chapter seven HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 7

■ ■ ■ Mr. Huang, a puzzled patriarch Last night, Mr. and Mrs. Huang were introduced to their future daughter-in-law, Vivian Lee. They had been eager to meet the woman whom their son Frank had met in med- ical school. Frank had told them that Vivian graduated first in her class at a private high school and held a biology degree from Harvard. He also had said that Vivian was from a well-to-do family: her father is a banker and her mother a university professor. The Huangs liked what they heard about Vivian because they both come from high- achieving families. However, when they met her they had a bit of a shock. The Huangs, who are of Chinese descent, had assumed that Vivian was Chinese, too. This had been a realistic assumption because Frank had always dated Chinese girls before and he knew that his parents wanted him to marry within their culture. Besides, Vivian’s surname is Lee. Last night, one look at the girl told them she was different from what they had expected. It turns out her father is a descendent of Irish immigrants. Her mother is a descendent of Kikiyu Kenyans. The Huangs quickly overcame their surprise and greeted Vivian warmly. They enjoyed their evening with Frank and his fiancée, and of course have no intention of undermining the couple’s engagement. But reading the newspaper at breakfast this morning, Mr. Huang wonders about the direction in which his family tree is bending. The paper contains an article about into . Among other things, the article reported that both White Americans and Black Americans fare less well on IQ tests, on average, than Asian Americans. For a brief moment Mr. Huang wonders if his future grandchildren will be less intelligent than any children Frank would have with a Chinese woman. He immediately dismisses this notion as ridiculous speculation and feels bad for even thinking it. Focusing back on the facts, Mr. Huang reminds himself that average IQ scores by do not tell much about how individuals achieve, particularly individuals like his grandchildren who aren’t even born yet. What might be more indicative, Mr. Huang ponders, is the fact that Vivian herself is highly intelligent. She has had a good upbringing and the best possible education. She and Frank are in an excellent position to raise their own children into intelligent, successful adults. Those children will have a mix of European, African, and Asian ancestry, but so what? What possible effect could that have on inborn brainpower? Defining intelligence information and how it takes cues from Smart. Quick-witted. Sharp. Clever. emotions (our own and others’). Thus Astute. The English language has many intelligence is a general capacity of the words that describe intelligence, which brain. briefly defined is the ability to absorb, Intelligence stands on its own as a trait, process, recollect, and apply information. but it also permeates all other aspects of is the word used by scientists personality. Sense of humor, risk-taking to specifically refer to the process of tendencies, and sexual attractiveness are thinking. just three examples of the many human Certainly one why there are so traits that relate to intelligence. many ways to describe intelligence is that Intelligence very clearly correlates with the trait involves so many applications of successes in school and work settings. the mind. Intelligence has to do with the Somewhat surprisingly, intelligence also Some researchers believe that “intelligence” acts like a wind ability to reason, to think abstractly, to correlates with overall success in living. in the sails, pushing one toward draw conclusions, to solve problems, to Less delinquency, greater wealth, better success in all aspects of life. learn from experience, and to remember coping skills, higher income, better Whether intelligence actually has that effect, and why, requires what has been learned. It also has to do health, fewer accidental deaths, and further research. with how the mind makes use of sensory longevity are all associated with higher intelligence, according to research. “Bright people have a tail wind in virtu- ally all aspects of life,” claims one researcher. 1

History of intelligence testing Intelligence has been more intensely studied than any other behavioral trait. Intelligence tests, first developed in the 19th century, have been so heavily researched, refined, and applied that the ones used today are fair predictors (though by no means complete predic- tors) of academic and professional achievement. Many scientists believe them to be “among the most accurate (in technical terms, reliable and valid) of all psychological tests and assessments.” 2

98 BEHAVIORAL is the father of the An early researcher into genetically based research into intelli- intelligence, Francis Galton, proposed that eminence in a gence. His 1869 book Hereditary Genius profession was an indication of is hailed as “the first quantitative analysis mental ability; when he was able of human mental ability.” 3 Galton pro- to show that certain families had posed that human mental ability is an more than a normal number of eminent members, he concluded inherited trait and that individual that mental abilities run in “genius” (as he called it) varies along a families. At the time (1869), continuum from very dull to very bright; this was a radical idea. the percentage of the population at any point on the continuum decreases as the extremes are approached. Galton was describing a normal curve of distribution, popularly known as . His idea about a range for was novel at a time when it was gener- ally believed most people had the same Inspired by Galton’s , other intelligence, with just a few being excep- scientists began to devise tests for intelli- tionally slow- or quick-witted. gence. One of these was the French psy- To explore the connection between chologist, . By trial-and-error intelligence and inheritance, Galton experiments with schoolchildren, both selected for study men of high stature normal and mentally handicapped, Binet in their respective profession – the law, deduced what the average child could literature, science, the military, and so accomplish at each age level. Binet forth. He assumed that high achievement teamed up with another , in a field correlated with high mental Theodore Simon, to create a test used by ability. He then observed how frequently French school administrators to identify the first, second, and third-degree rela- children less able to profit from instruc- tives of his selected subjects also tion in regular school classrooms. achieved high standing in their fields. The Binet-Simon scale included 30 He compared these frequencies to that tasks such as shaking hands, finding which could be expected based on a rhymes for words, repeating back a normal curve of distribution for intelli- sequence of random digits, and gence. Galton discovered that high answering logic questions. Performance achievers did in fact cluster in certain on the tests was evaluated to determine families, and concluded that genius was mental age. According to the Binet- therefore hereditary. Simon scale, a child had the mental age

