Why don't people want to have sex with their sister?
Or their brother or other family members.
It ends up that humans have a natural inbreeding avoidance system that develops pretty reliably in most folks exposed to the cues which I term kinship cues that are available during childhood.
Right.
Well, what about animals?
Because I understand there is this label, that's your brother, that's your sister.
How do animals actually detect who their relatives are?
We just take it for granted in humans, you can point and say, but animals don't have language.
So how do they know?
This is a really good question.
It's always fun to open up an interview with incest, incest avoidance.
Incest of you, yeah.
Yes.
And so So it's a really good question.
How do we know who our close genetic relatives are and why is that important?
Well first, it's important to know who your close genetic relatives are, not only for the purpose of not mating with them, because mating with close genetic relatives can cause a host of problems.
So it leads to less healthy offspring, for instance, and offspring who might suffer from greater genetic mutations.
So evolution engineered into our psychology a very sophisticated system to allow us to detect relatives, close genetic relatives and develop a sexual aversion towards them.
We don't even typically think of them as possible mating partners.
It's not foolproof, but this is what tends to happen.
And the other reason why we should have a system for naturally detecting and automatically detecting genetic relatedness is for altruism.
So being nice to your close genetic relatives follows from Hamilton's theory of inclusive fitness.
We're nice to other people as a function.
One way altruism can evolve is by being nice to people who tend to share genes by common descent.
But you asked the question of, so how do we do this?
And because humans aren't the only species that encountered this problem of avoiding mating with close genetic relatives for biological purposes.
And so other animals without language or culture.
They use cues, cues that correlated with another individual being a close genetic relative in that species.
You know evolutionary history.
So, whether it's being part of the same litter or a smell, or imprinting on a particular place or a marking, these are the kinds of things that evolution can engineer to help guide kin detection.
Humans have language, and so language and culture map very nicely onto these systems, but they're imperfect.
And so, even though we could join a sorority or fraternity and call people brother, sister or, in certain religions father mother, you know who your actual father and mother are.
You know well, with good certainty, you know who your mom is.
Who your daddy is is always an interesting question.
But certainly siblings are also individuals who you tend to correctly identify or would have, at least in ancestral environments.
So we don't use language.
Likely we just use the cues that correlated.
And so if you want to go around the horn of the nuclear family to figure out, how do we detect who our close genetic relatives are?
Well, how do you know who your mother is?
This is the female who tended to primarily breastfeed you.
So this type of imprinting or mapping onto the female who nursed you.
How does a mom know who her child is?
Well, that's kind of, yes, it falls out of you.
Unmistakable.
How does a child know who her father is?
This is not pinned down.
I mean, it is a question.
I mean, mommy's baby, daddy's maybe.
So the question about how it is that people how does people identify their father?
Really probably goes through understanding who is.
Have I correctly identified my mother and what males are investing in her?
Because males are going to rely on their paternity certainty in order to direct investment towards their offspring.
So, relying on what kind of who's investing in me heavily out, there could be one cue that females use.
But also the male that was around very early on in development has a better chance of being one's dad than the male that one's mom kind of is hanging out with later on in life.
So but it's a really it's a really good question.
So might phenotype type matching occur?
It could be.
I'm not a fan.
What does that mean?
So, sorry.
That is, do people use facial resemblance as a cue to understand who's likely a relative?
That hypothesis does have some interesting data backing it.
I'm not a fan of it, only because I think ancestrally, people looked really similar.
Not only that.
Just by the assortment of genes, siblings can look and fathers can look a lot like their offspring, or not as much like their offspring, but still be related with good certainty.
And so I'm not quite sure pinning how we determine kinship onto a few genes that happen to govern facial features is the right way to do it.
But maybe it contributes to be sure.
Certainly, when we see people who look similar, similar to us, that can spark a type of kinship, but i think that has more to do with a friendship and in group, out group tribalism maybe, or also we're always looking for people who might value us and identifying people who share features, any feature, like you know.
If you were to say, oh my gosh, i have a sister, her name is deborah lynn i'd be like, oh my god, i like you even more.
Oh yeah.
What's the naming effect?
There's more people called Butcher that end up being Butchers and more people called Travis that live in Travis.
And my mom and dad's names both start with a K. All right.
Well, whatever.
Oh, but they both start with a K. Well, that is very interesting.
I mean, the idea that we can we seek and we're always looking for people who might value us.
So looking for overlap in any dimension is something we do naturally to form friendships.
So.
Are you saying that the same mechanism that we use to identify who our kin is in order to do reciprocal altruism, I need to look after them more than I would look after a cousin or a third cousin or a friend or a stranger, is the same one that does incest avoidance?
So the system that is being used to identify kin for the purpose of being nice to them, like the inclusive fitness, is the same kin detection system that's operating for evaluating someone as a sexual partner.
Wow, that's so cool.
You don't think that's cool?
I think it's super cool.
I think there's I mean it's economical the idea that the brain computes one kinship estimate.
For every person I meet I have an estimate of what do I think the probability is not explicitly, not consciously, but by exposure to these cues my brain has kind of ratcheted up or not ratcheted up.
This estimate that tells me and I use to determine how related or likely that person is to be a relative.
And that is an input into systems about how nice I should be to that person and how avoidant I should be of them sexually.
Yeah.
How close my heart should be and how far my genitals should be.
Okay.
So has this been, this has to have been tested in adopted siblings.
So if you see pregnancy or breastfeeding um, But you don't share the like, early co-residence window.
Like, does that still trigger incest avoidance?
Like, you know, how can you play around with some of the triggers here to see what really works?
So my research focused on siblings.
I did a little bit of the parent offspring as well.
But the bulk of my research was on how do siblings figure out who they are, you know who's related to them.
And it looks as if there's two separate cues.
