Oct. 23, 2015 - Freedomain Radio - Stefan Molyneux
52:07
3108 Nature or Nurture? The Study of Twins | Nancy Segal and Stefan Molyneux
The nature versus nurture debate is one of the oldest and more fiercely debated issues within science. So what exactly is the nature versus nurture debate all about? Do genetic or environmental factors have a greater influence on your behavior? Do inherited traits or life experiences play a greater role in shaping your personality? Dr. Nancy Segal and Stefan Molyneux discuss the reality of the nature vs. nurture debate, the genetic heritability of Intelligence (IQ), personality, sexual orientation and what we have learned from twins studies in this areas. Dr. Nancy Segal is the Professor of Psychology at California State University, and Director of the Twin Studies Center. She is the author of many books including, Born Together-Reared Apart: The Landmark Minnesota Twin Study. For more, go to: http://drnancysegaltwins.orgTo order a copy of "Born Together - Reared Apart: The Landmark Minnesota Twin Study," go to: http:/www.fdrurl.com/nancy-segalFreedomain Radio is 100% funded by viewers like you. Please support the show by signing up for a monthly subscription or making a one time donation at: http://www.fdrurl.com/donate
She is a professor of psychology at California State University and director of the Twins Studies Center.
She is herself a twin and has been fascinated and writing.
And researching twin phenomenon for decades.
She's the author of many books, including one I highly recommend called Born Together, Reared Apart, the landmark Minnesota study.
Twin studies really help us get to the essence of what it is to be human.
How much of us is forged in the furnaces of biology and genetics and how much is open to our choice and free will.
So it's an intensely interesting topic for me.
I think it will be for you.
It was a very enjoyable interview.
Here is Dr.
Nancy Segal.
So, I wonder if you could just tell us what the latest state is in twins research.
It's such an important topic because I think it drills right down into the core of what it is to have an identity, it is to have a personality, it even is to have a cultural environment, and I think it blows away a lot of the misconceptions that people have about what influences us.
That is beyond our control, which I think is a very important thing to learn about yourself.
So where is twins research at the moment?
Have there been any leaps forward recently?
Well, I would say that there are a couple of leaps that have taken place recently.
And one is the publication of a paper this past year, a meta-analysis of many, many twin studies across many, many trades done in many, many different countries.
And it shows that Most traits have about a 50% genetic influence, and that's important.
I think in the past history of psychology in the US and many places, we all thought that we were blank slates in the products of our environments, but that is definitely not the case.
On the other hand, we're not solely the product of our genes.
50% of that variance is due to environmental effects, and so we have a lot of other factors we can look at.
Twin studies have also been used quite a bit in the molecular genetic techniques, which are really at the forefront of research right now.
And of greatest interest are those identical twins who differ in diseases, for example.
Why does one twin have a disease, the other one doesn't?
And so if we can try to figure out what causes certain genes to be expressed in one twin, but silenced in the other.
This is the whole purview of epigenetics, the turning on and turning off of genes.
Not differences in DNA, because identical twins share their DNA. And that's not quite strictly the case either.
But at any rate, what causes the gene to turn on and turn off?
This is information that can be used widely to understand cancer, diabetes, various other kinds of medical conditions among the non-twin population.
And there were also behaviors that have not really been studied that much in twins.
So the classic twin method, which is the comparison of identical to fraternal twins, To look at the genetic underpinnings of behavior are also still going on.
Now, let me first explain the classic twin method.
The classic twin method is based upon the presence of two types of twins, identical and fraternal.
The identical twins share all their genes, having divided from a single fertilized egg within the first two weeks after conception.
And the fraternal twins result when a woman releases two eggs at the same time or very close in time These are fertilized by two separate sperm from the father.
These twins share half the genes on average by descent.
If identical twins are more like intelligence, personality, social attitudes, height, weight, what have you than our fraternal twins, this tells us that the genes play some role in the contribution of that trait.
There have been some behaviors that have not been well studied using the classic twin method.
I came across one just today that's looking at how you react to certain types of sweeteners.
Do you rate certain sweeteners high intensity, low intensity?
That may sound kind of frivolous, but actually it's not.
This is very meaningful information to People who are interested in food preparation, dietary types of jobs.
So this is all important stuff.
Twin research is not just for twins.
It's for everyone.
Yeah, I mean, that last bit about sweets should be very helpful in helping me negotiate a discount from my dentist because I can say, look, it's not my fault that I have a sweet tooth.
No, I'm kidding.
That's, of course, it's always the great temptation with this information.
Now, sorry, just before we, because when people say, when you say, of course, that identical twins share the same DNA, we've been talking about epigenetics in this show for a while with a variety of experts.
There's a number of examples that you provide in your books about the degree to which even a shared womb is not the same as a shared environment.
One kid may be getting more nutrition, there may be different levels of various blood flows getting to the kids, and of course there will be epigenetic stressors that may hit one kid more than another.
I wonder if you can just help people understand the degree to which there can be divergence among even identically sequenced DNA siblings.
Well, you know, many people wrongly assume that identical twins are alike partly because they share the womb.
In fact, I'm surprised that identical twins are alike as they are having shared a womb because there are many influences going on there that do make for differences.
