The heritability of self-control: A meta-analysis | Hacker News Reader

The heritability of self-control: A meta-analysis

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81 pointsyasp65 comments

I think it's worth pointing out that "heritability" means something very unintuitive in the literature. It measure the fraction of the variability that can be attributed to genetic variation, as opposed to environmental factors.

This does not mean what people think it means. In particular, the changes in environment can drastically affect the heritability of a trait.

An example: suppose you measure how fast people can run. If you take people and forbid them from training (say, lock them in a room), the variability will be fully heritable, since no one is training and the environment is exactly the same. The difference will be whatever the genes say it is. Conversely, if you make some of them train and other not, the variability will include environmental components, namely, who trains.

This has obvious implications for how to interpret this and similar results, depending on whether you find high heritability a good thing or a bad thing.

No, the studies are very clear, we take the variance of nature and variance of nurture at a population level and see how much a standard deviation effects some observable trait. Of course if you look at extreme cases of nature or nurture like being locked up your entire life or being born with a birth defect then that part will dominate, but we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments.

Heritability (i.e. narrow-sense heritability as typically used in most research articles) is not so clear-cut as to be split between nature and nurture. Even the GP is slightly incorrect when saying:

> ...as opposed to environmental factors

because for heritability, the distinction is between the variance explained by additive genetic effects versus the total variance of the trait of interest. There are other sources of phenotypic variance like epigenetics, non-additive genetic effects, or complex interactions that fall outside the scope of heritability.

We have 3 sources of difference, genetic heritability, home environment and "others". The things you talk about would go under "others", and they aren't very interesting since we have basically no influence over them, as everything we can influence via nurture goes under home environment and nature via genetic heritage. So for example, of we compare growing up in a rich or a poor household (this includes going to a better school, better neighborhood, better food etc), most of these studies shows that it has almost no effect at all.

You influence "others" by putting your kids in a good school.

It's one of the main drivers of varying housing costs in the US.

Your parents determines your school, so the quality of your school can't be in "others". The only way school could be in "others" in these studies is if parents often put one twin in a good school and the other twin in a bad school, but I strongly believe that isn't the case.

In your own words:

> We have 3 sources of difference, genetic heritability, home environment and "others"

Clearly, school is not home environment.

School is determines by your home environment, hence it is a part of the home environment bucket. "other" is not: "everything except home environment and genes", it is: "everything not determined by the home environment or genes".

Your parents don't in all cases. I went to a good school and my brother went to a bad school. My parents didn't choose that. The good school did, it was selective in its students. Selective school aren't all that rare.

School is included in the shared environment because if you had identical twins they would be going to the same school and same classes.

I don't think this negates the parent's concern.

The parent uses an extreme example, but I think the underlying concern is: what assumptions get baked in when we assume the available environments are pretty normal?

Our modern environments are very abnormal compared to human environments for most of human genetic history. We can measure traits of statistically "normal" humans living in statistically "normal" environments and still ultimately be sampling in a weird corner of the possibility space.

Normal as in there is very little difference between the lives of most people in first world nations. They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. That is enough for kids to bloom. If you deny them any of those then there are problems, but that is not an issue even for poor people in the west.

>They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. [...] but that is not an issue even for poor people in the west.

Ooof. Just FYI this is actually horribly out of touch with reality. Go talk to a social worker sometime, or someone that runs a soup kitchen/shelter.

Or just check out the official government stats for the US: https://www.ers.usda.gov/topics/food-nutrition-assistance/fo...

To quote: "Both children and adults were food insecure in 7.1 percent of households with children (2.7 million households.

Although children are usually protected from substantial reductions in food intake even in households with very low food security, nevertheless, in about 0.6 percent of households with children (220,000 households), one or more child also experienced reduced food intake and disrupted eating patterns at some time during the year."

> we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments

So if you had some groups with generally fairly different genes and environments both, this would ascribe any differences just to the genes and throw out the environment aspect?

Conversely, if you make some of them train and other not, the variability will include environmental components, namely, who trains.

But then if you take everyone and train them to the max, i.e. Olympic athletes, then heritability comes back into the picture in a big way.

Indeed. I posted because I think intuitively people read that a trait is 60% heritable and assume that it's always true, when it is only true in the specific environment in which it was measured.

