#825 - Macken Murphy - The New Science Of Why Men & Women Cheat
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What's happening, people? Welcome back to the show. My guest today is Macken Murphy. He's an evolutionary biologist at the University of Melbourne, a writer, and a podcaster. Why do people cheat? Is it just the allure of novelty, dissatisfaction in their current relationship, fear of being left, retaliation for their partner cheating? Macken's brand new study gives so many fascinating answers to all of these questions. Explain

Expect to learn what the evolutionary drivers behind men's and women's infidelity are, what this new science says about the dual mating and mate-switching hypotheses, the top three reasons for why women and men both cheat, whether cheating is heritable, if there is such a thing as one-and-done cheating, the most common behaviors of someone who is being unfaithful, and much more.

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♪ Yeah, yeah ♪

You have caused some drama in the world of evolutionary psychology. A little bit of drama. I try not to get in trouble, but certainly this last publication might be a little controversial within the field. Sure. What have you done? What's the current state of the leading infidelity hypotheses?

Well, I mean, I guess we've got time to get into it, but it is a bit of a long story. So I would say that the background to know for someone who's just completely entry level here and has not heard about the Evo infidelity debate is that there's been a long running debate as to the evolutionary drivers of women's infidelity, female infidelity in humans. And

you know, during the late 90s and the early 2000s and to an extent the 2010s as well, I would say that most evolutionary psychologists would have said that the primary driver of women's infidelity from an evolutionary perspective is the powerful benefit of being able to obtain

better genes, right? Better in a fitness sense, obviously not in a moral sense. And we might end up saying, you know, the phrase good genes quite a bit on this show. And every time it's always good in a fitness sense. But in any case, the mainstream idea was that infidelity is a conditional strategy that women sometimes employ in order to obtain a

better genes for their offspring, right? So to pair the genetic benefits of one male with the parental investment benefits of another male. So everyone, when we're looking for mates, there are two things that they can give our offspring. They can give our offspring genes, obviously,

or they can give our offspring investment. And normally women get genes and investment from the same person. But the idea was, is that women's infidelity allows them to get genes from one person and parenting from another.

Let's say if they're with a mate who is very high investment, right? They love them. They've got lots of resources, but they don't necessarily have, you know, the heritable traits that a woman might want to pass on. So that was the mainstream idea for a very long time, almost 20 years. And then in the late 2010s, there was a bit of a reckoning, right? Which stemmed from the fact that during the 2010s, the...

original suite of experiments that were used to evidence this idea which from here on we'll call the dual mating hypothesis in this case i mean there's a few ways to use that term i'm using it to describe that specific strategy there was a bit of a reckoning because the original support for the dual mating hypothesis was based on these ovulatory shift experiments so the

The idea was, and it was a very clever hypothesis originally put forward by Steve Gangestad and Randy Thornhill, which is that if it's true that women's infidelity functions to pair

quote unquote, good genes with good parenting. Well, women can only get pregnant during a brief window in their monthly cycle. And so it would only really make sense for them to have affairs during that time, right? Because the risks of infidelity are evenly distributed, right? Infidelity is a very risky behavior. You could lose your relationship. You could be subject to retaliatory violence or social penalties, right?

And so it would make sense for women to engage in the genetic strategy during their periovulatory phase and the parental investment strategy during the rest of their cycle. And so that was their hypothesis. And the first tests, which were with, and this isn't their fault, but small samples and relatively primitive methods, those looked quite positive.

Then as methods got better, these effects either shrank or disappeared, depending on who you ask. Reanalyzing the original data? No, not reanalyzing the original data, collecting new data with better methods. Although there has been some questions about the original data as well. So one example of this is that some of the early studies would use

would determine when a woman was in her cycle based on self-report counting. So count since your last period, essentially. And that's just not, that's not a completely inaccurate method, but it's not exactly high reliability. And then later methods that use more, you know, direct tests, um,

And just better, bigger samples and also, you know, pre-registered in some cases, just better methods overall. They made this ovulatory shifts sub hypothesis of the dual mating hypothesis, right? They made this look less good. And so some scientists led by David Buss, but it was quite a large number, said, well, hang on.

Maybe it's not just that ovulatory shifts aren't happening. Maybe dual mating isn't happening, right? So dual mating is something that we see in some other animals to an extent. Like we see, for example, that red-winged blackbirds, the females will engage in infidelity with males who have more robust bodies, right? Fly catchers, another one where they've got nicer plumage, the affair partners.

Compared to the primary partner. So it's not something that's without precedent in the animal kingdom, but other animals like cockatiels, for example, when they have affairs, their affairs are geared towards something called mate switching. So the affair is a way of cultivating and obtaining a new and from a reproductive standpoint, probably overall better mate.

So they put forward this idea that, you know, hey, maybe humans are more like cockatiels than flycatchers. Maybe the underlying theory. So we've got dual mating this, you know, quote unquote, good genes, good parenting combo deal. Maybe it's not a combo deal. Maybe it's a best whole package type situation. Maybe that's what female infidelity is geared towards obtaining. So that was the history of the debate. And they put this alternative idea forward.

And it wasn't based on, you know, this new idea. It was a hypothesis that was put forward. It is a hypothesis that is put forward based largely on,

what we would call circumstantial evidence, right? So it's drawing together a variety of facts from past studies and forming inferences about them, right? About these, about what's happening from that. So it's not that there was some experiment that showed mate switching was very common in humans. It wasn't that we collected some, you know, awesome data set and it showed mate switching. That's not what happened. It was just an alternative hypothesis.

And then after that, Brooke Shelza tried to test the mate switching hypothesis in her population, at least the trading up function of it. She tried to test it in her study population, the Himba, that's a group of agro-pastoralists in Namibia.

And she didn't find evidence for the mate switching hypothesis. She found slight evidence for dual mating. And then she found evidence that a lot of women's infidelity in this area was geared towards obtaining additional resources from additional mates. So it has an additional function. And this is a theme that we'll probably talk about more.

So there was a little bit of evidence for dual mating. Women seemed to have put a higher premium on physical attractiveness and affair partners. But the mate switching hypothesis camp, at least in what I read, they seem to kind of

I won't say brush it away, but they seem to interpret that as just applying to that population, right? So it's like, okay, the mate switching hypothesis didn't work, but it's in this pretty unique population. And I think that's fair enough because the Himba do have a unique relationship to infidelity. And so what we wanted to do is we wanted to actually, you know,

set up an empirical design that directly pitted the predictions of the dual mating hypothesis against the mate switching hypothesis. And what did that design look like? Well, the mate switching hypothesis has quite obvious and intuitive predictions. If you're looking at the trading up function, some scholars, they would classify backup mating and breakup mating as part of mate switching. But we're looking at trading up. If women are cheating,

to obtain a better mate, then they should perceive their affair partners as better. Very simple prediction. Probably better looking, better specifically as a potential co-parent, since that's who they want to switch to. Overall mate value should be higher. Maybe a more attractive personality, right? I guess that could go both ways. And so what we did was we set up an experiment where we had them, where we collected...

women and men, so we collected a large sample of women and men who had actually had affairs. Because this was a problem with the previous literature, especially the literature in the mate-switching, dual-mating debate, not Brooke Schell's work, was that most of it was done on people who hadn't had affairs. Where do you find people that have had affairs?

I wish I could say something fun like Ashley Madison or something that we're recruiting on Ashley Madison, but that's not what we did. What we actually did was we put up a large survey that- Have you cheated on your partner? Come and do our survey. Yeah. Well, yeah. It was basically three questions. It was like, well, it was demographic questions. And then it was, have you ever been in a relationship that was sexually exclusive? In any of those relationships, have you slept with somebody else at any point?

And would you like to do our study? And we sent that out to, I think it was 1500 people. And quite a lot of people said, yeah, I actually have had an affair at some point, but it was a relatively small subgroup, let's say, that actually wanted to go through all the way and do further research with us.

So and that final sample was 254 people for those who are interested. So let's circle back to the predictions here. So if the mate switching hypothesis is true and we're looking at people who have actually had affairs, well, then women should rate their affair partners as more attractive in some way, but certainly more attractive overall and more attractive as a potential co-parent. Those would be the things that you'd really expect to see if the mate switching hypothesis were true.

The dual mating hypothesis has different predictions. So the dual mating hypothesis would predict that there'd be kind of this crossover effect where the affair partner is rated as better physically, right? Like physically more attractive, but parentally they should be less attractive, right? So if women's affairs...

function, evolutionarily, to pair good genes with good parenting, well, then the primary partner should have better parenting, right? The alternative wouldn't really make much sense. I'm not sure. I don't quite understand that. Why would it be the case? Why would dual mating not predict better parenting as well?

Because dual mating is pairing the good genes of the affair partner with the parenting of the primary partner. So it's essentially a process where women will have an affair, right? Or female animals, other species will have an affair and try to pair the genes of one male. And this, and this is, again, none of this is meant to be conscious. We're, we're looking at the subconscious evolutionary drivers of our behavior, the structured psychology underlying it. So it's,

So I guess to summarize, mate switching would predict that affairs function to obtain a better mate overall, whereas dual mating would propose that female infidelity functions to capture quote unquote better genes and pair it with better parenting, better investment.

And so these are distinct hypotheses. And, you know, I'll flag post here that or signpost here that none of this is meant to be conscious per se, right? It doesn't, this isn't implying that anyone's deliberately trying to

You know, in the same way that when we enjoy sex, right, we're not thinking consciously, oh, this is great because I'm going to get to have kids. In fact, we might be thinking the opposite, right? It's more what psychological biases undergird our infidelity. And, you know, we have very good reasons to suspect that infidelity did evolve. It appears cross-culturally. That's the first sign.

It appears, you know, this is something that your friend Stephen Stewart Williams likes to share, which is that if a behavior appears even where it is socially discouraged, it's probably not socially constructed. Right. And we see that infidelity is very harshly punished and people still do it. And then also humans are socially are mostly socially monogamous mammals.

And if you look at other socially monogamous mammals and other socially monogamous primates, extra pair paternity has some degree of presence. Extra pair copulation is documented with quite a high frequency. So we have very good reasons to suspect that this evolved. And so given the dueling predictions, right, that the dual mating hypothesis proposes that it's better physical attract. Oh, and here I actually, not to just over caveat, but

Why would physical attractiveness be a sign of good genetics, quote unquote? I would say listen to our last episode. I mean, Chris's last episode covers that in very high detail. But the short TLDR version would be that one, a lot of the things that we find conventionally attractive are just cues to health.

