Razib Khan One-stop-shopping for all of my content

May 24, 2017

Applying intelligence to genes for intelligence

Filed under: Behavior Genetics,Genetics,Intelligence — Razib Khan @ 12:10 am

Carl Zimmer has an excellent write up on the new new Nature study of the variants associated with IQ, In ‘Enormous Success,’ Scientists Tie 52 Genes to Human Intelligence.

The issue with intelligence is that it’s a highly polygenic trait for which measurement is not always trivial. You need really large sample sizes. It’s about ten times less tractable than height as a quantitative trait. There are still many arguments about its genetic nature (though a majority position that it’s not rare variants of large effect seems to be emerging).

But all in good time.

Science is divided into many different fiefdoms, and people don’t always talk to each other. For example I know a fair number of population genomicists, and I know behavior geneticists who utilize quantitative genomic methods. The two are distinct and disparate groups. But the logic of cheap sequencing and big data is impacting both fields.

Unfortunately when you talk to population genomicists many are not familiar much with psychology, let alone psychometrics. When it comes to the behavior geneticists many come out of psychology backgrounds, so they are not conversant in aspects of genetic theory which harbor no utility for their tasks at hand. This leads to all sorts of problems, especially when journalists go to get comments from researchers who are really opining out of domain.

Some writers, such as Carl Zimmer, are very punctilious about the details. Getting things right. But we have to be cautious, because many journalists prefer a truth-themed story to the truth retold in a story format. And, some journalists are basically propagandists.

Over the next five years you will see many “gene and IQ” studies come out, with progressively greater and greater power. Read the write-ups in The New York TimesScience, and Nature. But to my many readers with technical skills this is what you should really do:

  1. pull down the data.
  2. re-analyze it.

My plain words are this: do not trust, and always verify.

I’m a big fan of people educating themselves on topics which they have opinions on (see: population genetics). If intelligence is of some interest to you, you should read some things. Arthur Jensen’s classic The g Factor: The Science of Mental Ability can be quite spendy (though used copies less so). But Stuart Ritchie’s Intelligence: All That Matters and Richard Haier’s The Neuroscience of Intelligence are both good, and cheaper and shorter. They hit all the basics which educated people should know if they want to talk about the topic of intelligence in an analytical way.

April 8, 2017

Just because it’s not hereditary does not mean you can affect it

Filed under: Behavior Genetics,Culture,Genetics — Razib Khan @ 10:11 pm

A comment below from John:

Love to see a post about which human traits worth caring about are notable for having little or no hereditary component. It is all good and well to know what we cannot change, but it makes more sense to focus personally and as a parent on those things that aren’t genetically preordained.

This is a common sentiment I’ve seen. If you haven’t read The Nurture Assumption, please do so. I’d say a substantial reason I think that The Blank Slate is a good book is that Steven Pinker promoted Judith Rich Harris’ work.

With that out of the way: the implication in the comment above is that hereditary traits are the ones you have least control over, so you should focus on the non-hereditary traits. To some extent there is truth in this. Micronutrients are important. You don’t want to turn you children into cretins.

But a major problem with the idea that we can impact environmental impacts on characteristics is that on many traits we don’t know what those environmental impacts are. You can take a behavior genetic model and come to the following conclusion: within the population 50% of the variation is due to genes, 40% of the variation is due to non-shared environment, and 10% of the variation is due to shared environment (parents). We don’t really usually know what the non-shared environment means. It might be just developmental noise. It might be epistatic genetic effects. Or, in relation to behavior, it might be peer group, as Judith Rich Harris asserts.

We just don’t know. What that means is that the hereditary components are what you have legitimate effective control over through mate choice. And shared environment. These two combined are not nothing. And of course there is the impact of nation or community on the environmental in which propensities are expressed.

Addendum: The non-shared environmental variance was once explained to me as a “noise” factor. Just to give you a sense of how well we understand it.

December 18, 2012

Gene surfing with David Dobbs

Filed under: Behavior Genetics — Razib Khan @ 2:04 am

Over at National Geographic David Dobbs of Neuron Culture has an eminently readable and engrossing piece up, Restless Genes. I have never really read about ‘allele surfing’ on the wave of demographic expansion in the way that Dobbs’ rendered it. I certainly wouldn’t have been able to produce that sort of spare but informative prose.

