Psychometrics, intelligence, and public perception

Herrnstein and Murray (1994, pp. 22-23) stated six propositions concerning a g factor of intelligence. Because these propositions had been widely criticized in public media as being false and pseudoscientific, they are examined here for support in the scientific literature. All are found to be reasonably well supported. Most experts agree that there is a general factor g on which human beings differ. It is measured to some degree by most tests of cognitive aptitude and achievement, but more accurately by tests designed to measure it. It corresponds to most people's concept of intelligence. It is quite stable over the life span, and properly constructed and administered IQ tests are not demonstrably biased against different social groups. It is substantially influenced by genetic factors, but also by environmental factors. Some psychometric findings about g have been poorly presented to the public or widely misunderstood. The public is urged to recognize that (1) psychometrics (literally, mental measurement) is a rigorous scientific discipline that has resolved many questions concerning cognitive abilities; (2) general ability scores should be taken not as direct measures of hereditary intelligence, but rather as measures of rate of progress over the life span in achieving full mental development; (3) there are many other cognitive abilities besides g; (4) important sources of variation in g or IQ are environmental; (5) the IQ is possibly more an indicator of how fast the individual can learn that it is of the individual's capability of learning; and (6) much more research is needed to resolve questions about the role of individual differences in cognitive abilities in a democratic society. These conclusions can be reached whatever one's views may be about the validity of Herrnstein and Murray's claims about the significance df variation in intelligence for social problems.