So, you know, the things that we think are good looking, the reason that they're conventional is because they signal heritable benefits such as good health. And then another idea is just that physical attractiveness itself offers benefits and is itself heritable. Good looking people tend to have good looking children. And so it would make sense that given the tremendous benefits that come with being good looking, you would want a partner with quote unquote good looking genes.

Anyway, so different predictions. Mate switching predicts that the affair partner will be better overall and better as a co-parent. Dual mating predicts that the affair partner will be better looking, but worse parenting, right? Or yeah, worse parenting, really it's the primary partner should have better parenting is the correct way to think about it. And so what we did was we took...

Everyone in our sample, and we had them rate their affair partner and their primary partner separately on valid and reliable scales. And our study was pre-registered. It's a very diverse sample and compared for differences. So we had them rate their affair partner and their primary partner's physical attractiveness, parental attractiveness, mate value, their overall desirability, and also their personal attractiveness. Although to be fair, that could have gone, that could have gone both ways. And it might, it would have been interesting, but

not necessarily consistent or inconsistent with either hypothesis. And what did we find? Well, we found that affair partners were about two points more physically attractive on our scale on average, and primary partners were about three points more parentally attractive. So we had this crossover interaction between rating type and attractiveness, which

was really the best case scenario for the dual mating hypothesis. It's also very unlikely, just for those at home, it's very unlikely that you would find this sort of structure by accident because usually better looking people, because of the halo effect,

and just positive perceptions in general, they're going to get better ratings on everything. And so it's very strange for one group to be better looking, but worse parenting. This is a very unlikely thing to see if there's no structured psychological adaptation involved. So the dual mating hypothesis was, I would say, strongly supported, best case scenario, pre-registered study on actual women who have had affairs signaling this. And the mate switching hypothesis was,

There was no difference in mate value, overall mate value, overall desirability, even between affair partners and primary partners, no statistically significant difference and no statistically significant difference.

in personality either. So our study ended up being the best case scenario for dual mating and the worst case scenario for mate switching. So I guess we started this conversation with why would this cause controversy? Well, it kind of seems like everyone has been a little too hasty in dismissing dual mating based on the fact that the ovulatory shift studies don't replicate.

But the truth is, is that ovulatory shifts are just a sub hypothesis of dual mating and human sexuality is actually unusually stable across the cycle. And so maybe it was a, I mean, I still think it's a cool hypothesis and maybe more complex methods will prove that there are, there is something to, you know, human estrus, but.

The truth is that dual mating doesn't need this hypothesis. It's just a sub hypothesis. And the more important thing is that we do seem to have different priorities in our affair partners versus our primary partners. And one thing that I'll flag, maybe we can talk about this later because it's more confusing and maybe the most interesting result from our study is that men showed the same pattern. So men also, contrary to conventional wisdom, men also tended to cheat up in terms of physical attractiveness.

and cheat down in terms of parental attractiveness. A lot of people responded to our study basically saying, huh, I would have thought that men cheat down across the board, basically because it's easier, right? Kind of the man is only as faithful as his options, and most men have more options that are less attractive than themselves. That didn't really seem to be supported. And then in our qualitative data, we also didn't find any differences in novelty-based. So I would say that the overall picture

The dual mating hypothesis traditionally has focused on women, but I would say that it's really a human strategy in the sense that humans in general, it's different what benefits are sought, but humans in general seem to prioritize conceptive benefits in affair partners and relationships.

parental benefits in primary partners. This is just one study, of course. And, you know, I did design the study to be persuasive to myself. So I am persuaded by the result, right? But

There are other results that converge with us in terms of at least the physical attraction side of things that affair partners tend to be more attractive and primary partners less so. I've spoken for quite some time, so I'll... Not at all. What is the evolutionary function of men following that same pattern when it comes to infidelity?

It's a little confusing, right? So I know that you've obviously had a pretty intense crash course in EvPsych talking to all the world leaders in the field, let's say. And so you would be aware of the fact that if you ask an evolutionary psychologist, why do men cheat? They're going to say, oh, easy.

More mates means more offspring for male mammals. They're going to talk about, you know, Genghis Khan and they're going to talk about, you know, how the ceiling is basically unlimited for males.

man reproductively if he just has enough mates. Whereas for women, the ceiling, in theory, and if you believe the accounts of Valentina Vasilev, this is kind of a funny anecdote to illustrate the conventional abstract view. Valentina Vasilev was a

Russian peasant. And I believe she had 60 something children all with her husband. Right. And then her own husband. So she's the she would be if it's true, she'd be the world record setting mother as a woman. Right. The most prolific, the most prolific women, woman in childbirth.

And then her own husband, if you believe the gossip, her own husband outpaced her by having affairs and he had like 80 something. So the idea being that a woman can, in theory and potentially in practice, maximize her reproductive output with just one male, whereas a male can only maximize the reproductive output by seeking additional mates. So that's the conventional wisdom in EvSec. Our study...

It's not inconsistent with that, right? Like we didn't design our study to test that hypothesis, but then we didn't find support for this hypothesis where we expected to find it. So one prediction that I think would be pretty natural from that idea that men's infidelity is purely quantity driven, right? So the women's infidelity hypothesis, mate switching, dual mating, both of those are

Both of those are quality hypotheses. And then the main male hypothesis is a quantity hypothesis, right?

And so you'd expect, I think that you'd expect to find that men cheat down, right? To maximize their numbers, so to say. And then you'd also expect when you ask men why they cheated, you'd expect them to report variety driven motives at a higher rate than women. It could have been because of our study design. We also asked participants just straight up, why did you cheat? I believe we've got certainly in the Evo literature, the,

Maybe, I won't say this, but certainly one of the largest data sets on just people saying why they cheated from our qualitative data. And men and women both reported sexual boredom, a desire for novelty. There were no statistically significant differences in that area. Maybe a better design would find that. There was no sex differences in proximate reasons for why people cheat.

There were sex differences in proximate reasons, but not in the novelty area and not in the boredom area and not in the combined measures of both of those, not in the variety area generally. But I think that that's just because, I mean, maybe I'm being too generous, but I think that we have to be really skeptical. I think our quantitative data is really good, really reliable data.

Our qualitative data has unavoidable shortcomings that come from just interviewing people, right? If you just ask someone why they cheated, people don't have perfect insight into their own motivations. And then they also aren't perfectly honest, right? Humans are storytellers. We like telling stories where we're the hero. And so we're going to downplay motivations that are unseemly or subconscious. And we're going to play up motivations that are

flattering. I'll give you an example of this that's pretty stark. So we asked women, what motivated you to have an affair? And about 5% of them said, oh, it's because my affair partner was really hot. He was super attractive. That's part of the reason why I had an affair. So 95% of women didn't even mention it. But then in our quantitative data, women were 77% more likely

to prefer their fair partner's physical attractiveness than to prefer their primary partner's physical attractiveness. What a coincidence if that's not a motivating factor, right? So we have to be, I am happy with our qualitative data, but

we have to be careful with it. I think the only thing that it really shows is strategic diversity. How do you know that that's not just novelty seeking? It doesn't need to be better. It just needs to be different. Yeah. So there, there, there was, there was a bit of that. I would say that about one in 10 people in our, our, again, our, our quantitative data doesn't really get at novelty, but it does suggest that it's not just novelty because from a physical attractiveness perspective on average,

It was better, right? But that's the, the, my point being that physical attractiveness is inherently a subjective. You're asking you participant, what do you think about the rating of a and B, which I'm sure you can see is being open to just straight novelty itself. As you've said, we are not a clear pool of water that we can see down into the depths of, uh, if you were to get a

people to say okay show me a photo of both your affair partner and your main partner then let's get other people to rate whether they think which one is more attractive and compare that to their answers that would be fascinating that would be a very good test yeah how much of a role can you send me a photo of the person that you're in a relationship with and the person that you cheated on them with please that would be great thank you yeah the the ethical nightmares that you've just designed

Oh yeah. And by the way, I'm going to show these, I'm going to show these to loads of people. Yeah, yeah, yeah. Yeah. So that would be a bit ethically fraught, but a good, genuinely good study design. That would, that would be a test of our hypothesis, I guess one. And I think that that's a legitimate limitation. It could be that novelty itself is causing more physical attraction. That seems plausible to me, but.

If it were just positive illusions associated with novelty, I think you'd expect higher ratings overall. It's weird that this is only happening with physical attractiveness. So we all know that, you know, in the early stages of a relationship, we tend to have these, you know, very biased views, very positive. They granted everything. Yes, they're wonderful. They're perfect.

And so if that's what's causing the physical attractiveness gap, very peculiar that didn't happen for mate value, very peculiar that it didn't happen for personality and extremely peculiar that actually reversed for parental attractiveness. So it's a legitimate critique.

And I would be interested in, I would be very interested in the results of that study if anyone can get ethics approval for it. Oh, dude, I'm the king. I'm the absolute king of coming up with studies that you can't do. You know, I'm like one of those rock stars that never actually learned to play classically and is able to, like, I'll do it left-handed and upside down. It'll look awesome, but sound terrible. That's my sort of contribution to the world of Eve Psych and human-based psychology. Yeah.

That and giving us cool terms. Cool new names. I'm good at memeing. That's it. Memeing and coming up with studies you can't do. Dig into what else you learned from a qualitative perspective. What was interesting? What did men say? What did women say? And sort of how does that tie in with your new reinforced perspective of infidelity? Well, sure. I mean...

So the top motive, the first thing to notice would be that the top motivation for men and for women was relationship to satisfaction in their stated motivations. So,

The way we did this was we read, it took a very long time. We read all of the responses and our data is public, by the way. Other people can also look at, you know, if you want to read hundreds of reasons why people had affairs and get a gist, you can just access our data. It's fine.

And we read through all of these. We coded them for themes. So that's when you basically write down like, oh, this one mentioned that the affair partner was hot, that kind of thing. So we coded them for themes. And then we went through and we found the themes that were repeating themselves. And then myself and a lab assistant went through and we separately recoded these items to see which themes were occurring at what rate.

