Tag: Behavior Genetics

Sample size, schample size

By Razib Khan | November 15, 2011 4:15 pm

Ed Yong has a post up on a behavior genetic publication where the sample size is 23. The researchers report a correlation between a SNP on the OXTR locus and “prosociality.” To make a long story short the sample size suggested to Dr. Daniel MacArthur and Dr. Jospeh Pickrell that this was a spurious correlation. The bigger issue here is that there are functional reasons to assume that some genes are correlated with normal human variation in psychology and behavior, and a robust body of literature that these traits are heritable (trait value is highly predictive across relatives), but, the results associating a particular genetic marker with a given trait are much less robust.

But I immediately realized something interesting: a sample size of 23 may be small, but there is a sample size potentially of thousands! I know my genotype at this SNP from 23andMe. How about some 23andMe customers get together and produce some results, and then get published in PNAS? A sample size of 230 would be easy I think, and you could probably push it much closer to 1,000.

CATEGORIZED UNDER: Behavior Genetics
MORE ABOUT: Behavior Genetics

Twin studies are not useless

By Razib Khan | August 24, 2011 5:20 pm

A few friends have pinged me on this piece in Slate, Double Inanity: Twin studies are pretty much useless. The headline is bold, but the piece is just a sloppy mishmash. It’s really something amenable for a major “fisking,” but I generally don’t like doing that sort of thing, because it doesn’t seem a optimal allocation of time (though I have to note that the author seems to be implicitly using a colloquial form of the concept of heritability, which I think is going to confuse an already naive audience). A lot of the article is taken up with criticisms of political scientist John Alford’s behavior genetic findings on the heritability of ideology. I’ve had personal communication with other researchers in this area who actually are broadly critical of Alford’s methodology, but they’re still strongly invested in using genomics and behavior genetics to explore this issue. In other words, rejecting Alford’s conclusions does not entail that you just reject twin studies, as such.

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The end of environmental inequality means the rise of genetic inequality

By Razib Khan | August 15, 2011 11:36 pm

A few people have pointed me to Charles Murray’s comment at The Enterprise Blog, The Debate about Heritability of General Intelligence Radically Narrows, which alludes to the recent finding of genomic confirmation of the behavior genetic heritability measure for intelligence. Murray indicates that this should end the “debate” on the heritability of intelligence as a quantitative trait. As I implied earlier much of this debate had more to do with rhetoric and ideology than reality, in that I doubt many people support a very low heritability measure for intelligence ( < ~0.30) in developed societies when they don’t have strong ideological commitments. These commitments being that social policy can homogenize environments enough that only the genetic components of variation of a trait value will be important in the future, so that heritability values will go from ~0 to ~1.0.

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Half the variation in I.Q. due to variation in genes

By Razib Khan | August 10, 2011 11:38 pm

A new paper in Molecular Psychiatry has been reported on extensively in the media, and readers have mentioned it several times in the comments. I read it. It’s titled Genome-wide association studies establish that human intelligence is highly heritable and polygenic. But the fact is that I read this paper last year. Back then it was titled Common SNPs explain a large proportion of the heritability for human height. I kid, but you get the picture. The new paper establishes for intelligence what we already suspected: most of the genetic variation in this heritable trait is accounted for by numerous genes of small effect. You inherit variants of these numerous genes from your two parents, and your own trait value is to a large extent a combination of the parental values. The issue is not if intelligence is heritable, but the extent of that heritability.

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Blank slate when you want it that way

By Razib Khan | July 11, 2011 11:44 am

Tim Pawlenty debates Lady Gaga’s ‘Born This Way’ idea:

Gregory pressed, asking “Is being gay a choice?”

Pawlenty ultimately said, “I defer to the scientists in that regard.”

Again, Gregory pressed: “So you, you think it’s not a choice. … That you are, as Lady Gaga says, you’re born that way.”

Said Pawlenty: “There’s no scientific conclusion that it’s genetic. We don’t know that. So we don’t know to what extent, you know, it’s behavioral, and that’s something that’s been debated by scientists for a long time. But as I understand the science, there’s no current conclusion that it’s genetic.”

