January 29, 2014

Pinker on interpreting twin studies

More from the Edge symposium on what ideas should be retired from science. Here's one that's helpful:
Steven Pinker 
Johnstone Family Professor, Department of Psychology; Harvard University; Author, The Better Angels of Our Nature 
[Anti-] Behavior = Genes + Environment 
... Genes: Molecular biologists have appropriated the term "gene" to refer to stretches of DNA that code for a protein. Unfortunately, this sense differs from the one used in population genetics, behavioral genetics, and evolutionary theory, namely any information carrier that is transmissible across generations and has sustained effects on the phenotype. This includes any aspect of DNA that can affect gene expression, and is closer to what is meant by "innate" than genes in the molecular biologists' narrow sense. The confusion between the two leads to innumerable red herrings in discussions of our makeup, such as the banality that the expression of genes (in the sense of protein-coding stretches of DNA) is regulated by signals from the environment. How else could it be? The alternative is that every cell synthesizes every protein all the time! The epigenetics bubble inflated by the science media is based on a similar confusion. 
... Even the technical sense of "environment" used in quantitative behavioral genetics is perversely confusing. Now, there is nothing wrong with partitioning phenotypic variance into components that correlate with genetic variation (heritability) and with variation among families ("shared environment"). The problem comes from the so-called "nonshared" or "unique environmental influences." This consists of all the variance that is attributable neither to genetic nor familiar variation. In most studies, it's calculated as 1 – (heritability + shared environment). Practically, you can think of it as the differences between identical twins who grow up in the same home. They share their genes, parents, older and younger siblings, home, school, peers, and neighborhood. So what could make them different? Under the assumption that behavior is a product of genes plus environment, it must be something in the environment of one that is not in the environment of the other. 
But this category really should be called "miscellaneous/unknown," because it has nothing necessarily to do with any measurable aspect of the environment, such as one sibling getting the top bunk bed and the other the bottom, or a parent unpredictably favoring one child, or one sibling getting chased by a dog, coming down with a virus, or being favored by a teacher. These influences are purely conjectural, and studies looking for them have failed to find them. The alternative is that this component actually consists of the effects of chance – new mutations, quirky prenatal effects, noise in brain development, and events in life with unpredictable effects.

My impression of male identical twins is that many spend quite a bit of their formative years punching each other. More perhaps than non-twin brothers do, perhaps because they are so evenly matched that neither one has any reason to say to himself: I'd better just let him have it because if we fought I'd probably lose. This sibling violence presumably has random effects on how the identical twins turn out: while the total amount dished out and taken is about equal, the precise effects on different organs likely differs.
Stochastic effects in development are increasingly being recognized by epidemiologists, frustrated by such recalcitrant phenomena such as nonagenarian pack-a-day smokers and identical twins discordant for schizophrenia, homosexuality, and disease outcomes. They are increasingly forced to acknowledge that God plays dice with our traits. Developmental biologists have come to similar conclusions. The bad habit of assuming that anything not classically genetic must be "environmental" has blinkered behavioral geneticists (and those who interpret their findings) into the fool's errand of looking for environmental effects for what may be randomness in developmental processes.

A lot of things may be just that, say, one cell splits funny and that starts a cascade. For example, I almost died of cancer 17 years ago. Nobody has much of a clue why.
A final confusion in the equation is the seemingly sophisticated add-on of "gene-environment interactions." This is also designed to confuse. Gene-environment interactions do not refer to the fact that the environment is necessary for genes to do their thing (which is true of all genes). It refers to a flipflop effect in which genes affect a person one way in one environment but another way in another environment, whereas an alternative genes has a different pattern. For example, if you inherit allele 1, you are vulnerable: a stressor makes you neurotic. If you inherit allele 2, you are resilient: a stressor leaves you normal. With either gene, if you are never stressed, you're normal. 
Gene-environment interactions in this technical sense, confusingly, go into the "unique environmental" component, because they are not the same (on average) in siblings growing up in the same family. Just as confusingly, "interactions" in the common-sense sense, namely that a person with a given genotype is predictably affected by the environment, goes into the "heritability" component, because quantitative genetics measures only correlations. This confound is behind the finding that the heritability of intelligence increases, and the effects of shared environment decrease, over a person's lifetime. One explanation is that genes have effects late in life, but another is that people with a given genotype place themselves in environments that indulge their inborn tastes and talents. The "environment" increasingly depends on the genes, rather than being an exogenous cause of behavior. 
 