And then we ran statistical analyses to test for sex differences. So that's our methodology. Relationship dissatisfaction was the number one stated motivation for infidelity in both men and women. However, it was a big sex difference as well. So only 30% ish of men mentioned relationship dissatisfaction in their answers. So most men, even though this was the most common response, most men didn't bring it up.

Whereas 65% of women mentioned relationship dissatisfaction. So women were twice as likely to bring this up, essentially, over twice as likely. Even though it was number one for men? Even though it was number one for men, correct. Does that mean that men had a flatter distribution of reasons in that case?

Not necessarily. That inference would be correct if we coded them one-to-one, but the way that we coded it was that one affair could have multiple motivations. So for example, a participant might say, oh, I was in a long distance relationship and things weren't going well. She really wasn't treating me right. And my affair partner was

just gorgeous, right? That would be a pretty, that would be a pretty reasonable answer. That'd be the sort of thing that we'd see. And then that would get coded as attractive affair partner, long distance relationship and relationship dissatisfaction. So it doesn't necessarily mean flattered distribution of reasons because we can recode variables in this way, but great question. So historically, right? The whole women are more likely to have relationship dissatisfaction because

when they commit infidelity, that's an expected sex difference. It's something that pops up in the literature quite a bit since the 80s. Why? Why is it expected? Well, it's funny because the original logic was that it was evidence for the mate-switching hypothesis. Because it's like, oh, if women are usually dissatisfied when they have affairs, that means that they want their relationship to end, right? Two reasons I'm skeptical of this. One,

Women are, women often have higher relationship dissatisfaction anyway, right? Given certain circumstances, they might be more sensitive to cues that the relationship is not going well. There also might just be a difference where they're more likely to express dissatisfaction, even if dissatisfaction levels are in actuality, even between the sexes. That's number one. Number two, and this is more important and more deeply theoretical, which is that

Infidelity, as we discussed earlier, is a very risky activity and it is especially risky for women. So

based on martin daly's research i believe you might have spoken to uh no i haven't i'm i'm lining up i would have called him daily so i'm glad that you fact check me on it might be daily it might be daily i've only read his name i mean it's only it's only your industry mate so yeah i'm speaking i'm speaking to martin through a combination of rob kersban and steve um i think i think he'll be great

Yeah, no, he surely will be. He's written just some of my favorite stuff has been written by him. But some of his early research basically found that women's infidelity is more likely to result in relationship dissolution than men's infidelity. And so this is a funny way of thinking about this, but

In EvPsych, it's pretty common to think of relationship satisfaction as an internal regulatory variable that partially tracks the value of your relationship. And so if your relationship satisfaction, if you risk your relationship every time you have an affair and your relationship satisfaction is low, well,

then you're literally risking less than someone whose relationship... Exactly. Exactly. And so if infidelity is more likely to result in relationship dissolution for women than men...

then the risk is at a baseline higher. And so you should expect that women should be more likely, right, to be attuned to whether they have the infidelity discount that comes with relationship dissatisfaction. And so,

This has been interpreted as evidence for the mate switching hypothesis. And I think it's reasonable to say that someone who's relationally dissatisfied is more likely to be mate switching with their affair. And some people do mate switch, you know, several women in our sample, but only several said that they were mate switching. But I think it's reasonable to assume that they're more likely to be mate switching than someone who's really relationally happy. But I don't think it's reasonable to do the reverse inference, which is that because they're relationally unhappy, they're

they want to mate switch. There are plenty of people who are relationally dissatisfied, having an affair, but also want their relationship to keep going. And that's also quite intuitive to me, this idea that sometimes relationships are unhappy, but you want to stick things out. What do you make of the difficulty that women supposedly have in separating their emotions from

having sex with a guy that women will fall more when they are physically intimate with a man because there is a higher hurdle for this man to get over that it is her being more risky. Would it not be the case for mate switching

that women would be more likely to fall for that partner still, even if it's not, sorry, for dual mating, even if it's not for the purpose of mate switching while they're dual mating, would it not be more likely that they were going to fall for that partner in any case as a sort of a natural byproduct of the feminine desire to be emotionally intimate with someone? That's very clever. I haven't considered that. And I have to think about it more

Because, I mean, you're familiar with the mate switching hypothesis, but what Chris is referring to here, I believe, is that there's a one of the flagship pieces of evidence for the mate switching hypothesis is that women are more likely to fall in love with their affair partners than men are. And what you're saying is that women are more likely to feel emotionally entangled with sexual partners in general. And so that also isn't

necessarily particularly good evidence. One thing that I will note is that we didn't find that love for affair partners was coming up much at all, right? We're talking like 1%, 2%. I can't remember. It was sub 5%. Very few people in our sample, men or women, said that they were motivated by love for their affair partner. It just didn't come up very much. And so I'm a bit skeptical. I mean,

Maybe it is the case that women are more likely to be in love with their affair partner, right? But at least in their stated motivations, it doesn't seem to be a big factor in why they had the affair to begin with. And so that might be... Even though that's my favorite evidence for the mate-switching hypothesis, as you say, it might not have as much theoretical oomph to it as it seems to at first glance. And then also...

And there's an inference involved there where it's like, if they love them, that must be their motivation. And it's possible to be in love with your affair partner and have that be pretty low on the list of why you had an affair. Yeah. Yeah. I remember Andrew Thomas talking about...

what women say that they want in terms of traits when choosing for sperm donors. So everybody's a eugenicist, right? Everyone is, everyone is, whether you like it or not. And some people are more quantitatively and obviously eugenicists if they choose sperm donors or if they choose a, like if they go through IVF with a donor for either side, I suppose.

And one of the things that I thought was really interesting that Andrew brought up is women who choose sperm donors, it is the only time where the traits that you want in your future child are divorced from the traits of the man that is able to get you into bed to be able to create that future child. So you have this sort of weird territorial cutoff, which is what do I want my future kid to be like?

without having to jump through the hoop of what is the sort of thing that I find attractive that gets me into bed. So it's kind of a much more sterile, controlled environment when it comes to doing that. And given that, with regards to dual mating, it surprises me that things like personality didn't

include in that given that although you want sexy son hypothesis, presumably you want likable son hypothesis. It's interesting. In our pre-registration, we didn't make specific... I guess one thing that I'll note on the eugenics point is that I've heard a lot of people say the same thing of kind of like it's sexual selection is eugenics. I personally do see a difference between individual level what...

What traits do I want my child to have in the case of embryo selection, in the case of IVF and sperm donation? And then what traits do I want to be high frequency in society at large? That's a good, you're perfectly acceptable to do that. There's a difference between Tubi's concern about that gene erosion thing

That sort of scaling up, even though I think it's still largely ethical, that's more of a scaling up. That being said, the one conversation that I've ever had about embryo selection, I got called an actual Nazi for having. But it's okay. I'm over it. I mean, I'm not...

I'm not someone who's super into science philosophy. I'm sure that someone's listening and just thinking that I sound like a bit of an idiot. But I will say that I don't see a huge difference between... I mean, maybe I'm just thinking about this wrong, but I don't see a huge difference between selecting an embryo and selecting a mate at the individual level. Where I would start defining it as eugenics and start defining it as ethically...

abhorrent to myself would be when people are telling other people what they should do or when the government is getting involved and trying to adjust, yeah, trying to adjust any top down, trying to adjust the frequencies of genes in the population. I would see that, I would see that as very, very bad, but at the individual level, I don't really understand the

I mean, I also don't really understand embryo selection, to be honest. It's not my area. I'm an expert in very few topics, so we'll stick to those. It is interesting, of course. Anything else from the qualitative insights that you learned? Yeah, I think it would be cool to just go over the top three topics

motivations for... Oh, actually, can I just ask, though? What was Andrew Thomas... What was his actual conclusion on... Like, what traits did they want from sperm donors? Because that's very relevant to the dual mating. I can't remember. Let me see if I can pull it up. Andrew Thomas. The advantage of having 3,200 notes. Okay. She conducted an experiment where you asked chat GPT for mate preferences...

Uh, no, I can't, I don't actually, I don't actually have it on there. I certainly know that, um, uh, things like kindness, uh, were much more prioritized. It seemed to me to be, um, softer skills. What if you want to call it that sort of the soft skills of, of being a, being a person. Uh, so I think in there, uh, kindness, um, humor, intelligence, um, um,

Yeah, it was more pro-social stuff, I think, which maybe you would probably be able to predict pretty easily that you can look away from someone's dark triad adjacent personality traits because they're hot or cool or funny or something. Interesting. It's funny because embryo is just, you know,

Sperm donation embryo selection all of these it's all it's hard to know if it's stated or revealed preferences It's hard to know where to put it. There was a really cool study from Paul Eastwick and his colleagues Just awesome where they looked at this is very recent. I think it's still in press So it's not even fully published yet, but it is fully peer-reviewed. It's gonna be published as is and They looked at what people say they want in a partner and

And then they looked at how what they say they want actually predicts romantic evaluations in practice. So that stated preferences on one end and then kind of a version of revealed preferences on the other end. And there were some kind of funny examples. The number one stated preference trait was loyalty. That's what people said. It's like, what do you want in a partner? Number one thing, loyalty. And the number one revealed preference was being good in bed, a good lover.

So there's that. I took that table from your Twitter. So yeah, they said the first rank was loyalty. But to be fair, that ranked as number two.

It still ranked as number two. Yeah, that's the other thing is that it only got suppressed a little. The main thing that was shocking was how much women jumped. A good lover jumps from rank 12 to rank one. I know. Again, it goes back to what we were saying about the people want to tell stories in which they're the hero. It doesn't sound great. If you're asked by a psychologist, what do you want in a mate? And the first thing you say is good in bed, you sound quite

unhinged. But in practice, that might actually be more predictive of your romantic evaluations than anything else. And it certainly seems to be in this large sample. And then they also found that in general, I think the general gist of that table is that

Traits, physical traits are much more important than people say, and they're especially more important than women say. So for men and women. Sexy jumping from number 19 to number six. Yes. Yeah, that's a huge jump. Smells good.

That's another just physical trait, whether you smell good or not. What was that? I know it jumped to like number four, but it was smells good. Oh, number 15 to number four, attractive number 16 to number eight. Yeah. So if you want to contrast what people say they want and what people actually want,

One of the main things that's going to come up over and over again is that people understate, and this doesn't necessarily mean they're lying. It could just be that we don't have perfect insight into what makes us happy, but we understate how important physical attraction is. The black pill was right all along. You just need to smell nice. Yes, the new black pill just dropped. I'm smell maxing. Smell maxing. I'm so smell maxing right now. Yeah.

