Flaws in Eugenics Research

Garland E. Allen, Washington University

A display organized in 1926 by the American Eugenics Society showed a pedigree chart of guinea-pig pelts, with the caption: "Human Mental, Moral and Physical Traits Are Inherited in the Same Manner as Coat Color in Guinea Pigs." From our vantage point in the 21st century, it is easy to look back and dismiss such claims as naive. But how naive were they in the context of the period 1910-1935? To answer this question, we must look at flaws in eugenicists’ research methods, especially when they attempted to study human mental, behavioral, and personality traits.

1) Difficulty of defining traits. Traits such as eye color, stature, and blood group are easy to define and measure. Eugenicists, however, were most interested in mental and behavioral traits – such as epilepsy, intelligence, manic depression, feeblemindedness, alcoholism, and criminality. Not only are such traits highly complex, but they are also subjectively defined. This problem was recognized early on by critics, including geneticist Thomas Hunt Morgan, who wrote in 1932: "The main difficulty is one of definition... Accurate work in heredity can only be obtained when the diagnosis of the elements [trait]…is known."

2) Reification is the tendency to treat complex traits – especially behaviors – as if they were a single entity, stemming from a single cause. For example, eugenicists treated intelligence as if it were an innate quality of the brain that could be represented by a single factor. Morgan commented: "It is commonly assumed that there is one, and only one, criterion of intelligence – that we are speaking always of the same thing when we use the word… In reality, our ideas are very vague on the subject." Later experts recognized that there may be many "intelligences" – including mechanical, quantitative, visual/spatial, verbal, and abstract.

3) Poor survey and statistical methods. Seldom was a eugenic researcher able to personally interview family members going back more than two or three generations, in order to determine who showed the trait under study. At the time, few doctors and hospitals kept systematic medical records, so pedigree information often was obtained by second-hand reporting or even hearsay. Harry Laughlin, of the Eugenics Record Office, based many studies solely on information obtained from subjects’ own (self-reported) answers on questionnaires. Furthermore, Laughlin's conclusions were typically biased by the manner in which he collected data. For example, in his testimony before the congressional committee on immigration, Laughlin presented data showing that the proportion of southern/eastern Europeans in prisons and mental institutions was far greater than their proportion in the general population. However, he "creatively" used statistics to falsely exaggerate this claim. The institutional data was collected in 1921, during the peak of southern/eastern European immigration, and primarily from the northeastern states, where these populations were concentrated. However, the general population data was taken from the 1910 census, when southern/eastern Europeans were a much smaller part of the entire U.S. population. Laughlin's use of these and other bogus statistics provided the "scientific" basis for the Johnson Immigration Restriction Act (1924), which severely restricted newcomers from southern and eastern Europe.

4) False quantification is the assumption that if you can produce a numerical value (such as a score on an intelligence test) then it must be a valid measure. For example, eugenicists argued that IQ tests were accurate and culture-free measures of native intelligence – even though they contained questions that were obviously dependent on cultural background and experience. Tests were given under a wide variety of conditions, often by poorly trained administrators and sometimes even in pantomime when the subjects spoke no English. According to one set of IQ tests given to immigrants by Henry H. Goddard, 83% of Jews, 80% of Hungarians, 79% of Italians, 87% of Russians were classified as "feebleminded." Although most of these results were later retracted, Goddard’s test had dire consequences for immigrants who were returned home and for individuals who were consigned to mental institutions, and sometimes sterilized.

5) Social and environmental influences. Eugenicists sought genetic explanations of complex human traits to the virtual exclusion of other explanations. However, family pedigrees are as much documents of social inheritance as they are of biological inheritance. In addition to genes, families members share customs, life styles, and health practices (including diet) that can greatly affect the development of physical, intellectual and emotional traits. For example, Charles Davenport explained lineages of naval officers in terms of an inherited gene for thalassophilia, or "love of the sea." He neglected the obvious explanation that seafaring fathers had a strong influence on their sons' career choices. At the same time, laboratory geneticists were beginning to recognize that most physical and physiological traits are the product of interactions between genes and the environment. For example, fruit flies of the same genotype showed different phenotypes when raised at slightly different temperatures. Environmental input was recognized as being even more influential on the development of behavioral, personality and mental traits.

By the mid-1930s, eugenics research came under increasing scrutiny, and independent analysis revealed that most eugenic data were useless. A committee of the American Neurological Association reported that "[The definitional problem] invalidates, we believe, the earlier work which comes from Davenport, Rosanoff and the American Eugenics School with its headquarters at Cold Spring Harbor." According to an external visiting committee assembled by the Carnegie Institution of Washington: "Some traits such as 'personality' or 'character' lack precise definition or quantitative methods of measurement; some traits such as 'sense of humor,' 'self respect', 'loyalty' or 'holding a grudge' could seldom be known outside an individual's close friends and associates…Even more objective characteristics, such as hair form or eye color, become relatively worthless items of genetic data when recorded by an untrained observer."

These critiques, among other factors, prompted the Carnegie Institution to withdraw its funding and permanently close down the ERO in December, 1939.