Wednesday, March 30, 2011

How well do people rate their IQ?

Add Health participants were asked to rate their intelligence. They were also given a vocabulary test--a decent measure of IQ.

Here are the Pearson correlations between the two variables listed by race:

Correlation (sample size = 6,504)

Asians .44
Whites .36
American Indians .35
Hispanics .28
Blacks .18

Overall, the correlations are low. People are not good at evaluating how smart they are. But the ability varies by race. Asians are the most accurate; blacks the least. Objectively smart groups (i.e., Asians, whites) assess their IQs with greater accuracy than low-IQ groups (Hispanics, blacks).   


  1. "Objectively smart groups (i.e., Asians, whites) assess their IQs with greater accuracy than low-IQ groups (Hispanics, blacks)."

    Reminds me of Rushton's "Race, Evolution and Behavior" when research showed that black students thought themselves better than other race groups in each school subject (except math), despite performing worse than the other races.

  2. Smarter people in general have better self-knowledge.

  3. This is one of those cases where the regression coefficients are more interesting than the correlation. If you regress rated IQ on measured IQ, do you get an intercept of zero and a slope of 1 (which would indicate that they are unbiased but error-prone).

    It would also be cool to see a plot of rated vs actual along with a 45-degree line, so that you could see the bias and also the lower spread for higher IQ people if that conjecture is right.

  4. Maybe everyone rates themselves highly, and some people happen to actually merit it.

    Robin Hanson is a persistent critic of the Dunning-Kruger effect alluded to.


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