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.


Both the Neurocritic and the boy-king raise the issue of whether personality tests really measure anything. I have asked psychologists about this particular point before. Something like the Big Five personality traits are fun, but often strike me as parlor games. I haven’t gotten a very clear answer on the validity of these personality tests, though I probably haven’t asked anyone whose bread & butter was this particular area. The high heritability of personality traits suggests to me that the tests are measuring something consistently; if the results were random one wouldn’t see correlations within the family. I mooted my concerns and Jason Goldman pointed out that the tests may be consistent in measuring something, but may not measure what they purport to measure. The boy-king quotes a psychologist who attempts to reconceptualize how personality plays out:

This led Mischel to construct a new metaphor for human personality. While modern psychology still clung to a model of personality rooted in the humors of the ancient Greeks – we were born with a certain amount of choleric temperament and that was it – Mischel proposed a model of personality called interactionism. One of his favorite metaphors for interactionism concerns a car making a screeching noise. How does a mechanic solve the problem? He begins by trying to identify the specific conditions that trigger the noise. Is there a screech when the car is accelerating, or when it’s shifting gears, or turning at slow speeds? Unless the mechanic can give the screech a context, he’ll never find the broken part. Mischel wanted psychologists to think like mechanics, and look at people’s responses under particular conditions.

This is all fine, but this does not negate that people have different dispositions, all things equal. Additionally, even with non-linear gene-environment interactions there may be a genetic component of variation (though it wouldn’t show up as narrow sense heritability). I guess I’ll have to look at what Mischel says in detail, but the idea makes me even more confused and muddled as to personality.

The primary aim of the post is to foster and encourage discussion. I’m curious what David Dobbs, Jason Goldman, Daniel MacArthur, etc. think. If you’re a psychologist or psychiatrist I’m curious as to your opinion.

CATEGORIZED UNDER: Culture, Psychology
MORE ABOUT: Behavior Genetics
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  • bioIgnoramus

    “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.” If something non-contentious, and easily and accurately measurable, such as height, is still not understood in its relation to genetics, then perhaps it’s a bit optimistic to hope to sort out personality. I don’t mean “Don’t try”, just “Don’t be too surprised if you get nowhere”. It doesn’t sound compatible with Medawar’s advocacy of the Art of the Soluble.

  • Åse

    Well, some of my buddies do Personality stuff – I’m in on a corner, but far from expert (individual differences is always interesting in psychology, even when you use WEIRD subjects). The first thing that struck me was that they used Cloninger. My buddies (and me, yet mostly listening in) are working on a large longitudinal dataset on ageing done here in Sweden (it is not completed), where the first couple of waves used the Cloninger measure, with dichotomic answers. none of them are happy with this (and due to some issues, that research will switch over to something else). There seems to be some issues with validity of that scale. In June we sat and tried to weed among the items to make it fit onto the Big Five measure instead, and found some things. So, I think the first thing these guys (yes, they are all male) would say is that there is issues with the personality scale.

    Not that I think the Big Five would fare much much much better (this is a non-professional but informed opinion). I do think that Big Five captures some interesting aspects of personality which makes it possible to discuss personality differences. But, even that was distilled down from a god-awful lot of dimensions in lexicons, in self-assessments, etc, and seems to have several sub-sets. (This is Psych 101 stuff – in standard intro books, wedged in with the Freudian and humanistic overviews). So, I woudl not expect a “gene for” introversion anymore than I would expect a “gene for” IQ. But, I do think the evidence for a genetically inherited component in personality to be fairly strong.

    I like Mischels stuff (as taught to intro students – boy am I a qualifier today). But… I’m thinking personality research really needs a more evolutionary outlook.

    Overall, I was underwhelmed by the blog because it did not seem to say anything that was unexpected, to me anyway.

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  • http://starkreal.blogspot.com/ Todd I. Stark

    Mischel is actually a good example because he is not really a situationist in the sense that some psychologists are. He does consider dispositions very important, but he looks at them in terms of stable patterns of interaction with particular kinds of situations (“in this sort of situation, I tend to do this”) rather than as patterns that hold across all situations (“he’s introverted”).

    His position in generally well supported empirically I think since correlations of the same trait measured in different situations tend to be statistically significant (thus personality trait theory) but relatively weak (thus situation does play a role). However I think it is difficult to think in those terms consistently because it complicates explanation significantly.

    So for most folks, I think Mischel’s interactionism is a bit too nuanced. Conditional rules are hard to deal with for making generalizations.

    And on the other hand, situational psychologists are most fascinated with the ways in which the circumstances compel us rather than in our dispositions. Phil Zimbardo, for example, the psychologist behind the Stanford Prison Experiment, is a situationist in that respect.

    http://thesituationist.wordpress.com/

    kind regards,

    Todd

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  • http://infoproc.blogspot.com steve hsu

    Razib’s alma mater (University of Oregon; psych dept.) made some important contributions to Big 5 research.

    I spoke with a specialist in that department and he seems to think Big 5 has reasonable validity and reliability for a psych construct — basically as good as anything else other than IQ, which is by far the best.

    http://www.uoregon.edu/~sanjay/bigfive.html

    re: GWAS, even harder to do than height or IQ because outliers are harder to reliably identify, or, equivalently, measurements of the quantitative trait are noisier.