So one unmistakable cue that someone is a close genetic is a sibling is you see your mom.
And, to the extent, you've met the right woman as mom.
Your mom, you know pregnant, give birth to caring for breastfeeding a newborn.
That is an unmistakable cue, that that their kid, you know, breastfeeding from my mom, being cared for, you know, by my mom, is my sibling.
And that actually operates regardless of actual genetic relatedness.
So you can fake it, kind of.
You wouldn't need to give birth to it.
You would just have to breastfeed it.
Right.
And there's actually natural experiments that have shown this to be true.
So in Taiwan, there was – that's no longer – being practiced, but a form of marriage called minor marriage, where parents would adopt in a newborn girl into their family, either because they had a son or they were hoping to have a son in the next year or so.
And they brought up this adopted girl alongside their son until teenage years, when someone said and now you will marry.
Oh, God, but they didn't realize that they'd triggered this incest avoidance mechanism.
Correct.
But one of the interesting findings is that the adopted mom would oftentimes breastfeed the newborn.
And so what happened is that the son would have observed his mother breastfeeding a child that is, in fact, not an actual genetic sibling.
I imagine that doesn't lay a particularly good foundation for a future successful marriage.
No, but here's so we're going we're going to go a bit far field here.
But the idea is.
Here's one of the striking things about that particular natural experiment that occurred.
This was documented by anthropologist Arthur Wolf.
He found and reported that even among children who were raised together from very early age, many of them did marry and did produce offsprings.
So when cultural norms are that strong, it can actually cause you to do things that you otherwise might not choose to do.
Now, in those marriages, those unions tended to end more often in divorce and there were more extramarital affairs.
So the record-keeping was incredible by the colonial government.
So those marriages, when they were raised together from birth.
They tend to have fewer kids, but they did produce kids.
Great.
More marriage, more divorce and more extramarital affairs, compared to marriages where it was the traditional arranged marriage, where kids were just raised in their natal household and then met as adults.
OK, so the first one is breastfeeding.
So, yes.
So sorry.
So back back.
So the first really potent cue to who is a sibling is who did I see my mom caring for kind of this maternal investment?
The second cue.
So this is a great cue.
But what happens if you're the younger sibling in a pair?
You weren't around to see your mom care for your older sibling as a newborn.
What are you to do?
And so this starts to get into the Westermark effect.
So Edward Westermark was a Finnish social scientist, and he recognized that children who were raised together throughout childhood tend to develop a sexual aversion toward one another later in adulthood.
This has been termed the Westermark effect.
And what he was identifying is this second queue of co-residence duration.
So it's been operationalized as co-residence, meaning that if you're the younger sibling in a pair, you've got an older sibling.
How do you know that they're actually a genetic relative?
How does your brain figure that out?
You track how long that they lived with you under the same roof, receiving care from the same two individuals.
So it's really still about parental investment, shared parental investment, the amount of time that you see them being cared for by the same two individuals, predominantly probably mother, over the course of dependency.
And so this is why the longer the duration of co-residence during early childhood is, the more certain you are that an individual, again implicitly, is a genetic relative.
And this leads to not only greater altruism towards that person, but also greater disgust about the thought of sex with that person.
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When does the Westmark window start and stop?
Is there actually a clear cutoff?
So it was thought that perhaps there was a clear kind of imprinting period.
My research shows that it basically it just each year of co-residence seems to add a little bit of certainty, or I should say, reduces the uncertainty that someone is a genetic relative.
So it looks like throughout the period of dependency starting from birth.
Starting from birth is key.
And so individuals who kind of meet later on.
The effect still holds, but it's not as strong as people who are exposed to a sibling right from the get-go.
I imagine the potential for an absentee father to come back into a daughter's life later in her life.
This is one of the leapfrog avoided the Westermark window challenges that can cause some pretty uncomfortable outcomes.
Well, so I would say that fathers don't recognize their daughters by the Westermark effect.
So Westermark effect is going to be all about?
Yes, it's co-residence duration and that might make it seem like it operates for all family members, but it's really about observing who is investing in whom right.
So the idea of if I have an older sibling, I see that the same female who's feeding me, yelling at me, caring for me when I'm sick, and so forth, is also doing the same thing to another older child.
I have a good idea that that's my sibling.
And the longer they require that type of investment.
That's the kind of period of co-residence that we're talking about.
But you raise really important things.
So people who are not exposed to these cues, so what does this mean?
So this gets us into fun territory.
So people who are not exposed to these cues, they really don't map other people on as siblings.
And so fast forward to modern environments where you now have these sperm banks, right?
So you can have guys who are depositing their sperm and women are collecting it and they're having all these kids, and now there's all these half siblings running around, and now you can meet them.
In fact, I remember I don't know 10 years ago, but it was probably more like 20 at this point that there was a show like that kind of brought together all of these paternal half-siblings and they were really enjoying each other's company.
And I think there was one remark about even being attracted to one another.
And so you wonder, how does this happen?
Well, a couple of things.
There's a couple of things going on.
First, there's no natural sexual aversion that's developed.
There's no system that's activated to say, this is my sibling.
You telling me that you're my sibling, that a person is my sibling.
You know that's not really going to do very much to me.
You know, that explicit information.
It's like someone imagine someone knocking on your door and saying you know your mate that you've been living with for 15 years.
That's really your genetic relative.
And so it really wouldn't really change the way you feel.
You might say, well, maybe we shouldn't have more kids.
But in general, it's not going to kind of cause a disgust, I would guess.
But here's the other thing that's interesting.
By virtue of sharing, why is it you find like what's called genetic sexual attraction?
So it's been thought to be a thing.
Have you heard of this genetic sexual attraction?
That's good.
Maybe it's not out there.
Maybe I shouldn't talk about it.
