The second vigorously debated area that Geary refers to in Educating the Evolved Mind is intelligence. In the early 1900s statistician Charles Spearman developed a technique called factor analysis. When he applied it to measures of a range of cognitive abilities he found a strong correlation between them, and concluded that there must be some underlying common factor that he called general intelligence (g). General intelligence was later subdivided into crystallised intelligence (gC) resulting from experience, and fluid intelligence (gF) representing a ‘biologically-based ability to acquire skills and knowledge’ (p.25). The correlation has been replicated many times and is reliable – at the population level, at least. What’s also reliable is the finding that intelligence, as Robert Plomin puts it “is one of the best predictors of important life outcomes such as education, occupation, mental and physical health and illness, and mortality”.
The first practical assessment of intelligence was developed by French psychologist Alfred Binet, commissioned by his government to devise a way of identifying the additional needs of children in need of remedial education. Binet first published his methods in 1903, the year before Spearman’s famous paper on intelligence. The Binet-Simon scale (Theodore Simon was Binet’s assistant) was introduced to the US and translated into English by Henry H Goddard. Goddard had a special interest in ‘feeble-mindedness’ and used a version of Binet’s scale for a controversial screening test for would-be immigrants. The Binet-Simon scale was standardised for American children by Lewis Terman at Stanford University and published in 1916 as the Stanford-Binet test. Later, the concept of intelligence quotient (IQ – mental age divided by chronological age and multiplied by 100) was introduced, and the rest, as they say, is history.
what’s the correlation?
Binet’s original scale was used to identify specific cognitive difficulties in order to provide specific remedial education. Although it has been superseded by tests such as the Wechsler Intelligence Scale for Children (WISC), what all intelligence tests have in common is that they contain a number of sub-tests that test different abilities. The 1905 Stanford-Binet scale had 30 sub-tests and the WISC-IV has 15. Although the scores in sub-tests tend to be strongly correlated, Early Years teachers, Educational Psychologists and special education practitioners will be familiar with the child with the ‘spiky profile’ who has high scores on some sub-tests but low ones on others. Their overall IQ might be average, but that can mask considerable variation in cognitive sub-skills. Deidre Lovecky, who runs a resource centre in Providence Rhode Island for gifted children with learning difficulties, reports in her book Different Minds having to essentially pick ‘n’ mix sub-tests from different assessment instruments because children were scoring at ceiling on some sub-tests and at floor on others. In short, Spearman’s correlation might be true at the population level, but it doesn’t hold for some individuals. And education systems have to educate individuals.
is it valid?
A number of issues have been vigorously debated in relation to intelligence. One is its construct validity. There’s no doubt intelligence tests measure something – but whether that something is a single biologically determined entity is another matter. We could actually be measuring several biologically determined functions that are strongly dependent on each other. Or some biologically determined functions interacting with culturally determined ones. As the psychologist Edwin Boring famously put it way back in 1923 “intelligence is what the tests test”, ie intelligence is whatever the tests test.
is it cultural?
Another contentious issue is the cultural factors implicit in the tests. Goddard attempted to measure the ‘intelligence’ of European immigrants using sub-tests that included items culturally specific to the USA. Stephen Jay Gould goes into detail in his criticism of this and other aspects of intelligence research in his book The Mismeasure of Man. (Gould himself has been widely criticised so be aware you’re venturing into a conceptual minefield.) You could just about justify culture-specificity in tests for children who had grown up in a particular culture, on the grounds that understanding cultural features contributed to overall intelligence. But there are obvious problems with the conclusions that can be drawn about gF in the case of children whose cultural background might be different.
I’m not going to venture in to bell-curve territory because the vigorous debate in that area is due to how intelligence tests are applied, rather than the content of the tests. Suffice it to say that much of the controversy about application has arisen because of assumptions made about what intelligence tests tell us. The Wikipedia discussion of Herrnstein & Murray’s book is a good starting point if you’re interested in following this up.
There’s little doubt that intelligence tests are valid and reliable measures of the core abilities required to successfully acquire the knowledge and skills taught in schools in the developed industrialised world; knowledge and skills that are taught in schools because they are valued in the developed industrialised world.
But as Howard Gardner points out in his (also vigorously debated) book Frames of mind: The theory of multiple intelligences, what’s considered to be intelligence in different cultures depends on what abilities are valued by different cultures. In the developed industrialised world, intelligence is what intelligence tests measure. If, on the other hand, you live on a remote Pacific Island and are reliant for your survival on your ability to catch fish and navigate across the ocean using only the sun, moon and stars for reference, you might value other abilities. What would those abilities tell you about someone’s ‘intelligence’? Many people place a high value on the ability to kick a football, sing in tune or play stringed instruments; what do those abilities tell you about ‘intelligence’?
it’s all about the constructs
If intelligence tests are a good measure of the abilities necessary for learning what’s taught in school, then fine, let’s use them for that purpose. What we shouldn’t be using them for is drawing conclusions about a speculative entity we’ve named ‘intelligence’. Or assuming, on the basis of those tests, that we can label some people more or less ‘intelligent’ than others, as Geary does e.g.
What concerned me most about Geary’s discussion of intelligence wasn’t what he had to say about accuracy and speed of processing, or about the reliability and predictive validity of intelligence tests, which are pretty well supported. It was the fact that he appears to accept the concepts of g, gC and gF without question. And the ‘vigorous debate’ that’s raged for over a century is reduced to ‘details to be resolved’ (p.25) which doesn’t quite do justice to the furore over the concept, or the devastation resulting from the belief that intelligence is a ‘thing’. Geary’s apparently unquestioning acceptance of intelligence brings me to the subject of the next post; his model of the education system.
Gardner, H (1983). Frames of Mind: The theory of multiple intelligences. Fontana (1993).
Geary, D (2007). Educating the evolved mind: Conceptual foundations for an evolutionary educational psychology, in Educating the evolved mind: Conceptual foundations for an evolutionary educational psychology, JS Carlson & JR Levin (Eds). Information Age Publishing.
Gould, SJ (1996). The Mismeasure of Man. WW Norton.
Lovecky, D V (2004). Different minds: Gifted children with AD/HD, Asperger Syndrome and other learning deficits. Jessica Kingsley.