On Twitter there was some concern about the focus on DRD4. The issue is a general one in much of behavioral genomics, and I’m not too interested in rehashing the point. But the broader question of heritability of behavior remains. It seems to me that we have some ‘natural experiments’ now. For the past 50 years there have been a series of cross-cultural adoptions from Asia to North America and Europe. If human behavior variation across and within populations is substantially heritable than this might be a good place to start. Rather than focusing on genes, we need to focus on heritability first.

October 7, 2012

Distributing the origins of human will

Filed under: Behavior Genetics — Razib Khan @ 8:26 pm

In The New York Times David P. Barash writes about how parasites might influence our behavior. This should not be too shocking an idea to readers of this weblog, I’ve blogged about Toxoplasma gondii before, on which there has been a raft of publications over the past 10 years or so. My main issue is that like much of behavior genomics I wonder about the possibility of any terminus and conclusion to this line of inquiry (as opposed to being fodder for high publicity publications indefinitely). For any given personality trait we know that a small proportion (on the order of 10 percent) of the predicted variation within the population is due to variation in family environment (i.e., the impact of parent-specific choices). Of the remaining fraction it is about evenly split between genetic effects (i.e., the genes you inherit from your parents, and the consequent dispositions) and “other/non-shared environmental effects.”

This last is really just a residual; we don’t know what’s going on within the model. In The Nurture Assumption Judith Rich Harris posited that much of the remaining environmental component was peer effects. But there are ...

September 12, 2012

An evil disposition

Filed under: Behavior Genetics — Razib Khan @ 1:14 am

The thread below on the possibility of pedophilia being a biologically mediated tendency rapidly degenerated, to no one’s surprise. As I didn’t have the time to engage in strict moderation I had to close it. And I don’t want to reopen that particular topic. Rather, I want to focus on the issue of psychopathy exhibiting some genetic disposition.

I want to assert immediately that I’m not positing that you’re born a psychopath like you’re born with red hair. Rather, psychopathy is a set of traits whose upstream causes can be both genetic and non-genetic. In fact some cases of psychopathic behavior seems to be rooted in extreme social and psychological deprivation (e.g., orphanages in underdeveloped countries). Interestingly, this may be a case where the environmental input reshapes the developing brain, so that even though the individual may lack a genetic predisposition toward a particular psychology, they may now be biological oriented toward all the traits associated with psychopathy because of the nature of their neurological development.

Going to the model where some people exhibit a genetic disposition toward psychopathy, there are two dichotomous models I’d like to outline. First, there is a model where psychopathy is a deviation from the ...

September 9, 2012

Pedophiles: born that way?

Filed under: Anthroplogy,Behavior Genetics,Neurobiology,Neuroscience — Razib Khan @ 10:31 pm

Gawker published a piece on the neurological problems which might result in pedophilia, and naturally a lot of shock and disgust was triggered. The piece is titled Born This Way: Sympathy and Science for Those Who Want to Have Sex with Children. This isn’t something you want to click through to lightly. So fair warning. The neurobiological material did pique my interest:

“There was nothing significant in the frontal lobes or temporal lobes,” says Cantor. “It turned out the differences weren’t in the grey matter. The differences were in the white matter.”

“The white matter” is the shorthand term for groupings of myelinated axons and glial cells that transmit signals throughout the gray matter that composes the cerebrum. Think of the gray matter like the houses on a specific electricity grid and the white matter like the cabling connecting those houses to the grid.

“There doesn’t seem to be a pedophilia center in the brain,” says Cantor. “Instead, there’s either not enough of this cabling, not the correct kind of cabling, or it’s wiring the wrong areas together, so instead of the brain evoking protective or parental instincts when these people see children, it’s instead evoking sexual instincts. There’s almost literally ...

August 28, 2012

A political animal in the genes

Filed under: Behavior Genetics — Razib Khan @ 8:49 pm

Trends in Genetics has a review article, The genetics of politics: discovery, challenges, and progress. The main reason I point to these sorts of papers isn’t that I think they’re revolutionary. Usually they aren’t. Rather, the public domain has totally forgotten about this domain of study. Most of the informed and high-toned discussion presumes that almost everything of worthy note is socially constructed. If not, then the counterpoint is a crude caricature of genetic determinism which is refutable in a blink of the eye. It’s as if someone was commissioned to paint R. Daneel Olivaw, and ended up using crayon to sketch out the Frankenstein monster.

