PERSPECTIVE ON INTELLIGENCE : The Same Rules Shape People and Tomatoes : ‘The Bell Curve’ is based on a fatal error of bias. Genes dictate individual differences; environment shapes the blooming.
As I follow the debate over Richard Herrnstein and Charles Murray’s “The Bell Curve,” I am struck yet again by how difficult it is for Americans to think intelligently about intelligence. Partly this is because the history of research on IQ, heredity and race is marked with such loathsome prejudice.
Early in this century, H. H. Goddard, a leading educator, gave IQ tests to immigrants, including the non-English-speaking, as they arrived at Ellis Island. The results: 83% of the Jews, 80% of the Hungarians, 79% of the Italians and 87% of the Russians scored as “feebleminded.” Goddard concluded that low intelligence, which he linked to poor character, is inherited, and that “undesirables” should be kept out of the country or at least prevented from having children.
But partly we have trouble talking about intelligence because we think it is somehow unjust to recognize that people differ in their intellectual abilities, just as they differ in the ability to play football or the violin. No one would dream of forcing Itzhak Perlman or Joe Montana to suppress his talents in the name of fairness to others less gifted. But intellectually gifted children are routinely denied opportunities to develop and expand their abilities, often confined to classes that bore them to death.
If “The Bell Curve” was actually about the bell curve of intelligence, it mightwell have served to generate sensible discussion of this issue. There is no reason for anyone to get hot under the collar about the evidence that some proportion of intelligence (at least the specific kind of intelligence measured on IQ tests) has a genetic component. So, as all parents know and research confirms, do aspects of temperament, such as shyness and extroversion. In psychology, only a few die-hard environmentalists still believe that you can turn a timid toddler into another Bette Midler.
But “The Bell Curve” is based on a fatal error that makes a mockery of the authors’ claims to be impartial and unprejudiced. The error is to assume that genetic variation, which can account for differences among individuals within a group, is also the reason for differences between groups. This is the mistake that every racist since Goddard has made, so it is important to understand it.
Years ago, geneticist Richard C. Lewontin proposed the following “thought experiment”: Suppose you have a bag of tomato seeds that vary genetically; all things being equal, some seeds will produce tomatoes that are puny and tasteless and some will produce tomatoes that are plump and delicious. You take a bunch of seeds in your left hand and a bunch in your right. Though one seed differs genetically from another, there is no average difference between the seeds in your left hand and those in your right.
Now you plant the left hand’s seeds in Pot A. You have doctored the soil in Pot A with nitrogen and other nutrients. You feed this pot every day, sing arias to it and make sure it gets lots of sun. You protect it from pests and you put in a trellis so even the weakest little tomatoes will have some support. Then you plant the seeds in your right hand in Pot B, which contains sandy soil lacking nutrients. You don’t feed these tomatoes, or water them or sing to them; you don’t give them enough sun; you let pests munch on them.
When the tomatoes mature, they will vary in size within each pot, purely because of genetic differences. But there will also be an average difference between the tomatoes of enriched Pot A and those of depleted Pot B. This difference between pots is due entirely to their different soils and tomato-rearing experiences.
With people as with tomatoes, differences within racial, ethnic or national groups are partly genetic; but differences between such groups can be entirely environmental. Blacks and whites do not grow up, on the average, in the same kind of pot. Black children often receive fewer nutrients--literally, in terms of nutrition and prenatal care, and figuratively, in terms of education, encouragement by society and intellectual opportunities.
Moreover, cultural groups differ in a zillion ways that can affect performance on IQ tests. For example, anthropologist Shirley Brice Heath studied a small African American community in the South and found that black parents were less likely than white parents to ask their children “what,” “where,” “when” and “who” questions--the sort of questions found on standardized tests and in schoolbooks (“What’s this story about?” “Who is this?”). They preferred analogy questions (“What’s that like?”) and story-starter questions (“Did you hear about . . . .”) Teachers in the community used this information to modify their teaching strategies. They encouraged their black pupils to ask “school-type” questions, but they also incorporated analogy and story-starter questions into their lessons. Soon the black children, who had previously been uncomfortable and quiet, became eager, confident participants.
Similarly, if we want to explain why American children of all races perform so much worse in math and science than do students in Japan and China, we must look to the “nutrients” that Asian children get. Their parents have much higher standards for achievement than American parents have; their parents expect them to study hard to succeed, whereas American parents tend to think you either “have” math ability or you don’t; and Asian parents and children’s peer groups support academic achievement. In the United States, many white students who are good in math and science are considered nerds and dweebs, and many black students who excel academically are accused by peers of “selling out” to white society. Asians and Americans grow up in different pots.
Robert Plomin, a leading behavior geneticist, has observed that “the wave of acceptance of genetic influence on behavior is growing into a tidal wave that threatens to engulf the second message of this research: These same data provide the best available evidence for the importance of environmental influences.”
An intelligent social policy on intelligence would not direct us to conclude that “it’s all in the genes; there is nothing we can do.” It would direct us to make sure that all children grow up in the best possible pot, with room for the smartest and the slowest to find a place in the sun.