For example, as a child I went out of the way to create an environment for myself that was conducive to my tastes for the intellectual life (e.g., spending a lot of the time at the library -- and I benefited from living two-blocks from the library), but as a middle-aged man I've totally gone over the top in arranging my environment to suit my innate predilection.
  

28 comments:

Jokah Macpherson said...

"But this category really should be called "miscellaneous/unknown," because it has nothing necessarily to do with any measurable aspect of the environment"

This always bugged me. I'm glad I'm not the only one who feels this way.

In my accounting background, this would be called a plug.

Anonymous said...

For example, as a child I went out of the way to create an environment for myself that was conducive to my tastes for the intellectual life (e.g., spending a lot of the time at the library -- and I benefited from living two-blocks from the library), but as a middle-aged man I've totally gone over the top in arranging my environment to suit my innate predilection.

Yes but which genes dominate in such an environment? Genetic influence extends outside the body. Just because your genes are the only genes physically present in your environment, doesn't mean they are the only genetic influences or the dominant genetic influences. The environment includes other genes.

Anonymous said...

The bad habit of assuming that anything not classically genetic must be "environmental" has blinkered behavioral geneticists (and those who interpret their findings) into the fool's errand of looking for environmental effects for what may be randomness in developmental processes.


A lot of things may be just that, say, one cell splits funny and that starts a cascade. For example, I almost died of cancer 17 years ago. Nobody has much of a clue why.


It's not a fool's errand at all. The danger is in simply assuming "developmental randomness" as dogma and inhibiting the careful study of environment.

But Pinker is disingenuous and has an agenda (if only subconscious): he wants control over what's classified as "genetic". He's not really afraid of "environmental" explanations. What he's really afraid of is people searching the environment and discovering the extended phenotypic effects and phenomena of genes.

Anonymous said...

White Americans. From cowboys to cowards.

Anonymous said...

Based on my own admittedly small sample size, I have to say that I find the notion that children who grow up in the same family share an identical environment to be laughable. Parents do treat children differently, sometimes extremely differently.

Anonymous said...

"I've totally gone over the top in arranging my environment to suit my innate predilection."

Let me guess. Sailer lives in an underground bunker on a golf course.

Anonymous said...

this category really should be called "miscellaneous/unknown," because it has nothing necessarily to do with any measurable aspect of the environment


The inability to measure something is not an argument against the things existence, it's an argument in favor of better measuring techniques.

Anonymous said...

"but another is that people with a given genotype place themselves in environments that indulge their inborn tastes and talents."

There is a community. There's a church, a pool hall, a library, a movie theater, a ball park.

There are five people.
One spends most time at church, another at pool hall, another at library, another at movie theater, another at ball park.

So, they are in the same environment but they engage with it in very different ways. For each, the places they ignore might as well not even exist while they place they frequent could mean everything.

Also, mood affects how one looks at environment. If a person is shot with happy drug on monday, sad drug on tuesday, angry drug on wednesday, lazy drug on thursday, and crazy drug on friday, he will perceive and engage with his environment in very different ways on each of the days.

slumber_j said...

Anonymous said...
'"I've totally gone over the top in arranging my environment to suit my innate predilection."

'Let me guess. Sailer lives in an underground bunker on a golf course.'

An underground bunker well-stocked with Natty Light, from what little I can gather. In the Valley.

David said...

>The inability to measure something is not an argument against the things existence, it's an argument in favor of better measuring techniques.<

It can also be an argument for completely reconceptualizing the field. No instrument will tell you how many angels can dance on the head of a pin, correct?

That said, the resolution of these quirks might require big-time conceptual overhauling, but probably not.

I would prefer scientists to better measure mutations et al. rather than differences in how parents treat twins. The latter strikes me as much more idiosyncratic. After all, who truly understands parental behavior?

Anonymous said...

"gene" to refer to stretches of DNA that code for a protein

It's a bit shocking that Pinker does not seem to be aware of genes that code for rRNA and tRNA... Or is he intentionally trying to create confusion where there is none?

Also, there is not a single developmental biologist that is unaware of the role random events can play in gene expression and development of phenotype.

