’ surprise, the rat seemed to enjoy hitting the lever. In fact, they couldn’t coax the rodent away from it. The rat was like some crazed Morse code operator, repeatedly pressing the lever—up to two thousand times per hour.96 Often, the rat chose to depress the lever rather than eat or drink. Later, scientists discovered that dopamine was being stimulated by the electric impulses. Because of that, for many years, dopamine was considered to be the brain’s “pleasure chemical.” 97
Today, dopamine is considered to be much more. It’s widely recognized as critical to reward, learning, and addiction. Virtually all drugs of abuse (including heroin and other opiates), alcohol, cocaine, amphetamines, and nicotine activate dopamine. Also, natural rewards, like food, positive social interactions, and even humor, activate dopamine. And, of course, one of my favorites, sweets like sugar and candy cause a rush of dopamine to flood the bloodstream.98 This may be why some men bring candy to a woman on a first date, or why he gives candy at Valentine’s Day. He’s hoping to help accelerate her falling in love with him.
So did Aunt Bea really have the key to love? If you want a man to fall in love with you, should you douse him with sugar, bake him a pie, or ply him with cookies? I’m afraid not. While it does appear that dopamine is important in pairing up with someone, there is one problem: although dopamine skyrockets with sexual attraction, scientists have found that it’s subject to something called the “Coolidge Effect.”
THE COOLIDGE EFFECT
Legend says that one day President Calvin Coolidge and his wife were touring a chicken farm. Mrs. Coolidge was walking ahead of her husband when she spotted an amorous rooster. Quite taken by the affection the rooster was showing the hen, Mrs. Coolidge inquired of her attendant, “Is he like that all the time?” She pointed at the rooster Romeo.
“Oh, yes, ma’am. Every day,” the attendant stated.
Delighted, Mrs. Coolidge said, “Oh, you must show him to President Coolidge.”
The attendant ran back as instructed and said to the president, “Sir, your wife wanted me to point out that rooster to you.”
The president looked over and noticed the obvious affection the rooster was showing the hen and said, “I see. Is that rooster like that all the time?”
“Oh, yes, sir. All day, every day, sir.”
“I see. Let me ask you another question.”
“Of course, sir,” said the attendant.
“Tell me, son, is it the same old hen every day?” the president asked.
“Oh, no, sir, it’s a different hen every time.”
“That’s what I thought, son. Now run back and tell Mrs. Coolidge that.”
What President Coolidge noted was a phenomenon that’s regularly observed in the laboratory and has since been dubbed the Coolidge Effect. This activity was first observed in rats. In an experiment, scientists placed several sexually receptive females in a cage with one male. Prior to introducing the male, the researchers measured his baseline dopamine levels. After introduction, they discovered that the male’s dopamine levels began to rise, even when a screen blocked him from the receptive females. Once the male was given the freedom to mingle with the lady rats, his dopamine levels continued to increase as he mated with each of the females. He coupled up, again and again, to the point of exhaustion, all while maintaining his high dopamine level. Only after he was sexually satiated and slumped in the enclosure’s corner did his dopamine levels drop. At this point, he became unresponsive to the advances of the ladies. He remained uninterested, despite the licking enticement of the female rats, who were just getting started.
But just as it looked like our rat Romeo was down for the count, the scientists reignited his interest. No matter how tired he was, or how many times he had already mated, this little rodent love machine sprang back into action every time a new female was thrown into the mix. Even when surrounded by several willing (but been-there-done-that) females, the male rat’s dopamine levels remained depressed; however, every time a fresh, novel, flavor-of-the-minute female was introduced, his dopamine level shot up like a Texas gusher.99
Therefore, there has to be more than just boosting dopamine that causes someone to choose a partner and fall in love. There is. It’s not just the presence of dopamine that causes the bonding. Another study found that activation of the dopamine’s receptor causes the bonding.100 This means that dopamine levels can go up and down with relatively little effect. But when its levels stay high enough for a period of time, the receptors can get activated. It actually appears that the presence of elevated dopamine causes the body to produce the receptors. In the Emory University study, researchers found that after a male vole bonded with a female, he had a significant density of dopamine receptors after a period of time.101 This means that when the dopamine goes up and stays up, it triggers the body to produce the receptors. It’s these receptors that are necessary for bonding.