Get it out there.
Information has it.
I'll put it out there and I'll just kind of wipe it away.
So Genetic sexual attraction.
It's been thought that, oh, we actually really are attracted to our family members.
So Freud was right, and we kind of harbor these sexual desires.
No, not so much.
And so I would say probably.
What happens is that, by virtue of the fact that we share genes in common with our close genetic relatives, we develop very similar preferences, right.
So Imagine designing your perfect mate, right?
So what does your mate look like?
What do they like to do?
What do they like to eat?
When do they like to get up?
When do they like to exercise?
All these kinds of things.
You know, it's like you and then you finally meet someone.
It's like you like kung fu movies.
I like kung fu movies.
You like spicy foods.
I like spicy foods.
You like getting up really early in the morning.
Yeah.
You like reading and you like evolutionary psychology.
I mean literally, it is you imagine all these different traits that line up in your really good friends and the mate that you would design if you could suddenly meet a sibling.
And Well, I mean— i guess it depends how annoying your brother or sister is but a lot of people, a lot of people like to spend time with their brothers and sisters uh, not just because of the history that they've got together.
And if you remove the incest aversion, if you remove the disgust response and you're of the sex that that person is attracted to so well, why wouldn't you?
Why wouldn't you do this?
And uh, what you're saying is basically, if you, If you weren't brother and sister but you are but if you weren't, what would that be like?
It'd be pretty sweet because, you know, 50 of everything we are psychologically is at least in some part shaped by behavioral genetics.
Okay.
Well, I mean, 50% is a lot more than a lot of relationships that have lasted for quite a while.
I'm not quite sure what to say in response to that.
But what you did... So I'll just say, okay.
And the other thing is that what you bring up, though, is Jonathan Haidt's great experiment.
Are you familiar with the Mark and Julie experiment?
Maybe.
And moral dumbfounding?
Okay.
So Jonathan Haidt did a really great study on moral dumbfounding that had to do with inbreeding avoidance.
And he brought students into the lab or participants into the lab and he gave them the following scenario
Imagine there's Julie and Mark, and they're brothers and sisters.
They're brother and sister, and they decide they want to have sex.
And they decide, you know, they really want to.
They're adults.
They're consenting.
They're going to use like five condoms.
They can't get pregnant.
No one's going to know.
They're never going to do it again.
You wipe their memory and they'll never even remember it.
And no one's going to experience any emotional or physical harm.
It's something you really want.
So it's all positive, all win-win.
And so Jonathan Haidt would pose these questions to participants and say is it wrong for them to have sex?
And, you know, all the participants were like, yes.
And then he's like, well, why?
Well, the condom could break.
No, no, no.
Condom doesn't break.
They're wearing five of them and she's on birth control.
Everything's fine.
Someone could find out.
No, no, no.
And so, you know, they try to kind of find a way and a rationalization as to why it's wrong.
And finally, they just give up.
I don't know.
It's just wrong.
And so he called this moral dumbfounding.
And it's really a good question as to what's going on.
And are people saying that it's wrong because they're concerned about the harm that could befall Julie and Mark?
Most people still think that there could be a harm.
I actually think that the reason why people say that it's wrong is not because of Julian Mark.
I don't think people care about Julian Mark.
I think that people care about being in that room with Jonathan Haidt and the other experimenters to be like.
I think incest is OK.
I think it's OK.
Oh, so you think it's all just like observer effect stuff?
I think it's the idea that I could be going against a societal norm, that the majority is on the other side and I could be seen as a minority.
I think we are very sensitive to sticking our necks out on issues where a majority holds one and we are going to oppose it publicly.
Well, i mean, surely you could, you could just control this by changing the way that people submit their answers right.
You could submit them in complete anonymity.
You could do it through a form.
You could do it anonymously on the internet.
Has this been?
This has to.
If this is such a an obvious potential explanation, this has to have been tested.
I don't think it's obvious, because I think people have been so focused, as morality is cooperation.
And I think that morality, I mean, you wanted to talk about getting back into the disgust and morality stuff, but it's very possible that people are very sensitive about moral condemnation.
And anyway, I think you only get to this hypothesis if you think that people don't care about harm to themselves.
Okay.
What, what was that study where you asked men to imagine tongue kissing their sister?
Um, that was, uh, well, there's been a few, I've done other stuff like on positive things.
Sorry.
I'm keeping my foot on the neck of incest at the moment.
Incest avoidance, please.
Um, okay.
So Yes.
I've done a few studies.
So one of the ways that we have to collect data on what people find objectionable and disgusting is to ask them to imagine engaging in a variety of sexual behaviors.
And so how do you do this?
And ethically, right?
So asking subjects to imagine tongue kissing their sibling or having sex or, you know, taking a shower with them, right?
What's interesting about that is at least a while back, when I collected those data, females were all at ceiling.
You couldn't like one to seven, they'd be like 10.
Like you wouldn't, they wouldn't be happy.
The amount of variation that I found in female responses seriously, that the bars on my graph were like oh, basically touching.
There were very, very little variation all squeezed right up at ceiling.
So males, on the other hand, the variance structure was quite wide, which I found humorous.
But it all gets back to I mean, it's not humorous.
This is a very serious subject.
It actually it is.
And so it gets back to some of the cost of reproduction.
Females, when selecting a mate, have to consider all of.
I mean, they are on the hook for nine months, 10 months of gestation, three years of lactation.
And so getting a baby up and running is easily three, four years ancestrally.
So any bad decision in terms of investing time and energy into an offspring with a reduced chance of survival would have been heavily selected against.
Males, the opportunity costs are far less.
And so males, while they should not be pro-sibling incest, would find it slightly less horrifically objectionable as compared to females.
Women also usually have a lower disgust threshold than men, right?
