The Mismeasure of Man, by Stephen Jay Gould, is a survey and critique of 19th- and 20th-century theories that posited human intelligence was a fixed and measurable number. Gould argues that mainstream scientists were not immune to the widespread racist and prejudicial beliefs of their time, and that these unconscious biases underlie the history of biological determinism, or the argument that shared human behavior is innate and primarily controlled by biology. Under this argument, social and economic differences between human groups are the result of fixed and inheritable biological traits, rather than the result of systemic inequalities within society itself. In his book, Gould analyzes and critiques scientific attempts to prove that fixed numerical values can be assigned to individuals and groups through the measurement of intelligence as a single quantity.

The first part of the book focuses on the science of craniometry, which was at the forefront of biological determinism during the 19th century. During this time, scientific investigation focused on compiling numerical data measuring the sizes of human brains in order to arrive at a rational, objective methodology for ranking racial intelligence. Gould surveys the early scientific findings in this field, and also reexamines the work of leading scientists Samuel George Morton and Paul Broca. In reviewing the data collection tables and publications of Morton and Broca, Gould argues that once unconscious and prejudicial bias is removed, the scientific data shows there is no evidence for race-based intellectual difference. However, because quantifiable approaches of measuring intelligence were established scientific theories, published research was not only accepted, it paved the way for other race-based theories of intelligence, including evolutionary recapitulation and criminal morphology.

The second part of the book focuses on the use of intelligence testing in the 20th century. Gould examines the historical development of Alfred Binet’s IQ scale, his original intention for how the test would be used, and its transmutation into a means of proving intelligence to be a biologically-determined and inheritable number. In his review of research by H.H. Goddard, L.M. Terman, and R.M. Yerkes, Gould traces the widespread acceptance of intelligence testing in 1920s America and detailshow this movement influenced the isolation of so-called “feeble-minded” people, encouraged the intelligence testing and labeling of children, and negatively impacted national immigration policy quotas.

In the third section of the book, Gould introduces the work of Charles Spearman, Cyril Burt, and L.L. Thurstone, three intelligence researchers who popularized the statistical modeling tool of factor analysis. In science, factor analysis is used to reduce complex relational systems into a singular dimension, thereby simplifying systems and providing a reasonable means of interpreting disparate data points. In examining the history of mental testing, Gould provides a critique of Spearman’s “principal component” and argues that his general intelligence factor (g), was highly ambiguous and abstract. Relying on his own expert knowledge of factor analysis, Gould provides an in-depth, critical analysis of Burt and Thurstone’s rationale in using factor analysis to support their theories of racially-heritable intelligence. In the expanded edition of the book, Gould also includes a brief update on the modern influence of Spearman’s g factor in the works of Arthur Jensen, Richard Herrnstein and Charles Murray.

In his Conclusion, Gould notes that the development of science relies not just on new research, but also on the refutation of outdated ideas. In his view, while science offers many avenues for future research regarding the intersection of human behavior and human biology, scientists should be wary of asking questions that paint a limiting and inflexible portrait of humanity’s potential.

The revised and expanded version of The Mismeasure of Man includes two sections at the end of the book. The first section is an expanded critique of Richard J. Herrnstein and Charles Murray’s book The Bell Curve (1994) and its arguments regarding class stratification and inherited racial differences in IQ. The second is a collection of three essays by Gould that examine historical writings on race and biodeterminism by Thomas Browne (17th century), J.F. Blumenbach (18th century), and Charles Darwin (19th century).

Stephen Jay Gould was an American evolutionary biologist, paleontologist, and scientific historian. A Harvard professor and prominent research scholar, Gould published over twenty books and 300 essays on popular science, ranging in topics from evolutionary theory to sabermetrics (baseball statistics). The Mismeasure of Man was first published in 1981 to widespread acclaim, and received awards from the National Book Critics Circle and the American Educational Research Association. In 1996, Gould revised and expanded the book to include an extended refutation of The Bell Curve, which presents a 20th-century perspective of biological determinism and theories of inheritable intelligence.