EXAMPLE 6 IQ tests

Psychologists would like to measure aspects of the human personality that can’t be observed directly, such as “intelligence” or “authoritarian personality.” Does an IQ test measure intelligence? Some psychologists say Yes rather loudly. There is such a thing as general intelligence, they argue, and the various standard IQ tests do measure it, though not perfectly. Other experts say No equally loudly. There is no single intelligence, just a variety of mental abilities (for example, logical, linguistic, spatial, musical, kinesthetic, interpersonal, and intrapersonal) that no one instrument can measure.

The disagreement over the validity of IQ tests is rooted in disagreement over the nature of intelligence. If we can’t agree on exactly what intelligence is, we can’t agree on how to measure it.