We Need To Talk with Paul C. Brunson - Why Chemistry Isn’t Always Love! Dr Tara Swart

Episode Date: September 3, 2026

Dr Tara Swart reveals the surprising neuroscience behind love, attraction and relationships - from the hormones that drive bonding to the hidden signals our brains use when choosing a partner. She explains why oxytocin is so important for love and trust, how stress can affect our relationships, why smell can be a powerful attraction signal, and what happens in the brain when a new relationship becomes sexual. Tara also explores why delaying sex may help create stronger bonds, and how evolution continues to influence who we find attractive. We're Talking Relationship Neuroscience! (00:00) Intro (00:30) How the Brain Shapes Our Relationships (02:32) The Key Parts of the Brain That Affect Relationships (04:09) How Dr Tara Defines Love (06:40) The Brain Chemicals Behind Love and Relationships (13:00) How Smell Influences Romantic Attraction (16:38) The Science Behind Physical Attraction Learn more about your ad choices. Visit megaphone.fm/adchoices

Two and five Canadians will hear the words, you have cancer. That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation Walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcfwalk.ca.ca. Welcome to We're Talking. In this episode, I sit down with neuroscientist Dr. Tara Swart to explore how our brains shape the way we love, connect and build relationships.

Why do you believe our brain function is so important? How does it inform our relationships? I basically call the brain the CEO of the body. So it's got leadership over every aspect of your life. it's obvious with things like health and well-being. But if you think about the things that most people want in life, it's health, love, wealth, and, you know, perhaps some other things that keep us secure and safe

and then individual things. But it comes down pretty much to happiness, health, wealth and relationships. So, and I speak a lot about the other things and not so much about relationships, which is why I was excited to have this conversation with you today. I remember when I got my first request to speak on a podcast about relationships, I was getting my hair blown out. And I looked at this email, which came an hour before the podcast, and I thought, I'm a neuroscientist. I don't speak about that. But actually, obviously, it makes sense that, you know, one could, and I have done a lot more reset since then.

I would start with the, let's start with the negative side of the coin. Okay. Which is just that if anyone or both of the parties are under stress, and this applies to family and friends as well as romantic relationships, then there's a lowered capacity to operate at your best, which is inevitably going to affect your relationships, right? And then on the other side of the coin, if we're taking care of our brain and doing certain practices

that keep our brain not in the stress state, but in the love and trust state, then also equally you can see how conducive that's likely to be to you being able to care for a loved one as well as yourself. Yes, yes. So ultimately because you're seeing the brain as the CEO essentially of our life, right, that the brain ultimately is critical to our relationships. It's critical. So if we're looking at the brain in the most basic sense, what are the components of our brain, the main components as it relates to relationships? So that's actually much more multi-layered than you might think. Because we've got the outer quarter. which is kind of holding our working memory and what we need to do today and to survive.

And to some extent to thrive. So that will be, you know, don't have an argument with my wife, don't lose my job, put food on the table, pay my bills, etc. And then deeper in the limbic system, which is the size of your clenched fist. Okay. And then we've got this layer of cortex, which is quite thick now.

But since we've evolved from the cave, we see that love isn't in the outer cortex, it's in the limbic system and below. So love is an ancient structure in the brain. Interesting. Even when we couldn't speak and we had the limbic system with a very thin sliver of cortex around it, we had love. And then through the spine and other nerves, we have the gut brain axis. So actually that's important in relationships too, because if you live with someone and you share cutlery with them, share a bathroom with them, share a bed with them, kiss them, cuddle them. If you think about the skin microbiome, the oral microbiome,

and the gut microbiome, you actually start to share your microbiomes. And usually the healthier partner will donate cells to the one whose immunity isn't as strong. Wow, look at that. The importance of having a strong partner, literally. Literally. Literally. We had love before we could even speak, right? We had love. How do you define love? Well, that's that's the million dollar question, Paul. That's why you're here. In those sort of tribal times, it would have been about trust and bonding. And of course, people would love their children, but there would have been a larger element of wanting to see your genes survive. So if we look at animal studies, what do animals do if they love their children?

