Because no single characteristic defines intelligence, there can be no adequate process-based definition of intelligence. In principle, a combination of many empirically derived measures into a single index, as in a Binet test, would be appropriate. In practice, many of the relevant characteristics are simply impossible to measure. (Author/RD)

As a response to recent public debate about the nature of intelligence, this article reviews the "state of the art" in the study of intelligence, exploring significant conceptualizations of intelligence, the use and interpretation of intelligence tests, racial or ethnic differences in intelligence, and major issues yet to be resolved.…