This line of research has interesting implications for moral philosophy.

If the degree to which we are able to resist our impulses is partly determined by our genetics, does that affect our level of moral responsibility for our impulse-driven actions?

Or does it merely mean that people who are more "at risk" of having poor impulse control because of their genetics have a moral obligation to recognize that fact and take measures to combat the deficiency?

For instance, if I know that I have relatively poor impulse control, should I ask my spouse to handle our finances so I don't blow all of our money? And if I fail to do so, is that the moral failing I'm responsible for, rather than the moral failing related to making impulsive purchases?

The everything happens for a reason line of thinking always holds, sort of in a form of a question: is there such a thing as free will?

The questions are the same, whether you think traits are caused mostly by genes or mostly environment. Either way, everything has a cause.

Everything has a cause but the morality changes depending on the cause.

If a person has a heart attack while driving and runs over a pedestrian, that's a tragedy all around. If a person runs over a pedestrian because they were texting while driving that's irresponsible.

To paraphrase Nietzsche: the concept of free will was only invented [by subjugated group] in order to assign blame to [person/group in power] for their actions, and to do the inverse - justify one's (undesirable) position, i.e. "I'm in a subservient position because I choose to be, and not because I lack power / knowledge / ability."

https://en.wikipedia.org/wiki/Friedrich_Nietzsche_and_free_w...

In the end, I think it probably leads to a form of consequentialism. It doesn't matter if you are more or less inclined to certain actions, but simply what the consequences are.

I agree with you and I think the question itself might be putting the cart before the horse. We didn't develop moral philosophy so that we could punish murderers, we started punishing murderers first because we had to and then we started thinking about how to communicate the rules and navigate the fuzzy grey areas.

It may be that free will is a philosophical dead-end but if you get rid of it then it turns out it was never all that foundational to begin with.

Nietzsche was wrong. I think, therefore I am. Free will is self evident.

Since we are all playing word games. He was wrong, but now he is accidentally right as nothing is self-evident.

One thing to consider is the Pygmalion effect[0]: If you and the people around you believe you inherently lack the moral fortitude to resist those impulses, you are much more likely to make irresponsible choices. Your weakness becomes a self-fulfilling prophecy.

Then there is the risk of recreating castes. It is one thing if you abdicate the right and responsibility to control your finances, but what if that became institutionalized? What if only people who pass certain genetic tests have full citizenship rights? Maybe future governments will legalize gambling and recreational drugs, but only for those individuals that don't have a genetic predisposition to addiction.

[0] https://en.wikipedia.org/wiki/Pygmalion_effect

You could make castes based on measured behavior, not genetic predisposition which is obviously unreliable.

We do this in school by separating kids into different classes according to our guess of their ability. Not very reliable, but it can be better overall than treating everyone equally. We also do genetic "castes" with sports separating males and females. Again, some people end up on the wrong side of the fence but overall it seems to help more than it harms.

I kind of think we should do this in wider society too. As it is, naturally low intelligence or low impulse control people are just thrown in the deep end and expected to compete with people who are biologically superior. They can't win, so all kinds of negative social effects compound, like crime, poor health, poor mental health, and even lower economic success.

> We do this in school by separating kids into different classes according to our guess of their ability. Not very reliable, but it can be better overall than treating everyone equally.

Measured outcomes are generally worse overall. This system is popular with wealthy/high-status parents though.

The way to get better outcomes (in school and society) is to make sure that everyone has enough individual attention and support, not to sort and label everyone.

People who are impulsive or who integrate knowledge in a less regular way or ... are not “biologically inferior”; those differences are a complex trade-off, and our society needs a wide variety of personalities and thinking styles to function.

Respectfully, this sounds like a dystopia to me. In fact this exact structure has been described in multiple dystopian novels and movies [1]. Dividing people into castes that affect their options in life is a really really bad and dangerous idea for a litany of reasons. Regardless of whether it's based on an assessment or your bloodline, ...or anything.

Doesn't this sentence that you wrote ring any alarm bells for you? "Not very reliable, but it can be better overall than treating everyone equally."