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 99 of 12 if he or she could accomplish the conducted IQ tests to support theories tasks that matched the abilities of the about which types of people were more average 12-year-old. or less intelligent. At this point in In the early 20th century, a German American history, had been abol- psychologist named Wilhelm Stern came ished less than a hundred years earlier up with the idea of stating intelligence in and waves of new immigrants were terms of the ratio of mental to chronolog- coming into the country. Much was made ical age. The popular label for this ratio, over the weak IQ performance of or IQ, was coined American Blacks and of immigrants from later by , an American Eastern Europe. psychologist. Terman was a member of a In the latter part of the 20th century, committee assigned with the task of controversy arose over whether intelli- developing intelligence tests that could be gence tests were biased. Some questioned used to help sort the large number of Galton’s original work by pointing out inductees into appropriate that high professional achievement may assignments. have less to do with inborn intelligence Intelligence tests gained in popularity than with having the means for education after that war. The military continued to and social connections. Other critics use them for recruitment and placement noted that performance on IQ tests most purposes, and workplaces and schools accurately reflects whether you can read started to use them, too. Social scientists the language of the test and are familiar

In the early twentieth century, laws restricted immigration from Eastern Europe, based in part on the false belief that such people would dilute the intelligence of the American population.

100 BEHAVIORAL GENETICS Today, performance on IQ tests is con- Employers, the armed forces, sidered a reasonable predictor of success. colleges, and other important social institutions make use of IQ scores correlate reasonably well, intelligence and aptitude tests though imperfectly, with academic and to screen and place applicants. professional achievement and they corre- late to a lesser extent, though more than randomly, with success in social and personal aspects of life.

Measuring g Many intelligence researchers accept the that there is some underlying ability to learn that feeds into all cognitive performance. This ability is called g. with facts from the culture of those who The term stands for general cognitive create these tests. Critics also claimed ability. The concept of g was first articu- that scientists were interpreting data in lated more than 100 years ago by Charles ways that supported their pre-existing Spearman, a British psychologist, and it racial and cultural prejudices. refers to a basic, core ability to make use Advocates took some of these concerns of information. Some researchers refer to to heart and sought to create less biased, g by two other eponymous terms, “global more accurate tests. Many tests have factor” and “general intelligence factor.” been developed, each using a different Scientists debate whether g is an actual selection of tasks to measure intelligence property of the brain such as some neuro- in its various manifestations: mastery of logical mechanism at work (the minority vocabulary; text comprehension; math view) or merely an abstract property like skills; ; visual acumen; under- “horsepower” (the majority view). standing of universal concepts such as The concept of g derives from the up/down and in/out; grasp of general observation that any given individual ; speed of response; applica- tends to perform at about the same level tion of logic; and more. These tests on a diverse range of intelligence tests. continue to have an enormous role in Whether you give someone a math test or modern society. This is particularly true in a vocabulary test, an oral test or a pen- education, as attested to by the wide- and-paper test, a test with words or a test spread use of the SAT and other tests that with pictures, a timed test or an untimed measure scholastic aptitude. test: across all types of tests, most people

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 101 score somewhat consistently. ment to the theory of g. They suggest that A statistical procedure called factor g is comprised of distinct subsets of analysis is applied to scores on a variety of cognitive ability including fluid intelli- tests, weighting each differently gence (abstract reasoning), crystallized according to the complexity of the test’s intelligence (vocabulary and general cognitive demands, to arrive at a number knowledge), visual-spatial ability, for this pattern of consistency. That memory, and speed of processing. This number is called g, and it is roughly theory is also based on factor analysis: an equivalent to IQ, but is considered individual’s scores on certain types of slightly more pure. This is because the intelligence tests tend to correlate more pooling of data from many types of tests highly compared to the correlation of that dilutes the possibility that what is being individual’s scores on all types of tests. measured is a specific set of learned skills An alternative to the notion of g is the rather than a basic aptitude. idea that intelligence spans many Across IQ tests, g accounts for about different human abilities. One such 40 percent of the variance in perform- theory of multiple (proposed ance. Within any single test, most of the by Howard Gardner in 1983) holds that variance is independent of g. The signifi- humans have eight forms of intelligence: cance of that anomaly is that g is not the linguistic, logical-mathematical, spatial, only factor involved in cognition. kinesthetic, musical, intrapersonal, inter- Some researchers have added a refine- personal, and naturalist. Other similar

Researchers have observed that some people apply mathe- matical calculations and other problem-solving skills in real-life situations much better than they do on IQ tests.

