Most people don't understand "heritability"

By Razib Khan | January 29, 2012 1:08 pm

According to the reader survey 88 percent said they understood what heritability was. But only 34 percent understood the concept of additive genetic variance. For the purposes of this weblog it highlights that most people don’t understand heritability, but rather heritability. The former is the technical definition of heritability which I use on this weblog, the latter is heritability in the colloquial sense of a synonym for inheritance, biological and cultural. Almost everyone who understands the technical definition of heritability will know what heritability in the ‘narrow sense’ is, often just informally termed heritability itself. It is the proportion of phenotype variability that can be attributed to additive genetic variation. Those who understand additive genetic variance and heritability in the survey were 32 percent of readers. If you understand heritability in the technical manner you have to understand additive genetic variance. This sets the floor for the number who truly understand the concept in the way I use on this weblog (I suspect some people who were exceedingly modest who basically understand the concept for ‘government purposes’ put themselves in the ‘maybe’ category’). After nearly 10 years of blogging (the first year or so of which I myself wasn’t totally clear on the issue!) that’s actually a pretty impressive proportion. You take what you can get.

CATEGORIZED UNDER: Quantitative Genetics
MORE ABOUT: Heritability

Comments (14)

  1. I’m not sure the inferrence you make is warranted. One can understand a concept like additive genetic variance without being familiar with a more technical name for it.

  2. do you want to put money down on your line of argumentation? or are you just arguing like a lawyer? (personal experience is people trained in law are masters of using qualitative arguments to confuse stupid people)

  3. Ian

    As me what “heritability” is, and I could rattle off that definition without a thought. As me what “additive genetic variance” is and I’ve probably stumble around for a bit before coming up with a useful answer.

  4. #3, right. yes + yes = floor.

  5. Peter Twieg

    I have to concur with #1 and #3. I’m mostly familiar with the economics literature, wherein you’ll occasionally see articles (properly) discussing the heritability of some dependent variable, but I can’t think of a single one that has invoked the words “additive genetic variance.”

  6. #5, that’s because they assume you understand the concept. i’m not saying that basic concepts need to be defined. i’m saying that a lot of people misunderstand basic concepts. e.g., it’s almost impossible to to get the man-on-the-street to understand the importance of conceptualizing heritability as a population-wide statistic in my experience (which i have a lot of, more than almost anyone you’ll meet because i’ve been talking about the issue for nearly 10 years to non-technical audience) unless you decompose the concept a little. please address what i’m saying for god’s sake.

  7. @ #2 I think that there are a meaningful percentage of readers who understand the concept “additive genetic variance” but would describe it as “narrow” heritability. My intuition would put that percentage at something on the order of 10% to 35% of the people who say that they don’t know what “additive genetic variance” is, but just how many, I’d be hard pressed to guess.

    Of course, there are also probably some people who say they understand each concept for whom the definition they “know” is the wrong one, and that number probably isn’t insignificant either.

    One data point I bring to that intuition is a study that claimed that only 22% of professional economists understood what “opportunity cost” meant based on a multiple choice questionaire when legitimate arguments from the literature for every definition offered being correct could actually have been advanced.

  8. S.J. Esposito

    Razib, this may seem unrelated, or at best tangential, but I noticed you refer to your readership as ‘non-technical’… I’m curious to know how (or how much) the results of the survey changed your view of the readership. For example, did you previously believe the core readership to be more or less ‘technical’ than the survey results displayed?

  9. AndrewV

    @#7 They say they understand because they incorrectly assume they do.

    The idea that Razib will address more terms in the future is attractive to me, because my understanding of heritability was trending more towards the latter rather than the former definition he gave.

    For those in a similar cohort as myself (when I started primary school, slates and chalk, were standard use), I would suggest that being unaware of the technical meanings of the terms limits the experience considerably.

    Another example in my case is the term phenotype. There is a lot more to the definition than I had formerly assumed there was.

  10. Justin Giancola

    I thought you were going to Mr. Rogers everyone with that easy to understand chart!

  11. I’m curious to know how (or how much) the results of the survey changed your view of the readership. For example, did you previously believe the core readership to be more or less ‘technical’ than the survey results displayed?

    my opinion is not changed. as for technicality, i am a non-technical reader of cosmic variance 🙂 it’s contextual. many readers (perhaps a majority of regulars) have technical backgrounds, just not necessarily in the area of focus on this weblog.

    the PCA/ADMIXTURE results were a little disappointing to me. i think i’ll have to put up a post on ‘how to read a PCA/ADMIXTURE.’ you don’t need to know the technical details to understand the genetic result.

    re: importance of additive genetic variation. most people don’t have an understanding that heritability is best thought of as a fraction, which can vary when you change background conditions. that’s clear though if you understand that it’s (genetic variance)/(phenotypic variance). i say ‘most’ people because i have a lot more experience talking to smart, but non-pop/quant gen, individuals in regards to this issue. confusions such as shifts in heritability of height due to diet, etc., always reoccur.

  12. Emma

    Yes. Just last week, I was talking with a very smart mathematician colleague. For him, it was difficult to reconcile the high heritability of IQ and the strong Flynn effect. More generally, for most people without at least some background in the field, it is counterintuitive that the within group heritability value can not be extrapolated to the between groups level.

  13. #12, all is simple if you decompose heritability into its components. it’s a label. not the thing in and of itself.

  14. Siod Beorn

    You could just make a Khan Academy style course for this blog. Hell, if it’s good enough Khan might add it to the site. All you need is SmoothDraw3 (free), a screen recorder like fraps, a microphone, and reasonable control with a mouse.


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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


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