The idea of IQ / Russell Marks.

  • Marks, Russell.
Date:
[1981], ©1981
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: The idea of IQ / Russell Marks. Source: Wellcome Collection.

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    ogists know that I.Q. tests measured hereditary intel¬ ligence? How did psychologists move from the position that intelligence was hereditary to the position that I.Q. tests measured heredity? How did psychologists know that intelligence was unmalleable? These questions were never satisfactorily answered by the construct of individual differences. The construct nevertheless provided a plausibility structure which suggested an¬ swers to these questions and more important, conceptu¬ ally muddled these issues so that these fundamental questions were rarely asked. The American construct of individual differences was vintage American — combining Yankee ingenuity with European theory. While many of the ideas of the con¬ struct were not new to Western thought, as a system of ideas they reflected important new claims about human nature and knowledge of human differences and poten¬ tial. The construct of individual differences was a complex system of interrelated ideas, some of which I shall now delineate. First, the concept of individual differences was constructed on evolutionary theory that viewed human beings from a biological rather than religious, cultural, or other perspective. In examining human beings as evolved animals, evolutionary theory, as Stow Persons observed, posed the problems of development and of variation, which, in turn, led to questions of heredity and environment, child and animal psychology, and the study of racial and individual differences. Evolution¬ ary theory maintained that heredity and environment shaped human activity. Heredity and environment would replace human rationality, God's will or other formulations as the main determinant of human action. For the new psychologists, heredity was internal and led to the study of instinctivism; environment was ex¬ ternal and led to the study of behaviorism. The nature- nutture issue, as Darwin's cousin Francis Galton called it, was thus basically a product of evolutionary theory.® While early nineteenth-century psychology was des¬ ignated as mental science or intellectual philosophy and focused on mind and consciousness, late nineteenth- century psychology increasingly focused on studying man. -6-