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  • Translator: Paola Benedetti Reviewer: Denise RQ

  • 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 some 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 be a little more obsessed.

  • And, although we know what happens, we don't know how you get there.

  • There are certain chemical processes happen,

  • including the tipping point, where you have an increase;

  • and 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 I knew about love.

  • 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 enzymatic 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.

  • (Laughter)

  • 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."

  • 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.

  • (Laughter)

  • 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 three-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 anecdotal.

  • I didn't think there was any science behind it,

  • so I looked over at my cousin.

  • His face no longer said plausible.

  • I decided to continue with my grandmother

  • because of 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 to have sex until he falls in love."

  • "OK. Well, Granny, how do I know when he falls in love?"

  • She says, "Oh, 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 it.

  • (Laughter)

  • 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 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 walks 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?

  • Well, we know when humans fall in love, they show exclusiveness to one person,

  • so they started looking at other creatures that 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 in,

  • they will, 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.

  • 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 it with human romantic love

  • because dopamine goes up with a lot of things.

  • It goes up with gambling, chocolate, playing Candy Crush

  • (Laughter)

  • 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, "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.

  • The voles would meet. They'd have the vasopressin.

  • They'd 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."

  • 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 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!"

  • The exclamation 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 the University of Michigan,

  • came out publicly, and she said that she believed

  • that the vole studies and human romantic love were similar.

  • 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.

  • Dopamine increases when we're dating, when we're going to win;

  • we are excited: we're going to win the grand prize of love.

  • As long as you're dating and you're happy, your dopamine is 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, oxytocin increases.

  • 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 skyrockets 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?

  • If we look at it, dopamine...

  • 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, 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.

  • 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?

  • "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 test that they took was for testosterone.

  • What they found is, when a guy comes in, and he is single,

  • his testosterone is relatively high, but as 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? 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 single men had high testosterone,

  • where the men that were married had lower testosterone.

  • And here's the catch: in the men that were married,

  • and in 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 confirmed something for me that I'd 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.

  • (Laughter)

  • (Applause)

Translator: Paola Benedetti Reviewer: Denise RQ

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How Your Brain Falls In Love | Dawn Maslar | TEDxBocaRaton

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    Vivian Chen posted on 2018/09/20
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