Despite hysterical politically-motivated attacks on them that have sometimes turned violent, researchers into human intelligence have by now produced a coherent and compelling scientific picture, as explained in books such as the 1994 best-seller The Bell Curve by Richard Herrnstein and Charles Murray.

With one exception.

For uncertain reasons, all over the world, raw IQ scores have been rising, on average at the rate of about 3 points per decade. Thus, a test performance that a half century ago would have ranked at the 84th percentile (a score of 115) now is only good enough for the 50th percentile (a score of 100).

When IQ test publishers revise and renormalize their exams every decade or two, they have to make scoring tougher to make the mean stay at 100.

This is very strange. One of the more dubious-sounding implications is that if you go far enough back into the past, the average person would have been a complete dolt, and the greatest genius of that earlier age would have been no smarter than George W. Bush or John Kerry.

Rising test scores were pointed out by Reed Tuddenham in 1948, when he compared the better performance on the U.S. military's IQ tests of the draftees of WWII compared to WWI.

In the early 1980s, James R. Flynn, an American-born political scientist at the University of Otago in New Zealand, began to call this phenomenon to academic and then public attention. In his honor, in The Bell Curve, Herrnstein and Murray christened rising IQ scores the "Flynn Effect".

(Flynn says that if he had thought to name it, he would have called it the "Tuddenham Effect", although L. Wheeler may have noticed it even earlier, in 1942. For a discussion of other contributors to our understanding of rising test scores, such as Richard Lynn and Philip E. Vernon, see this 2005 Gene Expression posting, as well as its comments.)

Mainstream IQ researchers, who are used to being demonized when they are not being ignored, admire Flynn, who is politically a man of the left, for his fairness, geniality, insight, and devotion to advancing knowledge. The Flynn Effect has often been seized upon to dismiss IQ testing in general, especially by race-deniers who assume that it will cause racial gaps in IQ to converge out of existence. Flynn himself, however, has never joined the mob in unfairly attacking psychometrics—or psychometricians.

Nevertheless, the Flynn Effect did leave Flynn skeptical about IQ tests. Ulric Neisser wrote in The American Scientist in 1997: "Flynn concludes that the tests do not measure intelligence but only a minor sort of 'abstract problem-solving ability' with little practical significance."

But Flynn has now written a book offering his considered explanation of the Flynn Effect: What is Intelligence? Beyond the Flynn Effect. (The Psychometrics Centre at Cambridge University has posted online a lecture by Flynn summarizing his book.)

Strikingly, Flynn has changed his mind. He now sees the Flynn Effect not as undermining IQ testing, but as validating it. After decades of reflection, Flynn believes people really are more intelligent in some ways today —just as their raw IQ scores suggest. The reason: we get more mental exercise now than in olden times.

Flynn and his collaborator William Dickens of the Brookings Institute argue that people mold their own environments based on their genetic predilections. So genetically smart people choose more mentally stimulating environments, which makes them even smarter. As Steven Johnson points out, mental stimulation, even if it's just watching television or figuring out what the buttons on your new electronic gizmo do, is a lot cheaper today than in the past.

To help you understand how the Flynn Effect could coexist with the undoubted geniuses of the past, imagine two young men in, say, rural England in the 17th Century.

The first, Thomas, is a farm laborer, who spends much of his time in the fields not talking to anyone and goes to bed not long after dark.

He gets little mental stimulation. He'd like more. He went to a play once about a prince and a ghost who wants him to kill his uncle who married his mom. Thomas enjoyed it a lot, especially the fighting part at the end when everybody dies—but players seldom come through his (ahem!) hamlet and they are expensive when they do.

Thomas suffers from what Marx would later call, unkindly, "the idiocy of rural life." (By the way, the urban-rural IQ gap has narrowed from six points to merely two in recent decades as the countryside has come to enjoy most of the stimulations of the city.)

Thomas would score, say, a 60 on a modern IQ test, although he does his duties much better than a 60 IQ person would today. He just doesn't have much practice at the novel and abstract thinking that an IQ test measures. If he was 23 in 2007, though, with ten years of schooling, the telly on six hours a day, and a daily peek at the football news in The Sun, he might score a respectable 90.

One sunny day in 1665, Thomas is doing some chores for a widow who owns a farm in Woolsthorpe. She invites him into the kitchen for a glass of cider. The widow tells Thomas she wished she could get her son, who is the same age as him, to do some work around the farm. "But ever since he came home from Cambridge University because of the Plague, he just stays in his room, doing funny things you've never seen the like of. Here, I'll take him a glass and you can see for yourself."

She opens the door into a room that is dark except for a single dazzling beam of sunlight that strikes an oddly shaped piece of glass and then splits into all the colors of the rainbow. A young gentleman with a long thin nose sits bathed in colors, fiddling with another triangular piece of glass.

"Here you go, Isaac, a nice glass of cider."

"Thank you," Isaac murmurs, without raising his head.

"Ever since he came back from Trinity College, he's not much company," she sighs to Thomas.

For the next week, Thomas thinks a lot about the rainbow man. Is he a magician? But the few people he talks to don't have any idea what the fellow is up to. Thomas slowly forgets about Isaac Newton.

Unlike the local yokel, Newton brings his own incredibly stimulating environment with him, inside his head. Like the farm laborer, he occasionally sees an apple fall from a tree, but when he does, that gets him thinking about the system of the world. Indeed, what Newton needs to bring his smartness to superhuman levels is not more mental stimulation, but the peace and quiet those 18 months at home will afford him—that stupendous year and a half in which he worked on prisms, the calculus, and the beginning of the Law of Gravity.

