If you compare men who have had heart attacks with those who haven't, it turns out that the average height in the group who had heart attacks is lower than the average height of those who haven't. Does this mean that short men have more heart attacks than tall men? Does it mean that the gene for height comes handin-hand with a gene for blood pressure, cholesterol levels, or a predisposition to heart attacks? No. It means that older men are more likely to get heart attacks than younger men, and men shrink as they age. So what looks like a clue to an underlying genetic link is, in fact, nothing of the kind. Take a second example. People who live in temperate climates tend to get more colds in the winter. Thus, many of us come to believe that the cold weather actually causes sickness. Climate and colds are related, but not because one causes the other. Instead, one leads to the other. In cold weather, we spend more time with other people in close, unventilated spaces. Our immune systems become weakened because of the stress of staying warm. The winter weather does help explain our increased sickness, but it doesn't cause the common cold. Having black skin might mean you are less likely to get a high score on an IQ test, but that doesn't mean that black people are not as smart as white people.
We are a long way from knowing what it is exactly about intelligence that is genetic and just as far from knowing what gene or genes might explain a person's intelligence. But imagine that you are a researcher who doubts that the lower IQ scores of black children can be explained as a genetic difference. What would you do? You'd begin to try to identify other explanations for the difference. And that is just what researchers have been doing in the past fifteen years or so.
Some of the causes of group differences in IQ have been hidden in plain sight, just waiting to be identified. Claude Steele, from Stanford University, knew that stereotypes not only influence the behavior of the stereotyper, but they also have a huge effect on those who have been stereotyped. He reasoned that a powerful social stereotype affects people in the stereotyped group, even when no stereotyping or prejudice is active or present. In other words, stereotyping is "in the air" and shapes people all the time. When it comes to students taking important tests that measure their ability and might determine their future, the threat of potential stereotyping is particularly menacing. Steele and his colleagues reasoned this way: black students might worry, when in a testing situation, that if they do not do well, they will strengthen people's erroneous stereotypes. Worrying about this keeps them from doing their best on the test. In the kind of demonstration every researcher longs for, Steele tried a very simple manipulation. He removed the threat by telling students at the beginning of the test that this particular test had never shown any differences between groups. He learned a few startling and important things. Removing the threat in that simple way dramatically improved the scores of black students taking the test.