They protect them, they shelter them, they feed them, they defend them against attack. They usually, well, most mammals are not monogamous. So if they choose to be monogamous, then they're pairing up to defend those children. If they're the opposite of that which is promiscuous, then they're just trying to find as many females as possible to pass their genes on and then just leave the females. to defend the young, because if the environment's safe, they can do that. If it's an unsafe environment, then they're more likely to stay in the nest. Okay. The definition of love there is really around protecting and providing, in essence.

Is there an emotional aspect to love as well? Yeah, so again, I'm actually quoting from research about voles, little rodents. and prairie and pine voles are monogamous and marsh and meadow vows are promiscuous and the reason is that there's sparse shelter and food on the prairie so if the male vol was promiscuous there's a big chance that his offspring would die so it makes more sense for him to partner up

and stay in the nest and provide food and fend off aggressors But between the mommy and the daddy vol, there is a change in gene expression in brain receptors, both where they are and which hormones they bind with, and differences in the levels of the key hormones here, which are oxytocin, phase suppressing, dopamine, and testosterone. These oxytocin all the way through is, I would love for you to talk about these chemicals in the brain because it seems as if I often hear people, misquoting what, like, you're excreting dopamine. What does that mean? Like, are you really excreting dopamine? That sounds a little, you know, a little wild.

So what are the, what do you think are the most important chemicals in the brain as it relates to our relationships? I would put oxytocin at number one. It's the bonding hormone. And so that absolutely relates to romantic relationships, also bonding with your children, but also. So family, friends, social and work even. And society. I mean, when there are low societal levels of oxytocin, that's where we see the fabric of society

break down in terms of things like riots and turning against the structures that we have chosen to put in place to keep us safe like the police and the legal system. Okay. Can we pause on oxytocin? Because you said this is the most important, right? Okay. So oxytocin, men, women, we all produce it. How is it produced? What drives the increase in our production of oxytocin? So mostly through physical touch. So things like holding hands, cuddling, stroking. You would get it if you stroked your pet as well.

Bathing, because you're immersed in warmth, so it kind of feels like a hug. Obviously sex. particularly at orgasm, a really high kind of like levels of oxytocin then. And I think the one that, you know, if you've had a child, you know that incredible feeling of just being so in love like you're in a love bubble, that's oxytocin. You're producing that. So that's your perception. And it doesn't matter if the partner or the person is also producing oxytocin as well. No.

So I think you're referring to something that I speak about much more. widely, which is the effect of cortisol between people. So leakage of cortisol into the atmosphere affecting other people's stress levels. With oxytocin, it doesn't work like that. We're getting our own levels of oxytocin, and we could have very different levels of oxytocin for different reasons. And actually, this is one of the most damaging things to a relationship when the levels of oxytocin become very different.

So one partner is still bonded, but the other partner is losing that connection because it creates both often shows of contempt in the partner with lower oxytocin, but also a kind of need to hold on and fix things and try to make it better in the person who still has a lot of oxytocin and can feel that that's not mutual. Wow. Well, is there an optimal level of oxytocin we should be aiming for? I mean, should we all have a full tank in essence of oxytocin? I mean, like, you can't spread too much love, can you? I mean, the world, I think, will be a much better place if we all have, like, higher levels of oxytocin. All right, done. We should package this up. Can you, we should do this? Are people, no one's, because everyone injects everything else.

Can you, can you actually be, have oxytocin injected? I do not want anyone to do this. But if you Google oxytocin nasal spray, there is such a thing. Really? And in experiments where men and women were. asked to rate photos of people on attractiveness before and after. So they rated them just by looking at the photos. Then they took oxytocin nasal spray.

They rated everyone as more attractive afterwards. Oh, my gosh. But the stuff that's available on the internet, please, it cannot be clean. We don't know what it is. Don't do. All right, fair. That's interesting. A lot of people are running to Google oxytocin nasal spray.

So what are the other chemicals that you believe? are important. Two and five Canadians will hear the words you have cancer. That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation Walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcf walk.

