EDITORIAL Mainstream Science on Intelligence: An Editorial With 52 Signatories, History, and Bibliography LINDA S. GOTTFREDSON University of Delaware The following statement was first published in the Wall Street Journal, December 13, 1994. Mainstream Science on Intelligence Since the publication of “The Bell Curve,” it reflects a broader and deeper capability for many commentators have offered opinions comprehending our surroundings-“catch- about human intelligence that misstate cur- ing on,” “ making sense” of things, or “figur- rent scientific evidence. Some conclusions ing out” what to do. dismissed in the media as discredited are ac- 2. Intelligence, so defined, can be mea- tually firmly supported. sured, and intelligence tests measure it well. This statement outlines conclusions re- They are among the most accurate (in techni- garded as mainstream among researchers on cal terms, reliable and valid) of all psycho- intelligence, in particular, on the nature, ori- logical tests and assessments. They do not gins, and practical consequences of individu- measure creativity, character, personality, or al and group differences in intelligence. Its other important differences among individu- aim is to promote more reasoned discussion als, nor are they intended to. of the vexing phenomenon that the research 3. While there are different types of intel- has revealed in recent decades. The follow- ligence tests, they all measure the same intel- ing conclusions are fully described in the ligence. Some use words or numbers and major textbooks, professional journals and require specific cultural knowledge (like vo- encyclopedias in intelligence. cabulary). Other do not, and instead use shapes or designs and require knowledge of The Meaning and Measurement of only simple, universal concepts (many/few, Intelligence open/closed, up/down). 4. The spread of people along the IQ con- 1. Intelligence is a very general mental ca- tinuum, from low to high, can be. represented pability that, among other things, involves well by the bell curve (in statistical jargon, the ability to reason, plan, solve problems, the “normal curve”). Most people cluster think abstractly, comprehend complex ideas, around the average (IQ 100). Few are either learn quickly and learn from experience. It is very bright or very dull: About 3% of Ameri- not merely book learning, a narrow aca- cans score above IQ 130 (often considered demic skill, or test-taking smarts. Rather, the threshold for “giftedness”), with about Reprinted with permission of The Wall Street Journal copyright 1994, Dow Jones & Company, Inc. All rights reserved. INTELLIGENCE U(I) 13-23 Copyright 0 1997 Ablex Publishing Corporation ISSN: 0160-2896 All rights of reproduction in any form reserved 13 14 GOTTFREDSON the same percentage below IQ 70 (IQ 70-75 soning and decision-making. Conversely, often being considered the threshold for a low IQ is often a disadvantage, especially in mental retardation). disorganized environments. Of course, a high 5. Intelligence tests are not culturally bi- IQ no more guarantees success than a low IQ ased against American blacks or other na- guarantees failure in life. There are many ex- tive-born, English-speaking peoples in the ceptions, but the odds for success in our soci- U.S. Rather, IQ scores predict equally accu- ety greatly favor individuals with higher IQs. rately for all such Americans, regardless of 11. The practical advantages of having a race and social class. Individuals who do not higher IQ increase as life settings become understand English well can be given either a more complex (novel, ambiguous, changing, nonverbal test or one in their native language. unpredictable, or multifaceted). For exam- 6. The brain processes underlying intel- ple, a high IQ is generally necessary to per- ligence are still little understood. Current re- form well in highly complex or fluid jobs search looks, for example, at speed of neural (the professions, management); it is a con- transmission, glucose (energy) uptake, and siderable advantage in moderately complex electrical activity of the brain. jobs (crafts, clerical and police work); but it provides less advantage in settings that re- Group Differences quire only routine decision making or simple 7. Members of all racial-ethnic groups can problem solving (unskilled work). be found at every IQ level. The bell curves 12. Differences in intelligence certainly of different groups overlap considerably, but are not the only factor affecting performance groups often differ in where their members in education, training, and highly complex tend to cluster along the IQ line. The bell jobs (no one claims they are), but intel- curves for some groups (Jews and East ligence is often the most important. When Asians) are