For nearly a century, most psychologists have embraced one view of intelligence. Individuals are born with more or less intellectual potential (IQ); this potential is heavily influenced by heredity and difficult to alter; experts in measurement can determine your intelligence early in life, currently from paper and pencil measures, perhaps eventually from examination of the brain "in action". In Great Britain, the late Hans J. Eysenck was a strong advocate of this position; in the United States, Richard Herrnstein and Charles Murray defended it in their controversial book The Bell Curve (1994).
Recently, criticism of this conventional wisdom has mounted. Biologists question the coherence of a single entity called intelligence and the validity of measures used to estimate hereditability of a human trait; computer scientists challenge the notion of general intellectual competence, instead implementing more targeted "expert systems". Within the community of psychologists, Robert Sternberg has described practical intelligence, while Daniel Goleman has called attention to emotional intelligence.
My doubts about the standard view of intelligence grew out of my own decades-long research with talented children and with brain-damaged adults. I became convinced that individuals can be strong (or weak) in a certain area of skill, and that strength (or weakness) in one area cannot predict achievements in other areas. If a person is strong (or weak) in telling stories, solving mathematical proofs, navigating around unfamiliar terrain, learning an unfamiliar song, mastering a new game that entails dexterity, understanding others, or understanding himself, one simply does not know whether comparable strengths (or weaknesses) will be found in other areas.
Observation of different human talents is scarcely new, but my scholarly enterprise is. I define an intelligence as the capacity to solve problems or fashion products that are valued in at least one culture. I then set up eight criteria for what count as an intelligence; these criteria range from the development of areas of the brain dedicated to that skill, to the existence of populations like prodigies or savants with special gifts (or deficits) in that area.
Combing an enormous literature from neuroscience, psychology, and anthropology, I initially identified seven separate human intelligences - capacities that satisfied my eight criteria reasonably well. As illustrated above, these included linguistic, logical-mathematical, spatial, musical, bodily- kinesthetic, interpersonal and intrapersonal intelligences. All human beings possess these intelligences; indeed, cognitively speaking they constitute a definition of humans (as opposed to animals or computers). At the same time, because of the accidents of heredity and environment, no two individuals - not even twins or clones - exhibit exactly the same profile of intelligences. These differences add spice to life and complexify education.
Since the theory was first described in my book, Frames of Mind (1983), there have been two major developments. First, I have made various adjustments in the theory. My criteria are met by an eighth intelligence, called the naturalist intelligence (recognising plants and animals); and evidence is accumulating for a ninth intelligence, called existential intelligence (the human proclivity to ponder large questions about life, death, existence). Second, there has been enormous interest in the theory, exhibited first by American educators, and recently by educators in many other parts of the world, including Great Britain. This last event has prompted philosopher John White to publish a critical piece in The Independent on 19 February. While White acknowledges that "MI theory" may have had some beneficent effects in schools, he questions the scientific basis of the theory and cautions teachers not to take the theory seriously. I agree that teachers ought to take any scientific theory with a grain of salt. There is never a direct road from theory to practice. (Indeed Richard Herrnstein admitted to me that the belief that intelligence is difficult to change could lead one either to suspend interventions or to devote all resources to raising IQ.)
There have been wonderful and foolish applications of multiple intelligences (MI) theory. The theory is most useful when one has defined a specific educational goal; a recognition that individuals mentally represent the world in quite different ways can then help achieve that goal. Efforts to teach a difficult concept through diverse entry points, such as stories, graphs, dramatisation, logical disputation have unlocked such concepts for a wider range of students and have also led ultimately to a more sophisticated understanding. This is not an accident: an expert is an individual who can in fact think about a concept - like evolution or gravity or democracy - in several ways, and these ways will draw on different human intelligences.
In critiquing the theory, White uses the familiar ploy of saying that it is old news on the one hand, and that it is not supported by evidence on the other. He is wrong on both accounts. True enough, the authorities he cites - Aristotle and Gilbert Ryle - recognised different human abilities, but they did not have criteria for determining which abilities are indeed discrete, nor could they take advantage of new discoveries about the organisation of the brain. I believe that I am the first person to ground a multi-factor theory of intelligence not on test scores but on a synthesis of evidence from the biological, cognitive, and anthropological sciences.
As for the accumulating evidence, it has been strikingly supportive of my original theory - far more than I could have anticipated. I wrote at a time when evolutionary psychology had not begun to document the existence of different "mental modules" for language, music, and the like, and when artificial intelligence was still engaged in a fruitless search for "general problem solving algorithms." Both the idea of dissociable talents, and the specific list that I proposed, have proved remarkably robust.
White correctly notes that my original list depended on the judgment of a single analyst, who made his data available to others. However, White is naive if he believes that science begins in any other way. I expect that, with time, the list of intelligences will grow, and the boundaries among them may shift. For example, recent evidence suggests that musical processing may have integral links to spatial processing - a finding that, if confirmed, might generate a new cartography of intelligences.
I welcome the continuing improvement of the theory of multiple intelligences. As one who cares deeply about education, I believe that a scientifically- based taxonomy of different intelligences - and a consideration of how they can best be marshalled to teach and learn better - represents progress.
Indeed, I'm persuaded that in 50 years, our successors will laugh at the notion that one has to teach and assess all students in the same way. Rather, turning traditional "mass" pedagogy upside down, we will ask what is the best way to teach this concept or subject to this student and what is the best way for this student to demonstrate her understanding. MI theory and practices will facilitate this revolution.
The psychologist Howard Gardner is a professor at the Harvard Graduate School of Education. His most recent book is `Extraordinary Minds' (Weidenfeld and Nicolson).