
The heritability of self-control: A meta-analysis - yasp
https://www.sciencedirect.com/science/article/pii/S0149763418307905
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afthonos
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.

~~~
username90
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.

~~~
lucienlecam
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.

~~~
username90
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.

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BurningFrog
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.

~~~
username90
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.

~~~
BurningFrog
In your own words:

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

Clearly, school is not home environment.

~~~
username90
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".

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jawns
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?

~~~
rubinelli
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](https://en.wikipedia.org/wiki/Pygmalion_effect)

~~~
lopmotr
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.

~~~
jacobolus
> _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.

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BurningFrog
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...](http://humancond.org/papers/turkheimer00_three_laws_behavior_genetics)

~~~
narag
_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?

~~~
bobcostas55
>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.

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

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

~~~
bobcostas55
That's a candidate gene study, none of them replicate.

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username90
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.

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blakesterz
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.

~~~
carbocation
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.

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travisp
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](https://en.wikipedia.org/wiki/Heritability)

~~~
Gh0stRAT
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.

~~~
username90
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.

~~~
travisp
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.

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Mirioron
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.

~~~
stri8ed
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.

~~~
sixplusone
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.

~~~
stri8ed
No doubt, like all things genes, environment has a non-negligible impact.

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oyebenny
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.

~~~
lopmotr
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.

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

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

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oldgradstudent
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.

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username90
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.

~~~
oldgradstudent
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.

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

