Intelligence, capacity to learn or to understand. It is generally synonymous with intellect but is usually differentiated from intellect in practice to emphasize ability or efficiency in dealing with concrete situations and in profiting intellectually from sensory experience. In psychology, intelligence is somewhat more narrowly defined as the capacity to acquire knowledge or understanding and to use it in novel situations. Under experimental conditions, the success of a subject in adjusting his or her behavior to the total situation or in meeting the challenge of the specific situation may be studied and, to some extent, measured in quantitative terms.
Psychologists believe that the capacities measured in testing or laboratory situations are also significant in everyday life, in which individuals analyze or apprehend new sensory and mental data so as to direct their actions toward desired goals. Psychologists still differ, however, as to a precise definition of the comprehensiveness and functions of intelligence; one school of thought considers it as a sum of specific abilities best displayed in specific situations.
In the formulation of intelligence tests, most psychologists tend to adopt an eclectic concept, according to which intelligence is treated as a general ability operating as a common factor in a wide variety of special aptitudes. It is observed and measured by techniques focused upon these aptitudes singly or in combination.