KENNETH B. CHIACCHIA

Throughout human history, peoplehave tended to divide each other into groups. Most often, physical characteristics are used to distinguish between groups, and the groups are called races. Some people have long believed that many characteristics about a person could be determined by simply looking at the person’s race. Intelligenceis one trait that has been studied in an attempt to correlate it to racial groups. In fact, at present the best evidence does not strongly support the idea that the people of any race are more or less intelligent than those of any other race. In addition, intelligence testing is an imperfect science. Traditional tests are skewed to favor certain segments of society.

Saying that intelligence is partly genetic, programmed in the genes and inherited from one generation to the next, is vastly different than saying that genes underlie any racial differences. To give a classic example, scatter two identical groups of seed on a rich and a barren, dry plot of land. Within the rich plot, genetics will determine any difference in seed growth. But environment will cause most of the difference between the two plots.

Studies estimate that genes account for between 30 and 80% of our intelligence. Using meta-analysis, a statistical method that allows researchers to compare data from different experiments, a group of researchers showed that, when all these studies are taken together, genetics appear to determine roughly half of intelligence, environment the other half. Interestingly, the meta-analysis also suggested that pre-birth environmental factors such as the mother’s nutrition, which are difficult to measure in any study, might underlie most of the environmental difference. These results make some common sense.

We know that intelligent people tend to have intelligent children-but not always. Some studies have also suggested that intensive programs may make a large difference in disadvantaged children’s intelligence quotient (IQ) scores. The problem with this split is that unrecognized differences in either genetic inheritance or environment might skew otherwise carefully crafted studies of race and intelligence. This problem will haunt nearly every single study we discuss.

The question of whether human races possess different intellectual capacities comes, at least in part, from an early twentieth-century observation that African Americans’ IQ scores were, on the average, 15 points lower than those of white Americans. Recently, the black/white IQ difference has decreased; today it’s closer to 10 points. It’s difficult to see how a five-point change in the IQ difference between black and white Americans could have come about in less than a century if genetics caused the difference entirely. Even more interesting, Americans and western Europeans today score 15 points higher on identical IQ tests than their great grandparents did. A 15- point difference in IQ is significant (an IQ of 100 is “average,” 130 “gifted”); but we clearly aren’t more intelligent than our great grandparents. It seems that environmental factors can and do play havoc with our attempts to measure intelligence.

A number of researchers have undertaken studies to uncover the source of the 10-point IQ difference between the races. One type of study measures the IQs of children of different racial backgrounds who are raised in similar environments. African Americans, on the average, have 70