Bad Math

On the way into work today, I was listening to Forum, the KQED Public Radio show hosted by Michael Krasney. Krasney can be insufferable (he’s brilliant, and he really knows it), but he’s a pretty good talk show host. (His limited understanding of science notwithstanding.)

At any rate, today’s guest was Charles Murray, the irresponsibly idiotic libertarian who is most famous for writing “The Bell Curve”.  Murray was on to discuss his new book about the regulatory environment in the United States and his case for civil disobedience as a way to counter it (the book is “By The People”), but he was, of course, asked by callers to defend some of his more inflammatory previous statements. One such statement, “No woman has been a significant original thinker in any of the world’s great philosophical traditions,” he dug right in and defended. Basically, no, women aren’t smart, but they can’t do philosophy, either, based on his definition of what constitutes a significant contribution to philosophy. His exact words: “In philosophy, they’ve all been second-tier.”

Others can deal with that. Me, I’m writing to discuss the OTHER idiotic thing he said and then dug in to defend, namely that there must be a genetic difference in intelligence between people who are above the poverty line compared with those below it.

His argument, as presented this morning:

1. IQ is demonstrably lower in people living below the poverty line compared with people living above it. (True.)

2. IQ is significantly heritable. (True. He gives the figure of 50%, which, though I haven’t looked up the numbers recently, sounds reasonable.) Note to non-geneticists: “heritable” is a stand-in for “the amount of variation in this trait that we think is due to genetic differences. The rest is then due to environmental differences. Like, say, growing up in poverty.

3. If the first two assertions are true (they are), then it follows mathematically that there must be a heritable difference in intelligence between people below the poverty line compared with people above it.


Okay, so anybody with half a brain, an open mind, and basic math skills can see why “3” doesn’t follow from “1” and “2”. Let’s say we accept his unstated premise that IQ = intelligence. (Note: we know this is a dangerous thing to accept, given that IQ tests are biased towards particular cultures and types of education.) Even if that assumption is true, if HALF of intelligence is heritable, it does NOT follow that the difference in IQ between impoverished and not-impoverished people is found in that half.

Incidentally, the difference is about 13 IQ points, according to a 2013 Science paper. Since average IQ is set to 100 for all scales (and there are many), that means that poverty can reduce IQ by about 13% on average. Logically, then, ALL of that difference could easily be accounted for by environmental differences, which, by Murray’s own numbers, account for half of the variability in the trait.

What really chaps my ass is that Murray isn’t a dumb guy, nor is he in some way logic-challenged. He KNOWS his numbers are bad, and he presents them as if they are unchallengeable. And Krasney, to my annoyance, tried to challenged the validity of IQ tests instead of the math. The math is the low-hanging fruit, as is Murray’s dishonest approach to presenting it. He actually said, “This isn’t my opinion; it’s just math.”

Yeah, but it’s really BAD math.

Also, there are literally reams of scientific literature on the effects of poverty on the ability to learn (which is what IQ tests actually test). How well can you learn if you haven’t eaten sufficiently in a week, and are always worrying about where your next meal will come from? Or if you have to watch your younger siblings while your mom works her third job at night? Or if you live in a place where urban violence puts you in danger every day, and you’ve already lost several classmates to it? Murray is fond of the pretentious phrase “QED” (Latin, quod erat demonstrandum, usually meant to indicate that a thing has been proven). In this case: it is hard to focus on learning if you don’t eat enough, don’t have time to study, and have to worry you might get shot. You will probably therefore do worse on IQ tests. QED.

The thing is, he knows this. And yet he persists in saying that differences in IQ are due to genetic differences (without evidence), and that, therefore, people in poverty are there because they are less able than people who aren’t in poverty. When there is abundant evidence to the contrary.

Which makes him a bad person. QED.


1 Comment

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One response to “Bad Math

  1. Standing on my chair cheering!!!! Well done!

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