James Flynn, a political scientist working in New Zealand, observed in the 1980's that the scores of different groups of people on standard intelligence tests had consistently augmented over the past decades. Earlier researchers had failed to pay attention to that trend, because IQ scores are always calculated with respect to the average score for the present group. By definition, the average is set to 100. Someone who scores 20% more than the average would therefore get an IQ of 120. But if that person's score would be compared with the average for the corresponding group, tested one generation earlier, the final score would be about 130. Flynn was the first to systematically make such cross-generational comparisons.
Since then, the so-called "Flynn effect" has been confirmed by numerous studies. The same pattern, an average increase of over three IQ points per decade, was found for virtually every type of intelligence test, delivered to virtually every type of group. The pattern applied to some 20 countries for which data were available, including the USA, Canada and different European nations, although the rate increase varied somewhat according to country and type of test. The increase was highest, 20 points per generation (30 years), in Belgium, Holland and Israel, and lowest, 10 points per generation, in Denmark and Sweden. Although the data are limited, it moreover seems that the increase is accelerating. In Holland, for example, scores went up most (over 8 points) for the last measured period, 1972 to 1982. For one type of test, Raven's Progressive Matrices, Flynn found data that spanned a complete century. He concluded that someone who scored among the best 10% a hundred years ago, would nowadays be categorized among the 5% weakest. That means that someone who would be considered bright a century ago, should now be considered a moron!
Such a result has unexpected implications for the relation between intelligence and age. Older people tend to have lower scores on IQ tests than younger people. Until now, it was always assumed that this means that intelligence diminishes with age. However, this observation can be explained as well by noting that older people were raised in a period when the general level of intelligence was lower. Flynn showed that if people's IQ is evaluated with tests calibrated for the period during which they grew up, an old person scores as well as a young one. The reason that older people do less well on IQ tests is not that they have become more stupid with age, but that the younger generation simply got a head start.
One might expect that the Flynn effect would be more clear for tests that emphasize culture or education. The opposite is true, however: the increase is most striking for tests measuring the ability to recognize abstract, non-verbal patterns. Tests emphasizing traditional school knowledge show much less progress. This means that something more profound than mere accumulation of data is happening inside people's heads. None of the scientists who have studied the effect can offer a simple explanation.
Flynn himself admits that he is baffled by the results, and that he finds it hard to believe that his generation is significantly more intelligent than the one of his parents. He proposes the following argument. Compared to the previous generation, the number of people who score high enough to be classified as "genius" has increased more than 20 times. This means that we should now be witnessing, in Flynn's own words, "a cultural renaissance too great to be overlooked". Because he finds this conclusion implausible, he suggests that wat has risen is not intelligence itself but some kind of "abstract problem solving ability". But if we look at the ever accelerating production of scientific discoveries, technological innovations and cultural developments in general, the "cultural renaissance" does not seem such an absurd idea anymore. And whether you call the factor that rises "intelligence" or "abstract problem solving ability", the conclusion that people have become intellectually more capable remains the same.
To me, it seems likely that this intellectual progress is caused by a combination of factors, just like the general progress in quality of life. Some factors may have a negative influence on intellectual development, but most developments are positive and reinforce each other. The most obvious one is longer schooling, but this cannot explain everything, as Flynn found that the IQs of American children have been rising even during periods when the time spent in school remained the same. Stimulation by the media, and in particular by television, may be another one, but this cannot explain progress before the advent of television in the 1950s. Generally improved health and nutrition is likely to contribute too. It has been shown that poor nutrition in early age impairs intellectual development, but this only applies to children who have been severely underfed. A factor that may have been overlooked is that parents nowadays tend to pay much more attention to their children, thus stimulating their cognitive development. This is possible because parents tend to have less children to care for, to have more free time, to be more wealthy, to be better educated, and to have a better insight in the needs of their children.
A more general factor is that society as a whole functions at a higher intellectual level, proposing to the curious child more information, more intellectual challenges, more complex problems, more examples to be followed, and more reasoning methods to be applied. Just using everyday appliances, such as VCRs, microwave ovens, and thermostats, demands a more abstract type of reasoning, of which the older generation is often incapable. The increased complexity of life is likely to stimulate an increased complexity of mind. The growing use of computers for education or games at an early age is likely to further boost general knowledge, abstract reasoning and intellectual agility.