Okay. Qualitative, the rest of the qualitative stuff. Yeah, the rest of the qualitative stuff. So that was a diversion, but a happy one. And one that's actually relevant because we, in a way, we found the same result. Again, 5% of women mentioned that their affair partner was physically attractive, and then they were 77% more likely to prefer their affair partner physically. What a coincidence. But top motivations for women. Relationship dissatisfaction, number one.

And a high number one, again, most women mentioned that. Second place and second place by quite a bit, only 20%. That's still a high, 22% mentioned that their primary partner was uninvested. And this also illustrates an important point.

which is that not all women's affairs are explained by dual mating. It seems that there might be a psychological bias towards the dual mating strategy, but many women had affairs with affair partners who they perceived as less attractive, right? 77% more likely is not, you know, that's not an infinite gap. And then, um,

One of the reasons that many women cheated, one in five women cheated precisely because they thought that their primary partner wasn't invested enough. So if it's pairing good genes and good investment, that doesn't make a lot of sense for those women. And then the third most popular motivation for women was revenge. So 15.5% of women said that they were cheating to get revenge. Did they say what on?

Well, in this case, the 15.5% figure is revenge for their partner's affair specifically. So I remember I spoke to a guy who was kind of an unofficial marriage counselor in his neighborhood. And I asked him, why do women cheat in your experience? What do you see? And he very flatly said, he said, women cheat when men cheat. Now,

That doesn't seem to be 100% true, but there's certainly some truth to it in our data in the sense that women were much more likely to cheat for revenge. And you could interpret that as a genuine strategic difference. But since men cheat more than women, women have more opportunity to cheat for revenge, or at the very least, they have more opportunity to

At the very least, they have more opportunity to cite revenge as one of the reasons why they cheated. Whether it was going to happen or not. Yes. What is the state of who cheats more, men or women?

Oh, that's a pretty open and shut case. Men cheat more. Men say they cheat more when you ask them. Men say they get cheated on less when you ask them. So women report getting cheated on more. And then women who are the third person, right? So some people might say, oh, well, maybe women are just understating things. When you ask, you know, who's more successful as a mate poacher, women who mate poach tend to have a higher hit rate. So

There are three people involved in any given affair. There's the primary partner, there's the person who's cheating, and then there's the affair partner. And you can do studies on any one of those three groups, and you generally find the same result, which is that the man is generally more likely to have an affair. In some studies, it's not a big gap. In some cultural contexts, it's a huge gap. But that would be the overall result.

State of the science there. And so the revenge difference, it may just be downstream of the sex difference in committing infidelity. They have more opportunity to have an affair. What do you what do you learn from a woman's concern about investment from their partner?

It's a good question. So this is pretty consistent with, it's not consistent with the dual mating strategy, but it's consistent. And it's actually a really good thing to illustrate that women cheat for many reasons. They cheat maybe for traditional variety-based motivations, such as genetic heterogeneity or sexism.

you know, fertility backup. So some percent of couples are infertile. And so if you're mating with multiple males, you're really lowering the probability that that's going to result in the end of your lineage. There are many motivations for affairs. Revenge. So having it being an uninvested partner, low investment, I would say that it signals

I would say that it signals kind of the traditional of psych difference, which is that women's investment in offspring is largely obligate, physically obligate in the sense that women have to go through pregnancy and lactation. This is part of why women seem to be more careful about who they mate with more choosy. A lot of men complain about, you know, women having high standards for their mates, but really what do you expect, right? Like if you could get pregnant,

surely you'd be pretty careful as well about who you mate with. And so women's investment is partially obligate, whereas men's investment is not morally, but pragmatically entirely optional. Men have the option to seduce and abandon mates. And so you'd expect given that, that women would be very sensitive to cues that a man might seduce and abandon her and really try to avoid that

as much as possible. And so if they're in a relationship and they think, oh, my partner's not investing in me, he's not invested. Well, that's a huge signal that he's a low mate value mate, essentially. It's like, oh, this isn't going to work. And maybe that's evidence for mate switching, but maybe it's also evidence for a breakup or backup or just lowering the cost of infidelity. Again, the discount infidelity idea. I was going to say, this doesn't mean that no

woman ever leaves her partner to get into a relationship with the cheating partner. Yeah, reliably that does happen. And also I'm going to guess that if you looked at the cohorts of women and you were to find the one that said, I was worried about investment from my relationship partner, that would probably result in more likely of a pivot to the new

infidelity partner as a new relationship. I'm going to guess that that would probably be predictive of that because like, what am I sticking about for? If I'm going to have genes and investment and I don't have investment, then I might as well try and get genes and investment together. Yes, exactly. So the dual mating, it doesn't explain all of women's infidelity, certainly. And we did see some mate switching in our samples. Several women in our sample were mate switching. I'm wondering whether the...

era that we were in, in sort of 2017, when we look at the mate switching hypothesis, the dual mating hypothesis feels a bit icky to me. Like when you think about it,

when you think about, and maybe this is just me as a man, but thinking about some guy, male parental uncertainty, raising another man's children, whether this is or is not during a period of ovulatory shift where you're fertile as a woman. It makes me go like,

you know it's a little bit more a Machiavellian it feels like in that way whereas mate switching seems to just be okay you're monkey branching from one relationship to the other people have backup mates people have you know their friends females friends that are men often tend to have the attributes of the sorts of men that they would get into a relationship with which kind of has these sort of weird quasi orbiter backup mate things floating around a little bit uh

I wonder whether in a post-MeToo world, that was just a bit more... It was a little bit easier to digest, to have something that was a bit less like, oh! I know. I mean, I don't really... In terms of assessing theories, I don't really care about how icky they are or how...

Yeah, it just doesn't affect my assessment of the facts. I just want to know what's true, whether or not it's kind of gross. And I would say that the evidence points to this idea that this is a part of human evolution. I mean, in modern populations, quote unquote, cuckoldry is quite uncommon. Yeah.

1%, 2%, 3%. Those would be the sorts of estimates that you'd get from people who really understand the subject. That would be 1% to 3% are men raising a child that they are unaware is not their genetic offspring. Yeah, exactly. 1%, 2%, 3% of kids are in a you-are-not-the-father type situation.

The male sensitivity to parental uncertainty, though, has to exist for a reason. Yeah, exactly. If it never happened, exactly. How could we have such concern with paternity certainty if there was no paternity uncertainty to be concerned about? That's number one. Number two, the modern percentages...

They're based in a cultural context where infidelity has been highly suppressed socially. And they're based in a technological context where we can choose through contraceptives and whatnot, consciously, who you have kids with to some extent. There's much more control over it.

If you look at populations with less contraceptives, well, then you start to see rates of 5%, 10%, among the himba, 48%, really high rates of extra pair paternity. So some evolutionary psychologists have said, oh, dual mating isn't true because it happens at such low rates.

And it's like, well, first, reconsider that 2% number in terms of the 15% of women who have affairs. Reconsider it as a hit rate as opposed to an attempt rate. And then also reconsider it in the sense that

That's not nothing over millions of years from an evolutionary time scale, but also it's not necessarily relevant to our understanding of our ancestry given that we have contraceptives now and we really didn't then. What about men's motivations? What did you learn from them? Yeah, men's motivations.

I guess I actually do want to say one more thing on the icky point, because I think that there is a... And then I'll talk about men's motivations right after. I'll just go straight into it. I guess one issue from outside EvoPsych is this idea that the dual mating hypothesis is somehow... Or the mate switching hypothesis or any of these, that it's somehow sexist to talk about the evolved psychological influences on human sexual behavior.

The first thing that I would say to that is just that the of old psychological influences on men's sexual behavior are also very unfavorable, right? The portrait that you can paint of men's behavior using Evo psych is downright dastardly, right? It's, it's full of deception, uh, men's affairs, just, you know, as much variety as possible, you know, completely emotionally detached, right?

We've talked about the seduce and abandon strategy. All of this is very ugly. And it's important that we have, if we want to reduce ugly behaviors, it's vitally important that we have a good understanding of what's actually happening instead of deluding ourselves that other influences are at play. More, you know, comforting ones. Another thing...

is that the primary advocates for the dual mating hypothesis, I mean, the senior author on our paper, Candice, who you've spoken to, she has a gender studies degree. Everyone on our paper is a feminist, right? Like we all believe in, you know, gender egalitarianism. And, you know, some of the chief advocates for

dual mating elizabeth pillsworth back in the day marty hazelton even today these these are women and feminists who are interested in this topic so the kind of outside evo psych view that it's like oh this is like some kind of like anti-woman agenda now we're just interested in what's true what's false and we're trying to take the politics out of it as much as possible so we can just buckle down and do good science yeah you can talk about top motivations it's certainly um

It doesn't paint women in a particularly flattering light, but we're talking about infidelity. Yes. And most women don't cheat. But what this does show, I think, if you do get pushback, more pushback saying, this is unfair, this is you trying to control women's sexuality, this is you painting them as Machiavellian and all the rest of it, I think that what that betrays is the...

typical social expectation and interpretation of women's behavior, which is that sexually women are not the protagonists, that they are almost always responding. It's actually low key, quite a sexist

perspective on women that they don't have agency to go and chase down a new partner. It's the same people that will tweet, "You're too good for him, bae." Remember your value queen whilst also saying, "No, no, no, no, no. Women are never the ones that initiate. Women should never be the ones that so on and so forth." It's such a midwit take from people that pretend to be

egalitarian between the sexes. It's not. It's not. It's like the soft bigotry of male expectations. It's... Yeah, it's... So based. Such a good point. It's incredibly patronizing. Everyone's happy when you talk about men's evolved psychology. But then as soon as you talk about women's, it's almost as if the whole story is about men. And this is something that I see a lot in kind of public discourse is that, you know, if you...

label everything as

you know, the patriarchy, let's say, well, then you're basically saying that men are the only ones with their hands on the wheel. And that's a pretty patronizing view of women. Our lab views women and men both as active sexual strategists. And that's a much more... I mean, politics aside, it's just a much more accurate view. I mean, it would be weird if women weren't active sexual strategists. But it...

But also, I think it's even less flattering to just say, to just pretend that women are always acted on as opposed to active agents in their own rights, actually. I can't tell if we're being woke or anti-woke here. I'm sure that we'll be accused of being both.

