How does your brain fall in love? Is it something magical that happens to your brain? Or, is there something biological that happens to your brain that causes us to fall in love? That was my question.
This is what we know about love. We know that certain neurotransmitters increase and some drop. Your cortisol level, the stress hormone, increases causing you to feel nervous, while your oxytocin level increases causing you to feel amorous. A woman's testosterone goes up causing her to be more aggressive, while a man's drops causing him to be more passive. And in both, their serotonin level drops causing them to leave a little more obsessed.
And although we know what happens, we don't know how you get there. There are certain chemical processes that happen, including the tipping point where you have an increase in also an enzymatic reaction where you have a subsequent decrease, either of these would fit nicely into that missing section.
So I was pondering this, and I just happened to be on vacation. I was visiting my family and I have a cousin who is a PhD in biochemistry. So I decided to use the opportunity to pick his brain. I told him what we knew about—or what I knew about love, and I said certain neurotransmitters go up, certain ones go down; I think it may be biochemical. I looked at him and he gave this expression of plausible. I said some may have a tipping point reaction; he said plausible, or looked plausible.
And then I said others may be in somatic with a subsequent decrease, again he gave me the facial expression of plausible; he's not a big talker, so I thought this was going really well.
But before I could formulate my next question, my then 95-year old grandmother spoke up and she said, "You youngsters don't know anything about love!"
And I was shocked, and I said, "Yeah, I know; that's why we're talking about this."
She said, "Your problem is you young girls jump into bed too quick. You fall in love, but a boy doesn't fall in love that way."
And I kind of looked at her, and I said, "OK, let's talk a little bit more: how does a boy fall in love?"
And she said, "Back in my day, a girl knew if she wanted a boy to fall in love with [her], she couldn't sleep with him right away." Now I had heard that stuff before. There was things like the 3-Date Rule, there's the 90-day rule from Steve Harvey's book Act Like a Lady, Think Like a Man. But I always thought those were antidotal, I didn't think there was any science behind it. So I looked over at my cousin. His face no longer said plausible, but I get—I decided to continue with my grandmother because the date—the question was the date, I said, "How long do you need to wait before you have sex?"
She says, "Ah, you wait until you have sex, until he falls in love."
"OK, well, granny, how do I know when he falls in love?"
She says, "Ah, that's easy. You know he's in love when he commits."
I looked over at my cousin and I was like, "What do you think?" And he hung his head and he just shook. He said, "OK, granny, it's time to go home. I realized he was not buying any of this and my research had to continue on in another day.
I returned home and I hit the research library. The problem is there's not a lot of research out on how humans fall in love, primarily because of the way we do research. Imagine a guy saying, "Oh, I love you!" He falls in love and a researcher walking up saying, "Congratulations! Can I inject this into your brain to see if it has an effect?" You're not going to get many volunteers. So we had to rely on the next best thing: animal studies.
But what animals fall in love? What we know, when humans fall in love, they show exclusiveness to one person. So they started looking at other creatures that had mated exclusively and they ended up settling on these guys: the monogamous Prairie vole. When a Prairie vole finds a mate that they're interested, they will mate for—basically mate for life. So they started looking at the neurotransmitters to see what was going on. And what they discovered was, one of the first things that increases is dopamine. When dopamine increases, and if they block the dopamine, they would lose the loving feeling. So they thought, "Oh dopamine!" But they knew there was a problem: dopamine couldn't be with human romantic love, because dopamine goes up with a lot of things; it goes up with gambling, chocolate, playing Candy Crush, so it couldn't possibly be dopamine.
So they said, well we know there's another one that's involved in bonding, it's called oxytocin. And oxytocin goes up with mothers and children that causes them to bond. So they said let's take a look at that. So they looked at that, they found that when a female finds a man she's interested in, her oxytocin goes up by 51%, and then if they block it, she loses that loving feeling. So they said, ah, it must be dopamine and oxytocin. But there was a problem, it can't be oxytocin for a man because of testosterone. Testosterone blocks the effects of oxytocin. So they said, oh, it's got to be something different.
They looked at another one that had a similar formula to oxytocin, and that is Vasopressin. So they did the study again, they injected Prairie vole with, or the vole would meet, they'd have the vasopressin, they inject an antagonist, a chemical block to the vasopressin, he would lose that loving feeling. So they said oh, then it's got to be dopamine and vasopressin for males and possibly some testosterone, because we know that it goes up with that. So they said, ah, perfect; what does that mean for us? Is this applicable?
To find that out, I wrote to one of the head of the studies at Florida State University and I asked, "Is the vole study applicable to humans?" His response is a little embarrassing, he wrote back, 'Of course, Dawn'—explanation point—the explanation point is his. I didn't want to write back for further clarification, that was a little embarrassing. So I didn't have to. Fortunately, for me, Tiffany Love from the University of Michigan came out publicly and she said that she believed that the vole studies in human love—romantic love—were dissimilar. So great! Now what does that mean?
Well, if we look back at the mechanism, we can see that for females, that would mean dopamine increases and oxytocin increases. Well, dopamine increases when we're dating, when we're going to win—we're excited, we're going to win the grand prize of love. So as long as you're dating and you're happy and you're dating, your dopamine's going up.
Oxytocin goes up—it's called the cuddle hormone, or the trust hormone—so when you're kissing, cuddling, having a good time, the oxytocin is increasing and as you're dating a man and you're learning to trust him, your oxytocin increases. But there's a catch: oxytocin slowly builds up that way, but it sky rockets at orgasm. In other words, my grandmother might have been on to something. Remember what she said: "You girls jump into bed too quick, you fall in love", it was starting to look like the science was panning out from what my grandmother said.
So I looked at the other part: How does a man fall in love? Well, if we look at it, dopamine, of course, if he is having a good time, his dopamine is going up, but how does his vasopressin go up? Vasopressin goes up when a man is sexually stimulated. So if he's dating a woman he's sexually interested in, the vasopressin increases. But here's the catch: unlike oxytocin, the vasopressin drops when he has sex. So how important is that? Well, I looked into it further, Florida State University ran a study and they said, it's not just the neurotransmitters that are important, you have to have the receptors. And how do you get the receptors? You get the receptors with the presence of the neurotransmitters. The neurotransmitters tell your body to build the receptors, so you have to have the neurotransmitters high enough to build the receptors to then get them filled. So that means it takes some time.
But there was one other thing my grandmother said, you remember: See, you know a man's in love with you when he commits. Could commitment have anything to do with this? To find that out, I found a study from the United States Air Force. The Air Force followed over 2,000 servicemen for more than a decade taking various tests. One of the tests that they took was for testosterone. What they found is when a sky it comes in any single, his testosterone was relatively high. But soon as he gets married it drops. Remember what I told you about testosterone, it blocks the effects of oxytocin. Oxytocin is a bonding hormone.
So it was kind of looking like it could have something to do with it. But it needed further clarification: was it marriage, or was it actually commitment? They did a study at Harvard University, they took married men, single men and men in committed relationships, they tested their testosterone. This is what they discovered. Like the Air Force study, the men that were married—or sorry, single had high testosterone, where the men that were married had lower testosterone. And here's the catch: the men that were single or the men that were married and the men that were in committed relationships, the testosterone level did not differ. That means that the testosterone didn't drop when he got married, it dropped prior when he committed. So that means my grandmother looks like she was right. Women take a bigger risk and tend to fall in love when she has sex, and men tend to fall in love when he has commitment. So that confirms something for me that I always suspected, not just that women tend to fall in love with sex and men with commitment, something even more important, and that is my grandmother is brilliant.