centered somewhat higher than individuals have already been selected for for whites in general. Other groups (blacks high (or low) intelligence and so do not differ and Hispanics) are centered somewhat lower as much in IQ, as in graduate school (or spe- than non-Hispanic whites. cial education), other influences on perfor- 8. The bell curve for whites is centered mance loom larger in comparison. roughly around IQ 100; the bell curve for 13. Certain personality traits, special tal- American blacks roughly around 85; and ents, aptitudes, physical capabilities, experi- those for different subgroups of Hispanics ence, and the like are important (sometimes roughly midway between those for whites essential) for successful performance in many and blacks. The evidence is less definitive jobs, but they have narrower (or unknown) for exactly where above IQ 100 the bell applicability or “transferability” across tasks curves for Jews and Asians are centered. and settings compared with general intel- ligence. Some scholars choose to refer to these Practical Importance other human traits as other “intelligences.” 9. IQ is strongly related, probably more so than any other single measurable human Source and Stability of Within- trait, to many important educational, occu- Group Differences pational, economic, and social outcomes. Its relation to the welfare and performance of 14. Individuals differ in intelligence due to individuals is very strong in some arenas in differences in both their environments and life (education, military training), moderate genetic heritage. Heritability estimates range but robust in others (social competence), and from 0.4 to 0.8 (on a scale from 0 to l), most modest but consistent in others (law-abiding- thereby indicating that genetics plays a big- ness). Whatever IQ tests measure, it is of ger role than does environment in creating great practical and social importance. IQ differences among individuals. (Herita- 10. A high IQ is an advantage in life be- bility is the squared correlation of phenotype cause virtually all activities require some rea- with genotype.) If all environments were to MAINSTREAM SCIENCE ON INTELLIGENCE 15 become equal for everyone, heritability would al surveys continue to show, black 17-year- rise to 100% because all remaining differences olds perform, on the average, more like in IQ would necessarily be genetic in origin. white 13-year-olds in reading, math, and sci- 15. Members of the same family also tend ence, with Hispanics in between. to differ substantially in intelligence (by an 2 1. The reasons that blacks differ among average of about 12 IQ points) for both ge- themselves in intelligence appear to be ba- netic and environmental reasons. They differ sically the same as those for why whites (or genetically because biological brothers and Asians or Hispanics) differ among them- sisters share exactly half their genes with selves. Both environment and genetic hered- each parent and, on the average, only half ity are involved. with each other. They also differ in IQ be- 22. There is no definitive answer to why cause they experience different environments IQ bell curves differ across racial-ethnic within the same family. groups. The reasons for these IQ differences 16. That IQ may be highly heritable does between groups may be markedly different not mean that it is not affected by the envi- from the reasons for why individuals differ ronment. Individuals are not born with fixed, among themselves within any particular unchangeable levels of intelligence (no one group (whites or blacks or Asians). In fact, it claims they are). IQs do gradually stabilize is wrong to assume, as many do, that the rea- during childhood, however, and generally son why some individuals in a population have change little thereafter. high IQs but others have low IQs must be the 17. Although the environment is important same reason why some populations contain in creating IQ differences, we do not know yet more such high (or low) IQ individuals than how to manipulate it to raise low IQs perma- others. Most experts believe that environ- nently. Whether recent attempts show promise ment is important in pushing the bell curves is still a matter of considerable scientific debate. apart, but that genetics could be involved too. IS. Genetically caused differences are not 23. Racial-ethnic differences are somewhat necessarily irremediable (consider diabetes, smaller but still substantial for individuals poor vision, and phenylketonuria), nor are from the same socioeconomic backgrounds. environmentally caused ones necessarily re- To illustrate, black students from prosperous mediable (consider injuries, poisons, severe families tend to score higher in IQ than blacks neglect, and some diseases). Both may