Yeah, the last five minutes of our conversation is going to be a Rorschach test online. Correct. Dude, I've been using that all the time. Two memes that I'm yet to write into existence, one being an ideological Rorschach test. So a good example of this was Trump getting shot in the head. That was an ideological Rorschach test. That was either on one side, the Dems trying to take down

uh the candidate that was going to win through purposefully stopping the secret service from protecting him or that was trump attracting crazies in a world where he's enabled everyone to have a gun like he was just pick and the other one the other meme being a thinking in super positions so you have these two worlds that both exist at the same time and they collapse down into one and uh

It's interesting to see, you know, we talk about, okay, so you saying that women don't have agency sexually? Well, no, of course they do. Of course we need, in fact, they need to have more. It's like, right. Okay. So you're saying that they can make choices when it comes to their own infidelity. Yes. And you would surely expect that they would make strategically prudent choices. I mean, what's the alternative? So they're going to be culpable. They're going to be culpable for this thing. Yeah. It's so, it's so funny. Okay. Men's motivations. What did you learn?

Yeah, that was a rich segue. This now feels relatively lightweight by comparison. But again, top male motivation is relationship dissatisfaction again, but it's at relatively comparatively more frequency, comparatively lower frequency. That's the sense that I'm using relatively here. So about a third of men, about 30% said that they were dissatisfied

And about 16%, so significantly more than women, said that it was because they had an attractive affair partner. And about 14% of men said that it was motivated by sexual desire. And here, again, I just want to note that

The qualitative data is qualitative, and so it's subject to these reporting biases. It's subject to these interpretation biases. Are we really meant to believe that only 14% of men's sexual affairs are motivated by sexual desire? I mean, that...

surely it was part of it for much more men. It's just that it's not particularly flattering or self-flattering to talk about those things. And so men are going to be wants to report that at a lower rate because it seems a little inappropriate. That would be my interpretation of that. But it is interesting that there's a sex difference there. And that actually was something that's consistent with the mainstream Evo takes on, uh,

infidelity, that men's infidelity is somewhat more sexually driven, directly sexually driven than women's infidelity. Because for men's infidelity, the

Only benefit really is sexual. That's the mainstream take. It's not my take. I think that men cheat for a lot. Men and women both cheat for lots of reasons. Some men in our sample were mate switching. Some men in our sample had an affair because they wanted a new girlfriend. That happened at a similar rate to women as well. What was the rate of men saying that their partner wasn't invested?

I think it was 5%. Right, that's interesting. We're going to get on to talking about jealousy shortly, but just to kind of round this out, what are the exoplanets, the unspoken ghosts and sort of potential orbiters of infidelity hypotheses? Is there anything else that's still lurking out there in the ether that isn't dual mating, mate switching? Oh, yeah. Yeah.

So multiple investors is the elephant, has to be the elephant in the room. I mean, there's a few elephants in the room. One that I think you've talked to Jeff Miller, have you? Multiple times, yeah. Yeah, yeah, yeah. Actually, I've seen clips. So Jeff Miller had a hypothesis that didn't really get hardly any attention, which is that part of the affairs that we have are to

gain information, right? To calibrate our own mate value, to gain skills in seduction. And that theory is largely been brushed off, but it did pop up quite a bit that I can actually check the percentage here. It wasn't nothing, you know, about one in 20 people said that they were cheating for some variety of information acquisition, right?

What do you mean information acquisition? Are they fucking spies? What's going on? So, for example, one woman said that she wanted to

uh, basically wanted to obtain skills in seduction. Like she didn't phrase it that way, but it was like, I wanted to be able to do this. I wanted to have this ability. And so that's kind of a, that's a reason for infidelity. That's strategically legitimate where it's like, look, I don't really know my own mate value, or I don't really know how to get guys, or I don't really know how to get girls. And that's a very important life skill. It's going to be important throughout my life. Let me go work on it. Right. On the side that, um,

I wouldn't expect it to be the main motivation for infidelity, but it's a motivation. You can imagine someone who is, you know, let's say a college student, they're in their first big relationship, they're halfway through college and they realize, huh, I actually don't really know what I'm doing still dating. And I'm going to have to date my whole life, right? Until I get married at least. So let me go get some skills here. I said this about people who get into a marriage with the first person that they ever have sex with.

And it's kind of like being with your first ever therapist. I'm doing therapy at the moment and a lot of people, it's the first time I've ever worked with someone for this long in person, et cetera. People go, what's your therapist like? I go, I...

I think she's great, but I don't really know because I've got nothing else to compare it to. And it's kind of the same with that. And I suppose you just don't know, could I do better? Could I do any better? Is this really the best that I could do? Yeah. So there could be some mate value calibration that comes from engaging in infidelity to some degree. Multiple investors is worth talking about because that's

Most of the theories that we've been talking about for women's infidelity have been quote unquote quality driven theories. The difference is what qualities are being searched for. So again, mate switching is best overall whole package, whereas dual mating is the best combo deal. But both are quality motivated.

Multiple investors is a very interesting hypothesis. It seems to be the primary explanation of infidelity among the Himba of Namibia. And it's essentially that if a woman can't get enough resources from one man, well, then she can obtain supplementary resources from additional mates on the side.

So this wouldn't be a quality driven hypothesis. It would be a quantity driven hypothesis. It's just that the quantity or not necessarily quantity driven, but it's quantity of resources. And that could translate to quantity of mates. I would have to talk to Shelza about it, but it's a very interesting hypothesis. And I think it does happen. We didn't find a lot of evidence for it in our sample, unless you take the uninvested primary partner as evidence for it. Like, oh, this guy's not invested in me. Let me go get some investment somewhere else.

But very anecdotally, I have at least heard of people having maybe a kind of sugar daddy character on the side who it's like he's not particularly attractive, but you need to pay rent at the end of the month. And so this is something that you engage in. So I don't think multiple investors should be expected to be at high frequency in high SES countries and in high SES individuals.

But in situations where resources are scarce, that could very well be the main reason that women have affairs, to obtain additional resources. Do you know The Wizard Liz? Do you know that YouTube channel?

uh no right so her channel's huge but just has not come across my radar until recently she's got six and a half million uh subs on youtube huge hugely uh engaged instagram as well and she regularly does videos basically explaining uh how to get the princess treatment which is how to make

your man a man pay for your entire life uh pay your bills buy your car pay your tuition ensure that you're looked after treat treat you like a princess and uh if i was to speak to her i would very i would be very very interested in asking sort of what are the motivations for that what do you think about using multiple partners like really trying to dig in she's like super duper famous um and it's you know it's kind of tangential to this sort of boss bitch

thing but it's done in a very different sort of a way because obviously it's it's not focusing on financial independence and not needing a man it's a more uh

Some would say Machiavellian manipulative version of this to get the guy to pay for those things, uh, for everything that you should be showered in gifts, that it's very important that you're showered in gifts, that you should set the tone. She uses, I was watching this video from her yesterday. She says that you should lie to, uh, every new relationship that you're in and say that the guy in the previous relationship spoiled you because men will only work as hard as they feel like they need to, to beat your previous boyfriend. So,

Basically, if your last boyfriend...

beat and abused you and never cared for you your next one will just think well if I just don't beat and abuse her then I'm better so it's a very interesting like super interesting fascinating I'll send you some of the videos once we're finished up yeah I'll be interested to see if men start taking on that strategy because it's this is the first period in history where it's viable to be you know a boy toy or a dude I'm an aspiring fucking trophy husband have been have been for a very long time unfortunately you've got too much money for that

I still have hope. I'm still hoping for an heiress to step out of somewhere. Okay, so what about the role? How does this fold into your new sort of perspective on this? How does this fold into the discussion around jealousy, about sex differences in jealousy, about why men and women get jealous, its evolutionary function, et cetera? Well, I mean...

This is what's funny is that the dual mating hypothesis is more consistent with the evolutionary psychology literature on jealousy. I mean, it's quite conspicuous to me, but it doesn't seem to have been acknowledged generally. It's something that we've touched on earlier, which is just that if so, okay, well, to give everyone the download, if they don't have this information yet,

on average, it varies the degree of the sex difference, the size of the sex difference varies, and it also varies what people care about. There are plenty of cultures where everybody cares more about sexual infidelity or everyone cares more about emotional infidelity, but the general difference is that within a culture, on average, men will be relatively more concerned with sexual infidelity and women will be relatively more concerned with emotional infidelity. And

That makes sense if dual mating is the concern because men aren't protecting against a woman leaving them for another partner. They're protecting against the potential that they will be quote unquote cuckolded, right? They don't want, they're more upset by sexual infidelity because men can be cuckolded where women really, at least not in the same way, right? In a euphemistic way maybe, but not in the literal sense.

On the women's end, we've talked quite a bit about investment. They're going to be chiefly concerned or not chiefly necessarily, but they're going to be more concerned than men with losing investment because women's investment is more obligate. Men's investment is more, not morally, but pragmatically optional.

And so that's really the landscape in terms of sex differences and jealousy. It pops up everywhere it's looked for. And I will note, though, that some people have taken it. Some people have exported this F-Psych finding and said that, like, oh, women don't care about

at all about sexual infidelity. Their main concern is emotional infidelity. As long as it's just sexual, it's fine. That doesn't pop up. Women are very upset by sexual infidelity. And then also on the other end, men are very upset by emotional infidelity. It's just that relative to one another within a culture, you'll generally find the difference in that direction. And this makes sense under a dual mating view because men are paranoid about...

getting cuckolded. And then it also makes sense from a traditional kind of what women stand to gain from relationships in the view that it's like, well, if he is invested in her emotionally, then he might go off and raise her kids instead of mine. And maybe he's not invested in me. Men have paternity uncertainty. Women have investment uncertainty. That's how I'd summarize it.

A consequence of this being accurate, dual mating being the leading infidelity theory, would be more men being cuckolded ancestrally. Is that right? Yeah, and I think it's very reasonable to think that that happened quite a bit. I mean...