Talking to himself makes him smarter than does talking to other people, because, compared to him, they just don't have much worth saying.

How would Isaac Newton have done back then on a modern IQ test? I suspect he'd max out any test.

According to Flynn, massive IQ increases are not seen in all types of cognitive functioning, just in a couple of areas, which explains why kids these days don't seem all that much smarter, except at programming their new gadgets. The Wechsler Intelligence Scale for Children (WISC) is one of the most popular IQ tests. Here are its ten subtests, ranked in order from smallest to largest IQ gain over 55 years:

We see only small changes in the first three mental skills: general knowledge, arithmetic, and vocabulary. And yet these are the skills that come up most in our casual conversation

However, there have been substantial improvements in the next six subtests, most of which involve visual logic. The proliferation of visual imagery was one of the major changes in the social environment in the 20th Century. People have much more practice at decoding images quickly than in the past.

For example, consider how the television remote control and cable television led to channel surfing.

Before, you'd flick the On/Off knob on your TV, sit down while it warmed up, and spend about five minutes watching whatever came on while you slowly decided whether it was worth getting off your couch to turn to another channel—of which there were only a few. In the 1970s, however, viewers with remotes and cable started to rapidly shuffle through dozens of channels. They developed the ability to figure out quickly what was going on and whether they wanted to linger for more than a few seconds.

Finally, the fastest rising subtest on the WISC, Similarities, rewards abstract scientific thinking, what Flynn calls viewing the world through "scientific spectacles."

A child gets a maximum score for replying that dogs and rabbits are "mammals." A kid in 1947 who had never seen a nature documentary on TV would likely have said "They have four legs" or something else more concrete than the Linnaean category "mammals."

Flynn's WISC table points out that the surprising success of IQ tests—they are now 102 years old and appear to be as valid as they ever were since they matured between World War I and World War II—stems from the inventors of IQ testing anticipating which way the world would move.

Flynn told me in an email last week: "I often say to audiences that right from the start the framers of IQ tests themselves looked at the world through scientific spectacles and therefore anticipated the spread of such through the general population."

I also suspect that standardized tests have remained useful predictors of competence in part because the world, in going electronic, has gotten more standardized. Programming your cell phone is a rather like answering questions on the Raven's Progressive Matrices IQ test: it's purely logical and there's only one way to do it.

In contrast, early in the 20th Century, people dealt more with farm animals, crops, raw materials like wood, and simple machinery. A Model T could be jury-rigged in various ways to get it back on the road. But a DVD-recorder, like an IQ test question, is a black box that can only be programmed in a prescribed fashion.

So, it's by no means clear that people are getting smarter overall. But they do seem to be getting smarter at the things IQ tests measure … which have proven to be quite important in the modern world.

The Flynn Effect shows up less in the general factor of intelligence, the g factor, which accounts for roughly half of individual differences in intelligence. This suggests that if people are getting better at some tasks, they might also be getting worse at others.

And indeed, some non-IQ tests suggest that people are becoming less competent at dealing with old-fashioned physical objects in the real world rather than with images on glowing screens. One study found that British children had lost the equivalent of 12 points from 1975 to 2003. Richard Tomkins reported in the Financial Times:

"The results achieved by 11-year-olds had fallen to the level that children aged eight to nine had been achieving 30 years ago … A sample question involved pouring all the water from a tall, thin beaker into a short, fat one, refilling the tall, thin beaker to the same level and asking which contained the greater volume of water."[Are children getting cleverer?  August 12, 2006]

Similarly, the Vineland test of "daily living skills" has found a decline in basic ability to cope.

I suspect that people may be getting mentally quicker, but not more profound. For example, this year's hit comedy The Simpsons Movie contains several hundred jokes, at least an order of magnitude more than the number in the much slower-paced 1964 comedy Dr. Strangelove. Yet, I suspect the half-dozen best jokes in Dr. Strangelove will be remembered after all the laughs in The Simpsons Movie are forgotten.

Perhaps we're only getting smart enough to keep treading water as the world gets more complicated. Complexity for the sake of complexity seems to be our era's weakness.

For instance, I recently reread some of the old Time-Life science and nature books that families bought in bulk in the 1960s—such as The Forest and The Desert. They calmly featured text on one page and a picture on the facing page. That made them vastly more readable than the frenetic science books for sale to young people today. Contemporary science books for children are attention deficit-disordered, featuring dozens of images per pair of pages, along with captions, call-outs, and other distractions.

Flynn does hope that his Effect will someday narrow the sizable racial and national gaps in average IQ. But he doesn't have much evidence that it's happening yet. The collection of hundreds of IQ studies from all over the globe by Richard Lynn and Tatu Vanhanen has revealed few examples of convergence. The overwhelming finding from the first century of IQ research is the stability of these gaps.

Flynn advises that, whatever your genetic endowment, mental exercise will help you come closer to your potential: "The best chance of enjoying enhanced cognitive skills is to fall in love with ideas …"

May I take this opportunity to recommend making VDARE.COM part of your daily brain workout?

[Steve Sailer [email him] is founder of the Human Biodiversity Institute and movie critic for The American Conservative. His website www.iSteve.blogspot.com features his daily blog.]