For example, when identical twins split somewhat late in that 14-week period, meaning towards day 8, 9, or 10, It could be that one twin receives more nutrition than the other.
It could be that one twin has a marginally attached placenta.
Now, when I was a graduate student, I came across a really striking pair of identical twins, where one had less nutrition than the other.
And when I saw these girls at eight years old, one was a normal eight-year-old in terms of height, and the other was a tiny version of her sister.
Three or four inches short.
And today, they're seven inches apart because of this prenatal effect.
So the womb is just not a place that guarantees sameness for identical twins.
If anything, it guarantees difference.
And as I said earlier, I'm surprised identical twins are alike as they are given these kinds of influences to which they're subjected.
Right.
Now, this, of course, goes into the polarity of nature versus nurture.
And I remember when taking Psych 101, oh, those many moons ago, that it was explained to me sort of nature and nurture are like two ends of a field.
You get a dimension of the field, there's length and there's breadth.
But I like the way that you formulated in one of your recent books, which is that it's not nature versus nature, it's nature via nature.
And I wonder if you could help break that down for the audience.
Yeah, nature via nurture is the way that I put it.
And So what happens is that all of us have genetic predispositions, things that we like to do, people that we like, things that we gravitate towards.
I mean, imagine the job that you're in right now, but there were probably other jobs you could have had, but certain jobs you wouldn't imagine yourself in ever.
And so it's our genetic predispositions that lead us towards those.
So in a sense, we all create our environments.
We, you know, our houses are put together the way they are not just because things are thrown on a wall.
We chose to put them there and the reflection of us.
So environments really do reflect the genetic underpinnings of who we are.
And we believe that identical twins raised in separate homes are as alike as they are simply because they create similar environments from the opportunities available to them.
Right.
Personality is something that when I grew up, I guess, in England in sort of the 70s, and what was very big was economic determinism.
You were very much determined by your socioeconomic status, and there was some choice and so on with a lot of sort of affluent influences.
personality traits seem to have strong heritability is the degree to which meeting people after reading this kind of stuff is interesting because you know the first thing that when you meet anyone a lot of what you notice is sort of personal characteristics gender height race maybe and we assume that of course you know height and so on gender is outside of people's control but it's
Siegel, to think that when I meet people who are very gregarious, or who are quite shy, or who are defiant, or who are more helpful or compliant, that I'm not meeting sort of self-whittled moral choices, but to some degree I'm just saying, hey, genetics.
I mean, I just, I find that really fascinating.
Yeah, but it's not quite that way.
You're not just meeting a bunch of genes when you meet an extroverted personality.
Remember that Personality has about a 50% genetic influence, and so that leaves the other 50% to environmental features.
And we know now that that environment is not the environment you share with people in your home.
It's the outside environment.
It's idiosyncratic odd things that happen to you during your life.
Maybe you read an amazing book or took an amazing trip or met an amazing person that will reflect your personality.
It's not as if we are stuck with our genes.
I would say that a better interpretation is that genetic influence can be modified.
I mean, a shy child can be made to be a little more outgoing.
That shy child will probably never be an extroverted, gregarious person, but that shy child could be made to feel more comfortable.
And an outgoing, rambunctious kid who's always interrupting and annoying everybody could be made to calm down a little bit.
And I think that I also want to go a little bit into this nature-nurture dichotomy because I think this is crucial for people to understand and is so poorly presented in the press that I really like to set this straight.
And that is that you can think of nature and nurture in two different contexts.
One is that you can look at a population of people, say we're measuring height, and so I can look at the individual differences.
We've got tall people, short people, in between people.
There's variability among those people.
We can say that about 80% to 90% of the variability in that population for height is linked to the genetic differences among those people and the other 10% linked to the environmental differences among them.
They were partitioning genes and environment in a population sense.
If I take a single person, I cannot chop their height into a genetic and environmental component because in that case, Genes and environments are inextricably intertwined in that person.
Now, it could be that that person comes from a very tall population, let's say, where height is very highly genetically influenced.
But let's say that child had a really poor diet for some reason and their growth was stunted.
Even though the genes in general explain 80-90% of height, in that child it might be 90% environment because the child had a poor diet.
So I think it's very critical to keep those two contexts separate.
Yeah, we just had, I think last week, Dr.
Eric Turkheimer on, who was talking about the studies that showed that as socioeconomic status goes down, in particular for intelligence, environmental influences seem to go up.
I wonder, because has that shown up in twins research as well?
Well, that has certainly shown up in Eric Turkheimer's study, and that was really quite a good study that he did.
There have not been a lot of studies that have organized twins by socioeconomic status.
In fact, most twin research taps into the middle class volunteers from the normal range of environments.
But Eric has actually gone to more of the environmental extreme, so his contribution was quite noteworthy.
And as far as intelligence goes, a sentence that really stuck out for me in your book was, and for those, we'll put a link to the books below, and you should definitely go and pick them up.
When you talked about the degree to which twins' intelligence is similar to each other as the same person taking an IQ test at different times, that struck me as a very strong underpinning for intelligence being strongly influenced by heredity.
Yeah.
Well, the intelligence test, the Wexler IQ test, which is the one that's widely administered, does have a very high degree of test reliability, meaning that if you give the test to the same person at different intervals, you're going to get not an exactly same score, but something rather close.