[1] Here are a few I can think of off the top of my head:

* 3%, the tv show

* Brave New World (Huxley's book)

* Player Piano (Vonnegut's book)

The Pygmalion effect is fake. The original result was driven solely by wild outliers that indicate that those students were blowing the test deliberately or that the authors were incompetent, it was buttressed by inappropriate statistics, and, in an extremely familiar pattern now for any 'cool' environmental effect in social psychology, the hundreds of replications turned in ever tinier effects and to the extent that there is any effect, it is effectively zero in the long run: http://www.rci.rutgers.edu/~jussim/Teacher%20Expectations%20...

The `Three Laws of Behavior Genetics` need to be better known:

1. All human behavioral traits are heritable.

2. The effect of being raised in the same family is smaller than the effect of genes.

3. A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families.

http://humancond.org/papers/turkheimer00_three_laws_behavior...

2. How is two known?

3. Indeed. Birth order is for example one of them. This makes it even harder to know 2.

> 2. How is two known?

The primary tool of the trade is twin studies.

You compare (identical) twins, who have the same genes with siblings (shares half the genes) and unrelated people.

Most wanted are twins who grew up separated, so you can discerns environment from genetics.

And did they test all behavioral traits or how do you get to an unqualified "the effect of being raised in the same family is smaller than the effect of genes"?

There have been twin studies like this done for basically every trait, yes. Even things like how religious you are as an adult has basically nothing to do with which family you grew up in.

Because there hasn't been a single trait ever examined in which the shared environment influence is greater than that of the genetic one

2: Twin studies can control for different genetics and only measure environmental differences. Adoption studies can control for different environments and measure only genetic differences.

There is a recent Nature paper that uses a "relatedness disequilibrium regression" [1] that claims to show that twin studies overestimate heritability [2]

[1] https://www.nature.com/articles/s41588-018-0178-9 [2] https://geneticvariance.wordpress.com/2018/08/13/relatedness...

3. A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families.

This is the one that I can't understand how do they know. Consider the case in which some behaviour is the result of a combination of genes. One of them is on in 95% of individuals and off in 5%. When one of them is on, the fen. is on. It's still genetics but, unless you are certain of every gene that takes part in the combination, how will you know?

Actually, when they say that behavioral traits are heritable, are they saying that these genes are identified or is it just statistics?

>Actually, when they say that behavioral traits are heritable, are they saying that these genes are identified or is it just statistics?

Typically it's just statistics (usually based on twin studies). In the last few years we have started doing large Genome-Wide Association Studies (with sample sizes of over a million in some cases) which are a first step toward identifying the relevant genes.

But there are still many limitations: GWAS typically use SNP arrays which only measure specific points in the genome instead of sequencing the whole thing (because it's much cheaper). The SNPs identified may not be causal themselves but simply correlated with the causal gene.

Just a few weeks ago someone posted the following study on hacker news:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183507/

Here the authors claim that they were able to identify a particular gene that is likely to predispose an individual to extreme impulsiveness.

That's a candidate gene study, none of them replicate.

I read somewhere that the "neither genes or families" part is mostly peer group growing up. Also if you randomly get hit by a truck etc.

To me it is obvious that self-control depends significantly on your genes. I have ADD, but lived a long time without medication. I could barely do get anything done at all before I got medication, and then when I'm on medication I become one of the most dedicated workers you've ever seen. If something as simple as dopamine can have such a profound effect on my self-control then I have a hard time seeing how the myriad of other effects genes have on our brain can't also significantly alter our self-control.

One of the results from the abstract were interesting:

"The heritability did differ across informants, with stronger heritability estimates based on parent report versus self-report or observations."

Parents see their kids differently than the kids see them selves I guess? I wonder if we tend to compare our kids to their siblings when we report on things like this. I wonder if only children would have different parent reported traits on things like this? I guess we all see ourselves different than others see us.

We are probably not the most accurate observers of our external behaviors, since it’s too easy for us to mix memories of those with our internal state.

I think this quote basically says that "a parent's self-control correlates strongly with the parent's perception of a child's self-control" and this somewhat undermines the conclusion wrt heritability.

It's important to understand that the way many people understand heritability usually isn't what most scientific researchers mean when they say "heritable."

> Heritability is an important concept in quantitative genetics, particularly in selective breeding and behavior genetics (for instance, twin studies). It is the source of much confusion due to the fact that its technical definition is different from its commonly-understood folk definition. Therefore, its use conveys the incorrect impression that behavioral traits are "inherited" or specifically passed down through the genes.

