The Mismeasure of Man
Stephen Jay Gould
 The Mismeasure of Man is a critical analysis of the early works of scientific racism about the supposed, biologically inherited (genetic) basis for human intelligence, such as craniometry, the measurement of skull volume and its relation to intellectual faculties. Gould proposed that much of the research was based more upon the racial and social prejudices of the researchers than upon their scientific objectivity; that on occasion, researchers such as Samuel George Morton (1799–1851), Louis Agassiz (1807–1873), and Paul Broca (1824–1880), committed the methodological fallacy of including their personal (a priori) expectations to the conclusions, as part of their analytical reasoning. Gould describes Morton's rather imprecise technique of filling skulls with bird seed to obtain endocranial-volume data and how Morton had probably pushed down bird seed in the white skulls so that they had more volume. Gould re-worked Morton’s original endocranial-volume data, and concluded that the original results were based upon biases, selective data use, and perhaps outright falsification of the results. When said biases are accounted, the original hypothesis — an ordering in skull volume ranging from Blacks to Mongols to Whites — is unsupported by the data. The Mismeasure of Man presents a historical evaluation of the concepts of the intelligence quotient (IQ) and of the general intelligence factor (g factor), which were and are the measures for intelligence used by psychologists. Gould proposed that most psychological studies have been heavily biased, by the belief that the human behavior of a race of people is best explained by genetic heredity. He cites the Burt Affair, about the allegedly fraudulent, oft-cited twin studies, by Cyril Burt (1883–1971), wherein he claimed that human intelligence is highly heritabile. As an evolutionary biologist and historian of science, Gould accepted biological variability (the premise of the transmission of intelligence via genetic heredity), but opposed biological determinism, which posits that genes determine a definitive, unalterable social destiny for each man and each woman in life and society. The Mismeasure of Man is an analysis of statistical correlation, the mathematics applied by psychologists to establish the validity of IQ tests, and the heritability of intelligence. For example, to establish the validity of the proposition that IQ is supported by a general intelligence factor (g factor), the answers to several tests of cognitive ability must positively correlate; thus, for the g factor to be a heritable trait, the IQ-test scores of close-relation respondents must correlate more than the IQ-test scores of distant-relation respondents. Hence, correlation does not imply causation; in example, Gould said that the measures of the changes, over time, in "my age, the population of México, the price of Swiss cheese, my pet turtle’s weight, and the average distance between galaxies" have a high, positive correlation — yet that correlation does not indicate that Gould’s age increased because the Mexican population increased. More specifically, a high, positive correlation between the intelligence quotients of a parent and a child can be presumed either as evidence that IQ is genetically inherited, or that IQ is inherited through social and environmental factors. Moreover, because the data from IQ tests can be applied to arguing the logical validity of either proposition — genetic inheritance and environmental inheritance — the psychometric data have no inherent value. Gould proposed that if the genetic heritability of IQ were demonstrable within a given racial or ethnic group, it would not explain the causes of IQ differences among the people of a group, or if said IQ differences can be attributed to the environment. For example, the height of a person is genetically determined, but there exist height differences within a given social group that can be attributed to environmental factors (e.g. the quality of nutrition) and to genetic inheritance. The evolutionary biologist Richard Lewontin, a colleague of Gould’s, is a proponent of said argument in relation to the cognitive ability tests that determine a person’s intelligence quotient. An example of the intellectual confusion about what heritability is and is not, is the statement: "If all environments were to become equal for everyone, heritability would rise to 100 percent because all remaining differences in IQ would necessarily be genetic in origin", which Gould said is misleading, at best, and false, at worst. First, it is very difficult to conceive of a world wherein every man, woman, and child grew up in the same environment, because their spatial and temporal dispersion upon the planet Earth makes it impossible. Second, were people to grew up in the same environment, not every difference would be genetic in origin, because of the randomness of molecular and genetic development. Therefore, heritability is not a measure of phenotypic (physiognomy and physique) differences among racial and ethnic groups, but of differences between genotype and phenotype in a given population. Furthermore, he dismissed the proposition that an IQ score measures the general intelligence (g factor) of a person, because cognitive ability tests (IQ tests) present different types of questions, and the responses tend to form clusters of intellectual acumen. That is, different questions, and the answers to them, yield different scores — which indicate that an IQ test is a combination method of different examinations of different things. As such, Gould proposed that IQ-test proponents assume the existence of "general intelligence" as a discrete quality within the human mind, and thus they analyze the IQ-test data to produce an IQ number that establishes the definitive general intelligence of each man and of each woman. Hence, Dr. Gould dismissed the IQ number as an erroneous artifact of the statistical mathematics applied to the raw IQ-test data; especially because psychometric data can be variously analyzed to produce multiple IQ scores.