One figure in the history of differential psychology who does not get enough attention is Sandra Scarr. With a research career spanning nearly four decades, she was one of the most prominent people researching intelligence in the late 20th century.

Scarr’s scholarly work has been remarkably durable. Working at a time when research into genetic influences on behavior was extremely unpopular, she conducted high-quality studies that surpass the contributions of many of her contemporaries. Highlights include:

  • A large (for the time) adoption study of 845 family members in 224 families, who were related biologically or via adoption, to investigate the impact of the family environment on IQ (Scarr & Weinberg, 1978a). This was one of the first studies to show that shared environment had little or no impact on IQ in late adolescence and that children had lower heritability values for IQ than adolescents.
  • A study that was, for over 40 years, the largest admixture study to investigate the impact of genes on between-group average differences in IQ (Scarr et al., 1977).
  • The largest ever transracial adoption study of the effects of a positive home environment on IQ (Scarr & Weinberg, 1976; Weingerb et al., 1992).
Sandra Scarr in 1989.

Given the impressive level of her empirical accomplishments, it should not be surprising that her theoretical accomplishments are also worth remembering.

Scarr’s most notable theoretical contribution is the suggestion that heritability of intelligence might vary as a function of socioeconomic status (Scarr, 1971; Scarr & Weinberg, 1978a), an idea now called the Scarr-Rowe effect. While intriguing and plausible, the idea has fallen on hard times. Within wealthy nations, heritability of IQ seems to be approximately the same for people living in all typical socioeconomic strata (Tucker-Drob & Bates, 2016). Still, the Scarr-Rowe effect is a good example of how Scarr proposed testable ideas that suggested new lines of research.

Much more lasting is her proposal for how environments could be shaped by people’s genes. Although not the first to propose this, Scarr applied the theory to studies of deprived environments, interventions, twin pairs, and families and applied a developmental perspective to what before were scattered correlations in the literature (Scarr & McCartney, 1983). Her views about genetically shaped environments are now mainstream and form the basis for more sophisticated work on the interrelationships between genetic and environmental variables (e.g., Bates et al., 2018).

Substance and Style

In addition to making important scholarly contribution’s, Scarr’s work is highly readable. Scarr is the rare social scientist who could write an engaging article about a technical topic. Her articles are clearly explained and do not require advanced knowledge of methodology or psychology to understand.

Scarr always approached controversial topics logically and had no patience for people who placed ideology over science (e.g., Scarr, 1985). Although a self-proclaimed liberal (Scarr & Weinberg, 1978a), she recognized that humans were not infinitely malleable and that there were limits to what society could do to reduce individual differences in life outcomes (Scarr & Weinberg, 1978b). She had the ability to separate her politics from her science, which probably improved both:

We see no necessary connections between the scientific results reported here and any social policy. Science is not politics, nor are social policies primarily dependent on scientific evidence, however much we might wish sometimes that they were. Policy matters depend mostly on values, and in this society, many groups compete over the translation of their values into policies. . . . as scientists we have no special wisdom in policy matters. Our unique gift to the society is the most objective look we can manage at the nature of the human condition. Hopefully, that information will be noticed and used to improve human lives.

Scarr & Weinberg (1978a, pp. 690-691)

Although not a scholarly contribution, I admire Scarr’s quietude in retirement. She currently lives in Hawaii, growing coffee and breeding dogs. Some prominent scholars of her generation hang on for far too long and spend the rest of their lives defending their work. Not Scarr. She has ridden off into the sunset, leaving behind her research to speak for itself. It shows a great deal of confidence in her findings and security about her legacy.

I have only read a tiny bit of Scarr’s scholarly output, but I like much of what I have read. I think many other 21st century scholars will, too.

References

Bates, T. C., Maher, B. S., Medland, S. E., McAloney, K., Wright, M. J., Hansell, N. K., Kendler, K. S., Martin, N. G., & Gillespie, N. A. (2018). The nature of nurture: Using a virtual-parent design to test parenting effects on children’s educational attainment in genotyped families. Twin Research and Human Genetics, 21(2), 73-83. https://doi.org/10.1017/thg.2018.11

Scarr-Salapatek, S. (1971). Race, social class, and IQ. Science, 174(4016), 1285-1295. https://doi.org/10.1126/science.174.4016.1285

Scarr, S. (1985). An author’s frame of mind [Review of Frames of mind: The theory of multiple intelligences, by H. Gardner]. New Ideas in Psychology, 3(1), 95-100. https://doi.org/10.1016/0732-118X(85)90056-X

Scarr, S., & McCartney, K. (1983). How people make their own environments: A theory of genotype → environment effects. Child Development, 54(2), 424-435. https://doi.org/10.2307/1129703

Scarr, S., Pakstis, A. J., Katz, S. H., & Barker, W. B. (1977). Absence of a relationship between degree of white ancestry and intellectual skills within a black population. Human Genetics, 39(1), 69-86. https://doi.org/10.1007/BF00273154

Scarr, S., & Weinberg, R. A. (1976). IQ test performance of Black children adopted by White families. American Psychologist, 31(10), 726-739. https://doi.org/10.1037/0003-066x.31.10.726

Scarr, S., & Weinberg, R. A. (1978a). The influence of “family background” on intellectual attainment. American Sociological Review, 43(5), 674-692. https://doi.org/10.2307/2094543

Scarr, S., & Weinberg, R. A. (1978). Attitudes, interests, and IQ. Human Nature, 1(4), 29-36.

Tucker-Drob, E. M., & Bates, T. C. (2016). Large cross-national differences in gene × socioeconomic status interaction on intelligence. Psychological Science, 27(2), 138-149. https://doi.org/10.1177/0956797615612727

Weinberg, R. A., Scarr, S., & Waldman, I. D. (1992). The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence. Intelligence, 16(1), 117-135. https://doi.org/10.1016/0160-2896(92)90028-p

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