For most things, yes.
For most things.
You know, I tested this.
I asked women a whole bunch of different things about how disgusting...
You find a variety of things.
And you're absolutely right that women are far more disgusted by a great many things.
It ends up there are a couple of things that flipped, which were, you know, changing diapers.
Females are like that.
And then having sex during your period.
So that also that.
Sorry, it's gross.
It's all gross.
But so there you go.
So women are disgusting just specifically in specific situations.
I think just the word period or tampon grosses guys out a little bit more than women.
I think that's probably... Great.
We're way less familiar with it.
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So look, I'm an only child and I've realized that I don't have the same visceral disgust response that others have about sibling incest like i understand logically why it's a terrible idea but i don't get the same gut level recoil it's do you know what it's like it's like hearing smokers say i need a cigarette like i get the concept but i don't have the the craving or whatever or the opposite of the craving like i don't have that that aversion um Why?
I mean, is that normal?
Have you looked at people who it is literally like I don't have a language.
I guess someone could say, well, imagine having sex with your mom.
And I'm like yeah, like you've got the age thing that's already in there, on top of like the fact that she's my mom.
So I think for most people that have siblings, it's almost like they have a language of disgust that I don't have the understanding of.
Does that make sense?
Oh, 100%.
So I'll tell you about another study that I did.
That didn't get published, but it's enjoyable nonetheless.
And so I don't have a brother and my co-authors don't have opposite sex siblings.
So Lita Cosmides is an only child and John Tooby only had brothers.
And so the three of us sitting around talking about how to gross each other out with these acts.
It was actually, it was very disturbing talking about these things with your advisors.
I have a, I remember that conversation and being like, I'm done, I'm out.
So, but it was, we did another study, which was videotaping facial expressions.
At the time I started kin detection, no one had really started to look into the psychological aspects of it.
But one of the things that we had to do was validate disgust as a possible measure.
And in science, even though it's obvious if you just ask what emotion comes to mind if you think about tongue kissing a sibling most people, it's really gross.
And there you have your dependent measure.
You have to establish that.
So I set up a lab where I recorded people's facial expressions and did a variety of things to understand what facial, what muscles were actually activated in response to a variety of different acts, things that we know elicited disgust, but then also the sibling incest stuff.
And so there people are looking at the screen, seeing acts come up on the screen and just responding to them, or just reacting to them.
And most of them would have these, you know.
So, in addition to like eating your favorite dessert, it would be like, you know, putting your hand in a toilet and all these other things that you would see the muscles, the nose scruncher muscle for disgust, activate.
When I was matching what was on the screen to participants, because those are two different video feeds.
I remember seeing one of the matching up the, seeing a guy kind of smile like hmm.
And I was like, wait a minute, do I have the time, SMPTE time code right?
Like, am I matching it right?
Because it says like, tongue kiss a sibling.
Like, what's going on here?
I was like, oh, no.
And so I was like and I remember furiously going through all the survey pages, to be like please don't have a sibling.
Please don't have a sibling.
And it ends up the guy didn't have any sisters at all.
And so I found that really interesting.
It kind of gets to what you're talking about, the idea that it doesn't map onto anything.
And so it was like, imagine it was basically like, imagine having sex with a girl.
And he's like and so without that natural aversion, um it's, you don't have such a strong, a strong reaction.
Right.
Hmm.
Okay.
Next topic.
Uh, Yeah.
If incest disgust is so strong, why is incest porn such a huge category online?
You'd expect it to barely exist and yet it's massive.
Well, I mean...
Are they really siblings?
I mean, people do anything for money.
Well, I mean, first off, it's money.
And so the idea is, if people are going to pay and you need money, I mean sure people do stuff for money.
And people do gross stuff all the time.
No, no, no, no, no, no, no.
Why is there an audience for it?
Oh, why is there an audience for it?
Not why are people doing it.
I don't think that that many brothers and sisters are being employed.
That would be.
That would be a very special kind of relationship.
It would be a really special kind of business.
Yeah, i imagine that the margins would be really bad.
The amount of money you'd need to pay most people to have sex with their sibling would probably be pretty high.
Yes, why is there a big audience for it?
Why is there a big audience for it?
Well, I watched Game of Thrones and the idea that you know these two people.
What is it?
Jon Snow and you know Daenerys.
They were ended up being related.
I don't think that prevented people from watching that.
I think people aren't there.
It's just two people who are naked having sex.
And not only that.
So there's that.
There's that.
And then the idea of kin detection is imperfect, right?
Right.
So if you don't have a sibling and you're like, oh, well, this sounds kind of neat and risque.
Oh, right.
You're saying are you saying that incest porn is exclusively watched by only children?
I don't think I don't.
I don't.
My hypothesis would be that a guy with six sisters is not the person who's watching this.
That would be so that would be such a fucking good study.
You should do this.
This is your next study.
Your next study is to work out is to work out whether the likelihood of watching incest porn goes down based on the number of opposite-sex siblings that you've got.
Yes.
The world needs to know.
Okay.
Well, I'm really hoping someone in your audience will now undertake that.
This is you.
You're in my audience.
What else are you doing?
You've got, I mean...
I'm writing a textbook.
I'm starting a business.
Come on, man.
I'm busy.
Well, this can be another, you know, there's more stuff to do.
Anyway, I think you're right.
I think people don't.
It's not like.
In order to watch this incest porn, you need to observe.
These two people grow up in the same household as you for the first 10 years of your life and then watch it and then see.
Because the fantasy, I guess, is a.
I wonder whether it's a little bit of like contravening, you know, in the kind of the same way that dominatrix stuff or or um uh, being insulted or whatever it's like.
Oh, this is a social norm and by breaking it this is cheeky, but it's done in a safe way because you don't actually have the disgust response.