And identical twins who do have the same genes and who do have the same intellectual levels respond to the world the same way or are interested in the same topics.
I think actually when you reason it through, it's not so surprising that if Thank you.
Thank you.
We do find a range of IQ differences from about 0 to 1 to 29.
Environments can have potential salient effects on ability, but we cannot rest our conclusions on one pair.
If I just looked at that pair that differed by 29 points, I'd really have a lot of misinformation to give you.
We have to look at what the message is based on many, many different types of pairs.
Along these lines, what might interest you is that In my career as a research psychologist with a specialization in twins, I have come across a number of referrals from attorneys who had these cases involving identical twins who were accused of cheating at school and at college by their professors.
Why?
Because they turned in identical tests, identical assignments, things of that sort.
And the twins claim that they have not cheated, and their parents, who were quite concerned, bring these cases ultimately to court when the school is completely unsympathetic.
And I am working on behalf of the twins.
I believe they have not cheated.
I've seen too many examples of twins who turn in similar work simply because they think the same way.
Yeah.
It's hard to know because certainly I think as you mentioned that you were raised with a twin of course and when you get a particular influence, I was struck when you mentioned earlier that you may have read a great book or you may have had a great teacher who opened up your mind to a particular skill set.
When an idea hits you or a calling you could say hits you, it really is like a thunderbolt and of course you had exposure to twin research early on when you were younger and raised as a twin and that's become your life's work.
And the degree to which we have a choice when we seem to be pre-configured to emotionally and almost permanently respond to outside stimuli, and it makes a sort of life course for us.
I mean, the first time I read a book on philosophy, I was like, can't get enough.
Must make this my life's work.
I feel like a train track.
Once exposed, like a train on a track, once exposed to certain stimuli, but the stimuli is environmental.
The degree to which I respond to it, I assume, has some genetic component, but I really want to emphasize to people that you can do a lot of good by helping people in the world, rather than resigning yourself to the determinist view of genetics.
Geneticists would never discount the importance of the environment.
But I will say that, you know, think about yourself being exposed to philosophy.
You were in a position where you could be.
Now maybe your exposure to philosophy was accidental, but you were at a university environment.
And that's probably a function of your genes, interest in intellectual pursuits, things of that sort.
Maybe the philosophy was an accidental thing, but how great that you became passionate about it.
And just to set the record straight, I was raised with a fraternal twin, not an identical twin.
And so I was aware of differences from a very, very early age, and I found them extremely intriguing because we had the same parents.
We did so many things in common.
And yet we ended up being so different to the point that we complained to our mother that we had no one to play with.
And so I learned a very important lesson early on that the genes, and I didn't know they were genes at the time, but something fundamental about my sister and myself explained why we were so different and why we were so different from the identical twins I'd see at school who looked alike and moved alike and seemed to share so much social intimacy with one another.
Yeah, I think you mentioned that you generally had outside playmates compared to playing with each other, which again would, I guess, increase the peer influence on yourself and your sister.
Yeah, to some degree it did, and I think peers do have a very powerful influence.
But these were choices that we made, and I think that to say that genetics influences behavior is not to deprive us of choice.
I mean, if you think about the careers that we're in, I mean, You're in philosophy and you do radio and I'm a psychology professor.
I could have been a doctor.
I could have been a lot of different things, but there are a lot of things I couldn't have been.
I couldn't have been a construction worker.
I couldn't have been a boxer.
Those are things I'm not interested in and things I couldn't physically do.
We have a lot of choice.
For example, twin studies have shown that divorce has a genetic component to it.
Not that there is a gene for divorce, but it could be a difficult personality, a rigidity, things of that sort.
But genes don't make you divorce.
You decide, I could stay with a lousy marriage, or I could get out of it, or I could have some arrangement in between.
We have a lot of choices.
Genes don't tell us what to do.
They may guide us.
They may lead us.
Ultimately, it's up to us.
Well, also, there's, I think, a case to be made that learning about the genetic basis for personality gives you a stronger methodology or approach to dealing with difficult aspects of your own personality.
So if, for instance, you are naturally defiant, or you're into sort of win-lose negotiations, or you have a dominant trait to your personality, Isn't that sort of like knowing that you have a genetic susceptibility to heart disease that it can kind of push you in the other direction?
Say, well, this is who I am, so I can work harder to be better at compromise and so on, in the same way that if I have a genetic tendency towards diabetes, I'm going to want to eat better, exercise more, and use that information for the betterment of yourself.
I think that's quite correct.
I think that anything we can know about ourselves is informative and useful.
I think that this logic also extends to the area of sports.
Many people want to be great athletes.
And they just simply cannot be.
And they blame themselves.
They haven't practiced enough.
They haven't lost enough weight.
Whatever.
But I think that when you recognize limitations, then I think that you can really work better and make your life a lot more positive.
Knowing what you're good at, I think, is the key.
I think the key is finding out what you are good at, what makes you happy, and really sticking to that.
I think that, really, we have a lot of choices in that regard.
Right.
Now, I don't think any interview is really ever complete without a good penis amputation story.
So the story that you had in your book...
I know where you're going with it.
Yeah, so I'll let you take it from here because obviously I don't want to faint while I'm telling the story, so I'll let you take it from here.