102 BEHAVIORAL GENETICS theories propose different cognitive to add and subtract in a classroom. By the domains. The multiple intelligences same token, Liberian tailors are able to theory raises the possibility that measure- make precise arithmetic calculations ments of g capture some, but not all, when measuring customers but cannot aspects of intelligence, and that it may not do the same when tested. be possible to comprehensively measure This idea of multiple intelligences was the trait in full. first raised in the 1950s, about half a cen- Other researchers are highly critical of tury after g was proposed. It has not been the whole concept. Some argue that the as extensively applied and researched as construct of g is of no value in the search g. Indeed, among many scientists for the underlying neurobiological researching intelligence today, g is consid- g is the ability to learn that processes that contribute to cognition. ered beyond dispute. g is the core piece of underlies all cognitive perform- One scientist has decried “the unreality of data used in analyses that compare the ance. Some researchers are g and the fallacy of regarding intelligence intelligence of individuals and groups. seeking the genetic contributors to g,, while others question as a single-scaled, innate thing in the If the critics are correct, however — whether g is actually a real or head.” 4 Critics point out that if you alter if there is no g — then many of the con- useful concept. the underlying assumptions used in factor clusions drawn from intelligence research analysis, no single number g emerges. will have to be revisited. The reader is They believe that the positive correlations advised to keep this in mind while in an individual’s performance on various reading the next sections of this chapter. IQ tests do not have to do with any underlying factor, but rather simply reflect the individual’s life circumstances. Quantitative research into They assert that someone who is well fed, intelligence adequately sheltered, educated, and A great many quantitative studies have expected by family and peers to achieve, shown that IQ correlation increases as will do well on most tasks set before him genetic similarity increases. Quantitative or her. Someone in opposite circum- studies also provide evidence of environ- stances will not do as well, across mental influences on intelligence: the board. • In studies of identical raised Some suggest that g only reflects test- together, IQ scores do not correlate taking skills, not intelligence as it is used completely. You would expect near-per- in real life. For example, the social anthro- fect correlation between genetic equals pologist Jean Lave has observed that poor if IQ were solely hereditary. favela children in Rio de Janeiro easily do • In studies comparing blood relatives arithmetic when selling wares on the raised together to those raised sepa- street but perform miserably when asked rately, the IQ scores of the former tend

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 103 Children with strong early intelli- to be more similar than those of the estimates ranging broadly around 0.50. gence may tend to select environ- latter. Taken together, they suggest that genetics ments that nurture and support • In studies of family members not and environment are roughly equivalent the development of their intelli- gence. Thus their genetic related by blood (for example, parents in their influence on the variation in IQ. tendency would be reinforced and their adopted children), there The relative contributions of the shared by their environment through is modest, but statistically significant, and the non-shared environment also development. correlations of IQ scores. have been partitioned out in Most quantitative studies of intelli- estimates, and this had led to one sur- gence measuring modern Western popu- prising bit of data. Compared to most lations have produced heritability other behavioral traits, intelligence in childhood seems to be more significantly shaped by the shared environment com- pared to the nonshared environment. This could possibly mean that the home environment has a greater influence on a child’s cognitive development than on other characteristics, such as personality. Researchers are interested in how the contributions of genes and environment change over time. Do inherited character- istics become more important as one gets older, or does the influence of the environment become more important? Most studies of IQ kinship correlations show that genetic influence grows and shared environmental influence falls away almost completely. One possibility is that heritability increases with age because of - environment correlation. That is, as people grow up they are able to exert more control over their experiences. For example, children with higher innate intelligence might choose to engage in activities that stimulate their intellect such as pursuing formal education, reading, spending time in stimulating