You've got to try breakfast at And what better way than with a delicious pratt organic coffee starting with just one dollar all day, every day now until December 31st. You've got to try breakfast at A&W. At participating A&W locations in Ontario. So I rated oxytocin number one because it's the main one that correlates with love and trust. Okay. But there's one called vasopressin, which in both genders, is responsible for blood pressure, the number of electrolytes in your blood and blood volume.

But in men, it is also to do with bonding, aggression, but aggression related to protecting your partner and your young. Okay. And sexual interest. The higher, the vasopressin, the more sexual interest. Yeah. So if a heterosexual couple are dating and the woman's enjoying it, she's likely to have high levels of oxygen. and dopamine. And please remind me to come back to why dopamine is important next.

Okay. For the guy, it's going to be levels of dopamine, oxytocin and vasopressin as long as they're dating but haven't had sex yet. So the longer sex is withheld, the higher those levels are going to get in the man and the more likely he is to bond to the woman. Once they have sex, the level of vasopressin plummets. And so it changes. how influential oxytocin can be on their testosterone. Because yes, we both produce oxytocin, but because men produce so much more testosterone than women,

it has a buffering effect on oxytocin. Okay. So if you are, you know, wanting to form a bond, then you actually would try to keep the vasopressin levels high for as long as you can. If you have sex immediately with your partner, then there's a low likelihood that you will bond with them. bond with them. Well, let me just slightly rephrase that because I'm assuming they're not partners

yet. Okay, correct. Correct. So the bonding, the bonding may or may not come if you work on it, but in terms of the hormones helping you to get that to the right place to make this relationship more likely to succeed, it's going to go against that. It's going to go against that. So if we're thinking about neuroscience, if we're thinking about our brain, we're thinking about biology in trying to help us to form a connection, it sounds like you're saying it's to our advantage to hold back from having sex early. To delay.

To delay. And do all the other things that build up oxytocin, like hand holding, cuddling, stroking, kissing, and eye contact and obviously the other stuff that you talk about, like talking and listening. Talking is important, that stuff. But I'm just sticking to like the angle that I can bring you.

Now, how important you think smell is with regard to selecting a partner? This is a really interesting one. So of the five senses, I would say that for humans, visual is the first one. And that sound is the second one. So the voice and accent of the person. Okay. And smell is third and then touch and then taste. So smell isn't the biggest attractor.

but I think it's the biggest detractor. So let's say you had a fantasy about a supermodel your whole life and then you met her but she had bad breath. Yes. It would put you off. These are facts, yes. These are facts, yes. Yeah.

But in terms of bonding, we think this is partly mediated through smell. There is something called the major histocompatibility complex, which is an imprint of your immune system. So if you like someone's smell, it's likely that they, have a very different MHC to you because that's going to make your children essentially bilingual in their immune systems and that's advantageous for them.

Okay. And I'm sorry, MHC is... Major histocompatibility complex. I was trying to not make you make me say it again. Oh my gosh. Okay. So this is interesting. You know, people can go out with somebody that they don't necessarily think a really good

looking, but physiologically it's quite hard to be with somebody if you actively don't like their smell. If you like their smell, then it means it's more likely that their immune system is very diverse to yours, and that's why. Okay. So this isn't a predictor of a relationship success. It's a predictor of successful offspring. Yes, I see. And literally successful offspring mean the viability of that offspring, will they be able to survive? Not just will they be able to survive, But there could be many babies that would survive, but have quite a limited gut microbiome and MHC. Which means? But to give your children a bilingual or much more broad immune imprint is advantageous for them.

Wow. Well, do you advise people dating to see if they, to literally, to consciously examine if they like the smell of their partner? Yeah. Yeah. First date? And ongoing. Ongoing. Yeah. So literally like...

Keep gathering data. Lift up the arm and take a sniff. Yeah. Wow. Okay. Okay. So this is interesting because the importance of smell is something that I don't think is talked about enough, but I'm with you. It's incredibly important.

And it's an evolutionary gift that's been handed down to us. Because for animals, that's actually probably the primary one in terms. the primary one in terms of knowing who your cubs are, loving them and protecting them. Okay. And because of this immune system broadening, smell would be a much more important modality for animals than visual or sound. All right, fair. Can we spend a moment on visual and sound?