So, maybe dopamine is nature’s love potion? Cue the drumroll, please. Brrrrrum. Sorry, not so fast. Dopamine has a definite role in partner selection and in falling in love, but it’s obvious from the Coolidge Effect that it can’t just be dopamine. Dopamine can fluctuate too much, which would mean you would be falling in and out of love every couple of hours. And, barring teenagers, this usually doesn’t happen. Therefore, they began to suspect that dopamine might have a partner of its own.
THE PARTNER SELECTION NEUROTRANSMITTER HAS A PARTNER OF ITS OWN
Researchers have known for quite some time that other neurotransmitters are involved in forming bonds. In particular, oxytocin has been called the “love hormone” because it goes up when people are in love, but also because it creates the loving bond between mother and child. Oxytocin is also the reason we love our pets. Just looking at our dogs has been found to increase oxytocin levels.102
The Emory University research team decided to test what effects oxytocin had on mating with the voles. Since it’s known that oxytocin has an effect on females, they began by infusing the single female rodents. What the researchers found was that the oxytocin injections accelerated females’ pair bonding. In fact, now the female vole only required a few moments to be with a male before she bonded with him. But the most surprising part, unlike the earlier test that required mating for her to bond, a single infusion of oxytocin caused her to quickly bond with a male, without sex.103
Next, to verify it was the oxytocin and not something else causing the bond, the team injected a chemical to block the effects of oxytocin on already bonded females. They found that when oxytocin was blocked, they lost her partner preference. Combined with the previous dopamine results, this caused the Emory researchers to conclude that dopamine and oxytocin do not work sequentially but rather concurrently. It’s the actions of both neurotransmitters together that cause the female vole to bond with the male.104
It was beginning to look like dopamine and oxytocin were the magical elixirs of love. But there was one big problem. When a male of any species is around a female he’s sexually interested in, his testosterone shoots up. This by itself is not the problem. The problem is that testosterone blocks the effects of oxytocin. This means that bonding might be caused by oxytocin and dopamine in females but not in males.
The Emory University team understood this and began searching for another neurotransmitter that might affect male bonding. They didn’t have far to look. Vasopressin is a neurotransmitter found in males that’s very similar structurally to oxytocin. The team decided to investigate the effect, if any, that vasopressin had on male mate preference. The researchers measured the level of vasopressin in bonded versus nonbonded males. The team found that bonded males had higher levels of vasopressin. This, of course, by itself didn’t tell them much. It could still be something that happened with sex.
Therefore, to test if it was vasopressin that was causing the bonding, they infused the males with vasopressin without mating them to see if they still had a partner preference. Sure enough, the males with high levels of vasopressin bonded to a female even without mating with her. To verify the bonding effect of vasopressin, the team then used an antagonist to block the effect of vasopressin on the males. They found that the antagonist prevented pair-bond formation.105 This confirmed that vasopressin was involved in pair bonding. The conclusion of these studies indicates that oxytocin and dopamine are required for partner selection in females, while vasopressin and dopamine are needed for partner selection in males.
By now you might be thinking, “All these studies are great, but what does this have to do with my love life? I’m not a vole; I’m a human being. What does all of this have to do with me?” Let’s take a look.