I mean, they're not your siblings, that's true.
Yeah, this is whatever the thingy.
And julie uh uh, the mark and julie yeah, and julie, it's mark and julie.
All been watched, all right.
Um ayla, who i think you'll probably be aware of, she ran a poll, said if your very attractive cousin wanted to sleep with you, would you?
There was 12 000 votes and it was almost exactly 50, 50.
Uh, now i will say her audience is perhaps non-typical, like rationalist, sex positive, slightly autistic coded but uh, that number still surprises me a little.
It doesn't surprise me well.
First off, cousins.
Hot cousin 50, 50 cousins are it's Cousin.
Marriage is still, I think, one of the more prevalent forms of marriage worldwide.
And so as soon as you start to drop off of nuclear family members, the biological, deleterious and harmful effects of mating with close relatives drops off pretty fast.
What's the comparison to parent to sibling to cousin?
I mean, it really, it drops off really fast.
So within the nuclear family are the greatest risks, right?
So you have parent offspring, certainly mother child.
There's greater certainty.
But you know, degree of relatedness is, you know, 05.
Siblings tend to be on average 0.5.
But as soon as you go to cousins, you get to an eighth.
You go from, you know, a half to an eighth.
And so that's on average.
So I would say, especially when there are norms kind of pushing the all of that and you didn't live with them,
And so your struck.
Your kinship structure is more it's.
Your aversions aren't as strong as they would be to nuclear family members.
Would you have?
Is there such a thing as you observing the baby of your mother's sister growing up in the same household as you, being close to them, knowing that it's not being raised by your mother and but knowing that your mother and that woman are close and that woman raised that?
Is there such a thing as being able to tune up the cousin aversion?
Yeah, I bet you there is.
I mean just like there's an ability to tune up the sibling aversion by having someone come into the house and be raised by an adopted child and so forth.
And so I suspect that there's a lot more research that needs to be done on this.
And now that we have these amazing ways to collect massive amounts of data, it'd be very interesting.
You asked about a kind of imprinting period or developmental period, a sensitive period.
And the answer is, you know, We don't exactly know.
I mean, there could be.
My data, I collected data from like a couple hundred people.
And so the bins that I have, like I have most people 3 to 18.
They lived with their siblings, some 4 to 18, 5 to 18.
But imagine having the ability for every bin between 0 and 18, filling that with 10000 people, to kind of understand patterns.
And so that would be a really great study to answer the question definitively.
I agree.
OK, you had this fantastic article on crying, which I read a few months ago.
It is one of the best things that I've read in a long time.
I think it's really, really great.
So I want to talk about incest.
Now I can talk about crying.
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What's the evolutionary story behind crying?
Why would leaking water from your face ever be adaptive?
Um, it is.
Well, okay.
So before we get into this, I just have to say for the record, because it's an important record we've talked about disgust, but I've also done a lot of work on gratitude and other emotions.
And so.
But it's my work on gratitude that got me into tears, because gratitude um And so see how I'm kind of changing.
But gratitude, it's an important emotion that's responsible for jumpstarting friendships.
It is an emotion that identifies when other people value you, right?
So someone does something that you perceive to be a benefit.
You say, thank you.
You are basically saying you know I value you for having done that act and It would be great if you continue to do that act, with the promise that potentially we can form a cooperative relationship downstream.
But it all hinges on what we call kind of social value in the in the article.
It's called welfare tradeoff ratio.
But let's not talk about that.
It's really just about how I value you, how I perceive you to value me.
And so because when we're strangers, I don't think you will value me or I don't value you.
And then you something nice.
It's like oh I, how do I recognize, how do I positively reinforce that benefit, beneficial behavior, that positive behavior?
And gratitude seems to be the way that I say, hey, that was really great.
Keep doing that.
I think so much.
And so but it all hinges on these internal assessments of value.
So how do we get people to value us?
If you are, I promise this is going right straight to tears.
And so if I am big and strong and formidable, I can just get you to be nice to me, right?
Under threat of penalty.
Like I can impose costs.
I can beat you up.
I can have other people beat you up.
I have money.
I can do all sorts of things.
And so if I, I can use anger as one device and strategy in order to get you to value me.
I can also use gratitude.
We've talked about this in the literature as prestige and dominance, but I think it tracks a little deeper than that in terms of the strategies of how to get other people to value you.
But here's the thing.
If I'm on the other side, if I am low leveraged, if I'm in a situation, in a relationship where someone's imposing costs on me or threatening me right, how do I?
What do I bring to the table?
How do I negotiate?
You know, what's in my arsenal?
And so I could either just kind of give in and be exploited and manipulated all the way to the end.
Or I can try and kind of express that you are imposing too much of a cost.
You are asking me to deliver too high a benefit to you.
That's going to start digging into my own interests.
And tiered is one way that we use to communicate costs or, better yet, the intensity of a particular state.
So tiered.
I'm mapping it more onto sadness.
It's not necessarily just associated with sadness, but using sadness as an example, the idea that my tears communicate to you, you are starting to impose a cost on me that is threatening your value in this relationship as well.
It might be worth your while to stop.
And so...
It's a way, it's the.
It's a tool used by the lower leveraged to get other people to stop imposing costs or to start restart the delivery of benefits.
So kids cry, throw tantrums, saying you know you're not feeding me enough or you're not feeding me the right things, you know, because they're not big and burly and they can't be like.
You're going to make me that hot dog.
They're just going to cry.
I don't want mac and cheese.
So but they're.
So tears can communicate quite a bit.
More generally, they communicate value.
And so we associate them a lot with the negative value things that cost us but they can very much be associated with the positive side too.
It's indicating the kinds of things that I benefit, you know, that I find quite beneficial.