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Does heritability of political orientation matter?

By Razib Khan | June 17, 2011 2:40 am

At The Intersection Chris Mooney points to new research which reiterates that 1) political ideology exhibits some heritability, 2) and, there are associations between political ideology and specific genes. I’ll set #2 aside for now, because this is a classic “more research needed” area at this point. But as I mentioned in the comments the heritability of political ideology is well known and robust. From what I can gather most people assume it’s mediated through personality traits. In the comments Chris asks:

That sounds sensible. What i find amazing is that if the heritability of politics is so robust–and I agree, it would happen via personality–why is this so widely ignored?

There are I think several issues at work. First, many people are not comfortable within imagining that beliefs which they attribute to their conscious rational choice are not only subject to social inculcation, but that may also have an element of genetic disposition. Second, most people have a poor grasp of what heritability implies. Take a look at some of Chris’ commenters. The response is generally in the “not even wrong” class. Finally, what’s the actionable component to this? In other words, what are people going to do with this sort of information?

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CATEGORIZED UNDER: Behavior Genetics, Politics

Parents don't matter that much

By Razib Khan | June 16, 2011 1:53 pm

Update: Stephen Dubner emailed me, and pointed me to this much longer segment which has a lot of Bryan Caplan. So it seems like the omission that I perceived was more of an issue with the production and editing process and constraints of the Marketplace segment than anything else.

End Update

I play a lot of podcasts during the day as I go about my business on my iPod shuffle. One of them is Marketplace, which has a regular Freakonomics Radio segment, where Stephen Dubner “freaks” you out with incredible facts and analysis, often with a helping hand from Steven Levitt. With all due respect to Dubner and Levitt, this still has very pre-Lehman feel. Economics has “solved” the workings of the explicit market, so why not move on to other areas which are ripe for conquest by the “logic of life?”

In any case this week’s episode kind of ticked me off just a little. It started off with the observation that college educated women apparently put 22 hours weekly into childcare today, vs. 13 hours in the 1980s. I guess fewer latchkey kids and more “helicopter parents?” Dubner basically indicates that the reasoning behind this is many parents are in a “red queen” arms race to polish the c.v.’s of their children for selective universities. This makes qualitative sense, but can we explain an increase of 9 hours on average for the ~25% of women who are college educated on striving to make sure that their kids have Wesleyan as the safety school?

Let’s put our quantitative “thinking-caps” on “freakonomics” style. ~25% of adults have university degrees. ~80% of these have public university degrees, which are usually not too selective. Some of the ~20% are from not particularly elite religious colleges. So the subset of Americans who graduated from elite universities is actually not too large a number. You can include these as natural aspirants for the best spots for their children. And a proportion of the large remainder, I’d estimate ~90%, who didn’t go to a university which required a great deal of stress and c.v. polishing would certainly strive and hope for better for their kids. But can this explain a 9 hour average rise among tens of millions of women? Doesn’t seem to pass the smell test for me. I suspect there’s a more general norm of shifting toward “high investment parenting” among the college educated cohorts.

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CATEGORIZED UNDER: Behavior Genetics

Genetics existed before -omics

By Razib Khan | June 9, 2011 2:20 am

In the post below, Moderate marginal value to genomics, I left some things implicit. It turns out that this was an ill-considered decision. In reality my comments were simply more cryptic and opaque than implicit. This is pretty obvious because even those readers who are biologists didn’t seem to catch what I had assumed would be obvious in the thrust of my argument.

The point in the broadest sense is that DNA and genomics are not magical. Genetics existed before either of them. Understanding the physical basis of genetics has certainly been incredibly fruitful, and genomics has altered the playing field in many ways. But there was a broad understanding of genetics before DNA and genomics, both in a Mendelian sense and in the area of biometrics and quantitative genetics. In the earlier post I indicated that the tools for predictions of adult traits due to the effect of genes have been around for a long time: our family history. By this, I mean that a lot of traits of interest are substantially heritable. A great deal of the variation within the population can be explained by variation of genes in the population, as inferred by patterns of correlation between individuals in their traits as a function of genetic relatedness. This is genetics as a branch of applied statistics. It has great “quick & dirty” power, especially in agricultural science.