104 BEHAVIORAL GENETICS conversation, and engaging in work that Well-nurtured and stimulated challenges the mind. By contrast, children tend to perform better on IQ tests than children who lack children with lower innate intelligence such benefits. This is evidence for might gravitate towards non-intellectual the environmental contribution to activities. Thus, genetic tendencies would intelligence. be reinforced over time. The opposite possibility is that the effects of the environment become stronger as one gets older. Under this sce- nario, children who grow up in stimu- lating homes and who attend quality preschools would follow a higher intellec- tual trajectory than children whose early years are less supportive. They would get better grades in school, have a better chance of making it to college and have more motivation to enroll there, have the academic credentials to obtain intellectu- ally-challenging jobs, etc. Thus, the effects Molecular research of early environment would become mag- into intelligence nified over time. As the careful reader should realize by Another possibility is that the relative now, studies tell us nothing specific contributions of genes and environment about the genetic and environmental fac- remain stable over the lifetime. In 1997, tors underlying intelligence. Molecular data supporting this hypothesis emerged research seeks to bridge this gap, at least from a study of 240 pairs of Swedish in terms of identifying genetic contributors twins in their eighties. In this study, the to intelligence; in turn this may aid in the heritability of general cognitive ability search for environmental contributors. was computed at 0.62.5 This is relatively The operating assumption is that cogni- close to the heritability estimates from tion is a complex trait with many genes studies of younger subjects and thus sup- involved, each of relatively small effect. ports the proposition that the heritability There are exceptions to this general rule. of IQ does not shift significantly with age. As we described in earlier chapters, some More research is needed before the ques- people acquire damage to their brains, tion of how intelligence is affected by significantly affecting their intelligence, genes relative to environment over time from disorders such as PKU, Fragile X, can be answered. and early-onset Alzheimer’s. Each of these

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 105 disorders stem from problem in a imagine the variety of genes involved in a single gene. trait like intelligence is to picture the The general rule, however, is that cog- different products involved in the struc- nitive abilities are shaped by a multitude ture of a house. Concrete, plaster, wood, of genetic and environmental factors that plastic, nails, glass, metal — each serves a interweave throughout development. It is different purpose, yet contributes to the estimated that any single gene accounts overall structure. Endophenotypes are the for at best 1 to 2 percent of the variation equivalents of the products that make a in intelligence; discrete environmental house. They are the intermediate traits, factors likely make similarly modest con- the underlying processes that contribute tributions. This means that highly intelli- to a phenotype. For cognition, these gent people are blessed not with one endophenotypes would include such brainy gene, but rather with an abun- things as speed of information processing, dance of “positive alleles for high g,” as capacity of working memory, synapse some researchers refer to them.6 They dexterity, receptor functionality, and a may also have experienced favorable great many more elements of brain nutritional and nurturing conditions activity. (A diagram illustrating endophe- during their development and/or been notypes appears on page 86.) raised in an environment conducive to To use another metaphor, just as tiny intellectual growth. Persons with lower rivulets running down a mountain join intellect may possess an inordinate together into a mighty stream, each rele- amount of “negative alleles for high g,” vant gene contributes to the causal may have experienced unfavorable condi- pathway by which intelligence is formed. tions during their development, and/or For genetic researchers, the concept of may have been raised in intellectually endophenotypes narrows and makes unsupportive environments. more manageable the search for relevant Genes and environment interacting genes. Using genomic scans or association Endophenotypes are the through processes of development form a studies, they can look for correlations underlying processes to a trait. triple whammy: anyone who comes up between tiny but discrete aspects of brain For example, for the trait of favorably in all three categories has a function and specific alleles of single intelligence, endophenotypes might include speed of informa- strong likelihood of high g. Anyone who genes. This is how several candidates for tion processing, capacity of comes up short across the board has a “IQ genes” have been identified. working memory, and other traits. strong likelihood of low g. For those with The quest to find the individual genes A useful analogy can be found in a middling assortment, the likely range that contribute in some small but measur- the component parts of home construction such as bricks, for g is much broader. able way to intelligence bring to mind an lumber, and tools. To focus back on just the genetic con- old Chinese proverb: “In vain do men tributors to intelligence: one way to seek the source of great rivers.” Despite

