Nature vs Nurture: Mothers with multiple children have an intuitive grasp of behavioural genetics


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Lower scores equals more accurate estimates of genetic inheritance. From Willoughby et al 2018

By Christian Jarrett

Several prominent psychologists have recently raised concerns that the “radical left” has a stranglehold on free speech and thought in our universities. The psychologists argue this includes biological denialism: claims that differences between individuals and groups are entirely the result of the biased system or mere social constructions. More generally, many commentators are horrified by the apparent resurgence of far-right ideologies and their twisted interpretation of genetic science.

It’s timely, then, that a team of researchers, led by psychologist Emily Willoughby at the University of Minnesota Twin Cities, recently surveyed over 1000 online US participants, asking them about their personal circumstances, education, political orientation, and also to estimate the relative contribution of genes and the environment to variation in 21 different human traits, from eye colour to intelligence. This is probably the most detailed study to date of people’s insights into behavioural genetics, and the findings have just been published as a pre-print at the Open Science Framework.

Comparing participants’ judgments against the best estimates from the behavioural genetics literature, the researchers found a surprisingly high correlation of .77 (where 1 would be a perfect score). “People’s observations and intuitions about the genetic contributions to human traits are relatively informed,” the researchers said.

Participants’ estimates tended to group into four main categories: physical traits (height, eye colour etc); psychological (intelligence, personality); lifestyle (obesity, blood pressure); and psychiatric (depression, ADHD etc). One interpretation of this is that when making nature/nurture judgments, people tend think in terms of these approximate categories and they infer that traits within a category are subject to a similar level of genetic influence.

General educational level, and specifically participants’ genetic knowledge were related to the accuracy of their estimates, but only to a surprisingly modest degree.

What about political orientation? Left-leaning liberals estimated a greater genetic contribution to psychiatric disorders and sexual orientation compared with conservatives, while conservatives assumed a relatively greater contribution of genes to traits like intelligence and musical ability. This led to what the researchers called “a surprising sort of ‘balancing out’,” meaning that individuals’ accuracy did not differ by political persuasion.

The researchers believe this pattern is consistent with the idea that moral judgments are central to the political split in the USA. Right-wing participants more strongly endorsed the idea that some people have more innate aptitude than others, while the left-wing participants more strongly endorsed the idea that many stigmatised traits are largely innate and should therefore be treated with fairness and compassion, not judgment.

So there was no greater biological denialism or “blank slatism” by one political wing than the other, but rather a genetic cherry-picking to suit one’s own world view.

Interestingly, sexual orientation was something of an outlier in the study and the trait for which participants’ intuitions diverged the most from the published literature. The researchers do not offer any speculation for why this might be. Most participants strongly overestimated the genetic contribution to this trait, but conservatives did so less than liberals.

Surprisingly perhaps, more strongly related to overall accuracy than education, politics or genetic knowledge, were gender and having children. Women were more accurate in their estimations than men, and participants with non-adopted children were more accurate than those without. The most accurate judges of all were women with multiple non-adopted children. “Mothers may be uniquely observant of their children’s abilities, needs, and attributes,” the researchers said.

Willoughby and her colleagues took heart from these findings. “While it is clear that social and political biases do inform the magnitude of heritability judgments, the best predictors of these judgments are education and parenthood – an encouraging prospect indeed for the public understanding of findings from behaviour genetics.”

On a more sceptical note, however, this survey was based entirely on myriad correlations and can’t tell us too much about what influences people’s beliefs about behavioural genetics, nor how these beliefs develop through life. For instance, it’s plausible that beliefs about genetic heritability shape people’s political views, as much as the other way around. There may even be genetic influences on people’s insights into genetic inheritance, perhaps manifested through personality, intelligence and political leanings (only the last was measured in this survey).

In terms of better understanding the roots of some of the scientifically dubious beliefs on display on our college campuses and elsewhere, we probably need studies that follow people over time and that are focused at the more extreme ends of the political spectrum – only around 4 to 5 per cent of the current participants identified as very conservative and around 16 per cent as very liberal.

These issues aside, this study makes a novel contribution to a little studied topic, and the idea that mothers have a unique insight into behavioural genetics gained through the experience of parenting will surely resonate with many readers!

Free will, determinism, and intuitive judgments about the heritability of behavior [this paper is a pre-print that has not yet been subjected to peer review]

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest

7 thoughts on “Nature vs Nurture: Mothers with multiple children have an intuitive grasp of behavioural genetics”

  1. Was the analyses statistically controlled for variables like ‘income’? (A quick look at the paper didn’t seem like it.) So, it is possible that mothers with multiple children were of low income (perhaps of low education as well?) and this influenced in their perceptions. People with higher income may have been aware of the phenomenon of epigenetics (gene-expression being constantly influenced by our experiences, mind-states, etc – there is a growing body of evidence for this). I also feel that thinking the responses of the mothers were influenced by ‘observation of their own children’ is merely an assumption that the authors make.

    1. So you’re saying that being of low income might be associated with greater accuracy in estimates of heritability? Mothers with multiple children were more accurate right?

      1. I don’t have time to go through the article carefully, so I am not able to comment in detail. However, some of the issues that came to my mind were:

        – how was the accuracy of genetic knowledge tested when many of these questions are still not settled in the research literature. For example, if we take schizophrenia, genes appear to explain only about 0.001 percent of outcomes – see:

        – The participants were not directly asked to think about their kids to see the accuracy of their estimates – people may have looked at their siblings, parent’s family, other relatives and friends, etc.

        – I feel that a multiple regression analyses would have been a better analytical method in order to reduce the influence of confounding variables.

  2. “This led to what the researchers called “a surprising sort of ‘balancing out’,” meaning that individuals’ accuracy did not differ by political persuasion.”

    This isn’t what their data say. The “balancing out” only occurs when the heritability judgements for one of the characteristics (sexual orientation) is removed. See the middle paragraph on page 18 of the pre-print…

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