James R. Flynn is Professor Emeritus at the University of Otago, New Zealand. Flynn researches intelligence and is best known for the discovery that, over the past century, IQs have been rising at a rate of about 3 points per decade (the Flynn-effect). In advance of his new book on the subject, Clint Witchalls asked him about this and some of Professor Flynn's more recent research findings:

Clint Witchalls: How has our way of thinking and of solving problems changed over the past century?

James R. Flynn: Today we take it for granted that using logic on the abstract is an ability we want to cultivate and we are interested in the hypothetical. People from 1900 were not scientifically oriented but utilitarian and they used logic, but to use it on the hypothetical or on abstractions was foreign to them. Alexander Luria [a Soviet psychologist] went to talk to headmen in villages in rural Russia and he said to them: "Where there is always snow, bears are white. At the North Pole there is always snow, what colour are the bears there?" And they said: "I've only seen brown bears." And he said: "What do my words convey?" And they said: "Such a thing as not to be settled by words but by testimony." They didn't settle questions of fact by logic, they settled them by experience.

Your research found that we have gained 30 points on IQ tests in a century. What is the reason?

The ultimate cause of why IQs are rising is the industrial revolution. The proximate cause is how our minds differ from people in 1900 when in the test room. And the intermediate causes, of course, are more cognitively demanding work roles, more cognitively demanding leisure, more formal schooling, and smaller families.

Is it all gain?

It's not all gain. This is what irritates me when people say: "Flynn has shown that we live in the greatest of all possible worlds. We're so much brighter than we were." We take the hypothetical seriously. That means we argue maturely in moral and political arguments. We use logic on abstractions, which means we're potentially more educatable about science's view of the universe. It doesn't mean we actually are. You can develop scientific spectacles and use them all the time to defend creationism. It doesn't mean we're necessarily scientifically sophisticated, it just means you can argue for nonsense in a more sophisticated way.

Are there any signs that IQ gains are beginning to tail off?

To my surprise, Scandinavian countries tailed off in IQ at the end of the 20th century. But the latest data from South Korea, from America, from Britain, from Germany… they're humming right along.

What about developing countries?

You find large gains in Turkey, you find large gains in Kenya, and you find quite substantial gains in Brazil and the island of Dominica. Some developing countries are a mess, like Sudan and Saudi Arabia. In Saudi Arabia, where they have all of their own people sitting around doing make-work on oil royalties, they are not taking off.

How will developing countries catch up if developed countries are still making gains in IQ?

I think that they will improve quicker.

You found that there is a growing gap in the US between children and their parents when it comes to active vocabulary – the vocabulary used in everyday speech. What is the reason for this?

Since 1915, adults have made huge vocabulary gains and school children only modest ones. Now that's a symptom of the growing potency of teenage subculture. Rather than naturally socialising your teenage child to your speech community, they are resistant. They can understand what you say but they're reluctant to use your language and they want to retreat into their own dialect. In 1950 I could both understand my parents' language and use it. Teenage subculture is a modern phenomenon and quite bizarre. I was 16 years old in 1950 and it never occurred to any of us that we were in some blessed state that we wanted to perpetuate.

Bright people tend to lose their analytic ability in old age much faster than average people. You call this "the bright tax". Tell me a bit about it?

A good analytic brain is like a high-performance sports car and needs greater maintenance. That would be a physiological reason. Or, it could be that brilliant people, analytically, gravitate towards professions that make analytic demands. And that gives them a big exercise advantage on the average person, and then at retirement, it disappears. So it could be environmental. But we just don't know.

Does IQ have a positive correlation with happiness, fulfilment, etc?

Oh yes. Lewis Terman [the inventor of the Stanford-Binet IQ test] did a study of high IQ people. They tended to have more stable marriages, to be in better professions, etc. High IQ people have the cognitive abilities that our society designates as important to get the credentials that lead to better professions. And if you don't have financial problems, your marriage is less likely to break up. If your wife respects you, she is less likely to run off with the plumber.

Many child prodigies end up as failures? Is it possible that a very high IQ is pathological?

Well, it turns out many of them had autism or Asperger's syndrome. But today we are gaining an insight into why some of them have been very bad with people skills.

Is IQ not a very divisive tool? You're dumb. You're clever.

It is. It's inherently hierarchical.

But if it's divisive, why use it?

It yields interesting insights. Look what I've learned about teenage subculture. Or look at what we've learned about how our minds have evolved.