Because I think with visual, there's a lot of conversation around what is considered to be attractive. I would imagine that attraction, it's relative. It's relative. So what informs our perspective of physical attraction? I think we can probably all agree on certain looks that are quite universally pleasing. And I've used that word instead of attractive because you can look at someone. and say they're really beautiful, but not be attracted to them.

Okay. But, and of course this will vary around the world. So there are different ideals and different cultures, for example. I imagine there'll be something genetic. I always have this theory that you're either a gene pool expander or a gene pool solidifier. So you either go for someone that looks like they could be your sibling or you go for someone that's like completely opposite to you. Yes.

And I haven't got the science to prove that, but I have a lot of anecdotal evidence of it. All right. Fair. So I think there's so many factors involved here. It is obviously what people look like, what they sound like, what they smell like, what their values are, you know, common goals and interests, family situations. But it will probably be something partly genetic as well. Okay. And it will definitely be something that is an indicator to you of the other.

person's fertility. Even if you don't want to have kids, that is a factor in our choice of partner. So can we break that down? I've heard many people call it the golden mean. And I think, okay, is this really a thing? And ultimately what the golden mean stated was that if you look at a woman and look at the differential between her waist and hips, if the hips are, if the margin is 50% taller or greater. It suggests that she is fertile and so therefore appears to be more attractive. So certain cultures have...

Women tend to fall into more of an apple shape or more of a pear shape. And so if that's the norm in your culture, then you as a man are going to find that attractive. So you're describing more the pear shape, which applies to, you know, you know, many cultures around the world. But if you look at sort of like South Asia and Southeast Asia and the rest of Asia,

the shape is quite different. But for people of that culture, there's a different indicator of what look makes you look fertile. That's fascinating. And that comes from, that's just evolution. Yeah. So basically, there's a theory. about the monsoon diet for, you know, the sort of Asian diaspora, which is that it was advantageous to store a bit more belly fat

for times when, you know, it was kind of feast or famine. And so if you think about the fact that Indian women wear saris and they show their belly, that's attractive to Indian men. Okay. Whereas in, you know, the Western world, it's attractive to have a flat belly, a small waist and, you know, a larger bottom. Look at that. larger hips, yeah, yeah.

So all the same, all the same. Are there indicators for men that appear to be, I wouldn't necessarily, I actually, it would be still more fertile, right, for the men. So what are the indicators? Because I've always heard it's shoulder to waist ratio. The first one, which I'm sure you see on all of your data, is height. Yeah, that's just the absolute sort of given. And then, yes, broad shoulders, musculature.

But again, that will vary from culture to culture. If someone is not physically pleasing or the sound is not pleasing or the smell is not pleasing from that first interaction with them, should you give them another chance? I think I'm going to say something you're not going to expect. If the smell, smell is the biggest detractor. So if the smell is not pleasing, I would say probably not. With the other two, I would say give people a chance. So what I hear a lot of my friends saying is something about the way he dresses or, you know, the state of his body. And I always say those things can change.

But you can't change your smell. And you can't change your voice. You could change your accent if, you know, that was an issue. But so I think because I'm, you know, I'm just such an oxytocin person. I just want everyone to be happy and give more chances and let things work out. So, yeah, I think as long as you've got your boundaries and your intentions right, there's no harm in giving people a future. Like I said, in moderation, go on two or three dates.

Right. Don't drag it out for 10 dates if you really don't find them visually pleasing. But if it's something that could change, like if they change their weight or they, you know, toned up in a different way or they dress differently or something. then, you know, I think that could still be okay. You know, that was shocking to hear from you, but I'm with you. Oh. Yeah, I agree with that.

I absolutely agree. I absolutely agree. I absolutely agree. And if you want to hear the full unfiltered stories from today's guest, you can check them out on the We Need to Talk page. Drop a like, leave a comment, and hit subscribe. See you next week. Two and five Canadians will hear the words you have cancer. That's why.

Every step and dollar-raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation Walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcfwalk.ca.ca.