The great physicist Sean Carroll famously implored physicists to stop saying silly things about philosophy. Now people should stop saying silly things about IQ.

IQ and Construct Validity

He calls himself a ‘race realist’ yet echoes the same arguments used by those who oppose such realism. Blood alcohol concentration is very specific and simple; human intelligence by comparison is not . Intelligence is polygenic (as opposed to just a single compound) and is not as easy to delineate, as, say, the concentration of ethanol in the blood. He says IQ tests are biased because they require some implicit understanding of social constructs, like what 1+1 equals or how to read a word problem, but how is a test that is as simple as digit recall or pattern recognition possibly a social contract. He’s invoking a postmodernist argument that IQ tests do not measure an innate, intrinsic intelligence, but rather a subjective one that is a construct of the test creators and society. If IQ tests are biased, how is then that Asians and Jews are able to score better than Whiles on such tests; surely, they should be at a disadvantage due to implicit biases of a test that is created by Whites.

Regarding the common objections by the left that IQ tests don’t measures anything useful or that IQ isn’t correlated with success at life, on a practical level, how else can one explain obvious differences in learning speed, income, or educational attainment among otherwise homogeneous groups? Why is it in class some kids learn so much faster than others, and then many of these fast-learners go to university and get good-paying jobs, while those who learn slowly tend to not go to college, or if they do, drop out, and are either permanently unemployed or stuck in low-paying, low-status jobs? In a family with many siblings, is it not evident that some children are smarter than others (and because it’s a shared environment, environmental differences cannot be blamed). As teachers can attest, some students are just ‘slow’ and cannot grasp the material despite many repetitions; others learn much more quickly. Because IQ tests test for the skills that are required for learning, such as short term memory, someone who has a low IQ would find learning difficult and be unable to make correct inferences from existing knowledge. The picture assembly portion of an IQ test measures the ability to form coherence from related but separate pieces of information. Digit recall span measures short term memory, which is applicable for all sorts or real-world applications, such as remembering a school lecture or remembering instructions given by a boss or a customer.

All of these sub-tests are positively correlated due to an underlying factor–called g–that accounts for 40-50% of the variation between IQ scores. This suggests that IQ tests measure a certain factor that every individual is endowed with, rather than just being a haphazard collection of questions that have nothing to do with each other. Race realists’ objection is that g is meaningless, but the literature disagrees “…the practical validity of g as a predictor of educational, economic, and social outcomes is more far-ranging and universal than that of any other known psychological variable. The validity of g is greater the greater the complexity of the task.[57][58]”