"The approximate truth" is intended as a series of easy explanations of common things. I'm sort of distilling facts I've read from various magazines etc, so any scientific accuracy is lost long ago. On the other hand, I mostly stick to stuff that is found in more than one source.

The approximate truth about the FLYNN EFFECT

One of the most puzzling facts in modern science is also among the easiest to overlook, despite being (often literally) in front of our eyes. It is the "Flynn effect", the fact that each generation has a strikingly higher IQ than the previous.
This is not just hard to explain, it is even hard to believe, especially for the elder generations. Still, there is a lot of evidence. In particular, the practice of IQ testing army recruits. The numbers here are so large that random variations are canceled out, and the practice has continued without pause since World War I in the USA, somewhat later for most other western countries. It was the studies of old IQ tests that convinced James Flynn (University of Otago, NZ) that something peculiar was going on: Different IQ tests had been used throughout time, and the older ones were easier. When people tried an old test and a new one, they consistently got higher scores on the old ones.
The average Intelligence Quotient of the population should always be 100. To achieve this end, the tests have had to be regularly recalibrated and even replaced with new ones. New, harder ones. If this adjustment had been ignored, average IQ would have risen by a whopping 3 points per decade. If we could take an average recruit of today back to the first test, he would have been rated a genius!
Obviously, this must be a fairly new development. Because if we project this into the past, we won't get far. The Declaration of Independence written by people who could hardly tie their shoelaces? The great works of the Renaissance performed by grunting apes? Obviously not. So whatever the Flynn effect is, it must be fairly recent. Now, our century has seen a lot of change, mainly improvements in the standard of living. But is this cause or effect?
An obvious culprit is education. After all, kids today attend school for much longer than did their grandparents, and they spend more of the year in school too. Given the focus on learning and problem solving, education should be the main suspect. However, there is still something amiss. For one thing, the increase has been slow and steady, with no discontinuities for various school reforms in the various countries. More puzzling facts arise when we break down the standard IQ tests in their subparts. The ones that rely the most on knowledge (vocabulary, arithmetic) have improved the least, or even declined at times. All of the increase, and then some, come from the most general parts of the tests, such as pattern recognition and manipulation.
Well then, perhaps television has increased people's abilities in these fields? No, the trend had come a long way before the television became publicly known, even before it was invented. And again, there are no crests or dips in the curve at the introduction of various inventions.
Nutrition? We know that starvation or malnutrition in children can severely hamper their development of higher brain functions. This is still a very real threat to the future of poor countries, where food is not always plentiful and varied. However, do we really believe that children during the Great Depression generally were better nourished than the generation before? How about European children during the second World War? And for that matter, are the eating habits of young people today 10% better than a generation ago?
One last explanation is that the intelligence has not increased at all, only the competence at IQ tests. After all, people tend to perform better at subsequent tests than at their first. They are less nervous and know what to look for. But again, there has been no gradual increase in the use of IQ testing during the whole of this period. In fact, the high tide of IQ testing was before the WWII, when the placement of people in proper groups was still politically correct. Furthermore, the benefit of practice drops after the second test you take. And test subjects today will score better on the older tests regardless of which they take first.
In short, the Flynn effect has the sweeping breadth of global evolution, but happens on a time scale terrifyingly faster than evolution is thought to work. It is almost as if some invisible outside force has taken over human evolution and put it in the fast lane, though this is of course even less believable than the other explanations.
Apart from the Flynn effect, there are also other general changes in the human nature: For the same period, humans have grown gradually taller, though this may now be in the process of stabilizing. We have also become more androgynous, that is, men and women are becoming more alike. There is one exception to this, though: The (natural) size of young women's breasts is also growing at a slow but measurable pace... Somehow the human race is in a process of transformation at an unprecedented speed, and nobody knows quite when and where it will end.
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