For example, in sex differences the public debate veers between evolutionary psychological Leave It To Beaver, pre-scientific cultural traditionalism, and de facto Blank Slatism. On the one hand you have to deal with people who use “scare quotes” around the “highly speculative” “hypothesis” that males have a greater tendency toward inter-personal physical aggression than females (including in the comments of this blog, so spare with lectures about how this is a marginal perspective; I’m pretty sure I talk to people about behavior genetics a lot more than you do, though if not I’d ...

August 26, 2012

The heritability of impulse control

Filed under: Behavior Genetics — Razib Khan @ 8:35 pm

The above figure is from a paper I stumbled upon, Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies:

A meta-analysis of twin, family and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on impulsivity. The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity. Age, sex, and study design (twin vs. adoption) were all significant moderators of the magnitude of genetic and environmental influences on impulsivity. The relative contribution of genetic effects (broad sense heritability) and unique environmental effects were also found to be important throughout development from childhood to adulthood. Total genetic effects were found to be important for all ages, but appeared to be strongest in children. Analyses also demonstrated that genetic effects appeared to be stronger in males than in females. Method of assessment (laboratory tasks vs. questionnaires), however, was not a ...

The heritability of impulse control

Filed under: Behavior Genetics — Razib Khan @ 8:35 pm

The above figure is from a paper I stumbled upon, Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies:

A meta-analysis of twin, family and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on impulsivity. The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity. Age, sex, and study design (twin vs. adoption) were all significant moderators of the magnitude of genetic and environmental influences on impulsivity. The relative contribution of genetic effects (broad sense heritability) and unique environmental effects were also found to be important throughout development from childhood to adulthood. Total genetic effects were found to be important for all ages, but appeared to be strongest in children. Analyses also demonstrated that genetic effects appeared to be stronger in males than in females. Method of assessment (laboratory tasks vs. questionnaires), however, was not a ...

August 3, 2012

The poverty of inheritance

Filed under: Behavior Genetics — Razib Khan @ 8:02 am

Virginia Hughes has an important post up at The Last Word on Nothing, What Americans Don’t Get About the Brain’s Critical Period. In it she reiterates just how stupid the “Baby Einstein” culture is. The post is important to me specifically because I have a baby who I would like nudge in the direction of Einstein, but not by spending money on toys which exist mostly to salve the vanity and conscience of adults around her. With all that said, Hughes emphasizes that the key is to focus on children at the other end of the environment spectrum from my awesome one.

So I was prompted by her post to check out the links, as I’ve not explored this literature in a while. First, Variation in neural development as a result of exposure to institutionalization early in childhood compares Romanian orphans who were kept in that nation’s notoriously atrocious orphanages and those who were fostered. The authors assert that the placements of the latter were randomized, and the neurological differences were significant. I doubt this is that surprising ...

July 25, 2012

A horrible “natural experiment”

Filed under: Behavior Genetics — Razib Khan @ 1:13 am

Spanish Baby-Snatching Victims Seek Answers and Justice:

Most of these stolen children were entrusted to the care of Catholics loyal to the regime. The aim behind this was to rid an entire people of the “Marxist gene,” at least according to the theories of Antonio Vallejo-Nájera, the national psychiatrist of Francoist Spain, that were widespread at the time.

More accurately it should be Marxist meme. But it brings up the question of looking into the correlation between the traits of biological parents and their long-lost children.

Via Dispatches From Turtle Island.

July 15, 2012

Society seen through genes

Filed under: Behavior Genetics,Genetics — Razib Khan @ 1:39 pm

Over the past few months more and more articles like this one in the The New York Times are coming out, Two Classes, Divided by ‘I Do’:

Jessica Schairer has so much in common with her boss, Chris Faulkner, that a visitor to the day care center they run might get them confused.

They are both friendly white women from modest Midwestern backgrounds who left for college with conventional hopes of marriage, motherhood and career. They both have children in elementary school. They pass their days in similar ways: juggling toddlers, coaching teachers and swapping small secrets that mark them as friends. They even got tattoos together. Though Ms. Faulkner, as the boss, earns more money, the difference is a gap, not a chasm.

But a friendship that evokes parity by day becomes a study of inequality at night and a testament to the way family structure deepens class divides. Ms. Faulkner is married and living on two paychecks, while Ms. Schairer is raising her children by herself. That gives the Faulkner family a profound advantage in income and nurturing time, and makes their children statistically more likely to finish college, find good jobs and form stable marriages.