Let’s look at something simple, height. It’s a continuous trait which is rather concrete. No one argues that “height” is a social construct. In Western societies height is ~80-90% heritable. That means that most of the variation within the population of the trait can be explained by variation in one’s family background. Tall people have tall children, short people have short children, and so forth. Here’s a “toy” scatterplot which shows the relation between mid-parent heights and adult offspring heights (I made up the numbers):

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Moderate marginal value to genomics

By Razib Khan | June 8, 2011 3:10 am

In the comments below when it comes to genomic privacy I expressed a rather carefree attitude toward the future possibilities of dark prediction. Over at FARK.com the comments were rather uniformly alarmed, and influenced by Gattaca. For example: “It’s really kind of shocking how accurate Gattaca is turning out to be.”

Unfortunately I haven’t watched Gattaca. I read a negative a review when the film came out, and since I don’t watch many movies in any case I passed. This I’ve come to regret because of the influence of the film, whether it was great as a work of art or not, is strong enough today to routinely be referenced. It seems to have pretty good reviews on Rotten Tomatoes, and it’s got some staying power on Google Trends. I keep meaning to watch it on Amazon Instant Video, but then there’s the opportunity cost of time. So I did the second best thing, I read the plot summary on Wikipedia.

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CATEGORIZED UNDER: Behavior Genetics, Genetics, Genomics

How the "fierce people" came to be

By Razib Khan | May 6, 2011 2:12 pm

The pith: there are differences between populations on genes which result in “novelty seeking.” These differences can be traced to migration out of Africa, and can’t be explained as an artifact of random genetic drift.

I’m not going to lie, when I first saw the headline “Out of Africa migration selected novelty-seeking genes”, I was a little worried. My immediate assumption was that a new paper on correlations between dopamine receptor genes, behavior genetics, and geographical variation had some out. I was right! But my worry was motivated by the fact that this would just be another in a long line of research which pushed the same result without adding anything new to the body of evidence. Let me be clear: there are decades of very robust evidence that much of the variation in human behavior we see around us is heritable. That the variation in our psychological dispositions, from intelligence to schizophrenia, is substantially explained by who our biological parents are. This is clear when you look at adoption studies which show a strong concordance between biological parents and biological children on many metrics as adults, as opposed to the parents who raised the children. This doesn’t mean that environment doesn’t matter, but I believe we tend to underweight genetics in individual outcomes in our contemporary Zeitgeist, just as we may have overweighted it in the past.

At this point some of you may be wondering, “what, I hear about genes for [fill in the blank] constantly!” So why am I saying we underweight genetics? I think there’s a disjunction between the fixation that the public (and therefore the popular press) has on a specific biophysical candidate gene which is given almost magical powers of causal necessity and the more abstract and diffuse statistical genetic reality of correlations between parents and offspring whose effects seem to be distributed diffusely across the genome. The latter is a robust and ubiquitous phenomenon, but because it is not possible to frame the narrative as a “gene for X” it lacks power. In contrast, when you have a powerful gene of large effect whose variation in state has a concrete and comprehensible outcome the narrative is clear, precise, and distinct. There’s an unfortunate problem with this though: quite often the narrative is wrong because it is not robust. It won’t be replicated and stand the test of time.

ResearchBlogging.orgThe example of the “language gene,” FOXP2, is illustrative of the issues I’m pointing to in the most broad of terms. As a matter of fact FOXP2 is a much better candidate for being the “language gene” than is usually the case for the gene for X, but ultimately it is probably not alway useful to term FOXP2 the language gene when the faculty for speech is such a complex trait subject to many biological pathways. The putative “God gene” was a much worse case of a gene for X, and probably a good example of the problem I’m talking about. There’s a pretty robust body of evidence that religiosity has a heritable component, but there isn’t much evidence for a gene for belief in God.