If you look at even rural American populations, I've seen higher numbers, like close to 10% in terms of estimated. If contraception is low and infidelity is high, you're going to get

a lot of men raising kids that aren't theirs. Um, that doesn't happen a lot in the modern, in modern America, in modern Britain, in modern Australia, where there's contraception and strong social norms against infidelity. Uh, we don't really see, we don't really see a lot of that. So it's not really something to worry about in a modern context, but in an ancestral context, I would say that this would be a real worry. I will also note that, uh,

There's a great new paper, relatively new paper from, again, Berkshosa called the cockle tree conundrum, which is just pointing out that sometimes, you know, our conception of cockle tree doesn't isn't necessarily exportable in the sense that and this might sound strange, but sometimes.

you know that a child isn't yours, but it still makes evolutionary sense to invest in them. So for example, among the Himba, there's tremendous status to be gained and social clout from being a good father to your wife's affair partner's children. So you would be- That's pro-social in some ways. Yeah. So it's like you would be, because, and you got to keep in mind that

You know, they've probably played both sides of the field here. So they've probably got eggs in other nests themselves, to use a metaphor. And so it's kind of in everyone's best interest to be like, you know, let's just invest in the kids that are in our nest. It's a free-for-all. It's a pool. Well, this is kind of like the human equivalent of the why female chimps mate with multiple males metaphor.

because the risk of infanticide gets reduced because each male is uncertain about whether or not that child

might be his i'm not sure if that's even true but it seems to me this seems to be a more kind of uh yeah socially enforced equivalent of that uh yeah i would call that a yeah i would call that a tangentially related hypothesis for sure i i don't know how high and this is something that you should talk to martin dally about actually is because he's his cinderella effect book is just um

The truth about Cinderella. So yeah, that is such a fun one about infanticide and humans. I say fun. Oh my gosh, don't clip that. Ruthless. But yeah, interesting. I really did mean it when I said I don't care how gross the theory is. I just want to know if it's true. But I don't know how much infanticide has actually played a role in humans, but it's kind of funny. And this actually relates back to the political conversation we were having earlier.

is that some of the initial theories from Sarah Hardy on women's infidelity in humans were related to paternity uncertainty. And hilariously, given that, you know, this is something that Louis Bichaud pointed out to me, which is that

in the 70s, 80s, and 90s, these findings on women as sexual strategists, dual mating, paternity uncertainty creation, these sorts of things, they were championed at that time as feminist ideas and pushed back upon by right-wing people who wanted women to... They had this archaic view of women as passive and not engaging in the sexual marketplace as active agents.

And now, today, we have the complete political reverse where it's the same set of scientific findings, but it's the super feminist groups that are saying, oh, that's just not true, da-da-da-da-da. They're kind of acting like the old right-wingers. And it's the really misogynistic groups, such as, you know, the tail end of incels and such, who are holding up these same findings and saying they're great. So...

I think that that's better evidence than I've heard for anything that these facts are neutral. And if you have an agenda, you can collect a set of facts and spin them in a way that fits whatever agenda you like. The same findings that today we call sexist were originally championed by feminist scholars. And that's just the way the cookie crumbles. Wow.

Well, the horseshoe is very horseshoe-y and it ends up being a total fucking circle eventually. Yeah, it's more like a merry-go-round in the history of this debate. The same sexual findings that were considered liberal are now considered conservative. And if you give it another 20 years, it'll probably flip back. Meanwhile, we're just going to keep our heads down and try to figure out what's actually going on. What are the predictors of infidelity? How can you tell if someone's going to cheat?

Okay, there's actually a long list here. The most obvious one would be have they cheated on a past partner?

Once a cheater, always a cheater. This lines up with our folk psychology. It's not exactly true in the sense that many people cheat on one person and then never cheat again, but it's true enough, let's say. So there was one longitudinal study from Kaelinopp that found that if someone had cheated in their last relationship, they were three times more likely to cheat in their next relationship. Have you got any idea what the base rate is? Oh, the base rate of infidelity? Yeah.

It's difficult to find in dating couples. I'll say two things that I'm quite confident in. I would say that about a fourth of marriages will encounter infidelity at some point in their lifespan. And I would say that about half of people, maybe a little more than half in men, a little less than half in women, but somewhere floating around that kind of mid-range, not like a super majority or a super minority.

will cheat on somebody at some point, but that doesn't mean that they'll cheat on you specifically in one relationship. So for example, there are plenty of people who cheated on their college boyfriend or college girlfriend, and then they never cheat again for the rest of their lives. But given that most people have several relationships, and also given the data showing that most people report getting cheated on by somebody at some point, I would say that the inverse is also

though it doesn't logically necessarily follow, I would say that it is likely that about half of people will cheat on somebody at some point, but I would love to see better data on that. Unfortunately, the really good data has been collected on marriage and married couples. And, uh,

Again, I would say that a conservative and reasonable estimate would be about a fourth of marriages will experience infidelity, and it's usually going to be the man who does it. Okay. What else? Someone was a cheater in the past. That's a pretty good predictor that there might be in future. What else? Yeah. Extra pair interest. We are naturally quite sensitive to extra pair interest. We notice it. So people tend to notice if their boyfriend is constantly checking other girls out.

that seems to predict infidelity empirically. I believe there's even a study where they tested how long a man's eyes lingered on other women, and that was predictive of infidelity, which is kind of funny. And extra pair flirtation, that sort of thing, I would be attuned to that. There are people who are, let's call it laser focused on their partner. And then there are people who you go to the social event and they just want to talk to

Talk to all the hot guys or all the hot girls and they, they, that kind of thing that probably doesn't, doesn't bode well. Narcissism is another thing to look out for. That's another thing that I think people find quite intuitive and a general history of, and I don't, I don't say this in like a loaded way, but a general history of promiscuity, I would say it would be something to look out for. Like if you're, if you're a woman and you're,

you're choosing between two guys and one guy, he's slept with over a hundred women. He loves going to the club. He loves having one night stands. He rarely has long-term relationships. And the other guy has had like two long-term girlfriends and has never had casual sex. If you're choosing between those two guys, which is more likely to cheat on you,

I think it should be obvious, but it is statistically backed as well, that the guy who has more of a history of monogamy is going to be more faithful in practice. I've given you five things there, so I think maybe four, I'm not sure. That's quite a bit. I seem to remember a line from one of David's books, maybe The Evolution of... I can't remember.

where he said that the single biggest predictor of extramarital sex is premarital sex. That's probably true. That's probably true. I love that line. I'm stealing it, but I'll have to check it. Yeah. I just wonder how true that is. I wonder whether it's the case, you know, is it

Is it just sociosexuality all the way down? Oh, yeah. That's such a driving force that the person who wanted to have a novelty in their teens and in their 20s, you know, how much of that is setting a particular type of habit, you know, damaged goods? Yeah.

How much are you damaged goods? How much have you set some sort of lifestyle routine versus how much is this like a natural outgrowth of you and your nature as a person? You know what I mean? Yes, I completely agree. I think that it's possible. I mean, I don't find it completely implausible, this idea that it's like if you practice having one night stands overnight,

over and over again throughout your 20s. Maybe in your 30s, it'll be hard for you to not do that when the opportunity arises. But I also think it's plausible that as you say, and this would be what I would think is that it's sociosexuality all the way down. So it's like if you want novelty and you're just holding yourself back from it, I'm not sure that that actually will. Maybe the ritual of doing that will help you in a marriage.

but maybe it won't. Also, maybe you want those things, you want to be sexually unrestricted, but women just don't like you. And so when you're married, the first time that you get the opportunity, maybe that's the first time that you take it as well. So I would say that if someone is, I think that, yeah, it's kind of, you know, humans seem to exist on

partially on this spectrum. And it's a construct, but it's a useful construct of sociosexuality. Some people are quite, let's say, unrestricted. They like to have sex without love. They like to have casual sex. And some people are quite restricted. And the people who are more restricted, the people who don't have sex with people who don't love them, the people who would feel uncomfortable getting naked in front of a stranger, those people are probably going to be more faithful to you. And I think that's pretty reasonable.

And I think, you know, for all the internet discourse, I know that every podcast, I want to put like a moratorium or like a ban on body count because I've talked about it before so many times. But yeah, I would say that

Body count is a kind of a dull proxy, but it probably is a proxy for likelihood of committing infidelity, at least in the studies that I've seen. Yeah, I suppose the reason the body counts an interesting discussion, the reason that it comes up so much is it's such a low resolution rough signal in the same way as saying your bank account shows how hard you work. You know, it's it's this sort of odd singular figure that you can compare. Everybody has one.

Everybody has one. Everybody has a bank account. How much money is in your fucking bank account? How many people have you had sex with? I would say that it probably isn't predictive. I mean, I think there was one... Actually, I won't quote it because I don't remember the exact stats. But I think it's pretty intuitive that if you've got one person who's only slept with one person before you and another person who slept with 100, who's more likely what? They're going to cheat on you with the third person they've slept with or the 101st. I think it's pretty intuitive.

What are some of the common signs that a person is cheating? Signs that a person is actively cheating? I mean, a lot of these aren't literature backed, but you do hear them from relationship counselors and relationship psychologists and things like that. I would say that in, I don't think that you should be, I don't really have prescriptive claims that

In my personal life, I wouldn't really want to be in a relationship where everyone's snooping on each other's phones all the time and accessing each other's technology. But conversely, anecdotally, you do see it a lot where people who get cheated on, they say that their partner became very digitally secretive, very protective of their phone, right? They go to the bathroom, leave the room, and they are sure to take their phone with them, right?

never leave their phone unlocked, never let you use their phone for any reason. I would say that that would be something that would be somewhat... I would say that that would be somewhat suspicious. I suppose there are plenty of reasons why someone might be digitally secretive that aren't infidelity, but it's also hard to imagine carrying out a full-blown affair in a modern context without keeping digital secrets. That would be very Stone Age in nature. I would say that...

Yeah, I mean, signs that they're actively cheating are much more difficult because we don't have as much research on it. Well, by virtue, the people who are actively cheating are trying to conceal it. So who's going to blow the Tom Cruise Mission Impossible mission whilst it's still underway? Yeah, exactly. So...

Yeah. Yeah. Do you want to take part in my study that'll completely, you know, expose you to unnecessary risk? Yeah. In your secret operation. But I would say that cautiously millions of years of evolution has prepared your brain for this moment of, uh, you know, detecting a partner infidelity potentially, maybe, maybe it's only tens of thousands of years. It depends. It depends how deep monogamy goes in our lineage. But point being, I would say that

Trusting your gut to some extent is probably wise. If you think something's fishy, there might be. With the caveat that you got to look at your personal history. If you know that you're someone who's just morbidly jealous, you're really oversensitive to that sort of thing, then...

