A Californian neuroscientst called V.S. Ramachandran has written a highly informative and entertaining book called The Tell Tale Brain. I recommend it to all who are interested in brain/mind issues. His approach is rather open-minded, for a neuroscientist, that is.
Ramachandran has a few tough words for the proponents of a single number to describe “g”, or general intelligence.
Ironically, the IQ evangelists (such as Arthur Jensen, William Shockley, Richard Herrnstein and Charles Murray) use the heritability of IQ itself (sometimes called “general intelligence” or “little g”) to argue that intelligence is a single measurable trait. That would be roughly analogous to saying that general health is one thing because life span has a strong heritable component that can be expressed as a single number – age! No medical student who believed in “general health” as a monoloithic entity would get very far in medical school or be allowed to become a physician – and rightly so – and yet whole careers in psychology and political movements have beenbuilt on the equally absurd belief in a single measurable general intelligence. Their contributions have little more than shock value. (page 171)
To which I say, not so fast, Dr. Ramachandran. What you think is plausible is actually piffle.
- the various diseases of the body are not even roughly analogous to the ability or abilities of the mind to engage in thought;
- we use statistical aggregates all the time as a stand-in for measuring ongoing phenomena (temperature, gross domestic product, mortality figures).
- You do not have to understand how cars work to understand the significance of their cost and their longevity. Likewise with intelligence testing.
More to the point, intelligence testers and neuroscientists are engaged in entirely different pursuits. The intelligence testers are concerned with outcomes, neuroscientists with causes.
Let Murray and Herrnstein speak for themselves. From The Bell Curve at pages 22-23:
- there is such a thing as a general factor of cognitive ability on which human beings differ.
- All standardized tests of academic aptitude and achievement ,easure this general factor to some degree, but IQ tests expressly designed for that purpose measure it most accurately.
- IQ scores match, to a first degree, whatever it is that people mean when they use the word intelligent or smart in ordinary language.
- IQ scores are stable, although not perfectly so, over much of a person’s life.
- Properly administered IQ tests are not demonstrably biased against social, economic, ethnic or racial groups.
- Cognitive ability is substantially heritable, apparently no less than 40 percent and no more than 80 percent.
Or let us hear from Geoffrey Miller, who describes himself as a left-wing secular humanist Jew, and who has written The Mating Mind and Spent: Sex, Evolution and Mating Behavior. From page 186 of Spent:
General intelligence (a.k.a. IQ, general cognitive ability, the g factor) is a way of quantifying intelligence’s variability among people. It is the best established, most predictive, most heritable mental trait ever discovered in psychology….Intelligence predicts objective performance and learning ability across all important life domains that show reliable individual differences.
The irony about general intelligence is that ordinary folks of average intelligence recognize its variance across people, its generality across domains, and its importance in life. Yet educated elites meanwhile often remain implacable opposed to the very concept of general intelligence, and deny its variance, generality and importance. Professors and students at elite universities are especially prone to this pseudohumility….
Similarly, general intelligence is not a mental organ, but a latent variable that emerges when one analyzes functional efficiencies of many different mental organs(such as memory, language ability, social perceptiveness, speed at learning practical skills, and musical aptitude.)
Intelligence (says Prof. Miller at page 189 of Spent) is positively correlated to:
- brain size
- speed of performing basic sensory motor tasks (“reaction time is a factor”, as the cop said in Blade Runner)
- height
- symmetry of face and body
- semen quality (!)
- health, physical and mental
- longevity
- sexual attractiveness for long term relationships
Intelligence: the gift that keeps on giving. If you want to see what life is like when you lack the necessary minimum, go live in Detroit.