But I thought it was a fascinating example of the degree to which biology may be embedded in the brain.
That's right.
A number of years ago, there was a case in Canada, quite extraordinary, of identical twin boys who had difficulty urinating.
And so their mother took them to a hospital, and the idea was that they would be circumcised.
When the doctors circumcised the first child, they used an electronic device that was much too strong for the child and really ablated his penis.
And the parents were dumbstruck, didn't know what to do, so they were advised by Dr.
John.
I'm sorry, just ablated may be something not too clear to people.
It was...
Yeah, yeah, destroyed.
I mean, basically removed and left, as the mother said, a piece of string.
That's what it looked like.
So the parents didn't know what to do for months, and then they saw a television program that featured a Dr.
John Money from Johns Hopkins University whose specialization was gender and gender switching, things of this sort.
He used to do operations on infants with ambiguous genitalia, ambiguous genitals.
So at any rate, The parents were quite excited by this doctor and visited him, and he was quite keen to take on their case, and you can see why.
Because here you had the perfect genetic control.
You had a child who was perfectly normal, raised like a boy, and then John Money advised the family to raise the other child as a girl.
Now, when they made this change through surgery, through hormones, things of that, the child was about 18 months old.
I remember I was in graduate school then and I was told that that was the window before which you could alter a child's gender identity, turn a boy into a girl, a girl into a boy.
Well, the experiment never worked.
Despite John Money's claims that it did at conferences and in some of the chapters he wrote, it was not working.
And it took years until the truth came out.
This child, despite being dressed in dresses and being treated overly like a girl, I mean, the mother made a real effort to be a really girly, girly mother, you know, with white shoes and lace and all that sort of stuff.
It simply did not work.
And then nothing happened with this case.
We didn't hear about it.
And then my wonderful colleague, Dr.
Milton Diamond at the University of Hawaii, doubted that it ever could have worked.
He's a specialist in gender identity, does a lot of work with transsexualism.
He and I have collaborated on some twin cases.
And he finally got a hold of a social worker who was on that case in Canada, who also admitted that it wasn't working, but because he was under the guise of Dr.
John Money and didn't want to He never said anything.
Anyway, the upshot was that the parents finally told the child when he was 17, and he quickly switched back and became a male, did marry a woman who had had three or four previous children.
Unfortunately, the story has a very, very sad ending, and that ending is that the twin brother committed suicide from schizophrenia, and eventually this other one did as well.
So it had a very, very sad ending to it.
If people are interested in this, they should read a book called As Nature Made Him, written by the journalist John Colopinto.
But I guess this is all a long way of saying that biological givens have a very strong effect on many of our behaviors, and gender identity is one of them.
And I guess related to that is the question of homosexuality, which you talk about quite a bit in your book.
I made the case years ago that I thought that there was a very strong The correlation between genetics and homosexuality, but of course the rebuttal to that is that the correlation between homosexuality or lesbianism and twins is not obviously one, it's not zero.
I think it was about.4,.5 if I remember rightly.
So how does twin studies help elucidate the challenge of gender identity, homosexuality, and so on?
Well, sexual orientation does have a genetic influence.
We suggested that in our studies of twins raised apart.
In our studies of twins raised apart, we also showed that among our few identical males, it was a stronger genetic influence because it was greater match among the females.
We had four sets of females where one was a lesbian, one was not, and there were no concordant pairs or no pairs where both were.
Now, that was a very small sample from which you cannot draw strong conclusions.
But the best study I've seen recently was done in Sweden in 2010, a population-based study.
And there they found that the genetic influence on male sexual orientation was about 38% females closer to 15 or 20.
So it seems to be stronger in males.
It's less than we thought previously.
You know, when the research first went on with Franz Coleman, he found 100% genetic influence on male homosexuality.
But that's because he did his research in gay bars, where you're going to have an unrepresentative population of people.
Although we should admit that it's a very fun place to do research.
I've never done it, but I'll take your word.
Anyway, then some years later in the 1980s, there was an anonymous survey done by the Australian twin population.
And they found a somewhat lower link to genetics, maybe at 50% or so.
But at any rate, homosexuality or sexual orientation is a very complex behavior that may have many, many differences.
There are many different sources, genes being one of them.
There's some research showing that when mothers give birth to several sons, then four, fifty, or six, seven sons may be at a higher risk for homosexuality, possibly because of mother developing antibodies toward male hormones.
These are theories, these are not proven, but the idea of later born males having a higher rate of homosexuality has shown the mechanisms still...
But certainly genetics is a primary one.
Right.
Where did the sort of, I know I hesitate to bring up Freud, because I know that he's not exactly at the high point of his acceptance or value in the psychological community, but some of the Freudian arguments around, you know, dominant mother, weak father, and so on, does these hold any weight when it comes to understanding or understanding?
Trying to untangle the challenges of the development of same-sex sexual orientation.
The interesting thing is that we do find that parents of children who are homosexual or transsexual do tend to treat them differently.
But the key is that these parents don't just decide to treat them a certain way.
They are responding to the behaviors these children evoke.
And that is best illustrated by a pair of twins that I studied.
These were two identical females, one of whom changed her gender to a male, went through sex reconstructive surgery and hormonal replacement therapy and all of that.
