There is wide agreement in the field of psychology that intelligence is a multifaceted construct, although the specifics vary between theories. Thus, there are multiple definitions of intelligence, each of which reflects a particular theory or conceptualization; some of these conceptualizations are the basis for intelligence tests or tests of cognitive ability. This entry reviews the early theories of intelligence before discussing several contemporary theories.

As theorists and researchers learned more about human capabilities, the measurement of intelligence, or what we now refer to as cognitive ability, became grounded in theory. The extent and quality of research supporting each theory varies, as does the utility of any theory for the measurement of intelligence. There are numerous measures of intelligence, with most of today’s tests operationalized (at ...