Play a cautious hand. I was going to say there's thousands of people right now who are like vindicated. The people who are adamant at all times that something's going wrong. There was this interesting study that I saw on SciPost.

The top four behaviors that signal commitment within relationships on social media. Number one, deleting dating apps. Number two, ignoring flirtatious messages. Number three, indicating relationship status online. And number four, unfollowing potential alternative mates. Research has found that individuals with high attachment anxiety reported significantly higher levels

discomfort, worry, and jealousy when imagining their partner interacting with an attractive alternative on social media. This confirmed that such scenarios are particularly distressing for anxious individuals. Interestingly, the partner's high commitment behaviors on social media successfully increased perceived partner commitment and the perceived devaluation of alternatives, regardless of the participant's attachment style. However, these behaviors did not

significantly enhance feelings of security or relationship satisfaction for anxious individuals as hypothesized. This suggests that while explicit commitment signals are important, they may not be sufficient to fully alleviate the deep-seated insecurities and fears associated with attachment anxiety. You have to send me that. That's very cool. And also I would say that the, you know, it's modern, but that doesn't mean that it doesn't have some evolutionary roots. This

broadcasting that you're in a relationship on social media. What it reminds me of most is I spoke to one of, if not the leading experts on Gibbons on my podcast species, and we were discussing monogamy and Gibbons. So Gibbons are our closest socially monogamous relatives. And one thing that they do is they sing duets together. And part of that function, I mean, it's got many functions, but part of that seems to be to broadcast the pair bond.

To basically say, the Gibbon pair will sing a duet, say, hey, everybody, just so you know, we're still dating. It's the relationship status update on Facebook. Yes, exactly. And so whenever I see someone just kind of put up, you know, their girlfriend posts them and then they share the story or vice versa, it's kind of like...

It's kind of like you're doing a Gibbon duet in the sense that you're both signaling, hey, everybody, alternative mates, we're in a relationship. So there's no... And we're doing well. So that sort of thing...

It has its roots, I would say, in a very basic evolved desire, even if the behavior itself is not evolved, obviously. There's no selection on Instagram posting, at least not yet. Not yet. That will be soon. Yeah. What have you learned about what counts as cheating? That there's major variety. I mean...

I mean, it's hard to know because a lot of this is from the gray literature. But some I mean, if you're in an open relationship, for example, even sleeping with someone else is not necessarily cheating. So and then on the other end, some people who are in very, let's say, sexually restrictive relationships would say that pornography is cheating or that even fantasizing about other people is cheating or that light social flirtation with other people is cheating.

And there's a huge spectrum as to what's considered cheating, what's not, what's considered just disrespectful versus full-blown affair. For what it's worth, our study only looked at the study that we spent the first half hour or so discussing today. We just looked at sexual affairs. And it's possible that if we, you know, women are more likely to engage in emotional affairs than men based on the existing data that we have on that subject. And it's possible that purely emotional affairs are more geared towards mate switching. That would make sense towards to me.

Oh, that is interesting. Yeah, like what is the function of non-sexual emotional affairs, like where a woman is daydreaming about her co-worker crush but isn't actually acting on it? Oh, dude, you're blowing my mind. You're blowing my mind because this... You chose a particular bar to classify infidelity and by design...

that bar would lend itself toward the dual mating hypothesis more than it would lend itself toward the mate switching hypothesis. That is correct. However, I will also say that it's not cheeky. I wasn't rooting for the dual mating hypothesis. If anything, I was rooting for the mate switching hypothesis, but

tried to stay as emotionally neutral as possible. I was surprised by the results. And I'll also say that to give the devil its due, advocates of the mate switching hypothesis, they do think that the

Or they did think, maybe this research will change their minds, that the primary function of women's affairs, sexual affairs, is to obtain a new mate. So the sexual affair test, I think, was a fair one. Because look, we're looking at extra pair mating. We're not looking at extra pair flirtation, which can have even more functions.

I mean, sometimes you'll flirt with someone who's not your partner or one will flirt with someone who's not their partner just because they want to be more popular at work or they want to get a raise or they want the airport. They want going through the airport to be slightly smoother. That's literally, I was about to say, if I want a second Lotus Biscoff,

on a Delta or something. I better hope that it's one of the female air hostesses that comes around because if it's that miserable looking bloke with a beard, I've got no chance. If I can flip my eyelashes in the right way at some lovely lady, then maybe I get a second biscuit. Yeah, I mean, I'm just, I'm so fascinated by that, by what constitutes beauty

cheating and the sort of emotional infidelity versus the sexual infidelity uh it's a term we haven't used yet but monkey branching sort of from one relationship to another the slang for mate switching yeah where you are um sort of dipping your toe and just how invested is this person just how funny is this person just how good are the how good does he smell uh before we get to how good of a lover is he how good of a lover yeah before we get to that so i'll ladder up all the way um

before I get to that one. And it's also, I suppose, the thing from an operational perspective, for want of a term that makes it sound less like a military fucking undertaking, it allows more culpable deniability for anybody. Did you sleep with him? Look, I haven't even touched...

Anybody. Darling, I've never touched anybody. It's like, well, that's not what I was asking. It's a much safer form. An emotional affair is much safer. And so you're insulating yourself against the costs while you're engaging in it. I think that makes a lot of sense. I will also say that one of the strengths of the mate switching hypothesis is that because it is about sexual affairs, it's also about emotional affairs, but because it is about sexual affairs, is that it acknowledges something that's true, that it's

Helen Fisher actually said this to me. She said, you learn a lot about someone between the sheets, right? There's a lot of mating relevant information that is obtained through having sex with someone, how conscientious they are, how much they care about you versus themselves, how athletic they are. You get a lot of information.

Is cheating heritable? Have you looked at that? The behavioral genetics of cheating? Yeah, I mean, everything's heritable. I'm not a behavior geneticist, but there have been studies on this subject and it shows that, you know, I mean, genes code for proteins and regulatory molecules that build and operate your brain. It would be bizarre if genes had no influence on any behavior. Like for a behavior to have zero genetic input would be peculiar. And

There hasn't been a ton of research on this, but there have been some twin studies, some candidate gene studies, and candidate gene studies are always a little more questionable. But the twin studies, I find that study... Again, I'm not a behavior geneticist. I do find that study design quite persuasive. And those indicate that, yes, cheating is heritable. Hey, talking about gene embryo selection, imagine if you could... I'm going to select for a

scoundrel chad of a son. I'm going to have him just absolutely decimate Stockton on Tees in the northeast of England. Well, the reason that that's, I mean, that's very funny, but I suppose the reason that that is, and the reason that I think, I don't know why embryo selection is coming up so much, but I guess the reason that I think that this whole project might be a little unlikely is

is that the genes that affect one's propensity to cheat, it's not going to be one cheating gene. It's going to be thousands of genes that each do hundreds of different things, right? In all likelihood, at least by my understanding, it's going to be like, you know,

the influence of one gene that has a tiny effect on risk-taking propensity, another gene that has a tiny effect on sociosexuality, another gene that has a tiny effect on honesty, right? All these genes that have tiny effects on things that are good in some contexts and bad in others. And so in order to genetically adjust someone's probability, what does someone who has 0% of the cheating genes,

look like. Maybe they're super boring. Have you seen this new, I think it's Jakob or Jakob Forte

Examining the fraternal birth order effect and sexual orientation insights from an Eastern European population. Jakob Fort and colleagues examine the fraternal birth order effect. Why by men with more older brothers are more likely to be gay. This seems at least slightly relatively robust. Analyzing data from Croatia and Slovakia, they find that the fraternal birth order effect exists for lesbians too. Women with more older brothers are more likely to be lesbian.

It's strange. I mean, so not my area, but very interesting. Fascinating, dude. I thought that was so, so cool. I mean, you know, I had Dr. James Cantor on the show and he's just, he's spicy and lots of people really don't like him. But I, for me,

uh, parasexuality. Is that it? Um, the one where it's like all sorts of weird sexualities. Uh, he is, he's just the best. And, uh, he, he taught me very much. He's, he's gay. And he taught me a lot about the birth order effect, but the fact that it occurs for lesbians too, I thought was a bit, a bit confusing. And also I, I,

I would just love for there to be like a really, this is something that I don't know if we'll ever get it because it might not be adaptive, but it would be so cool to get this

an adaptive story of homosexuality that works but at the end of the day it just matters what's true and I just I haven't heard I haven't heard an EvSyke story that one makes a lot of sense and two actually has good data behind it but it's also not my area I can't give you the data but I can give you one that's got a good story so if but it only works as guys it really doesn't work as for females and this female thing throws a huge spanner in the wrench the works of it which is

If you have had multiple males go through the same woman, your mum, it is likely that the sex ratio is going to be skewed toward men, which makes it less likely that you as a man are going to be able to find a female mate.

And so you become a kin helper, essentially, and invest in your brother's offspring. I think so. Yeah. I mean, that's, again, very interesting. Doesn't fit with this new finding on. Absolutely. Totally fucking pointless. Like, why would the lesbian? No, no, no, no. We need more of you. Like, we really the men, all of your brothers. Well, maybe not your brothers.

Yeah. It seems more of a, I mean, it seems more of a, I think that it seems like more of a spandrel. Like that would be the sort of hypothesis where it's like there's selection on, like I've heard, again, this is so not my area, but yeah,

You know, I've heard stories about maybe that maybe certain strong selective biases select for genes that also, you know, at a low dose there, there they lead to certain things that are very selectively advantageous. But if you get a high enough dose of them, then you become purely same sex attracted and the buck stops there. Yeah.

I guess my favorite hypothesis that might have been true in our ancestry, just doesn't seem to be particularly true now, would be this idea that it would be this kin selection idea. That it's like in some circumstances, because we see this in other animals, in some circumstances, it makes more sense to invest in your kin's offspring than your own offspring. Because they share 50% of your, your kin shares 50%. Born basically to be an alloparent. Yeah, born to be an alloparent.

early warning sort of detection system about the sex ratio and then downstream from that. Okay. I met an evolutionary biologist who liked that and he called it, I don't know if this is his name, but it's such a funny one. He was gay and he called it the rich gay uncle hypothesis. And I was like,

Huh. It kind of is true. And I looked it up and it's like, oh yeah, gay guys do tend to make more money and they do tend to invest a lot in their nephews. I was like, this is kind of cool, but it doesn't seem to be, it doesn't, it's again, it's just hypothesis. And I actually don't think it's true. I think it's more likely that not everything is explicable by evolutionary. So I mean, I wish it was, but it's fine. That's the, that's Evzike's biggest hurdle is that it's so fun to come up with stories that we tell too many. And so you have to be very conservative with your hypotheses and test them rigorously.