And they said that from the time they were toddlers, The parents treated the one child as a girl, dolls, lace, all this sort of thing, and gave boy toys to the other one in sports equipment.
But it wasn't that the parents decided to do this.
The children just naturally craved and asked for these kinds of experiences.
And so it's the children driving the behaviors.
I always tell parents, you don't bring up your child, they bring you up.
It's the children driving the behaviors.
Well, unless you're willing to be just brutally dominant as a parent, which of course is never recommended, everything to do with child raising is a negotiation, and your parenting has to alter depending upon the nature of your child.
Otherwise, you're just trying to put everything into the same box, which probably doesn't have the same shape.
Well, exactly.
I always tell parents, too, that if you try to treat your children all alike, that's not very fair treatment.
It's a much fairer, more equitable situation when you treat each child in kind, when you respond to their individually values.
I express talents and tastes and preferences.
What works for one child may not work at all for another child.
And I also believe that parents of one child are environmentalists, whereas parents are two geneticists.
And to me, the most intelligent parents are the parents of fraternal twins, because they can see right away in that crib, they've got two different kids, despite the similar environments.
One of the most revealing cases I ever studied in my second book, Indivisible by Two, concerned a mother who gave birth naturally to quadruplets.
And they were composed of four boys but two sets of identical twins, which, if you organize them every which way, yields four sets of fraternals in addition to the two identicals.
And where she tried to kind of decouple the pairs, she said it was fruitless because the identicals just aligned so well.
Right.
Okay, let's move to another topic that I find absolutely fascinating, and for which, you know, based upon a layperson perspective, the approach within psychology seems to pendulum back and forth.
I remember reading a book in the 80s, that birth order, it explains everything!
And then it sort of went to the other extreme and said, birth order, it explains nothing!
And, you know, I guess that Aristotelian mean is kind of sitting in the middle now.
Where does birth order and its importance on...
Well, in terms of twin studies, I have to say that birth order really doesn't mean almost nothing, except in terms of birth order if it's a natural delivery, because typically the firstborn child has an easier time of the delivery than the secondborn child.
Birth order studies, I think, are quite messy in twin research because if you do a cesarean section, Does the first one who comes out, is that the first one or the second one?
I mean, it doesn't mean anything.
Now, where birth order may have a slight effect is that some parents choose to tell the firstborn child or to treat the firstborn child as the older one.
That happens in some cases, not in all.
That might have a slight effect in terms of the child's responsibility or outgoingness or dominance, but again, that doesn't happen in all cases.
It could conceivably.
But in terms of birth order research, I think in terms of ordinary families with ordinary siblings, if it has an effect, it's very, very slight.
Very, very slight.
There's so many confounding factors, gender, spacing, what goes on in the family at the time, personalities among siblings.
It's a very convoluted field.
And family configurations can change substantially between, yeah, you could move countries, you could adopt a new religion.
There's so many things could happen, right?
Yeah.
And actually, in some cultures, too, in twin births, the child who was born second is actually considered the older one because they've had more time to cook, if you will.
They're more well done, I think, in the parlance.
Yeah, that's rare.
Now, IQ development is one of these things that I find obviously fascinating.
I think there's some decent evidence that says, you know, higher IQ in general is better for a society.
You tend to be more law-abiding and often will make better decisions, better deferral of gratification.
But one of the things that is really slippery, I think, when it comes to IQ and its development, I'm just going to give you some numbers, of course, from your own book and ask you to...
Tell us what they mean in more detail.
So you wrote, genetic differences among people explain their IQ, and it's estimated to be 20%, right?
So you can explain 20% in infancy, 40% in childhood, 50% in adulthood, and 60% in adolescence, and 60% In adulthood.
So it's almost like IQ is something that hardens over time and so on.
Because I know that in America, of course, in particular, with the Head Start program, we talked about this with Dr.
Turkheimer, there is, of course, a desire to bring up the IQ, particularly of disadvantaged groups or groups who have historically scored lower ethnic groups in the IQ test.
Let's move them up.
And there is this bulge followed by this not bulge.
And I think people don't really understand the degree to which your destination, I'm paraphrasing, obviously correct me where I go with strength, but your destination IQ is to some degree a lot more fixed than your starting IQ, that it does tend to harden over time.
Well, what happens is that when children are living at home under the thumb of their parents, they tend to be more alike.
Let's talk about two siblings.
But then as they age, they tend to forge their own pathways, if you will.
They have greater freedom to express the genetic potentials.
New genetic factors may kick in.
And so while people may think that as you get older and experience the environment more intensely, genetic influence should go down, just the opposite happens because you're getting more into your own individualized genetic trajectory.
And so what's very fascinating is, let me talk about another pair, another kinship that I study, which may interest your listeners, virtual twins.
I mention those in my book as well.
Virtual twins are same age, unrelated children raised together from birth.
So they're these kind of exotic twin-like creations, but they share no genes in common.
And so I have been tracking the IQ development of these kids.
I'm sorry, just to interrupt because it took me a little while to figure out what this was, but an example of this could be a woman who maybe she thinks she's infertile, she's going for adoption, she gets the adoption, and at the same time she has a baby.
So you end up with that sort of scenario.
Okay, sorry, please go ahead.
But she has the baby, and then the child who's adopted is available because the kids have to be near an age.