What does all this have to do with dopamine receptors and novelty? The DRD4 locus has been implicated in a lot of behavior genetic variation, and dopamine receptor genes are often pointed to as “master controllers” of a sort for various aspects of personality and life outcomes. Dopamine as a neurochemical has myriad functions, so variation in its production controlled by genetics is a natural candidate of interest for researchers. The problem is that the nature of this sort of statistical and sexy science is that there’s going to be a natural gravitation toward significant results which later turn out to be false positives. Before moving on, I do want to reiterate that as a gene for X the dopamine receptor loci are much better set of candidates than the “God gene,” but here the devil is in the details.

Let’s see what the argument in the paper which triggered The New Scientist piece is. Novelty-seeking DRD4 polymorphisms are associated with human migration distance out-of-Africa after controlling for neutral population gene structure:

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Love and arranged marriage

By Razib Khan | April 29, 2011 12:46 am

In the wake of yesterday’s review of a paper on heritable variance in trait preferences realized in romantic partners I couldn’t help but be intrigued by this new study out of PLoS ONE, Evolutionary History of Hunter-Gatherer Marriage Practices. It’s actually a pretty thin piece of work in all honesty from what I can tell. They wanted to query ancestral ranges of marriage patterns by mapping the cultural variation in customs onto a phylogenetic tree. To generate that tree they took mtDNA sequences, which to me seems kind of old school. Using the cultural patterns present in living hunter-gatherer groups they presumed they could infer the ancestral state.

So combining these two sources of data they generated this:

They conclude:

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CATEGORIZED UNDER: Behavior Genetics, Evolution

It's about heritability….

By Razib Khan | March 27, 2011 2:25 pm

I’m going to promote a comment:

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CATEGORIZED UNDER: Behavior Genetics, Genetics, Genomics

Friends & genes & heritability

By Razib Khan | January 19, 2011 2:56 pm

A few people have inquired of the PNAS paper On sharing genes with friends. I avoided comment in part because I’m skeptical of the findings. So much behavior genomics just hasn’t panned out over the long term, and is probably susceptible to the issues which fuel the “decline effect”. Statistical significance is a random variable too. The fundamental issue which I want to emphasize is this: many behavioral traits are highly heritable, insofar as the correlation between relatives of trait value is in direct proportion to their genetic correlation. But, just because a trait is heritable does not mean that you can affix the variation to a specific set of genes. That is because the character of genetic architecture varies, and it may be that for many behavioral traits with some biological basis the causal variants which are responsible for the range in trait values are distributed across thousands of genes, and so are of very small effect.

Carl Zimmer relayed the depth of skepticism in the scientific community yesterday, and today Dr. Daniel MacArthur reviewed the paper. Here are the top line reactions:

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CATEGORIZED UNDER: Behavior Genetics, Genetics, Genomics

When genes matter for intelligence

By Razib Khan | January 12, 2011 3:01 am

Image credit: Aleksandra Pospiech

One of the interesting and robust nuggets from behavior genetics is that heritability of psychological traits increases as one ages. Imagine for example you have a cohort of individuals you follow over their lives. At the age of 1 the heritability of I.Q. may be ~20%. This means that ~20% of the variation in the population of I.Q. explained by variation in the genes of the population. More concretely, you would only expect a weak parent-offspring correlation in I.Q. in this sample. At the age of 10 the heritability of I.Q. in the same sample may be ~40%, and in mature adulthood it may rise to ~80% (those are real numbers which I’ve borrowed from Robert Plomin). Many people find this result rather counterintuitive. How can a trait like intelligence become “more genetic”?

Remember that I’m talking about heritability here, not an ineffable “more” or “less” quantum of “genetic” aspect of a trait. In other words: does variation in genes due to different parental backgrounds matter for a trait? Second, the nature of psychological traits is somewhat slippery and plastic. As I’ve noted before the correlation between a score on a 10-world vocabulary test and general intelligence is pretty good. You can expect people with high scores on the vocabulary test to have higher I.Q.’s than those who have low scores. But if you take an individual and lock them in a room without human contact for their first 15 years, they are unlikely to exhibit any such correspondence. You don’t have to be a rocket scientist to understand why. Quantitative behavior genetic traits are complex and are subject to a host of background conditions, and express themselves in an environmental context.