My first question was, “Is this work with voles applicable to humans?” To find out, I wrote to the lead researcher of one of the studies, Mohamed Kabbaj, a professor of biomedical sciences and neurosciences at the College of Medicine at Florida State University. I asked him if the social bonding mechanism and/or neurotransmitters are applicable to humans. His response was almost embarrassing. He wrote back, “Of course, Dawn!” 106 Yes, the exclamation point was his. His e-mail included an example of mother and child bonding being highly regulated by oxytocin. I was hoping to get an example about love, but I was beginning to wonder if I would ever get a confirmation.
Fortunately, I found love. Tiffany Love, that is. Tiffany Love, a researcher at the Molecular and Behavioral Neuroscience Institute at the University of Michigan, has thankfully come forth to say that she believes human social bonding mechanisms are linked to neurotransmitters, similar to that of the voles, and that they are engaged in human romantic love.107 Yahoo!
So the next question is, how do these neurotransmitters cause you to fall in love? One day you’re walking along, minding your own business, when you meet someone new. You find this new person attractive. You get a little closer to investigate, and the next thing you know, you fall in love. What happens between the time when you meet and the time when you fall in love?
If you look at the vole studies for a clue, the first thing you’d expect to happen is that your dopamine would rise. And, in fact, that’s exactly what we see. Researchers at the Institute of Cognitive Neuroscience at the University of London found that attraction activates the dopamine regions in the reward center of the brain.108 They also found that the greater the attraction, the greater the reward activation. In fact, if the attraction is not reciprocated, the firing pattern decreases, but if the attraction is mutual, and particularly if it’s surprising, watch out—this means game on. That’s one of the reasons random, unexpected encounters can be the best thing when it comes to finding love. Your dopamine surges give you a euphoric, intoxicating feeling that makes you crave more.
Next, you would expect your oxytocin levels to increase. And again, that’s what scientists have discovered. Researchers in Israel found that oxytocin levels are highest in new lovers—higher than singles and even new parents.109 That’s why the world feels so warm and friendly early in a relationship.
How this works when it comes to love is that each time you have a date, or you talk or think about the other person in a favorable manner, your reward circuit adds a little more oxytocin. Oxytocin is the neurotransmitter of trust. So slowly, as you’re getting to know and trust someone, your oxytocin levels increase.
Researchers in Sweden decided to test the effect oxytocin had on women’s attitudes toward men. In their study they administered an oxytocin nasal spray to both single women and women in relationships and then measured any changes in their behavior. They discovered that women became friendlier to men. The effect was greatest on single women.110 In other words, the oxytocin seemed to motivate a woman to get closer to a man. Its effects were highest on single women, because nonsingle women were already close to a man. Oxytocin gives you a feeling of trust and safety. The world no longer feels like a big, scary place; now it feels warm and inviting, and your feelings of anxiety plummet.
To test the theory that oxytocin helps you get closer to another person, researchers at Duke-NUS Graduate Medical School’s Cognitive Neuroscience Lab gave participants either oxytocin or a placebo; then the participants were shown video clips of men and women. A day later the participants were shown pictures of men and women and then asked to decide which of the individuals they would like to learn more about and spend time with. The participants displayed an increased preference for people they had been introduced to immediately following the administration of oxytocin.111
Oxytocin can be self-amplifying. That is, it produces a type of positive feedback loop. Each time a couple interacts by socializing or looking at each other, holding hands, or touching each other, small bursts of oxytocin are released. Oxytocin levels increase as the couple continues to interact by talking, touching, and cuddling. A phone conversation produces a little gust that causes you to want to go on a date. Then you go on a date and get a little more oxytocin, which makes you want to kiss good night. Then, you kiss good night and get another heaping gob of feel-good.
This amplifying effect causes a couple’s oxytocin levels to increase over time. Oh, and I’m not talking a little bit higher—the oxytocin level from being single to being in a new relationship is almost doubled! 112 Oxytocin has also been found to increase eye-gazing in couples, which in turn induces the production of dopamine.113 The two neurotransmitters work together, amplifying each other and intensifying the couple’s connection.