Or sometimes two adoptees become available at the same time.
There's other ways these can get created, but those are the two main ways.
Anyway, so when the kids are young and living at home, their IQ correlation is about 0.25, which is pretty low.
Just as a benchmark, the correlation between identical twins at the same age of these virtuals would be about 0.86.
But as these kids age, their IQ becomes less and less alike.
And it's because they're forging their own genetic identities, if you will.
They're less under the thumb of their parents.
So genetic influence goes up.
And that's why those figures you cited go from 20 to 40 to 60, I think, to 80.
That was a wonderful study shown by some researchers at Pennsylvania State University.
That's what we find with twin studies.
And some other wonderful work that tracked twin research was done by the late Ronald Wilson at the University of Louisville, where he tracked twins from birth through age about 13, 14, 15.
And he showed that identical twins do converge as they get older.
And not only that, they show coordinated periods of what he called spurt and lag, intellectual growth, intellectual decline, or, you know, And national twins were all over the place.
So their patterning was different.
Identical twins was the same.
Yeah, and you point out, I think, that adoptive siblings who have some correlation between IQ when they're at home, when you get adolescence and adulthood, the IQ correlation between adoptive siblings goes even below cousins at 0.15 and I think functionally approaches zero.
It does.
It goes down to about zero.
And that seems kind of counterintuitive in a way because everyone sort of thinks that if you're living with somebody, they should make relatives alike.
But in fact, it doesn't.
And to the extent that you are like the relatives you're raised with, it's because of your common genes, not your common environment.
Oh, that is something that's so hard to untangle, and it's something that I've really been trying to hammer into my audience repeatedly, that when we look at it and we say, oh, well, you see, the parents who read a lot to their kids, those kids grew up very literate, and it's like they're very smart, and they really like books and all that, and so we think, we get anyone to read...
Books to their kids and they're going to end up the same way.
But the reality seems to be that smart people like books and it's the genes that they're passing on rather than the books that they're reading that seem to provoke the similar love of books and their kids.
The example you're giving is a wonderful example of what we call gene environment correlation, passive gene environment correlation.
Because if parents read a lot to their kids and the parents are smart and the kids are smart, parents pass on both environments and genes to their children.
So how do you know which one is active in this case?
You don't know.
I think a really nice comparison is what was done at the University of Texas where they looked at the IQ scores of mothers who had given away their children for adoption.
So they had the IQ score of the biological mom, the adopted away kid, and the adopted parents of that kid.
And you know who was more alike?
The biological kid and the biological mom who were not together as compared to the adoptive mom who raised that adopted child.
I think that that comparison is a very, very informative one.
When parents and children are raised together, this is the whole problem with the old family studies where they would look at similarities and say, oh, it's the environment.
It's the genes.
They're confounded.
You can't separate genes and environments in intact biological families.
You simply cannot.
It would be as if someone was sick and took drug A and drug B and got better.
You don't know which drug made you better unless you vary out the factors.
So, a lot of these family studies that looked at families and said it was the environment, I think are really pretty passe at this point.
I think most people would say that.
And dare I say that there may be a slightly less than honorable profit motive on people who wish to dangle the carrot of high IQ in front of parents who, of course, would generally choose higher IQ, all other things being equal.
You know, that Mozart effect, you know, that study that said, oh, you listen to Mozart and your IQ goes through the roof, which I think was later debunked.
But there is, of course, parents who want their kids to do well are very susceptible to this idea that there's X, Y, or Z that you can do that's going to make your kids' brains explode like supernovas.
Yeah, I mean, I think there are things we can do to help children, to make children smarter, but I would also caution parents that if you simply read and read and read to your child, that child, you know, it's not as if more reading makes more IQ. That child's going to be bright anyway, and the child will probably seek experiences that are meaningful on their own.
Now, for some children in the family, maybe too much reading is too much stimulation, and that child will sort of shut down.
I think I'm not saying you shouldn't read to your child.
I'm just saying that there are individual differences in how children will respond to that and how much they will improve based upon that kind of training.
I think it's just, it gives parents a more realistic idea of what they may accomplish.
Parents who think they're going to play Mozart and read to children and end up with geniuses, I think are going to be disappointed.
And end up feeling bad as a result.
I mean, I think knowing as a parent, knowing the limitations of what you can achieve, what I've taken out of the research that I've been doing for the last couple of years and talking with experts like yourself is it's hard to make a child.
It's easy to break a child.
You can mess up a child and make them, as one of the researchers pointed out, You know, lock a child in a cupboard for 10 years, yes, they're not going to reach their full potential, starve them of nutrients prenatally or postnatally, and they're not going to achieve their full potential.
But once you go over a certain threshold where the minimums are met, there's not a lot.
I mean, you can have fun parenting, and I think there's definitely things that you can do to stand off the rough edges of your kids a little bit, but you can't make the kids into what you want because there is such a ceiling of genetics.
Along those lines, I would also add that we know more about what to do to help children from impoverished backgrounds, extra diets, schooling, things of that sort.
But then when we get to that upper level, then we're kind of held back.
I mean, how much more reading or how much more intellectual stimulation will improve them, right?
So I think we know more about what to do to humiliate effects at the lower end.
And finding the personality aspects that are more innate to your children can really help release them into directions that are more convivial to them.