  • http://infoproc.blogspot.com steve hsu

    An earlier version of this comment seems to have vanished, but perhaps both versions will appear :-)

    Here’s a good reference for Big 5:
    http://www.uoregon.edu/~sanjay/bigfive.html

    Since personality is harder to measure reliably than IQ or height, and also much less heritable, it will be much more challenging for GWAS.

  • http://johnhawks.net/weblog John Hawks

    I know from some experience that behavior responses in 18-month-old children are strongly heritable. Not all these are “personality” sensu stricto but many are obviously analogs of “personality” traits later in life (fear/approach, etc).

    There are two related questions about finding genes to account for heritability of personality traits. One is whether the brain has a given set of “dials” to adjust responses, which would map as highly recognizable axes in the space of behavioral variation. The other is whether evolution has tweaked these dials *once* or *many* times in our recent history. A lot easier with current methods to find the genes if there was a singular event.

  • John

    Razib, do you refer to Lehrer as the boy-king to bust on him b/c he’s a friend of yours? If he’s not a friend, it sounds a little condescending.

  • Chris T

    Single gene or even small number of genes explanations never made much sense for explaining highly complex phenomena such as intelligence and personality (or even height). If they did, such characteristics should be far more discrete than the continuous range we observe. In all likely hood, very few phenotypic expressions will likely be explainable in terms of a single or a few genes.

  • quidnunc

    I suppose one could think of ways to disconnect stability of traits from genes which account for heritability to some extent if one could find stability in the environment. For example, in the attractiveness literature personality traits are associated with different levels of attractiveness and the effect is greater in adolescence. Many of the researchers in this area tend to believe a good gene theory to explain the pairing. An alternative that there is also stability in the environment between people due to unrelated traits such as looks which fixes how they are anticipating and reacting to others. So environment could explain some of that stability through traits which might not seem immediately related. It could also make it difficult to tease out effects of genes if there are other similar effects of that size from traits or environment which don’t seem relevant because we can’t trace out the causality.

    It might be better to search for more basic traits which aren’t so abstracted. There might be few genes of large effect for traits such as nervousness which fundamentally alter dispositions that lead to personality differences but is too messy to make sense of or find effects working backwards from personality outcomes.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    jonah lehrer is a rhodes scholar who has published two books before the age of 30. “boy-king” is meant as a joke, and a reference to the juxtaposition between his influence and the fact that his photo on his blog kind of does make him look like a scared 13 year old.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    If they did, such characteristics should be far more discrete than the continuous range we observe. In all likely hood, very few phenotypic expressions will likely be explainable in terms of a single or a few genes.

    what’s the genetic architecture where it turns continuous? i’ve read it’s hard to figure out beyond 5 genes of similar effect whether a trait is continuous or discrete. skin color is a trait where i think many perceive it to be continuous, but there are several large effect QTLs which explain most of the pop variance (though i guesss small effect QTLs could influence the trait on the margin producing the shading).

  • http://scienceblogs.com/mikethemadbiologist Mike the Mad Biologist

    Another issue is that all of the personality tests are self-reported: we don’t actually know the ‘right’ answer to the questions, only the answer given by the subject.

    Seems that would crush R^2.

  • gcochran

    10 alleles can fake a continuous distribution pretty well . It might be better if we looked at other measures of personality than self-reported tests. What about being a convicted murderer? That’s a biologically significant event.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    murderer/non-murderer is a dichotomous trait. would be nice to have something more continuous. the N for serial killers is kind of small, though they have ordinal range.

  • Yawnie

    Serial killers Henry Lee Lucas and Bobby Joe Long were distant cousins

  • waqas

    well i’m neither a psychiatrist nor a psychologist n not even a biologist for that matter but i ‘ve following observations to make….human behaviour in its totality is fundamentally a different subject matter than say human body, modern psychology n its methods are inadequate to make any sense of something as random as human behaviour…linking every personality trait to a specefic gene is meaningless in itself because behavioural traits like nervousness are not physical constants…psychology needs new tools of analysis n requires to change its methodology to make any sense

  • LeeMSilver

    If you read the original article describing the research, you’ll find numerous serious problems with the way the study was conducted. The GWAS approach is designed to work with a sample of unrelated individuals. But the sample set used by Wray and colleagues consisted of 5117 subjects, who only came from 2567 families. The sample set also included 1702 monozygotic twins (797 pairs), and it also included an entire cohort of people diagnosed with bipolar disorder. All of this substructure can muddy the waters, which seems to be perfectly fine to Wray and colleagues whose language gives away their bias against GWAS.

    However, the really fundamental problem is the subjective complexity of all the traditional scales for measuring personality. For thousands of years, breeders tried to find patterns in heredity, with no success. Mendel succeeded not by stuffing multiple measurements into individual traits but by eliminating all the variables except one or two in each experiment. This won’t get you the genes for “harm avoidance” (which has no objective meaning) but it could uncover loci that influence the response to one important question in the harm avoidance panel, before investigating the next.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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