It has been used to predict everything from the fall of America to the decline of Western civilization. A drop of just one point has been known to ruin a life. A decrease of 15 points can signal the inferiority of an entire generation.
The stock market? The gross national product? The budget deficit?
No, the IQ test.
Intelligence testing is in the news again. A recent headline in The New York Times said, "I.Q. Scores Are Up, and Psychologists Wonder Why." According to the American Scientist, average scores on IQ tests have been rising significantly and continuously all over the world, and they have been doing so for most of this century.
On broad-spectrum tests, Americans have gained about three IQ points per decade, or 15 points over a 50-year period. Yet the cause of the increase remains unknown. Are we getting smarter, or are we just getting better at taking tests?
Greater sophistication about tests does play a role.
But there are other factors. Ulric Neisser, professor of psychology at Cornell University, posits several: improved nutrition, better education, different child-rearing practices, and technology.
If you were asked to choose which factor contributed to improved scores, the best answer probably would be "all of the above."
The notion that human intelligence could or should be measured didn't just happen: It was invented, coming to us from Victorian England.
Not to be outdone by the British, Americans were quick to adopt the concept of mental testing. But being ardent admirers of the French, too, we seized upon the basic form created by Alfred Binet, a passionate measurer not only of intelligence but also of head size, lung capacity, eyesight, and hearing. He was especially interested in ear shape, which he believed showed character.
Mr. Binet's legacy, popularly called the IQ test, was more enthusiastically accepted in America than in Europe, and ultimately its results were given greater weight here than anywhere else in the world.
The biggest spurts of interest in the test have come at distinct moments in our history.
The turn of the century brought unprecedented waves of immigrants, whose very presence raised questions about who was who. Our position of international leadership was disputed in two world wars. And now, our growing diversity again challenges our national identity.
It appears that, in times of uncertainty, it's comforting to rely on standardized measurements to tell us who we are.
In the 1950s and 1960s, students in the US were tested to categorize their abilities. Today, it's still mostly children who are tested, but typically only those who have been observed to be either "gifted" or learning-disabled.
Yet, these scores can't really measure true intelligence. Yes, they draw on specific abilities important to academic success - verbal and visual capabilities, and special aptitudes such as math, reading vocabulary, and memory.
But other equally important attributes such as creativity, humor, wisdom, and compassion aren't included on any scorecard.
The unexplained rise in IQ scores only undermines the concept of intelligence testing. If intelligence increases, it cannot be innate. Yet our brains are biologically, chemically, and structurally about the same at the end of the century as they were at the beginning. There is no such thing as a fin de sicle brain.
Just as Alfred Binet believed ear shape shows character, his IQ test as a measure of intelligence may be no more than a myth.
* Susan Weiner is a freelance writer in Miami.