I mean, when I was growing up, I had the math abilities of your average soap dish, but on language I'm quite good.
And so if I'd been put into a whole bunch of sort of math classes, it would not have done that much for me.
On the other hand, you know, putting me in language classes and creative writing, public speaking and all that did a lot of good for me.
And I think that's kind of the dance that you have to get involved with your kids, that you can't make them into what you want.
But through negotiation with the stronger aspects of their personality, you can really help them to achieve what comes naturally and most beneficially for them.
Well, this is what we mean by sensitive parenting.
The best parenting are parents who are sensitive to the individual differences in their children, can be sensitive to their personalities, to the things that they're good at, and really try to nurture these kinds of things.
And as I said earlier, sensitive parenting means that you're attentive to each child individually and not just treating them all the same.
So two things I wanted to mention here because the moment that we start talking about genetics, of course, a lot of people are very excited and a lot of people are kind of nervous because it seems like there's the potential for a caste system to emerge within society that, you know, the high IQ people with the high IQ genes, they float to the top and everyone else just kind of have to swim in the middle or the bottom and so on.
But I think it's important also to remember, and this is true for parents, if you have a particularly strong ability, There is, of course, the regression to the mean.
I wonder if you could help people understand how this helps to cycle things in society so we don't get any kind of semi-permanent caste system.
Yeah.
Well, regression to the mean works in terms of IQ. It works in terms of things like height and weight.
Let's use the height example.
I think it's a little bit simpler.
Two tall parents, on average, are going to have tall children, but some of those children are going to be shorter than they are.
Some medium-sized parents are going to have medium-sized children for the most part, but some of those kids are going to be taller on average and some will be shorter on average.
Some short parents are going to have short kids, but some of those are going to be taller.
Everybody shifts around.
And that's why there's movement within these different sort of categories.
And IQ works in the same way, that bright parents are going to have brighter kids on average, but some of those kids are going to be a little bit less smart.
And some of those medium parents are going to have medium IQ kids, but some of those are going to be smarter, and so they'll move up along that distribution.
Yeah, natures keep shuffling, so it helps us from getting too complacent.
Now, when it comes to the three, the genetic shared environment and non-shared environment.
Shared environment, I understand it basically being sort of the family structure.
The non-shared environment is just a big bucket of everything else.
Maybe you got an illness, or maybe you won the lottery, or maybe you just met particular friends or whatever.
When it comes to religiosity, that to me is a really fascinating idea, because When people say, well, parents don't have much influence and so on, and then I think, well, you know, if you grew up in Saudi Arabia, well, you're likely to conform to the religious and social norms within Saudi Arabia.
Now, of course, that's a bit more of an aggressive regime, to put it as nicely as possible, when it comes to conformity.
But it seems parents would have a huge amount of influence on the degree to which children conform to religious – if the parents are religious – to religious norms when they're young.
But I think you've pointed out and other researchers have pointed out that there does seem to be a genetic fertile soil for certain religious or spiritual experiences that once the parents are not saying, you know, get up, put on your Sunday best, we're going to go sit in a pew for an hour – That the children tend to drift more towards what moves them emotionally, and that has some genetic basis.
Right.
We came to that conclusion based on the studies the twins raised apart, and it really surprised us too.
But one thing I will say is that we need to define religiosity, and that refers to one's The extent of religious commitment, participation in religious activities, which ones, how frequent, that sort of thing.
It does not refer to affiliation, and that pretty much comes from the home.
I won't say that no one changes affiliation, but that pretty much seems to come from the home environment.
But the degree to which people take part in religious activities does seem to have a genetic component, and the best example I can give is the one I gave in the book, Born Together, Reared Apart, Which concerned these two twins, Sharon and Debbie, who grew up in very different homes, one religious Jewish and the other Christian.
And both of them were extremely religious individuals, unlike the adoptive siblings they had, who were exposed to the same environments who were not religious.
And when Debbie and Sharon came together, they understood and respected each other's religious commitment and faith.
And they kind of entertained the idea that maybe now that we found each other, we should have the same religion.
But they both decided independently, we're not going to.
We're going to keep our faith.
And they both discussed the fact that they both respected each other a lot more for that.
So, yeah.
So, again...
I think the extent to which we are religious, living at home, we do what our parents want, this sort of thing.
But just like other things, once you're out there on your own, you're free to express your genetic potential and be the person that you want to be in terms of religious activities.
Yeah, I mean, Freud talked about the sort of oceanic feeling, and he had, of course, all of these.
It was a wand with your mother's breast and so on.
But I do think that the people who have that spiritual component, to them, it seems incontrovertible that they are experiencing something genuine within the universe, whereas the people who don't seem to have that particular emotional or psychological characteristic view it as, you know, hippy-dippy nonsense that doesn't whereas the people who don't seem to have that particular emotional or psychological
And these two people engage, or these two groups, I guess, engage in a kind of intellectual argument that I think is kind of covering up a genetic diversity that is relatively unacknowledged.
Yeah, I think it is.
But I think that context also makes a difference.
Now, I think about those two twins I mentioned, Sharon and Debbie, who grew up Jewish and Christian.
They both agreed that if their positions had been reversed, they both would have adopted the religion of that particular household because they like religion.
