If having a theme park based on your work is a sign of educational influence, Walt Disney is probably near the top of the tree - which may, regrettably, be an accurate reflection of reality. But among serious education theorists, I suspect only Howard Gardner has achieved so much. The Explorama at Danfoss Universe in Denmark is a theme park with exhibits embodying the multiple intelligences he is famous for having identified. And while Uncle Walt might be a little uneasy about some of what is found in his parks, Professor Gardner says when he first saw the Explorama, he thought: "This is what I have been thinking and writing about."
In Frames of Mind (first published in 1983) he rejected the theory that dominated the previous century - that there is a single "general intelligence" that we all have to some greater or lesser degree, which can support any of a wide range of traits, skills and achievements. Under this theory, Leonardo da Vinci and Winston Churchill, cricketer Don Bradman and Haitian abolitionist Toussaint L'Ouverture, Miles Davis and Marie Curie, all have high IQs; they just turned those IQs to different ends.
The single intelligence or "g" theory ought to be familiar - it was the basis for the 11-plus, IQ tests and Mensa, and it underlies the thinking of some writers who accuse progressive educators of undermining excellence in schools. I was embarrassed that, until encountering Professor Gardner's work, I shared the assumption that there was a single intelligence, so was relieved to learn that he had too: "I never thought about it much, but I certainly accepted the notion that some people are smart and some are dumb, so I wasn't sceptical about the whole testing milieu in which I performed quite adequately," he said.
But his early research, especially on patients with brain damage, so-called savants and prodigies, made him increasingly sceptical of the "one intelligence" view. This led to the development of his famous multiple intelligences (MI) theory, according to which there are seven distinct intelligences: verbal-linguistic; logical-mathematical (together these correspond roughly to "g" theory); bodily-kinaesthetic; interpersonal; spatial; musical; and intrapersonal. He has subsequently added an eighth: naturalist. Everyone possesses these intelligences but to varying degrees, he says.
Professor Gardner was not the first to doubt the "one intelligence" view. In the 1930s, LL Thurstone identified seven "vectors of mind"; and in the 1960s, JP Guilford proposed a remarkable 120-150 mental "factors". But his predecessors shared with "g" theorists the assumption that intelligences could be measured through standardised tests, using proxies for real achievements to identify levels of intelligence. Professor Gardner doubts that intelligences can be measured this way, and has recently criticised educators who believe they can.
The impulse for standardised tests is understandable, but elaborate tests would be extremely resource-intensive and, because most real achievements hinge on the combined use of several intelligences, disaggregating the influences would be difficult. When I asked Professor Gardner about the criticism that he has not tested his theory, he replied: "If someone wants to create the tests, more power to them." But no single scientist can do everything and science is, after all, collaborative.
He adds, rather mischievously, that anyone who wants to assess their own intelligences could simply go to Danfoss and "test" themselves on the exhibits. From outside psychology, I find Professor Gardner's refusal to limit his conceptual imagination by what can easily be tested both disarming and sensible.
It's always a puzzle why some academic theories influence education practice while others do not. I asked Professor Gardner why he thought his theory had been so influential: "First of all, any educator knows that kids differ from one another on multiple dimensions and that IQ testing produces both false positives and false negatives. To have a Harvard professor write a big book that critiques IQ tests and suggests other ways of classifying students, plus lucky timing, probably combined to give me 15 minutes of fame over 20 years ago.
"A second factor is that because I did not make strong educational suggestions (writing primarily as a psychologist), educators were free to draw just about any inference they chose, and many did just that."
The timing was crucial. When his theory hit the stands, educators were ready for it as they might not have been in the 1930s or even the 1960s. The grip of "g" theory had been loosened by progressive education and increasingly heterogeneous pupils. Since the 1960s, compulsory schooling has been extended, leaving teachers hungry for ways of making these years valuable to their charges.
In light of MI, "g" theory seems dogmatic. We all know of people with the ability to solve complex mathematical equations but who cannot read people; or those who can barely read but are able to fix a lawnmower with their eyes closed. My favourite example is the footballer who sparkles on the pitch but whose verbal skills seem limited to a partial grasp of 10 cliches.
It is hard for people to let go of the traditional view, and Professor Gardner's comment that he performed "adequately" in the testing regimes of his childhood helps to explain why. Schools in England and the US have long been organised around rewarding verbal- linguistic and logico-mathematical intelligences. Success in those areas has yielded substantial benefits; policymakers, journalists, and other commentators tend to have excelled in these intelligences. It is convenient, therefore, for people who have done well to downplay their achievement, attributing it to the fact that resources and kudos were concentrated on the things they happened to be good at.
Some educationists are critical for a different reason. If the world of work is set up to reward just one or two intelligences, they say schools should aim to develop those rather than all eight, which might give children with bodily-kinaesthetic or musical intelligences a false sense of security for their future prospects.
There's something to this, but less than you might think. Schools should, indeed, focus on what the job market rewards. But MI is helpful in identifying how to do this; schools have traditionally neglected the interpersonal and intrapersonal intelligences that employers value.
Anyway, schools should prepare people for an all-round rewarding life, rather than as fodder for the job market. MI theory helps us work out which capacities to develop in children so they can enjoy and do good in their lives.
Professor Brighouse teaches Philosophy at the University of Wisconsin, Madison.
Frames of Mind: The Theory of Multiple Intelligences (Basic Books, 1983)
Multiple Intelligences: New Horizons in Theory and Practice (Basic Books, 2006)
Good Work: When Excellence and Ethics Meet, co-authored with Mihaly Csikszentmihalyi and William Damon (Basic Books, 2002)
Howard Gardner Under Fire: The Rebel Psychologist Faces His Critics, edited by Jeffrey A. Schaler (Open Court, 2006).