So, you know, someone delivers a hugely unexpected gift. to you it's you know you could be moved to tears right someone does something and and donates a kidney or does something you know life-saving the idea that you could be moved to tears by such um by such behaviors it's showing and illustrating um it's illustrating high value so it's very much like the scream but it's used by the lower leveraged in a an interaction what does lower leveraged mean means the person who is less likely to get their way in an interaction.
So it could be the less physically formidable, the lower socioeconomic status, the less attractive, the smaller.
Wow.
Okay.
Okay.
I get it.
So women cry more than men.
Kids cry more than adults.
Have you looked at trying to control this stuff?
So for instance, let's say that you had a woman in a relationship, but she was socioeconomically more successful than her partner, she was the primary breadwinner, or you had a mate value discrepancy where the woman was a higher mate value, more famous, more statusful, trying to rebalance these scales.
Do we tend to see that change?
I would say you probably absolutely do.
But there's always the fun crocodile tears, right?
So those are the fun ones where it is people who use tears because they know what they do.
And so you know psychopaths, dark triad people will pull out crocodile tears in order to get you to think that they care more.
And so that's always an interesting feature.
But you can tell, I came up with one way to tell.
This has not been studied, or at least I don't think that this has been studied, and I'd love to study this.
So if you've ever cried Like, if you're like me, even in a movie, a dark movie theater, if I like start crying, I like start to stare.
So it's like, dry up, dry up.
Don't let anyone see you crying.
You know, it's like you kind of like you hide and you don't want anyone to see you.
You don't want anyone to see you.
It's kind of like I don't want to be perceived as weak or low leveraged or someone who you can now take advantage of and exploit or anything like that.
Right.
So I don't, I don't want to have lost any ground in any type of leverage, you know, in any relationship.
Again, it's not explicit, but it's just like we tend to hide these things.
But people who are trying to use their tears for more manipulative purposes will cry and be like don't you see my tears?
These are tears because I care.
And so I think people who use crocodile tears need them to be on display.
Oh, that's so great.
Yeah.
Allow me to put a billboard up so that my tears can run down the front of it.
But isn't it strange that people who are crying and they've got you know if this theory holds true, and at least a good bit of the time, I think it does.
People are.
I'm trying to tell you I value you or the thing that you just did, or you were imposing costs on me and I would really like you to stop.
I need you to see this, but also I'm ashamed of the fact that my body and my face and my eyes and the water has betrayed me.
So I'm going to hide, but I'm going to show, but I'm going to hide, but I'm going to show you, but I'm going to hide.
Like there's a tension going on here.
There is.
I'm not giving up too much ground in this relationship, but just for this one instance you should know that you've gone too far.
So an interesting thing is that what has been studied are tears and anger at the same time, because women, when they get angry, also tend to tear up.
So if you're in a situation where you are You're out leveraged.
So you're in a group situation and you're not being valued and people are pissing you off.
Right.
And so and you say something.
Right.
You're angry.
You're like if you had, you know, if you had muscle behind you, you'd be in good shape.
But if you find that you're the only one making a case for something.
So women in these situations, they tend to get angry, but also tear up.
It's like, but again, it's that tension.
It's like, if I could, I would, but I can't.
So I won't.
Yeah, that's so great.
And I don't think I haven't seen guys get do the angry cry thing in quite the same way.
Their rage is able to sort of burst through it a little bit more.
I think in most situations, yeah, no, I don't think that's a tactic for males who don't.
So listen, I mean there is a big difference in.
There are huge sex differences when it comes to formidability.
Walking around the world where, you know, around in modern times, I mean, I love modern times.
Like I can walk around without really under threat of being like, you know, hurt.
And so but that's relatively recent in human evolutionary history.
Like there were.
You know, you go somewhere foreign and suddenly you realize like maybe I shouldn't be walking around alone.
This is this is I'm going to hire someone, you know, tomorrow.
And so the idea that females are less formidable and they are at risk of being you know?
I mean, you walk around and it's here's what I was told.
I don't know if this is true.
Tell me if this is true.
That when guys go into a room, a new room, new people at a party, wherever it is a bar the first thing they do, or one of the things they do naturally, is they kind of sweep the room.
Like, who else is there?
What other guys are there?
And kind of take a kind of back of the nap, make a back of the nap in calculation about who's bigger, who's more formidable.
Like, who can I take?
Who's dangerous?
Who should I be wary of?
And who don't I have to worry about?
Kind of thing.
Is that something men do when they walk in a room?
Yeah.
I don't know whether it's that conscious.
I don't think it's conscious.
There's certainly stuff that happens that's kind of interesting.
Like if you're in a room, this is a cool way to look at it.
If it's a mostly guys room, ideally an all guys room, because as soon as you throw women in the mix, it becomes messy.
But if you've got a table, you'll see what is the angle of the chair?
What are the angles of the chairs mostly pointed toward?
And you will see that there is a head of the table, even if there isn't a head of the table.
Another way that this happens is when somebody starts speaking.
When a guy starts speaking in a room, what is the likelihood that some or all people shut up?
But I've been in rooms with some guys real, real statusful guys that if they fart, everyone will decide to be quiet.
And you can really tell an awful lot about where the hierarchy falls by who's nearby proximity to that person, whether they will keep talking, whether they're happy, whether they look regulated or whether they sort of seem a bit more sycophantic, appeasing.
So it's all that.
I mean, that's me getting, that's actually me getting a little bit feminine, I suppose, with it, as opposed to the more like brusque shoulders back type way.
That's more like status game playing, like relational stuff.
But there's still, even the formidability, I think will play a big part of that too.
I think if you've got some big fucking dude in the room and he starts speaking, I think your, let's say formidability, status and resource cues, something like that.
Like how big are you?
Who are you?
And what do you have?
Something like that.