Now some may debate which comes first, dopamine or oxytocin? For example, Abigail Marsh, associate professor of psychology at Georgetown University, states: “People who excite romantic feelings in us also probably trigger increases in oxytocin, which results in an increase in dopamine, and then we find that person someone we want to stick with.” 114
At this point, which comes first probably doesn’t matter. When it comes to dating, it appears they work in tandem. This would make sense. As you get excited to be with someone, you produce dopamine, which causes you to want to be around him or her, which causes you to produce oxytocin. The more oxytocin you have, the more you want to be around the other person, and if that interaction continues to be positive, you produce more dopamine.
Eventually the two neurotransmitters build up until you reach a tipping point. On the other side of this neurochemical summit is the exciting sensation of falling in love.
LAUREN’S STORY
This slow buildup of oxytocin is the ideal way to fall in love. However, things don’t always work as we expect. Take Lauren’s story, for example. Lauren wasn’t looking for a relationship and had no intention of falling in love. She had just graduated college and was starting a new job in a new town. Her goal was to meet new friends and have some fun.
She joined a meet-up group for single young professionals in the area. They planned different activities to explore the city and to network. One Friday night, Lauren joined the pizza and bowling meet-up. That’s when she met Josh. He was also new to the area and starting a new career. They hit it off immediately. The two were on the same team and ended up winning. Afterward, Josh asked her if she would like to get a drink. She did, and they ended up talking for hours.
Josh texted her on Saturday to say he had a great time and wondered if she had plans that night. They planned their first real date. During the date, Josh said he really liked her, but since he was just settling in, he wasn’t sure he was ready for a “full-blown” relationship. Lauren readily agreed, stating she was only looking for something “casual.”
That evening they participated in a whiskey-tasting event and then decided to stop by Josh’s place. He said that the whiskey had affected him more than he liked and that he’d call an Uber to get her safely home, or if she would like, she was welcome to stay there for the night. Lauren decided to stay. They had a few more drinks, talked, and eventually fell into bed and enjoyed a hot and steamy night. Over the course of the next three weeks, Lauren and Josh hooked up periodically, once even spending the entire weekend together.
Then one evening Lauren was out with a couple of coworkers and spotted Josh. Lauren ran over to say “Hi,” but Josh was rather standoffish and distant. Lauren quickly figured out why. Josh was on a date with another woman. Lauren became irate, asking Josh “if he was sleeping with her too?” Lauren stormed out of the restaurant in tears. Why did she have such a response to someone who she herself described as “just casual”? Somewhere over the course of those weeks together, Lauren had fallen in love.
You see, oxytocin builds up slowly as we spend time with someone. But you get a huge surge when you have an orgasm. Because of their sexual relationship, Lauren had quite a few of those. Since she also liked Josh, she was producing dopamine, and because of the sex, she was producing oxytocin. Those two neurotransmitters built up quickly, and she tipped over into love.
But Lauren falling in love was not the big problem here. The real problem here was that Lauren fell in love, while Josh was still just “being casual.” That’s because men fall in love differently.
WHY MEN FALL IN LOVE DIFFERENTLY
Recall how I mentioned that testosterone blocks the effect of oxytocin. When a man meets a woman he’s interested in, his testosterone goes up. So although his oxytocin may be surging, it doesn’t affect him like it affects a woman. A little sex and she’s on her way to love. But, in a kind of cruel twist of fate from Mother Nature, a little sex may actually prevent him from falling in love. Allow me to explain.
Taking a lesson from the voles, to find out how a man falls in love, we need to take a look at vasopressin. Fortunately for us, a Swedish team decided to look at the effects of vasopressin on a human’s love life. The vole study made it clear that vasopressin was important in pair bonding, so scientists decided to see if a similar effect could be found in people. The team studied 553 couples to determine if vasopressin contributed to the satisfaction of marital (and long-term) partners.
