Now the man who first observed this effect, the psychologist James Flynn, has made another observation: intelligence test scores have stopped rising.

Far from indicating that now we really are getting dumber, this may suggest that certain of our cognitive functions have reached — or nearly reached — the upper limits of what they will ever achieve, Professor Flynn believes. In other words, we can’t get much better at the mental tasks we are good at, no matter how hard we try.

If we are to make any further progress, we will have to start exercising different parts of our brain, particularly the parts controlling language acquisition and empathy, according to Professor Flynn, an emeritus professor at the University of Otago in New Zealand.

In a lecture in Cambridge yesterday, he said that the study of intelligence has for too long been asking the wrong question: “The questions are not ‘Are we getting smarter?’ and ‘Are our children really smarter than we are?’ If the rise in IQ scores meant that we were smarter, that would mean our grandparents were dull and our great grandparents idiots, which is clearly not the case. The question should be, ‘Have certain cognitive skills risen?’ And the answer to that is yes.”

What accounts for our rise in intelligence test scores, Professor Flynn believes, is social and environmental changes that have given us the opportunity to exercise the kinds of skills that IQ tests measure.

We increasingly fill leisure time with cognitively demanding pastimes, such as puzzles and computer games. We have also developed a more scientific way of viewing the world. “In 1900 if you’d asked a child what do a dog and a rabbit have in common, they might have replied with a concrete answer like, ‘Dogs are used to hunt rabbits’. Today a child would be more likely to say, ‘They’re both mammals’. We classify things scientifically.”

Another factor in rising test scores concerned our ability to deal with complex abstract ideas. This is demonstrated in our ability to absorb abstract “shorthands” — for example the term “market” to signify laws of supply and demand.

Professor Flynn believes there is no reason to believe IQ gains will go on for ever. He points out that although gains are still robust in America, they have stopped in Scandinavia.

“Perhaps their societies are more advanced than ours and their trends will become our trends,” he told his audience at the Cambridge Assessment Psychometrics Centre. The end of IQ gains over time do not necessarily mean the end of cognitive progress, but the advances we have made so far will be of little value unless we “take the next step”, Professor Flynn said.

The challenge for humanity now is to enhance our ability to debate moral and social questions intelligently. One way to do this might be to concentrate on reading great works of literature which expand our vocabulary, critical acumen and emotional maturity.

But the fact that, as a society, we are unwilling to make the sacrifices necessary to preserve the environment, suggests we still have a long way to go on this front, Professor Flynn said.

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