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On the "liberal gene"

By Razib Khan | October 31, 2010 2:54 pm

Jim Manzi has already posted on the warranted skepticism of DRD4 being reported in the press as the “liberal gene.” Here’s the original paper. The main issue I have is not with the original research, but the inevitable confusions in the media which always arise. First, we know that complex behavioral phenotypes such as religiosity and personality seem to be heritable. That is, a set of genetic variants within the population seems to track the variation in the trait (just as with I.Q.). But, it’s been a much longer haul to actually connect a specific genetic locus to said variation, though the dopamine related genes are always brought forward as candidates. Additionally, particularly when it comes to politics there’s the norm of reaction looming. One might grant that same genetic variation which predisposes Swedes in Sweden to being on the Left or the Right is operative among ethnic Swedes in Minnesota, but most of the difference is actually between population, and a function of the differing environmental milieus of the Upper Midwest and Scandinavia (though perhaps there were strong selection effects operating upon those who chose to leave Scandinavia for the USA). Finally, as with personality, there’s the problem of characterizing the phenotype in the first place in political orientation. Not insoluble in my opinion, but far less clear than something like height, or even intelligence.

The big picture is that variation on most complex behavioral traits has some upstream genetic correlates. And, we can get some sense of the magnitude (or lack thereof) of the effect in a given environment. But like fMRI the introduction of DNA probably adds more glitz than substance at this point. We’ve long known many traits which we think as purely reflective and environmental have a partial biological basis in disposition. Clearly an area to be continued….

CATEGORIZED UNDER: Behavior Genetics, Genetics
MORE ABOUT: Behavior Genetics

American family values: where even the dull can dream!

By Razib Khan | September 27, 2010 5:03 pm

ResearchBlogging.orgOne of the issues when talking about the effect of environment and genes on behavioral and social outcomes is that the entanglements are so complicated. People of various political and ideological commitments tend to see the complications as problems for the other side, and yet are often supremely confident of the likely efficacy of their predictions based on models which they shouldn’t even been too sure of. That is why cross-cultural studies are essential. Just as psychology has overly relied on the WEIRD nature of data sets, so it is that those interested in social science need to see if their models are robust across cultures (I’m looking at you economists!).

That is why this ScienceDaily headline, Family, Culture Affect Whether Intelligence Leads to Education, grabbed my attention. The original paper is Family Background Buys an Education in Minnesota but Not in Sweden:

Educational attainment, the highest degree or level of schooling obtained, is associated with important life outcomes, at both the individual level and the group level. Because of this, and because education is expensive, the allocation of education across society is an important social issue. A dynamic quantitative environmental-genetic model can help document the effects of social allocation patterns. We used this model to compare the moderating effect of general intelligence on the environmental and genetic factors that influence educational attainment in Sweden and the U.S. state of Minnesota. Patterns of genetic influence on educational outcomes were similar in these two regions, but patterns of shared environmental influence differed markedly. In Sweden, shared environmental influence on educational attainment was particularly important for people of high intelligence, whereas in Minnesota, shared environmental influences on educational attainment were particularly important for people of low intelligence. This difference may be the result of differing access to education: state-supported access (on the basis of ability) to a uniform higher-education system in Sweden versus family-supported access to a more diverse higher-education system in the United States.