If you had these buckets and there is this invisible score that is above everybody's head, which is some sort of aggregate of all of those things put together.
So like the really formidable guy who nobody really knows that much, and the really statusful guy who might not be quite so formidable that that would be an interesting but like who do we?
Oh well, actually I'm physically a little bit weaker.
So maybe I'll be more scared of the formidable guy, but statusfully I'm a little bit stronger.
So I don't mind the, the, you know what I mean?
Like how, where am I in the pecking order?
All of that is done in a not very long when you sit down in a room.
I imagine at the back of my mind,
Yeah, no, I think that stuff, I think the nonverbal behavior is really interesting.
Someone that I've read and listened to in terms of the podcast is Joe Navarro, who's done a lot of this work on nonverbals.
And so it's fascinating stuff if you haven't had him on.
Yeah, he's great.
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So if, if tears are um telling another person i value this thing, or you're imposing costs on me and i would like it to stop, why do we cry when we're on our own?
Oh, because i think that we have dramas played out in our head all the time.
You know like we very easy to imagine a whole bunch of stuff.
Typically it's not just.
You know, nothing sparks us.
Usually there's a thought or some type of sequence.
But who are we crying to?
Oh, I think it's simulating.
I think there's simulations all the time.
It's just like you know.
Haven't you ever, you know, you know laughed like I?
I work, you know, in my place on my own.
And if anyone were ever to watch like, they'd be like she's crazy because she's laughing all the time.
Just by thinking about some of these things, you know it's hard not to chuckle.
And so, but what's that all about?
It's like me thinking about stuff, you know?
And so I think that when we think about things, we can absolutely simulate what would be my, what would be my reaction in this particular situation.
So that kind of playing with possible events that could play out to be prepared for them and so forth. okay i i think most people and me too i think that sounds a bit surprising because not that it's not true but i'm like i'm not gaming this out like i don't want to be fucking in a ball of tears on the floor at the moment having just watched this dog come home to or this this soldier come home to his dog after you know three years away and now the dog faints and now the daughter's there and you know But am I confusing the fact that those people are here with me?
Is it the fact that my...
Whatever system, crying system, is unable to detect the fact that that's virtual or not?
Is it the fact that it's unable to detect the mental imaging that we've given versus a real situation?
Is it the fact that our mental situations are just so powerful that it doesn't matter if there's other people around, that we experience them as if it was happening in front of us?
I think you have empathy with score one for not being a psychopath.
I wish I cried less.
I wish I, I wish I, I wish I was less of a pussy.
I my crying threshold is you know, the discourse threshold thing we said before my crying threshold is embarrassingly low.
It fucking blows.
That's our, listen, empathy is not overrated.
And so I would say, you know, I think that first off TV and story, we evolved with storytelling.
We evolved, with people in front of us telling stories about people and about you know um, you know our ancestors, and so forth.
But I think that when we see them on TV it's a little confusing to our ancestral brains, that's for sure.
And so, but hearing about these things and putting yourself in a situation and simulating, I think, is or being, you know, showing empathy and putting yourself in the shoes of other people and what you would experience,
Because there are people who don't have that ability, right?
So you have people who you know, people who psychopaths, for instance, who do not have a capacity for empathy and would not cry.
What about when grief because some let's say somebody's passed away?
Who are you crying to?
They're gone.
What are the tears for?
Well, i think you're showing other people your need state um, that's one thing, but I think a lot of things are going on at that point in time.
So being upset and depressed and grieving the idea that it's a loss.
And typically we would have been around.
I mean, there's no such thing as privacy to a hunter-gatherer.
So something happens and you would have been around other people and kind of this automatic response of I am in a need state would have potentially been quite beneficial.
I, you know, I haven't done, so I, I, I, a lot of this is speculation.
So the, the.
So just to stay on.
You know terra firma here I the paper really was about.
I was very curious researchers who had been studying tears showing that you, you show subjects emotion faces emotion, displaying various emotions.
And if you add tears to some of those emotions, they're easier to recognize.
And when I was, so I'm the editor of the Fields Journal, Evolution and Human Behavior.
And so I had one of these papers in front of me, and it struck me, like there's a lot of research on tears, that it hasn't been hooked up with the cognitive side of things what's going on internally and what this signal value is.
And it had struck me that no one really thought about is tearing an adaptation like what's going on here.
And so thinking about when we tear and what might be going on.
It seemed to be very much tied to social value, right?
So being around people who value us, and we are going to try to get them to stop imposing costs or try to elicit more benefits from them.
Obviously, I talk science speak, but that's not consciously available to us.
We just cry and it has the effects that it does on the people around us.
Okay.
So positive events.
The reason we cry at positive events is like, this is good.
Do more of it.
Like an encouraging thing.
This is a value to me.
And I wouldn't do this ridiculous thing if it wasn't.
Yeah.
Reliable signal of receptiveness.
Yeah.
You're marking this is of high value to me.
I perceive the events and what's going on now to be registering in my brain as high value.
Okay.
Why not make our whole body shake?
Why not raise our hand in the air and wave it?
Because crying is here to lubricate our eyes.
That's why the tear ducts exist primarily.
Why has our emotional system repurposed that?
Why don't we shit ourselves?
Why don't we just yell?
Well, maybe you do.
I don't know.
Why tears?
What is it about the water coming out of the face that is particularly useful for this?
It's front and center.
And so it is something that is readily available.
It's a really good question.
And so this was obviously one of the main questions that our reviewers had is like this.
Why this?
Why now?
And so one possibility is that it was built off of.
So if you have an onion and you hold it close to your eyes and the acids kind of interact and you start to tear up,
And so the idea is that this is a negative stimulus.
So it's already kind of being associated with.
There's something negative in the environment that is affecting me.
And so that very much could have been the bootstrapping way that more negative stuff could then have been registered by other people.
