Tests of general knowledge had long been used by psychiatrists as quick measures of intelligence but psychologists eschewed them because they were thought to measure education, not “innate ability”.  This changed after the Army IQ tests in World War I included one in their battery and found general knowledge to have an exceptionally high correlation with full-scale IQ, and when David Wechsler added general knowledge to his test battery, he found the same thing.

“Who’s Oprah?” is an example of a general knowledge question.   Indeed in the 1970s there was a billboard in Baltimore asking “What’s an Oprah?” as part of a campaign to get people to watch her co-anchor the local news, one of the rare fails of her career.  Oprah hated the billboard saying “people were expecting the second coming, and all they got was me.”

Oprah was much happier when she got demoted to co-hosting a local low budget morning show because here she could be spontaneous, show emotion and say whatever popped into her head.

Had David Wechsler lived long enough to see the rise of Oprah in 1986, he might have thought “Who’s Oprah?” would make a good question for his general knowledge (Information) subtest, because Wechsler believed that good items for this subtest are those the average American, with average opportunity, has a chance to acquire for himself, so for example, the distance between two important cities was considered by Wechsler to be a much better question than the distance from the Earth to the sun.

The average American adult has had so much opportunity to learn who Oprah is.  They could flip on her TV show.  They could hear about her on the news.  They could see her on the cover of the tabloids or her own magazine when they go to the grocery store.  Indeed with so much opportunity to see and hear about Oprah,  any native born American adult who doesn’t know who she is might have a problem learning, and absorbing and retrieving information.

Indeed according to a new CNN poll, only 2% of U.S. adults have never heard of Oprah, so not knowing who Oprah is, puts you in the bottom 2% of general knowledge (a measure of IQ) and the bottom 2% is defined by IQ tests as an IQ below 70 (U.S. norms).  In some U.S. states people with IQs below 70 can not be executed, because they’re considered too impaired to be culpable.

By contrast back in July 2015, a whopping 41% of Americans had never heard of Bernie Sanders.  Not knowing who Bernie Sanders is in July 2015 implied an IQ below 97; slightly below the national average but still very normal.

Of course in reality, one’s score on general knowledge is never based on a single question, and IQ is seldom calculated from a single subtest.

One might argue that “Who’s Oprah?” is a poor measure of IQ because intellectual types have better things to do than watch daytime TV.  Indeed Jonathan Franzen once claimed that he had never seen her show!

However this argument is debunked by what Arthur Jensen called the spread of g (general intelligence) effect, where high IQ people are more knowledgeable even about non-intellectual topics.  For example Jensen interviewed a hard-core baseball enthusiast with an IQ in the 70s (probably lower since in those days tests with old inflated norms were still used) but was shocked by how little he actually knew about baseball, despite his lifelong obsession with it.

By contrast a learned professor who believed only idiots watch sports was ashamed by how much he knew about baseball.  Jensen believed this was because high IQ brains are like a sponge that just naturally absorbs everything in their environment, even things they’re not actively attending to.

I once had a discussion with a member of the Mega society who was very disappointed to learn that general knowledge had such a high correlation with IQ, perhaps because he felt this correlation undermined the tests somehow.

The fact that knowledge tests are so heritable (supposedly) is surprising to those who expect “culture reduced” tests to better reflect the biological basis of intelligence than tests that are highly mediated by culture.  This is known as the heritability paradox.  Indeed the “fact” that knowledge tests are among the most heritable thas caused some to believe that the high heritability of IQ is not about tests directly measuring biological functions, but rather about those being genetically predisposed to learn seeking out environments where they can do so.

However according to Jensen, the heritability paradox is not a paradox at all, but rather easily explained by the well known concept of aggregation.  To correctly answer “Who’s Oprah?” you must for example, understand a talk show host while she’s on TV talking about adultery.  You must remember this understanding.  The next day you might hear someone say “I saw Oprah on TV talking about infidelity”.  You must know that infidelity is related to adultery, and this must cause you to remember you too saw a talk show host talking about that very topic, and thus infer her name is Oprah, and then you must store that knowledge in long-term memory and retrieve it when asked “Who’s Oprah?”.

So what looks like a single cognitive task (knowing who Oprah is) is actually multiple complex cognitive tasks packed together, so with each general knowledge question, you’re measuring a long sequence of brain functions in the time it takes to measure one, making them incredibly efficient measures of intelligence, at least for people who share the culture of the test.

An argument within this argument is whether tests of acquired knowledge really are more heritable than culture reduced tests.  Most heritability studies are based on comparing the phenotype correlation of MZ twins raised together with DZ twins raised together, but this method assumes both pairs are equally similar in environment .  A better method is using MZ twins raised apart and in the most famous of these studies, the culture reduced subtests (performance IQ) of the Wechsler scales were actually more heritable than the culturally loaded ones (verbal IQ).