We've spoken about repeat people that are consistently being cheaters, the culprits. What about people that are repeatedly victims? Is there such a thing as a repeat infidelity victim? Some people always get cheated on, other people manage to sail through completely smooth. If I'm remembering correctly, in the Kalanop study,

people who were cheated on in their last relationship were twice as likely to be cheated on in their next relationship. And some people hear that and they think of it as like,

Oh, that's just lightning striking the same spot twice. Oh my gosh. But the truth is, is that lightning does tend to strike the same spots because there are things that affect the probability of where lightning hits. So this isn't victim blaming, but it's possible that someone is very low skilled in mate guarding, let's say. They just...

don't do that effectively. And so they consistently get cheated on. Or another thing, like we often see that people are attracted to narcissists. We know that narcissism co-varies with infidelity. And so if you're someone who finds, you know, super cocky guys, really sexy, well, you're going to pick those guys over and over again. And then you're going to end up

picking, you're picking a trait that co-varies with infidelity. And so you become repeatedly victimized to it. Again, not victim blaming, just stating the reality that sometimes people's strategic decisions have an influence. Another possibility though, is that this is based on self reports, right? Did you get cheated on in your last relationship? Did you get cheated on in this one?

And it's plausible to me that some people are too suspicious and over-report infidelity, or some people are just really good at catching cheaters. Like, they've got a skill there. And so, you know, everyone, maybe the rate of getting cheated on is relatively evenly distributed between the two groups. But the group that gets cheated on a lot are constantly catching it. I mean, and, you know, it's plausible to me that, you know, if you're someone...

like myself, for example, who wouldn't go through their partner's phone, right? I would just feel like that was like a gross thing to do. I mean, I can certainly imagine circumstances. I'm not going to say I've never done it or that there wouldn't be circumstances where I could, but just that it would generally, that would be something that I would find very aversive. There would need to be some really legitimate reason. Well, then maybe I'm more vulnerable to infidelity, but I'm also just more vulnerable to not noticing it. So there is this effect.

where people who get cheated on in the past are more likely to get cheated on in the future. And people who haven't been cheated on in the past are less likely to be cheated on in the future. So winners keep winning and losers just lose more, right? That seems to be the case, but it could be a detection bias. It could be a, as you like to say, a skill issue, just not good at skill issue, man. Yeah. Not good at detecting it or not good at picking mates or, you know, but, uh, it's an interesting phenomenon. I'd love to do more research into it, but it's not my research.

That's fascinating. Yeah. It's the consistent themes that you find throughout your life if they continue to come up.

have to have something to do with you. Maybe it's you. Yeah, it has to have something to do with you. And maybe it is that you're unbelievably good at detecting. But given that not everybody cheats all the time, maybe it's that you're good at picking cheaters. Maybe that's your skill. I think the most likely explanation is that you're attracted to traits that co-vary with infidelity. So if someone says to me, why does everyone cheat on me? The first thing that I would ask is,

In a less callous way, why do you keep dating cheaters? Yeah, what is it that you're predicting? Yeah, what are you attracted to that's causing this problem? Because if you think narcissistic bad boys are super hot, well, problem solved. Maybe not. Mystery over. Yeah, Sherlock Holmes over here. I've solved it. And vice versa for men. If you're a man and you're attracted to a really dark triad kind of...

sexy, flirtatious women. Maybe maxing out on that. And it could also be a prioritization issue. So let's say you're the sort of guy who puts physical attractiveness above all else. You don't pay attention to personality. It's just who's the hottest girl that likes me. That's who I'm going to date.

And then it's like, why do they all cheat on me? It's like, well, maybe you should have considered shared values. You weren't selecting for loyalty. Yeah, you didn't select for loyalty. So a bit of a skill issue, but we won't victim blame too much. What does this new study, this new insight, how does it inform your...

perspective on how natural or unnatural infidelity is, ancestral mating strategy, sort of monogamy versus monogamish versus serial monogamy versus polygyny. Does it sort of adjust your worldview at all? No, but I'm so glad you brought this up. One thing that I will say is that, again, I want to emphasize that my study is just one study and I look forward to more research, hopefully research using the same paradigm where we look at actual

people who have had affairs that try to investigate women's infidelity more. And then also that even though the top line conclusion is a, you know, a pre-registered win for the dual mating hypothesis, best case scenario and worst case scenario for mate switching. We also found that some women mate switch and women cheat for a variety of reasons, including obtaining additional resources, getting revenge, et cetera.

How does it affect my view? Really not that much. It definitely affects... I thought that mate switching would be much more common. And I found David Buss's arguments very eloquent and persuasive for the mate switching hypothesis. And I'm a huge fan of David Buss. So I thought that maybe this would be a win for the mate switching hypothesis. I was kind of surprised it wasn't. So I guess it changed my view in that sense. But...

It didn't change my view as to whether we're naturally socially monogamous mammals because most socially monogamous mammals engage in extra pair mating and most have some degree of extra pair paternity. So the idea that we, a socially monogamous mammal,

also engages in extra pair mating and also has some degree of strategic evolution in the context of extra pair paternity, neither of those things were particularly surprising. A lot of people hear the word monogamous. So the way that

The way that folks at home use the term monogamous is different from the way biologists use monogamous. Generally, when we talk about monogamy, we are distinguishing between genetic or sexual monogamy and social monogamy. And most species that are labeled monogamous are only socially monogamous. So there's some degree, you know, plenty of them don't cheat, but many of them do. One example, and this would be a very unethical study to perform in humans is

Our closest socially monogamous relative, the Gibbons, there was a study in the 1990s, the scientist named Reichard, he or she, I can't remember, they went out into the field and just watched Gibbons having sex and tried to tabulate how often was it with the primary partner and how often was it cheating. And a full, you know, 11 to 12% of the time, it was not the primary partner.

So that's not 11% to 12% of Gibbons cheating. That's Gibbons having sex with other partners at that rate. So usually with the primary partner, but very oftentimes not. So some people are going to hear this and think naively because they don't have, and there's nothing wrong with this, but because they don't have the kind of biological anthropology context,

they might think, some people might think, oh, Macken's infidelity research suggests that humans aren't naturally monogamous. I would say,

On the contrary, it's completely consistent with us being socially monogamous. And given that, again, most women do not execute a dual mating strategy in this way. Most women get their genes and parenting from one partner, both in terms of their psychology and the psychological mechanisms undergirding their behavior and in terms of their actual behavior. Uh,

And, but, but in any case, they're, they're going to, some of you are going to hear this and think, oh, this means that we're not naturally monogamous. It's consistent with us being socially monogamous. It's just a, it's just a question of how sexually monogamous we are. So fascinating stuff, man. So interesting. And, uh, I think I'm, I'm going to like throw a little bit of money into the ring that there's something missing with the way that the studies are being done for ovulatory shift, uh, that, uh,

It seems too unlikely to me that we could have all of these converging and it would be so useful for ovulatory shift to happen.

uh, for it to not actually have an effect. Cause it seems to me that each time that it comes up, it sounds really cool and it's sexy explanation and then it doesn't replicate or there's, there's something in the data that does whatever. And it, it just, to me seems like such an obvious mechanism for evolution to take advantage of, you know, the original pill.

The original pill, the original contraceptive control for women, concealed ovulation with behavioral change that occurs during that period of time. No one knows, maybe not even her. And it would just be, I don't know.

I also feel the exact same way in the sense that I think that maybe more sophisticated study designs that look at partner qualities and look at relationship qualities as mediators, maybe those end up validating the ovulatory shift hypothesis. But I will note again and emphasize that the dual mating hypothesis does not need ovulatory shifts. For example, one might intuitively think that

in monogamous relationships, right? Fully sexually monogamous relationships. It would only make sense for a woman to have sex at ovulation because sex has risks and that's the only time she can get pregnant. But instead we see that there are benefits to having sex outside of the cycle, outside of that part of the cycle. And it's possible that there are benefits to having sex with one's affair partner outside of that part of the cycle as well, in terms of seduction, in terms of mate acquisition. I mean...

It's funny. I was talking to a couple of ovulatory researchers at a conference

And one of them said offhandedly, but it was so clever. They said we'd have more success testing a weekend weekday shift hypothesis because so much more cheating happens on the weekend versus the weekday. And that really puts the that really puts the cycle shift effect sizes into comparison. It's not like it's not like humans are werewolves. And depending on what part in our hormonal cycle, there's like noticeable changes. Humans part of being human.

part of the defining characteristics of our species or the suite of defining characteristics is that we exhibit remarkable sexual stability across the cycle. And even if we exhibit dual mating, it's not inconsistent that that stability translates to infidelity. Hell yeah. Mac and Murphy, ladies and gentlemen, dude. Chris Williamson. I really appreciate you. Your work's fascinating. I love the fact that you can communicate it this well. And I'm excited to see what you do next. I will be seeing you in Australia in only...

a couple of months time when I'm out there for my tour. So are you guys still going to be there? I've got tickets. I have got tickets to your, to your, uh, Australia concert of sorts. Oh yeah. Yeah. I'm going to come out and play the banjo. So if anyone is, if anyone is going to, uh, Chris's, uh, Melbourne show, uh, that's, uh,

That's it. That's it. It's going to be, I'm sitting in one of the regular seats. It's going to be a, it's going to be a very easy opportunity to meet me as well. I'll be doing, I'll be doing an unofficial meet and greet in the aisle. Where should people go? They want to keep up to date with your work, the podcast, all of the things. Where do you want them to go?

If you Google my name, everything comes up. My podcast is Species. The app that I have for couples is Coupley. And, you know, I've got a course on human evolution. If anyone wants to learn about those topics. Very good. Highly recommended. I bought it. Go and buy it if you want to learn more about this. Thank you, Chris. And so, you know, there's a few ways to get more time with me, but all of them can be found through Google. Oh, yeah. Macken, I appreciate you, man.

Chris, I appreciate you. Thank you so much for having me back on.