106 BEHAVIORAL GENETICS formidable obstacles, some researchers are and memory. Investigations into pursuing this quest. Hundreds of molec- IGF2R, whether or not they confirm this ular studies have been conducted, and particular gene as having anything to do several genes contributing to cognitive with intelligence, may shed light on how function have been tentatively identified insulin figures in cognition. Following the in humans, mice, and even in fruit flies. trail of other implicated genes may offer One such gene achieved some promi- new insights into how intelligence nence in a 1998 study. Named IGF2R, emerges in human beings. the gene is on Chromosome 6 and is an acronym for “insulin-like growth factor-2 receptor.” Insulin-like growth factors are Predicting individual hormones that affect the work of the intelligence nervous system. In this particular study, Molecular research sheds light on genetic Several genes have been researchers conducted scans of a segment inputs, but not on specific individuals. investigated as being potentially involved in intelligence, including of Chromosome 6 in high-IQ children and IGF2R gene researchers made this very one called IGF2R, located on a control group of children. A tiny but sig- point in their published results. They Chromosome 6. None of the can- nificant proportion of the high-IQ chil- specifically noted that more than half of didate genes has been confirmed. dren were found to have a particular the high-IQ children did not have 5 In any event, there is certain to be a great number of genes allele for IGF2R, Allele 5, compared to for IGF2R, while almost a quarter of the involved. the control group children. Allele 5 also control-group children did. When and if was found in slightly greater proportion in the gene IGF2R is confirmed as having a tests on children with extremely high role in IQ, it will not be a signpost for IQs, high mathematical ability, and high who’s bright and who’s not. It may, how- verbal ability. 7 ever, be recognized as an intelligence sus- A follow-up study by the same ceptibility gene. researchers failed to confirm the hypoth- Suppose molecular researchers esis that the IGF2R gene is associated someday identify the scores of genes that with cognition.8 Other genes proposed as weave together into cognition. They fur- candidate “IQ genes” have not been ther identify the “positive” and “nega- confirmed, either. But the point of this tive” alleles for each gene. Then they do research is not only to discover the par- a genome scan of an individual to count ticular genes that help shape intelligence. the number of “positive alleles” present. It also is to understand how intelligence is They still will not be able to state with affected by an overall biological/environ- certitude anything about that person’s mental/developmental process in which intellectual abilities. Scientists might be genes play a part. For example, there is able to offer a likely range for that indi- speculation that insulin may play a role in vidual’s intelligence, but it would be a

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 107 supportive environments may be able to build intellect even in individuals bequeathed with a relatively poor set of genetic material. Some researchers specu- late that the environment during prenatal and early childhood development are particularly important factors for intelli- gence. A child who receives adequate in the womb, is nurtured and stimulated as a baby, and is exposed to early education can obtain important boosts to cognition. One psychologist asserts, “We have demonstrated that intellectual skills often believed to be innate are extremely sensi- tive to the environment.” 9 This psycholo- gist has conducted research that produced correlations between the verbal stimulation provided by parents and the vocabulary and grammatical dexterity acquired by children. Other researchers have found correlations between many other specific environmental conditions and intelligence.10 But the key word here is correlation. Researchers have not yet found a way to move beyond correlation to identify discrete environmental equiva- guess all the same. This is because genes lents of genes that mold behavior. Even if you are born with weak are probabilistic, not deterministic, for the Even if every genetic and environ- eyesight, your vision can get reason that should be obvious by now to mental input were identified, prediction close to perfect using corrective the reader — they operate within envi- will never be perfectible. To understand procedures and lenses. In the same way, even if you are born ronments over time. why, think about weather forecasting. with “weak” intelligence, environ- Eyesight makes a useful example here. Meteorologists today make use of a great mental interventions can boost Presume that nearsightedness is a genetic deal of data concerning atmosphere, your brainpower dramatically. trait. If you inherit your father’s nearsight- terrain, precipitation, temperature, ocean edness, a pair of eyeglasses can correct currents, and all the other discrete vari- your vision to 20:20. In the same way, ables that coalesce into rain on this side

108 BEHAVIORAL GENETICS of the mountain and sunshine on the other. As a result, weather prediction is more accurate than it used to be, but because of the nonsystematic way these variables interact it may never be exact. Similarly, as scientists learn more about the processes by which genes and envi- ronment interact over time, they might get better at predicting individual intelli- gence. Yet, because the inputs are nonsystematic, such predictions will never be precise and sometimes they will be really wrong.

Mr. Huang’s speculations ables including occupation, education, Many studies have analyzed academic income, wealth, and place of residence. Black children given IQ tests score achievement by race. This research may The original intention of this study was to similarly to White children of the be of interest to Mr. Huang, who is won- learn about cerebral palsy and other same . dering about the cognitive prospects of health complications from childbirth, not future children born to his son, who is of intelligence. However, many thousands of Asian descent, and his future daughter-in- pieces of data were collected on the sub- law, who has European and African jects, including IQ scores for the more ancestry. than 59,000 children born to these There is reason to believe that race and mothers, obtained at ages four and seven. intelligence are not related biologically. According to this data, when sorted by Important data on this point comes from SES there is very little difference in IQ The National Collaborative Perinatal between Black and White children.11 Project, a study that began in 1959. Some Despite the significance of this finding, 48,000 pregnant women were enrolled it has rarely been cited in scholarly papers from several major U.S. cities. A roughly on intelligence. What has gained more equal number of Black and White partici- prominence is other IQ testing data col- pants were involved. Importantly, the lected before and since (mostly from sub- socioeconomic status (SES) of the subjects jects in the upper tiers of SES) and pooled covered a broad span. SES refers to one’s together to draw bell curves for the popu- position within a hierarchical social struc- lation as a whole as well as for various ture, and it is determined by several vari- subgroups.