...

> Heritability measures the fraction of phenotype variability that can be attributed to genetic variation. This is not the same as saying that this fraction of an individual phenotype is caused by genetics. For example, it is incorrect to say that since the heritability of personality traits is about .6, that means that 60% of your personality is inherited from your parents and 40% comes from the environment. In addition, heritability can change without any genetic change occurring, such as when the environment starts contributing to more variation...High heritability of a trait, consequently, does not necessarily mean that the trait is not very susceptible to environmental influences. Heritability can also change as a result of changes in the environment, migration, inbreeding, or the way in which heritability itself is measured in the population under study. The heritability of a trait should not be interpreted as a measure of the extent to which said trait is genetically determined in an individual.

https://en.wikipedia.org/wiki/Heritability

The example I heard that really drove this point home for me is that humans almost all have 10 fingers, and the ones who don't are almost entirely due to the environment (frostbite, table saw accidents, etc) so the number of fingers on a human hand is actually a low-heritability trait.

Did they actually do a twin study on finger count, or are you making things up? Otherwise you can't know for sure. For example, I'd bet that propensity to lose limbs correlate strongly with willingness to engage in risky activities, and risk taking has a significant genetic component according to other studies.

Even if you're right (and finger count is a common example for students to teach the concept of heritability), this will run counter to what people think when they hear "heritability."

Most people wouldn't think "number of fingers is heritable because their propensity for risk taking is genetic" they would say it's because the number of fingers we are born with is genetic, which would be a mostly incorrect reason for any heritability statistic on number of fingers. I think your possible explanation about why number of fingers might be fairly heritable only reinforces my point about what most people understand about heritability.

And, for the same reason, while risk taking seems to be heritable, we don't know the particular genetic contribution to risk taking.

I've wondered for a long time whether being hardworking is a "talent" that some people naturally have more of. Self-control being heritable would be some support for that idea.

I always thought it erroneous when people say somebody "has the genes to be a great X" but made nothing of it. The ability to actualize those genes, itself, requires good genes for "executing" (motivation, discipline etc..). So if somebody is lazy, but with "great genes", then those genes are in fact not great.

I think the idea many people have is that being hardworking is something you decide on your own and not related to your genes. Being lazy is seen as a character flaw that a person could change rather than something more innate. I think they're right to a degree, but I'm also guessing that it's easier for some people to not be lazy than others.

But if you factor in environmental influence, such as having a tiger parent, then the great genes for X would still be activated without requiring the complimentary execution genes. Nurture nurtures nature.

No doubt, like all things genes, environment has a non-negligible impact.

Have you heard of "learned industriousness"?

I had not heard of the term, but the ideas behind it are what I've considered. My own guess is that it's a mix of both genes and behavior. If being hardworking was based purely on the environment then I suspect that we would see a lot more success in treatment of ADHD without drugs. But it does make intuitive sense to me that it is something you can build up as well.

It's scary if we found this to be genetic. Only because you know the potential consequences humans using this information. Fast forward to clone wars.

No because we already know IQ is largely genetic. Whatever fears you would have about impulse control, you should already have about IQ. In real life, people prefer to have inferior children that are their own, over superior children that aren't really their own.

Of course it is heritable. The uncomfortable question is if its genetic.

With the monozygotic twin correlation being twice the dizygotic twin correlation, what other explanations are there?

Is been fairly well established empirically that monozygotic twins are treated differently than dizygiyic twins. Specifically, they share a much more similar environment than dizgoyic twins.

In other words, the equal environment assumption does not hold in reality.

How do you prove that? Environment are in large parts shaped by your genes. If you are an easy to please baby then your parents will like you more. If you sit quietly and study in class your teacher will like you more. If you are good looking people will want to be your friend. Basically the environment adapts to your natural traits and makes them stronger. This variance gets attributed to your genes and not nurture, since the environment was shaped by genes and not by artificial means like parental intervention.

Even if we accept this argument (I don't, to be clear), it could well be that what's heritable is the way MZ twins are treated versus the way DZ twins are treated, not self-control.

In that case, the fact that twin studies conclude that self-control is heritable is an artifact of the twin method.

Would be great if we get more info on epigenetic or gene expression.

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