So, to the extent that that was possible, that would have been one possible lineage for how this came online.
Okay.
I, I seem to... You're buying that?
To a degree, to a degree I do.
I don't, the answer is I don't know.
But another part of it, another part of it is, okay, yeah, front and center, right?
Here it is.
It's very hard to ignore.
It is for most people I think it would take a bit of even me with my wimpy cry threshold, takes a bit of work for me to get it going.
So usually for most people, apart from the psychopaths, a pretty reliable signal of authenticity.
So it's uh not, it's not cheap, it's not that cheap.
Um, another thing has to be you really need your eyes, like you really really need your eyes to see, and if you choose to have water pour out of them, you have temporarily incapacitated yourself.
And if you again, another sort of reliability, a costly signal add-on yeah yeah yeah yeah yeah, yeah.
That all that all makes good sense, i think.
I mean look, this paper was just written.
It kind of throws out a whole bunch of ideas and now it's time to say put it through its paces, test it and you know, see where it goes.
I think that you know on the positive emotion and negative emotion, so things like gratitude, but also depression and sadness and pain.
I think that there's a lot of work to be done.
That's a good point.
Why do people cry during... I remember the last time I cried due to pain, physical pain.
And I was, I think, 13.
And it was one of my first adult cricket matches.
I don't cry due to pain anymore.
Physical pain.
I don't think that there is an amount of physical pain that I would be put in.
It would have to get toward the emotional pain.
It would have to be an emotional element of this.
Is it just that as you grow up from child to adult, you are able to better understand your capacity to deal with pain and the fact that it doesn't necessarily have an emotional component to it?
Like, why is it that kids cry when they bruise their knee, but I don't?
I mean, I still cry when I hurt myself.
Like, I mean, I think, yes, and I don't tell anyone.
So it's a really good question.
Listen, as a kid, I think, the idea that I need help, you know like, help me, I'm in pain and this, and or you know, stop this, Stop this.
Unattach this bristle.
Do something.
I think that it definitely is a signal.
I'm trying to actually think about it now.
Because I've cut myself with a knife.
And have I cried?
I think I've cursed more than I've cried.
Isn't that strange?
Isn't it strange?
Because it's not, you know.
But I guess, look, the same or similar stimulus can cause different responses.
Some breakups may cause somebody to shout and scream in someone's face.
Mm-hmm.
Because the specifics, the flavor of that one was cantankerous.
It was aggressive.
It was adversarial.
And then another may be loving and painful and melancholy.
And those two would have very different responses.
In one, somebody may not cry.
And in another, they may.
So I want to throw I want to give you a harebrained idea that I had.
And I don't think it's going to pay out.
But I but here's what I was thinking.
So, you know, after a breakup and you just you cry and like you cry uncontrollably.
And I was thinking so while I was crying, I was like, why am I crying?
This is like I got to stop crying.
This is like I want to stop crying.
Like this is done.
Let's be done with this.
And so.
But then I was wondering the function of it.
Is it like a data dump in the sense of someone that you held such high value for?
And then you realize and you simulate and you realize they don't value you anymore and that cost and that kind of ratcheting down of someone valuing you.
Right.
Because you have to literally have that time, to have that realization that they do not care about you at all.
And so, but the idea that potentially crying might be a way that you know it.
Just it's a, it's a.
So yes, our social value is ratcheting down, but might that it's all chemically mediated.
So the question is, is it, are you also ridding yourself of that?
So I was.
If I had like a well-funded lab, you know, I would think like if you could possibly capture people's tears as they are going through a breakup to see whether or not you know the pre kind of level of I don't know oxytocin, whatever it is.
That kind of governs social value and attachment and closeness, but is it kind of being dumped out through the tears to kind of help, kind of reestablish?
So good.
I think that's great.
I think that's really cool.
I think that's really cool.
And I think that someone needs to give you a million dollars so you can go and do it.
Um, what it makes me think about is how much of crying is about changing other people's behavior and how much is about recalibrating our own emotional state.
I think there could be Multiple things going on.
I think there's probably because I think that, just like shouting can be done in most emotional states, like different types of shouting could be used to help express anger, as in joy or gratitude or shame.
Like, you know, you find that the volume and amplitude of our voice can definitely do that.
So why?
And those are different types of emotions.
Some are internal calibrating.
Some of them are other calibrating.
So my anger and gratitude is to calibrate you.
All right.
So but my shame and my pride is calibrating me potentially.
So the in any case, I think that you just put your finger on a really interesting thing, that there's probably multiple things going on.
So cool.
So cool.
Deb Lieberman, ladies and gentlemen, you're fantastic.
You're part of this weird like council mason masonic, like group of cool, keep going doing evolutionary psychology and everybody needs to follow you and uh, i think your works, i think your work's wonderful and um, i enjoyed speaking with you at hbs and uh, i think that you need to keep doing more stuff.
So where should people go if they want to check out all of your fun, cool work about incest?
Well actually, on the Center for Evolutionary Psychology is a whole list of a great set of papers, not only on kinship inbreeding avoidance altruism, but also morality and anger and cooperation and coalitional psychology.
So Center for Evolutionary Psychology is where I would direct everyone.
And also you can read about it in the textbook that is hopefully forthcoming at the end of 26, beginning of 27.
And if you will permit me just to say one thing as an academic, and the frustration that I often hear a lot of people who want to get access to these things is that they're hit with these paywalls.
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When's that available?
Can I get that now?
Check an app store soon.
Media Byte.
We are on it.
Okay.
When do you think it'll be launched?
When will it be launched?
Hopefully late 26.
Okay.
Well, hurry up because I need that.
Deb, you're great.
Keep doing your thing.
Thank you.
You too.
Be well.
This is great.
Books.