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 109 Looking at these bell curves, Accounting for disparities Mr. Huang might be relieved to learn that in population IQs people of all races and ethnicities can be The discrepancies described above have found at every IQ level, including the been used by some people to argue that high end of the curve. On the other hand, there is an intrinsic, biological difference Mr. Huang might be disturbed to learn between people of different racial and that the bell curve for White Americans is ethnic groups. “Most experts believe that centered somewhat lower compared to environment is important in pushing the East Asians and Jews. The bell curve for bell curves apart, but that genetics could Black Americans and Hispanics sits even be involved too,” according to an essay lower. Mr. Huang also might be troubled on intelligence signed by a large number by U.S. Census Bureau data indicating of researchers in the field and published that, compared to Asian Americans, a in in 1994.12 smaller percentage of White and Black There are many possible explanations Americans complete high school, have for how the environment pushes the bell college degrees, and are in professional or curves apart. It is speculated that the managerial jobs. Asian culture’s emphasis on achievement Whites do better than Asians on some could account, in part, for the compara- measures; for example, their unemploy- tively higher I.Q. performance of Asian ment rate is lower and their home own- Americans. It should be noted here that ership rate is higher. But Blacks do worse “Asian American” is a very broad term than both Asians and Whites on several that encompasses Asian Indian, measures. For example, even when Bangladeshi, Cambodian, Chinese, Blacks and Whites achieve equally well Filipino, Hmong, Indonesian, Japanese, on standardized tests such as the SAT, Korean, Laotian, Pakistani, Thai, the former are outperformed by the latter Taiwanese, Vietnamese, and others. academically. Grade point average is lower, they drop out of school at higher rates, and the time to graduation is longer. This has been called the over-prediction phenomenon: for Blacks, performance on standardized tests over-predicts their aca- Education is highly revered in demic achievement compared to Whites Chinese and Japanese cultures. with the same score. In other words, This could explain in part why even when Blacks are as well prepared Chinese-American and Japanese- American children, as groups, academically as Whites, they do not tend to do well in school. perform as well academically.

110 BEHAVIORAL GENETICS Of these groups, the “” label best fits Chinese and Japanese Americans because they rank so highly on various measures of achievement. Different immigration experiences could explain the much lower levels of achieve- ment for other Asian American popula- tions. Similarly, the immigration struggles of Hispanic Americans might account for their lagging IQ scores relative to Whites and Asians. The , segregation, and discrimi- nation that have his- torically experienced since slavery days and continue to experience could account for their relatively lower achieve- ment, as a group, on IQ. Another recent theory is that African Americans perform less well academically because they suc- cumb to about themselves. were given a section of the verbal part of A number of studies have demonstrated the GRE test. Some of the students were Research suggests that academic that people’s performances suffer when told that the test was to measure their performance suffers when people feel they are being watched or they know they are being watched, when ability, while others were told that the judged or when they feel some- they know that their performance has a test was simply a problem-solving task. thing important rides on the consequence (for example, that they Interestingly, Black students underper- results. might lose a prize), or when they are formed White students only in the groups aware that they are different from others that had been told their ability was being in the test group (for example, if they are measured. The researchers ascribed this the only female being tested in a group of phenomenon to “ threat.” males). Therefore, it could be that the In their words, mere fact of being African American in a …whenever African American culture that stereotypes Blacks as inferior students perform an explicitly may be sufficiently disturbing to impair scholastic or intellectual task, they performance. face the threat of confirming or Indeed, this is the finding of a ground- being judged by a negative societal breaking study published in 1995. In this stereotype — a suspicion — about experiment, groups of college students their group’s intellectual ability and

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 111 competence. This threat is not age seven. The new study used the NCCP borne by people not stereotyped in twin and SES data along with advanced this way. And the self-threat it causes model fitting techniques to parse out the – through a variety of mechanisms relative contributions of genetics and — may interfere with the intellectual environment. The researchers concluded functioning of these students, partic- that genetic influence varies depending ularly during standardized tests.13 on socioeconomic status. The researchers also argue that long-term According to the abstract (summary) of effects on Blacks of may the study, “In impoverished families, be for them to reject the ideal of academic 60 percent of the variance in IQ is achievement, to lose interest in achieve- accounted for by the shared environment, ment, to put less effort into it, and as a and the contribution of genes is close to result, to achieve less. zero; in affluent families, the result is Class (which closely parallels race in almost exactly the reverse.” The implica- this country) could be another environ- tion is that the quality of the environment mental factor that pushes the bell curves has a swamping effect; impoverished con- apart. A 2003 study made fresh use of ditions tend to suppress genetic potential, twin data from the National Collaborative while enriched conditions tend to allow Perinatal Project (which, as we men- genetic potential to flourish. The study Based on twin studies, researchers have suggested tioned previously, had been underappreci- concluded, “Although there is much that that the environment may have ated). The NCPP included so many remains to be understood, our study and a greater impact on the develop- mothers and their children that it con- the ones that have preceded it have ment of intelligence for children tained data on more than 600 twin pairs. begun to converge on the hypothesis that raised in impoverished environ- ments compared to those raised NCCP researchers were able to locate the developmental forces at work in poor in rich environments. about half of those pairs for IQ testing at environments are qualitatively different from those at work in adequate ones.”14 How would genetics push the bell curves apart? It would mean that “positive alleles for g” are more prepon- derant in one racial group than another. Such differences among geographically dispersed human populations could con- ceivably have occurred through the forces of natural selection. Since environments and genetics work together over development, the human group that achieves best on intellectual