Vasopressin is encoded in men by a particular gene. There are three versions of the gene, a larger version (the gene with two copies), a medium version (the gene with one copy), and a small version (the gene with no copies). The bonding effects are inversely proportional. The larger version of the gene produces vasopressin with the weakest bonding properties. Therefore, the men with two copies of the gene showed a lower partner bonding score (PBS). They also had less partner satisfaction, less affection, more relationship problems, and were less likely to be married or cohabiting.
On the other hand, the men with the small version of the gene had the highest PBS scores, greater partner satisfaction, showed more affection, and were more likely to be married.115 But for our purposes, the version of the gene is not the important part. The significance here is that these findings indicate that the pair-bonding findings in voles are indeed comparable to humans.
Also, unlike oxytocin, which is blocked by testosterone, a man’s vasopressin appears to be enhanced by it. When adult male rodents that were castrated at birth were given vasopressin, they showed no bonding tendency. However, when vasopressin was dispensed to a male that had been castrated as an adult and already had testosterone in his system, he showed some bonding tendencies.
Taken together, these results suggest that there may be a synergistic effect with the combination of dopamine, vasopressin, and testosterone in men that may cause them to fall in love.
Figure 5. How Men Fall in Love
Now at this point, you’re probably thinking, “this neurotransmitter stuff is all great, but what does it mean for me?” Now, you know I didn’t drag you through all this biological drama just to drop you. Here is the critical part: now that you know which neurotransmitters are involved in the process of falling in love, you hold the magic ticket.
HOW MEN FALL IN LOVE
If you recall, I began this chapter with a conversation with my cousin and grandmother. Well, it was mostly a conversation with my grandmother, because my cousin just nodded. The point is, by now you can probably guess who was right. The process of falling in love is a biochemical reaction. In women, oxytocin and dopamine build up until the levels reach the tipping point and result in falling in love, while in men testosterone, dopamine, and vasopressin must build up over time until levels reach the tipping point of falling in love
But what about what my grandmother said? Is there any merit in the assertion that sex and/or commitment have any effect on falling in love? For a woman to fall in love, her oxytocin level needs to rise. This happens slowly, as she spends time with a guy. But this is not the only way she gets oxytocin. A woman also gets a huge burst when she has an orgasm. That’s right—having sex can cause a woman to fall in love quicker, like my grandmother mentioned.
But what about the other part? What happens if she waits to have sex? Will it cause a man to fall in love? If you recall, one of the main neurotransmitters involved for a man to fall in love is vasopressin. Vasopressin increases in a man when he’s sexually excited. However, there’s a catch. Although it goes up when he does (mechanically speaking and otherwise), it also goes back down after he does. That is to say, vasopressin becomes elevated when a man is sexually stimulated, such as when he’s thinking about sex, but it decreases rapidly after he has an orgasm.
In other words, my grandmother might be on to something. Although I mentioned that the elevation of oxytocin and vasopressin are important for people to fall in love, I left out one more important thing. Researchers at Florida State University discovered that it’s not just the amount of the neurotransmitter that’s important; you also have to have the receptors for the neurotransmitters.
The formation of the receptors, like the ones I mentioned with dopamine, takes time and the process gets started by the presence of the neurotransmitter. That is to say, your body produces oxytocin or vasopressin, then the presence of the oxytocin sends a message that receptors are needed. Your body then builds the receptors for the neurotransmitters.116 However, as you can imagine, this process of building new receptors doesn’t happen right away.
Therefore, delaying sex with a man causes his vasopressin levels to increase and stay up long enough for the receptors to be built and then filled. Once that happens for a long enough span of time, it can cause him to fall in love. In fact, in one study, researchers found that an increased amount of receptors caused the prairie vole to bond faster even without mating.117
But what about the part grandmother said about commitment? Remember, I asked, “How do I know when he falls in love?” She answered, “You know he has fallen in love when he commits.” Was she on to something or was this unfounded? For the answer to that, we need to take a look at a study conducted by the U.S. Air Force.