The story is set up ...

June 27, 2012

Heritability of behavioral traits

Filed under: Behavior Genetics — Razib Khan @ 11:48 pm

As a father the content of my conversations with friends and acquaintances has changed somewhat. Whereas in my offline life discussions of behavior genetics rarely came up, now they loom large implicitly and explicitly. Though the vast majority of people I interact with have graduate degrees or are pursuing graduate degrees in the life sciences almost none of them are aware of the magnitude of the heritability of most bio-behavioral traits.

For those of you who forgot, heritability is a population wide statistic which assesses the proportion of variation in the population you can attribute to heritable genetic variation. So if heritability is 1.0 all of the variation is due genetic variation; offspring are just a linear combination of their parents. If heritability is ~0.0, then there’s basically no correlation between parents and offspring. Though, as I said, heritability is a population-wide statistic, it can be informative on an individual level. For example, the heritabiilty of height is ~0.90 in the Western world. To give you a sense of the expected height of the offspring of two individuals, just take the average (in sex-controlled standard deviation units) and shift it back toward the mean by 10%. There is going to be ...

Heritability of behavioral traits

Filed under: Behavior Genetics — Razib Khan @ 11:48 pm

As a father the content of my conversations with friends and acquaintances has changed somewhat. Whereas in my offline life discussions of behavior genetics rarely came up, now they loom large implicitly and explicitly. Though the vast majority of people I interact with have graduate degrees or are pursuing graduate degrees in the life sciences almost none of them are aware of the magnitude of the heritability of most bio-behavioral traits.

For those of you who forgot, heritability is a population wide statistic which assesses the proportion of variation in the population you can attribute to heritable genetic variation. So if heritability is 1.0 all of the variation is due genetic variation; offspring are just a linear combination of their parents. If heritability is ~0.0, then there’s basically no correlation between parents and offspring. Though, as I said, heritability is a population-wide statistic, it can be informative on an individual level. For example, the heritabiilty of height is ~0.90 in the Western world. To give you a sense of the expected height of the offspring of two individuals, just take the average (in sex-controlled standard deviation units) and shift it back toward the mean by 10%. There is going to be ...

June 26, 2012

Genes can be criminogenic

Filed under: Behavior Genetics — Razib Khan @ 10:40 pm

As a follow-up to my post below, I just wanted to check some recent literature on crime and heritability. I found this, Heritability, Assortative Mating and Gender Differences in Violent Crime: Results from a Total Population Sample Using Twin, Adoption, and Sibling Models:

Research addressing genetic and environmental determinants to antisocial behaviour suggests substantial variability across studies. Likewise, evidence for etiologic gender differences is mixed, and estimates might be biased due to assortative mating. We used longitudinal Swedish total population registers to estimate the heritability of objectively measured violent offending (convictions) in classic twin (N = 36,877 pairs), adoptee-parent (N = 5,068 pairs), adoptee-sibling (N = 10,610 pairs), and sibling designs (N = 1,521,066 pairs). Type and degree of assortative mating were calculated from comparisons between spouses of siblings and half-siblings, and across consecutive spouses. Heritability estimates for the liability of violent offending agreed with previously reported heritability for self-reported antisocial behaviour. While the sibling model yielded estimates similar to the twin model (A ≈ 55%, C ≈ 13%), adoptee-models appeared to underestimate familial effects (A ≈ 20–30%, C ≈ 0%). Assortative mating was moderate to strong (r spouse = 0.4), appeared to result from both phenotypic assortment and ...

June 25, 2012

Why marriage & fatherhood might not matter as much as you think

Filed under: Behavior Genetics,blank slate,Conservatism — Razib Khan @ 11:11 pm

While I was on blogging hiatus single motherhood and the whole Dan Quayle flap came back into the news. Here’s Mitt Romney:

The American culture promotes personal responsibility, the dignity of work, the value of education, the merit of service, devotion to a purpose greater than self, and, at the foundation, the pre-eminence of the family.

The power of these values is evidenced by a Brookings Institution study that Senator Rick Santorum brought to my attention. For those who graduate from high school, get a full-time job, and marry before they have their first child, the probability that they will be poor is 2%. But, if those things are absent, 76% will be poor. Culture matters.