To say that this somehow means that Behavior =/= Genes + Environment makes no more sense than saying that poker game =/= skill + luck. I honestly thought that Pinker is smarter...

Anonymous said...

I would prefer scientists to better measure mutations et al. rather than differences in how parents treat twins. The latter strikes me as much more idiosyncratic. After all, who truly understands parental behavior?


I repeat, the fact that you don't understand something does not mean that it does not exist or is not important. Where would science be if this attitude had been applied to light? Sound? Gravity?

Anonymous said...

The future.

Gene therapy for the rich.

Bean therapy for the poor.

JayMan said...

"For example, as a child I went out of the way to create an environment for myself that was conducive to my tastes for the intellectual life (e.g., spending a lot of the time at the library -- and I benefited from living two-blocks from the library), but as a middle-aged man I've totally gone over the top in arranging my environment to suit my innate predilection."

It looks like you're describing gene-environment correlations. While they sound plausible conceptually, and they are rather popular with those interested in heredity, there actually isn't much evidence that they matter much at all. Meng Hu had a great discussion on the topic:

The Genetics of Intelligence « Meng Hu’s Blog

Pinker raises an important, and much under-considered matter with developmental noise.

However, to quote myself at HBD Chick & Staffan's:

However, what’s left over, after you’ve accounted for “attenuated heredity” may be what’s known developmental noise. This is “environmental” in the sense that it’s not inherited, but is essentially random and not subject to controlled manipulation.

Or we think it’s random. See Kevin Mitchell on it:

http://www.youtube.com/watch?v=KDFh74eENuw

And finally, perhaps most poignant of all, but greatly underrated, is the fact that that identical twins are not actually genetically identical, but possess subtle differences due to de novo mutations. While behavioral geneticists and others like to ignore these, identical twins are our metric of the effects of heredity. We think we can precisely measure the genetic effect vs “environmental” one by looking at identical twins raised together – anything different between them must be due to environment, so the story goes. But the differences between them could be due to genes, so in reality, we have no idea how big the effect of the “environment” truly is.

These differences are starting to recognized as being potentially powerful, as seen from the differences of supposedly (but not truly) genetically identical mice:

All mice are the same, until they’re not | Science News

Genetic tests that can distinguish between identical twins are becoming available. This is an underappreciated goldmine in future research into genes and environment.

Anonymous said...

And finally, perhaps most poignant of all, but greatly underrated, is the fact that that identical twins are not actually genetically identical, but possess subtle differences due to de novo mutations. While behavioral geneticists and others like to ignore these, identical twins are our metric of the effects of heredity.

They ignore them because most mutations are neutral.

JayMan said...

@Anonymous:

It's more for the sake of convenience. We don't if we it is justified to make the assumption that the effects of these mutations can be ignored. Some and perhaps even all of the difference between identical twins could stem from these mutations. Again, twins are our metric on the effects of heredity. Think about it.

Anonymous said...

Stephen Pinker is completely essential reading.

What does astonish me, is that his writing is so politically incorrect yet he seems not to suffer 'Watsoning' because of it.

Is this all down to his pleasent manner and genteel moderate tone?

Nick - Pretoria

Anonymous said...

Passive environment vs active environment.

Imagine a poor community. Bad.

But the culture of the people is actively engaged in pushing kids toward meaning goals. Good.

Imagine a rich community. Good.

But the culture of the people is passive in its attention to children. Bad.

Anonymous said...

"I've totally gone over the top in arranging my environment to suit my innate predilection."

Blacklisting by MSM helped some.

When you got nothing left to lose, you might as well be you.

Prof. Woland said...

"Binary Genital", sounds like a great name for a rock band.

Anonymous said...

Does anybody know what a "confound" is?

Can any two knowledgeable people give the same definition of "gene expression"?

That expression appears to mean whatever the speaker/writer wants it to mean.

If that's Science, Bill Clinton never told a lie.

Michael said...

Now this one is really good. A besetting vice of the modern age is to assume we know all the factors involved and just have to figure out the exact proportions - but there can be no mystery in this grand scientific age.

What's genius? Why it's IQ+personality traits like openness! There is no mystery in genius - how could there be? This is the age of science. Because we know absolutely everything there is to be known about intelligence in the form of the infallible IQ test so clearly, no mystery there, and if it isn't a kind of pure intelligence not captured by our perfect IQ tests, then it must be something else that we know. But there cannot be chance or mystery.