The U.S. Air Force followed 2,100 veterans for more than a decade, giving them a physical exam about every three years. One of the things they measured was the servicemen’s testosterone levels. What they discovered was rather remarkable. The study found that the veterans’ testosterone levels fluctuated with their marital status. Single servicemen had rather high testosterone, which is not surprising. However, the surprising part was that once a man married, his testosterone level plummeted. Not only that, it stayed low as long as he stayed married. Once he was contemplating divorce, his testosterone level began to rise again. In fact, the researchers found that men’s testosterone levels doubled just before and after their breakups. This made their testosterone levels the best predictor of divorce.118
Imagine if you tuned in to the Maury Show one day and saw women bringing their husbands on. Instead of a paternity test, they ask Maury for a testosterone test, saying, “Maury, I think my husband’s thinking about leaving me. Can you test him?” Then we watch as Maury opens his famous manila envelope to announce, “Yes, he’s thinking about divorce.” Or better yet, “No, he still loves you. Now go home, you two, and have a good time.”
The point of these test results is that when a man marries a woman, his testosterone level drops. But at what point does it drop? Does it drop when he marries or when he commits to a woman? To find the answer, researchers at Harvard University decided to run some tests. They had 122 men fill out a relationship questionnaire and provide a saliva sample for testing. The results revealed that men in committed, romantic relationships had 21 percent lower testosterone levels than men not involved in such relationships. Furthermore, the testosterone levels of married men and unmarried men who were involved in committed, romantic relationships did not differ.119 This suggests that it’s not marriage that causes his drop in testosterone but rather the commitment to a monogamous relationship that causes the nosedive.
This, of course, caused my grandmother’s statement to come rushing back into my head. “You know he has fallen in love when he commits.” Maybe she was really on to something. By holding off on sex, you give vasopressin a chance to build up, but even more significant might be the commitment. When he commits, his testosterone level drops. As I’ll explain in more detail in Chapter 7 (“Falling in Love”), a man’s testosterone level drops when he falls in love. This can happen naturally when all three neurotransmitters build up to the tipping point or it can be caused by a commitment. This drop in testosterone is significant for a man to be in love. A higher testosterone level blocks the effects of oxytocin, but with the lower testosterone level, the bonding effects of oxytocin can occur.
Therefore, by delaying sex and asking for a commitment, you’re ensuring that he falls in love with you, either by the action of vasopressin or by the action of oxytocin. This supports my grandmother’s assertions to wait until you’re in a committed relationship to have sex. Once a woman has sex, her oxytocin level skyrockets, causing her to fall in love. Therefore, when you wait and ask for a commitment, it ensures that you both fall in love at the same time. This, of course, confirms something I already knew: Granny is brilliant!
RECAP
For a woman to fall in love, she needs a combination of dopamine and oxytocin.
For a man to fall in love, he needs a combination of dopamine, vasopressin, and testosterone.
Dopamine: We get a sudden, short-lived burst of dopamine when we like something, but we build a sustainable level when we work (for men) or if we wait (for women) for something desirable.
Oxytocin: Women slowly build up oxytocin when they interact socially and touch and talk with someone they’re attracted to. They get a sudden burst when they become sexual. Men, on the other hand, build up oxytocin, but testosterone blocks its effects.
Vasopressin: Men increase levels of vasopressin when they get sexually excited, but they quickly lose the level when they ejaculate.
Testosterone: A man’s testosterone level drops when he commits to a woman, making him more susceptible to the bonding effects of oxytocin. And his levels stay low as long as he’s committed.
Now I realize that there is a big gap between meeting someone and asking for a commitment. That gap is the dating process. Fortunately, you can use the knowledge gleaned from this chapter to safely and successfully navigate through the dating process by understanding what effects these rising and falling neurotransmitters have on you and your partner. I’ll also explain how and when to ask for that commitment.