I’ve been ragging on the cultural Left on this weblog recently because of the delusions that those of this bent simply won’t let go of in the quest for utopian egalitarianism. But one aspect of the American cultural and political scene is that Left and Right often operate with similar presuppositions, only weighting the emphasis differently. While the cultural Left puts the focus on nearly infinite possibilities of individual self-actualization, the cultural Right has backed itself into a corner of individual moral perfectionism which borders ...

May 17, 2012

What if you are more likely to be a psychopath?

Filed under: Behavior Genetics — Razib Khan @ 11:47 pm

In the comments below Nathaniel Comfort asks:

What I do, as a historian, is take something apparently simple and make it more complicated. I wonder about how your curves, e.g., would be applied in real life. *Specific* couples, *particular* children–individuals, cases, persons, context.

I’m asking things like:

-What would your hypothetical psychopathic lovebirds do with that information?

Comfort is referring to this figure I generated, which shows the potential distribution of outcomes for two individuals who tend toward more psychopathy than the general population. It seems to me that this question is easily answered if simply replace “psychopathy” with “odds for heart disease.” Endophenotypes aren’t magical, they’re just sometimes hard to characterize. But once you get a good grip on them you can make standard quantitative genetic predictions. One of the points I wasn’t clear about in the chart is that I assume that the “trait” being measured is the tendency toward psychopathy as measured by a paper & pencil test in one’s youth. This does not entail that an individual in fact behaves like a psychopath. Rather, it simply implies that they’re odds of behaving like a psychopath as an adult ...

May 15, 2012

Genes are overrated, genetics is underrated

Filed under: Behavior Genetics — Razib Khan @ 11:53 pm

A few days ago Nathaniel Comfort pointed me to this post, Genetic determinism round-up. If you are curious go read Comfort’s whole post. I honestly didn’t enjoy it very much, I think I got what he was saying, but there were all sorts of circumlocutions around the overall message. But I agree one one thing in particular: an emphasis on concrete and specific genes for traits is a motif in science journalism that can be very frustrating, and often misleading. Nevertheless, that’s not the only story. I believe our current culture greatly underestimates the power of genetics in shaping broader social patterns.

How can these be reconciled? Do not genes and genetics go together? The resolution is a simple one: when you speak of 1,000 genes, you speak of no genes. You can’t list 1,000 genes in prose, even if you know them. But using standard quantitative and behavior genetic means one can apportion variation in the population of a trait to variation in genes. 1,000 genes added together can be of great effect. The newest findings in genomics are reinforcing assertions of non-trivial heritability of many complex traits, though rendering problematic attributing that heritability to a specific set ...

May 9, 2012

The bell curve of personality?

Filed under: Behavior Genetics — Razib Khan @ 10:27 pm

I stopped reading much in the area of personality and behavior genetics a few years back. The main reason is I had a really hard time believing there were very good quantitative measures of many of the traits. A secondary issue, though probably nearly as important, is that some friends were making it clear that they strongly suspected that a lot of the studies in the area of behavior genomics were “underpowered” in a statistical sense. These two issues gnawed at me to the point where I pretty much threw my hands up in the air. Mind you, I accept that personality is substantially heritable. But just because something is heritable does not mean that it is obvious that you’ll be able to detect “the gene” implicated in the variation of the trait. I accepted decades of findings in behavior genetics. But it didn’t seem like we were going anywhere beyond it.

Now a new paper out in PNAS uses genomics to shed light on this issue in the same manner as with intelligence or height. The paper is The genetic architecture of economic and political preferences, ...

April 11, 2012

Genes: still a pretty big deal

Filed under: Behavior Genetics,Nature vs. Nurture — Razib Khan @ 12:24 am

Many people say that having children gives you a much better sense of the power of genes in shaping behavior. At least in the abstract sense that is not true in my case. I accept the “conventional wisdom” from behavior genetics that “shared environment” (colloquially, parental input) is relatively marginal in effecting much long term change within reason (i.e., if you don’t beat your kid over the head with a baseball bat and such you don’t have much influence).

To review, on many bio-behavioral traits the different choices parents make seem to account for on the order of ~10 percent of the differences you see in the world out there amongst their (biological) offspring. Of the remainder of the variation about half of it is attributable to variation in genes, and the other half to unaccounted for non-shared environment. In The Nurture Assumption Judith Rich Harris proposes that that last effect can be reduced down to social environment or peer groups. Her line of argument is such that parents are important because of the genes they contribute, and, the environmental milieus which they select for their offspring.

On one level I ...

Older Posts »

Powered by WordPress