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CATEGORIZED UNDER: Cognitive Science, Culture, Psychology

By our genes, though not alone

By Razib Khan | September 14, 2010 11:31 am

David Dobbs over at his new digs has a massive post on the relationship between behavior genetics, genomics, neuroscience, environment, and culture. It’s titled The depression map: genes, culture, serotonin, and a side of pathogens, and he concludes:

In a sense, these studies are looking not at gene-x-environment interactions, or GxE, but at genes x (immediate) environment x culture — GxExC. The third variable can make all the difference. Gene-by-environment studies over the last 20 years have contributed enormously to our understanding of mood and behavior. Without them we would not have studies, like these led by Chiao and Way and Kim, that suggest broader and deeper dimensions to what makes us struggle, thrive, or just act differently in different situations. GxE is clearly important. But when we leave out variations in culture, we risk profoundly misunderstanding how these genes — and the people who carry them — actually operate in the big wide world.

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CATEGORIZED UNDER: Behavior Genetics

Heritability, personality, and genomics

By Razib Khan | August 9, 2010 1:20 am

This post by Neurocritic, Bad News for the Genetics of Personality, is going to get a lot of play. The boy-king of the cognitive neuroscience blogosphere has already smiled upon it, and extended the analysis a bit. The short of it is that one needs to be very skeptical of the idea large effect QTLs in personality genetics. In the post the Neurocritic reviews a paper, A genome-wide association study of Cloninger’s Temperament scales: Implications for the evolutionary genetics of personality, which performed a genome-wide association, and found basically nothing despite a large sample size. I’m not that surprised as genomicists I know have expressed lots of skepticism of previous work in this area. The implication here is that personality may be like height or I.Q., having a genetic component, but not one whose genetic architecture is easy to elucidate with current methods.

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CATEGORIZED UNDER: Culture, Psychology
MORE ABOUT: Behavior Genetics

Investing in a nanny state for social returns

By Razib Khan | July 28, 2010 10:13 am

Jonah Lehrer has a post up, How Preschool Changes the Brain over at Frontal Cortex. He reports on a paper, Investing in our young people, which has been around for about 5 years. The top line of it is this, an investment in a $2,500/year (inflation adjusted) pre-school program in the early 1960s seems to have been effective in improving the life outcomes of at-risk low SES young black Americans tracked over their lives up to the age of 40. Their measured I.Q.s were not initially high, 85-75, 15th to the 5th percentile (though the median black American IQ is ~85, so not so low within ethnic group). They did gain an initial I.Q. boost, but like most of these programs that boost disappeared over time. But in terms of their non-cognitive skills there remained an appreciable effect which impact their life outcomes. What were these non-cognitive skills? To me they resemble classical bourgeois values rooted in low time preference. Willing to be a “grind,” work hard and forgo short-term pleasures and not cave in to impulses with short-term gains and long-term costs.

Here’s a figure from the paper which I’ve reedited with labels:

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CATEGORIZED UNDER: Behavior Genetics

Saving is heritable, but culture matters a lot

By Razib Khan | July 26, 2010 10:58 am

The nature and character of your financial decisions is shaped by your genes. That shouldn’t be too horrible. Many decisions are the outcome of a combination of heritable and non-heritable predispositions. But I have to honestly express a bit of alarm at this segment I just heard on Marketplace, There’s only so much you can teach your kids. Here’s the subhead:

For better or for worse, kids take after their parents — but studies show parental influence only goes so far when it comes to how your children will handle money.

I’m not one to be worried about “genetic determinism” (usually just an insult which describes very few scholars), but this is a bit ridiculous. First, the primary research, of which you can find a pre-print online, seems to indicate that around ~30% of the outcome of financial decisions are heritable. That is, that ~30% of the variation in financial decisions within the population can be accounted for by variation in genes within the population. Additionally, there’s some context missing. The researcher expresses surprise that monozygotic twins converge in behavior as they age, and that parental influence tends to wear off as people leave the home. I don’t know if the researcher was taken out of context, but this is a totally unsurprising result. Over time shared home environment, what your parents model and teach you, tends to wear off, and gene-environment correlation increases the correspondences between particular genetic makeups and behaviors (i.e., identical twins resemble each other more at maturity than in their youth). For most behavioral traits heritability increases with age.

But the problem that microeconomic analyses like this create is that they confuse the public as to the relevance of charts such as this:

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CATEGORIZED UNDER: Behavior Genetics

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