Saturday, December 28, 2019

Which is more important for education attainment: your IQ or your dad's social class?

While I am convinced that genes are a strong influence over people's lives and that the impact of the parenting is wildly exaggerated, I am open to data on these questions--I call myself Inductivist after all.

This meta-analysis of 15 heritability studies conducted in a variety of countries and decades found that shared environment explained a sizable portion of the variation in educational attainment; to be specific, almost 40%. That's a much higher average than typically seen in heritability studies.  The authors also found that shared environment was stronger for women and for people studied prior to 1950, suggesting that factors like family financial support have mattered more for women and for people in the past.

We can use General Social Survey data to answer a related question: Is educational attainment due to IQ or dad's socioeconomic status (SES)?  First, let's see how strongly each predicts years of education completed (I limited the analysis to data from 2010-2018, sample size = 947):

Standardized OLS regression coefficients

Model with Father's SES only
Father's SES  .37***

Model with Child's IQ only
Child's IQ   .45***

IQ is the stronger of the two predictors, but nurturists might argue that father's SES causes child's IQ which, in turn, determines educational attainment. We can address this question by entering both into the model as predictors. By doing so, we can see if the link between IQ and education shrinks to nothing once we've accounted for the influence of dad's SES.

Model with Father's SES and Child's IQ
Father's SES   .24***
Child's IQ  .44***

When both predictors are entered into the same equation, the father's SES/child education correlation is reduced, but the impact of IQ on schooling is basically unaffected. We can interpret these findings this way: How far you go in school is influenced by your dad's social class (consistent with the meta-analysis), but your own IQ is much more important. The strong correlation between IQ and schooling is not at all due to the tendency of high-status men to both have smart kids and to help them continue in school.

By contrast, part of the reason why father's SES is linked to child's educational level is because high status men have smart kids, and smart people naturally go further educationally. Once you take into account the pathway from dad's status through offspring IQ to completed education, the link between dad's class and child's educational attainment is weakened substantially. In other words, factors beyond the kid's IQ, like family financial support, are not as strong important as they look.

I looked at females only and got the standardized coefficients of .23 (dad's SES) and .43 (child's IQ), so the process works the same for girls as well as boys.

I also looked at mom's SES, and I found very similar results.

***p < .001, two-tailed test

UPDATE: The strong correlation between IQ and years of education reminds me of Taleb's anti-IQ argument: IQ-type tests get you into college, so there is a built-in correlation. There might be a link between test score and which college you get into, but there is no such circularity with how many years of school you complete. Regardless of your test score, you can get admitted to some college.

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