They like the structure of it.
They like the community.
They like the whole practice of it.
It resonated with who they were.
Context makes a difference, but the big point is the religiosity aspect.
Which religion is maybe doesn't make that much of a difference here, but the religiosity does.
Right.
Now, I'm going to put you in the ghastly position of trying to summarize your life's work.
And the reason that I want to do that is that, obviously, I'm going to hope that people read your book and other people get involved in this conversation.
but there's so much to me that is really, really important in what it is that you do and can be very informative to us.
You know, as a society, we're always trying to make big, complex decisions with very scarce resources, and I feel like a lack of knowledge of the interplay between environment genetics and let's just toss free will in there to make it spicy.
We're constantly misapplying resources because we're trying to change height with magic or something like that, And on the other hand, though, there's things that we really could do that would be great, which maybe for various politically correct reasons or people's concern about the determinants of genetics, we kind of avoid.
You mentioned sensitive parenting.
If you could talk a little bit about that and where you think the twins' research and the relationship between genetics and environment can help us make better decisions about how to improve the lot of the societies we live in and its members.
Well, for sensitive parenting, as I said, parents need to be responsive to the individual differences in their children.
And that all comes from the genetic differences among those kids.
And you asked me to summarize my life work, so I'm going to go over that now.
And, you know, I've been interested in twins probably since the day I was born, because when you're a twin, you just naturally are drawn to all things doubled.
And so I actually...
I think of my twin research at two levels.
One is using twins as a research model to look at genetic and environmental influences on behavior.
I use twins in many, many different ways, the classic identical fraternal twin comparison.
I also study some very exotic Kinships, such as the virtual twins I mentioned, the same age unrelated kids.
I also study people who look alike but are genetically unrelated as, again, a kind of twin-like relationship.
And they're very important for one reason, because some critics of twin research have said that identical twins are alike because people treat them alike based on their appearance.
And I believe that people do treat them alike, but it's because they evoke certain responses from people based on their genetically influenced personalities.
But I reasoned that if look-alikes That look-alikes should be as alike in personality if people simply react to their appearance.
And you know what?
Look-alikes are nothing alike in personality.
So my belief about twin research was upheld.
But there's also another way of studying twins, and that is looking at twins for twins themselves.
You know, what are the special issues in twinship?
What's the best way to raise identicals, fraternals?
Do you separate them in school?
What about if one gets invited to a birthday party?
I believe in staying active in both of these domains.
For one thing, I like to see twins up close and personal.
I get a better sense of what the problems are.
I get a better sense of the whole phenomena.
That can help me in my research lab to try to figure out what are the issues that need addressing.
There are so many things that we still don't know about.
Twin language, for one, is a term that everybody uses.
It refers to the special gestures and words that some twins, mostly identical, develop when they're toddlers.
And it's kind of charming and fun to listen to, but it can lead to delays in normal language development.
And we don't really know a lot about the origins of it, but I have learned from parents that older siblings, while they don't use that language themselves, are able to translate for parents.
And I probably shouldn't even call it a language that's not So why not use these siblings to understand the genesis of this behavior?
So there's a lot of things that we still can do, a lot of really creative things still left out there.
I'm absolutely fascinated with twins who were born apart and with twins who were switched at birth.
And I had studied seven or eight cases of switched at birth twins in another book of mine called Someone Else's Twins.
I'm sorry, what does switched at birth mean?
Switched at birth means that twins are born in a hospital, And a nurse accidentally exchanges one twin with a non-twin child in the nursery, such that a single twin grows up with the wrong parents, and the parents of the twins grow up or grow up raising a pair of unrelated, alleged fraternal twins.
And typically, the discovery is made when they're adults, when somebody confuses one twin for the other, says, I know you, and says, no, you don't know me.
And of course, the twins have no idea, but they're brought together because of this mistaken identity.
You may have read a New York Times article several months ago about the switched twins from Bogota, Colombia.
I was down there in Colombia studying that case and am in the process of writing a book about that right now.
So these are very fascinating cases because when you think about it, the unrelated fraternal twins are virtual twins, but they believe they're twins.
So they're kind of a subcategory of that.
So I think that by looking at these unusual exotic twin ships, we can potentially get a lot of information.
So you mentioned you're working on a new book.
I wonder if you can give us a wee teaser.
An extension of what I learned about the twins who were switched in Bogota, Colombia, and I'll just leave it at that.
I think that'll whet people's appetites.
All right.
Well, I really appreciate your time, and I also wanted to thank you for taking the time and effort to translate what is often very ivory tower research into easily digestible, very enjoyably written, and consumable.
Mass media writing.
Because a lot of the stuff that goes on, there's such a dichotomy between what goes on in the conversations between the experts, I've noticed this with IQ as well, and what goes on in the population, the general consciousness of the population.
They seem to be kind of worlds apart, or maybe there's just a huge amount of lag between the two.
So the work that you're doing to fire sort of cannons of knowledge over the ivory towers is really appreciated.
And I put a strong recommendation in your writing and your blog is, you know, elegant and consumable and enlightening.
And I really, really appreciate that effort.
Well, my pleasure to be here.
All right.
Thanks so much.
Hopefully we can talk again soon.
And this is Devan Molyneux from Freedom Aid Radio.