All phenomena must be explained through known factors in some interaction and no admission of mystery or chance can be made. It' a kind of mad scientist hubris that makes our age blind. Of course I'm not saying the mystery need be final, although in many cases it will undoubtedly prove so, but that at the current moment, there is a huge mystery surrounding such things as intelligence, nutrition, and other phenomena, and to pretend that we know about it is worse is far worse than simply admitting that the state of current science is on very shaky ground.

Nutrition is another good one. My roomate is a nutritionist, and he will plainly deny any health pehnomena that is not grounded in known nutritional factors. When I point out that we don't know everything about nutrition and that in fact we know precious little, he can't accept it.

Does that sound unintelligent? It's the rule of the age we live in. My roomate's a smart guy in some ways- he'd score high on an IQ test - but he has a kind of stupidity or blindness that impedes progress. But wait, I can't say that, because either he is smart or he is stupid. It's probably personality. It can't be that his mind has a defect that he simply can't see complexity and uncertainty in a situation.

ben tillman said...

Stephen Pinker is completely essential reading.

What does astonish me, is that his writing is so politically incorrect yet he seems not to suffer 'Watsoning' because of it.

Is this all down to his pleasent manner and genteel moderate tone?

Nick - Pretoria


He has the "right background". And he's not politically incorrect enough to tolerate scientific study of what that means.

http://www.kevinmacdonald.net/Pinker.htm

Anonymous said...

It's more for the sake of convenience. We don't if we it is justified to make the assumption that the effects of these mutations can be ignored. Some and perhaps even all of the difference between identical twins could stem from these mutations. Again, twins are our metric on the effects of heredity. Think about it.

It's not an entirely unreasonable assumption since we know most mutations are neutral. Also as novel mutations they're not the products of specific selective pressures.

There are no perfectly controlled experiments, even in more rigorous fields like physics. The point is to get a sense of the probabilities.

Anonymous said...

We also have to deal with the nurture gene.

We tend to see nurture as opposed to nature, but nurturability may be more hardwired into some than others.

Nurturability has the nurturing side and the nurtured side.

Nurturing side of the nurture gene wants to nurture.

Nurtured side of the nurture gene is receptive to nurturing.

It may be that some individuals--and some groups--have stronger nurture genes.

Some women really love their kids while other women see children as a nuisance. Take the film GEORGY GIRL where Charlotte Rampling hates her kid and just wants to go off and have fun again. But Lynn Redgrave has a nurturing gene and adopts the baby though not hers.

Likewise, some kids are very receptive to nurturement while others are not so very much.
Among animals, puppies more so than kittens. Puppies want to grow closer to humans as they develop. Kittens grow more distant from humans as they mature.

(Oddly enough, dogs are louder and more aggressive yet also more obedient and docile; cats are gentler and more timid yet more fierce and stubborn.)

http://www.youtube.com/watch?v=u8YCQ8j55VM

Consider laughter.

Some might say laughability is natural, i.e. some people are born with the funny bone; others might say it's a case of nurture, i.e. people exposed to more jokes will laugh more.

But what we call 'nature' is, to an extent, one's innate tendency to be nurturing and/or nurtured.

Those born with the funny bone are more likely to tell jokes and laugh at jokes.

Consider two people. One is prone to laughter and the other isn't.

Both can be nurtured to laugh because even humorless people will laugh at something. So, some might say laughter is a case of nurture.
But, those with the funny bone will be more responsive to the nurture of laughter. They will be the first to laugh. And they will be more likely to wanna spread the joy of laughter to others by 'nurturing' others toward humor.

Those without the funny bone may be made to laugh too, but it takes more effort. They can be nurtured to laugh but their nurture gene of laughter isn't as powerful as it is with some other people.

So, nurture too is partly a case of nature.

Anonymous said...

The cottage industry around nurture.

Nurture Vulture.

David said...

>that you don't understand something does not mean that it does not exist or is not important<

I didn't say it doesn't exist or is unimportant.

pyrrhus said...

I have taught a pair of id twin girls. The dominant one, now about 8, has gradually grown noticeably taller than her sister,
.Environment?