There is a recently published Primer in Current Biology on Intelligence written by Ian Deary, which is hidden behind a paywall, lest it be read by anybody other than a fully paid up current biologist. Strange world, the one in which scholars write things for nothing in order that other citizens should have to pay for the privilege of reading them. Such payments made some sense when publishing required printing, but rather less now, when the transmission of bytes is close to free.
Primer. Intelligence. Ian Deary. Current Biology Vol 23 No 16 R673 2013.
I will be using the article as a framework for a series of posts, taking one theme at a time, picking out some highlights and adding some extra bits. My target audience is bright people who don’t believe in intelligence. For a variety of reasons, they think it unseemly to acknowledge that they can think faster than others. This is not altogether stupid, because in many genocides it is the intelligent who get slaughtered. Excessive modesty may have some survival value.
“Some people are cleverer than others. It is a prominent and consistent way in which people differ from each other; the measurements we make of people’s cleverness produce scores that are correlated with important life outcomes; it is interesting to discover the mechanisms that produce these individual differences; and understanding these mechanisms might help to ameliorate those states in which cognitive function is low or declining.”
Deary distinguishes between cognitive psychologists who are trying to find out how the mind works and differential psychologists who mostly focus on how people differ in the workings of their minds. The latter try to show precisely the ways in which people differ, and try to discover the causes of those differences. The two tribes don’t communicate very well. Cognitive psychologists, in my view, are missing a trick. A very brief vocabulary and/or digit span test or, with more time, a group intelligence test, would give them important data, and help place their results in the context of human differences.
Deary identifies four major sources of scepticism about intelligence:
1 The concept appears to be too general. People argue that they are better at some skills than others, and assume different modules are involved, such that we are all good at some specific mental skill.
2 Historical events in intelligence research which are discreditable. In the UK, the 11+ missed out people who later showed demonstrable talent; cases of probable fraud in reporting results; over use and over-interpretation of intelligence tests; controversies about intelligence differences between ethnic groups; or claims that “ordinary” intelligence has now been replaced by tests of “multiple” intelligence.
3 “It is possible that clever people develop a kind of cognitive noblesse oblige; they kind of know they have won the lottery on a valuable trait, but they think it is bad form to acknowledge it.”
4 They probably haven’t read good quality research on the topic.
I find that most of the hostility about intelligence comes from bright people, who keep up with the broad sweep of newspaper reports and popular books, but have not looked at good quality research. Despite this lack they are surprisingly vehement when they ridicule IQ.
So, it would appear that intelligence is most disparaged by the intelligent. “Define intelligence” they demand, with a knowing smile. Personally, I have found that the only answer is to show them a photo of George W. Bush. (But I am getting ahead of myself). There are three types of answer: a quip, an explanation, and a formula.
The Quip: “Intelligence is what you need when you don’t know what to do”. Carl Bereiter coined this elegant phrase. It captures the ultimate purpose of intelligence, which is to help you cope with the unknown. The best intelligence test is the puzzle to which no one knows the answer. For example, is there a detectable particle which gives objects mass?
The Explanation: “Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings — ‘catching on,’ ‘making sense’ of things, or ‘figuring out’ what to do.” Linda Gottfredson and 52 leading psychometricians agree with this explanation. http://www.udel.edu/educ/gottfredson/reprints/1997mainstream.pdf
The formula: g+group+specific skill+error, where g accounts for about 50% of the variance. (I have written this in English, but it should be displayed in eigenvalues).
So, let us look behind the formula (in English) “In 1904 Spearman found that people who perform well on one type of cognitive test tend to perform well on others. That is, if cognitive test scores are ordered so that better performance equals a higher score, the correlations between them are all positive. There is shared variation among all types of cognitive performance. Spearman called this shared/common variance g: an abbreviation for general intelligence. In the 100+ years since then, every study that has applied a diverse battery of cognitive tests to a decent-sized group of people with a mix of ability levels has re-discovered the same thing: there is some cognitive variance shared by all cognitive tests. Typically, if one applies principal components
analysis, just under half of the total test score variance is accounted for by the first unrotated principal component.”
This finding of 50% of the variance in ability being due to g is matched by another finding: IQ-type test scores are highly reliable, and highly stable. For example, when the same intelligence test is taken at age 11 years and repeated at almost 80, about 50% of the variance is stable.
So, half of intelligence is due to a common factor, and half of the variance is stable throughout life.
Unfortunately, by this stage in the argument, we will have lost probably half of the intelligent readers. They are still smiling at the idea of anyone defining their intelligence. Can you please send them this link?