112 BEHAVIORAL GENETICS scales would be the one that has advan- tage in both environmental and genetic departments. And so while one could speculate that Asian Americans have a greater assortment of “positive alleles for g” than any other racial or , alternate hypotheses also could be pro- posed. For example, it could be that Asian Americans are not more gifted genetically As a well-known example, the alleles that than other groups, but they are advan- lead to the blood disorders of sickle cell taged environmentally. Or it could be that disease and thalassemia appear more fre- African Americans are so disadvantaged quently in African and Mediterranean environmentally that their equivalent or populations, respectively. Such facts jus- even superior genetic gifts cannot make tify the quest pursued by some up the difference. researchers to discover the “IQ genes” But this is all speculation. The difficulty that would explain why some racial and in researching racial differences in cogni- ethnic groups dominate in intelligence It is possible for two people of tion lies in the fact that racial identifica- testing and achievement. different races to be more related genetically to each other than tions are less a biological fact than a social Researchers might be able to obtain they are to some people from construct. Population genetics is the usable data on the their own respective race. branch of science concerned with gene question through molecular techniques. frequencies — the prevalence of alleles in For example, it may be possible to deter- populations. As any population geneticist mine ancestry of subjects through DNA will tell you, there is more genetic diver- analysis, give them intelligence tests (that sity between individuals of one popula- are not culturally biased), and see how tion than there is between population those whose lineage traces back to Asia groups. A White person from Denmark perform on these tests compared to those may be more similar genetically to a Black whose ancestors come from Europe or person from Sudan than to another White Africa. Dane. Your “race” (as determined by your In the final analysis, though, the own choice or as assigned by others) answers will have to do with populations, yields less data useful to behavior not individuals. Mr. Huang cares not research than specific information about about how Asian Americans, White your particular biological ancestors. Americans, or Black Americans fare as Yet considered on a statistical basis, groups in terms of intelligence. He cares some alleles do occur more frequently in about the potential of his individual, some racial and ethnic populations. mixed-race American grandchildren.

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 113 Perhaps some day, when scores of sus- , nurtured in America and ceptibility genes for IQ have been identi- other western countries, led to the aggres- fied, microarray analysis could determine sive promotion of childbearing among the number of alleles associated with high educated White women. This is an cognitive capabilities that are possessed example of positive eugenics. It also led to by Mr. Huang’s descendents. That is not the institutionalization of the “unfit” to yet possible. Even if it were, the data prevent their procreation and to the would produce only a measure of prob- extensive use of sterilization on those able potential. What happens over time declared feeble-minded or insane. These with that potential — whether it is maxi- are two examples of negative eugenics. mized or wasted — remains outside Sterilization victims often were poor anyone’s full control. and/or non-White and in most cases con- sent was not obtained. In the U.S., more than 40,000 eugenic sterilizations were Eugenic concerns conducted in thirty states between 1907 In an ideal world, Mr. Huang would and 1944. never even entertain the notion that a Eugenic ideas were adopted to hideous grandchild with a superficial racial differ- effect by the Nazi government in ence might have inferior intelligence. But Germany, which sterilized hundreds of the world in which Mr. Huang lives is not thousands and killed millions on the ideal. There is a long history of humans grounds that they were diseased, of low seeking to find distinctions between intelligence, or politically troublesome. groups in order to declare that one is They targeted enemies, primarily the better than another. Jews, and used eugenic arguments to Francis Galton, cited at the beginning justify their policies. of this chapter as the father of modern After World War II, eugenics fell into genetics, is also the fellow who coined disfavor, though some policies such as the term eugenics. It comes from the sterilization remained in effect in a few Greek for “well born,” and stands for the countries for many more years — in the idea that human races can be improved U.S., through the 1970s. Yet the basic through selective breeding. Tied to this philosophy of eugenics endures. In 1994, philosophy is the concern that humanity controversy over eugenics re-emerged will degenerate without deliberate inter- with the publication of The Bell Curve. vention. Conceived in noble ideas about In this book the authors described a the betterment of mankind, in practice “dysgenic trend”: the poorly educated twentieth century eugenics was base and were reproducing more rapidly compared shameless. to the well educated. The authors

