ARE PEOPLE GETTING SMARTER?

See Physical Anthropology: The Core, Chapter 4, pages 106-107;

Physical Anthropology, 6^th edition, Chapter 8, pages 191-193.

The secular trend refers to the tendency over the last hundred years or so for each successive generation to mature earlier and grow larger. In the 1980s a similar phenomenon was described for intelligence as measured by the Stanford-Binet, Wechsler, and other intelligence tests. The average IQ score has increased each generation since these tests were first administered shortly after the beginning of this century.

This phenomenon of increasing average IQ scores is called the Flynn effect after James R. Flynn, a political scientist from New Zealand who first described it. Flynn, using data from 21 countries including the United States, found that average IQ scores rose about three points each decade since the tests were first given.

A score of 100 is defined as average on an IQ test. What is considered to be average, however, is recalculated based on each group of people of a particular age that take the test at a specific time. We can compare 1989 scores to those of previous years on the Wechsler and Stanford-Binet IQ tests. The average person in 1989 scored about 10 points higher than the average person in 1960, and 24 points higher than the average person in 1918.

Charles Murray and the late Richard J. Herrnstein, the authors of the book The Bell Curve: Intelligence and Class Structure in American Life, propose that people at different socio-economic levels are characterized by different levels of intelligence. They imply that these differences are, in part, a reflection of different genes. Since different percentages of different "racial" and ethnic groups occupy various socio-economic classes, they imply that different groups have different potentials to achieve various intellectual levels.

If valid, the Flynn effect implies that the average intelligence of a group, as measured by standardized tests, is much more complex than Murray and Herrnstein's correlations. It indicates that IQ is not fixed but fluid. Indeed, the data not only shows that IQ scores have risen from generation to generation, but that the average IQs of different groups have changed relative to one another over the years.

Some Asian immigrant groups scored a couple of points less on IQ tests than the average of all "white" Americans when they first entered the United States. Just a few generations later, however, the descendants of these Asian immigrants scored about 7 points above "white" Americans. The reasons for this increase appear to be the vigorous work ethic and the pressures put on many Asian-American students by their parents to succeed in school and to seek professional careers.

As with the secular trend, the reasons for the Flynn effect are not clear. Explanations range from today's children having more practice taking tests to better nutrition. However, these reasons have been rejected by most researchers. In fact, Flynn is not even convinced that the rise in IQ scores really means that people are more intelligent today than in the past; in fact, he thinks this is an incorrect conclusion. Like others, Flynn is baffled by the effect named after him.

Many investigators in the area of intelligence see the Flynn effect as indication of the great effect of nongenetic factors on IQ scores. Genetic change does not occur fast enough to account for significant change in IQ scores over the last 80 years. Just what does account for the changes, however, remains a mystery. Answers to this mystery might help us understand what is being measured by IQ tests and the nature of whatever that phenomenon happens to be.

References: J. Horgan, "Get Smart, Take a Test: A Long-term Rise in IQ Scores Baffles Intelligence Experts," Scientific American (November 1995), 12-13; R. Jacoby and N. Glauberman, The Bell Curve: History, Documents, Opinions (New York: Times Books, 1995).