114 BEHAVIORAL GENETICS claimed that race and class differences in The Nazis used pseudo-scientific IQ are primarily genetic and immutable.15 eugenic theories to justify the oppression and mass murder Many people from the fields of genetics, of Jewish people and other sociology, and statistics have presented non-Aryans. Today, some people strong scientific arguments against these fear that behavioral genetic claims. Nonetheless, the debate itself theories could be distorted to advance the idea that some gave fresh sustenance to the perception people are better than others. that race matters. Genetic discoveries open the door to new ways to practice eugenics. For example, it is now possible to select children based on genetics. Selection techniques fall into two categories: selec- tions for therapeutic — to avoid serious medical disorder — and selec- tions for enhancement — to obtain a desired trait. DNA can be obtained from fetuses through amniocentesis and other tech- niques used for prenatal diagnosis, and some parents now use this information to decide whether or not to continue a preg- that prenatal screening today is imper- nancy. DNA also can be obtained from fectly implemented; Cystic fibrosis embryos created through in vitro fertiliza- testing in the has resulted tion, and parents sometimes use this in some terminations of healthy fetuses information to select which embryo or due to misinterpretation of results, embryos to implant in the mother. according to medical geneticists.16 At the present time, prenatal diagnosis Prenatal diagnosis also can be used to is used primarily to determine the pres- select for sex, either for medical reasons ence of problem alleles linked to single- such as if the family has a history of an gene disorders, so as to avoid giving birth X-linked medical disorder (in which case to a child with a fatal illness. For they would select for a girl), or if the example, in the U.S. standard prenatal parents simply prefer to have a child of a care now includes a DNA screening test particular sex (in which case they most for cystic fibrosis. Tests for many other often select for a boy). diseases will probably become routine in It is not possible to genetically select for the coming years. It should be mentioned such behavioral traits as pleasant disposi-

CHAPTER 7: HOW IS INTELLECT MOLDED BY GENES AND ENVIRONMENTS? 115 tion, athleticism, altruism, or high intelli- • Will parents feel obliged to select for gence. One reason it is not possible is that enhancement so as not to disadvantage we do not yet have solid proof about any their child? of the genes that play any part in these • How will selecting for particular traits behavioral traits. Even if and when all affect the parent-child relationship? relevant genes are identified, genetic • What are the psychological, legal, and selection for a behavioral trait will be social ramifications when children do complicated by the fact that many genes not meet the potential expected by are involved. their enhancements? Yet as research advances, it may In the end all such questions may be become feasible to identify the many moot, because complex behavioral traits genes associated with a behavioral trait such as intelligence may be forever and to engineer embryos to carry all the beyond our ability to engineer. The more known “positive alleles” for that trait. we learn about behavioral genetics, the Would such engineering actually create a more likely it seems that we will never be Genetic research could make it child who grows up to have the desired able to completely predict or control how possible for parents to pre-select the behavior characteristics of trait? Possibly yes, but possibly no, our children think, how well they think, their children — or at least to try. because the effects of genes on behavior and what they do with their . Even if such genetic selection are determined by their environmental could be done, the unforeseeable effects of the environment would context over the course of development. make the results uncertain. A more likely possibility is that Notes enhancement opportunities will be mar- 1 , Professor of Education, University of keted by genetic testing companies before Delaware, quoted in Holden, C. (2003, pg. 192). there is any solid scientific basis to their 2 Gottfredson, L., et al. (1994, pg. 13). products. This, of course, would be 3 Wozniak, R. H. (1999). 4 See Gould, S. J. (1995, pg. 2). ethically problematic. Many other ethical 5 See McClearn, G. et al. (1997). concerns also attach to the possibility of 6 See, for example, Chorney, M. J. et al. (1998). genetic enhancement for behavioral 7 Chorney, M. J. (1998). traits: 8 Hill, L. et al. (2002). 9 University of Chicago psychologist Janellen Huttenlocher, • When and if enhancement technology quoted in Wickelgren, I. (1999. pg. 1832). becomes available, who will have 10 See Wickelgren, I. Ibid. access to it – only the rich, or everyone 11 Nichols, P., and V. Elving Anderson (1973). equally? 12 Gottfredson, L., et al. (1997, pg. 15). 13 See Steele, C. M. and J. Aronson (1995, pg. 797). • Who decides what enhancements are 14 Turkheimer et. al. (2003). Abstract quotation from pg. 623. desirable – individuals or society? Study quotation from pg. 628. 15 Herrnstein, R. J., and C. Murray (1994). 16 See Concar, D. (2003).

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