intelligence quotient n.
Abbr. IQ, I.Q.
An index of measured intelligence expressed as the ratio of tested mental age to chronological age, multiplied by 100.
A number meant to measure intelligence. Once the standard measure of human mental capacity; now widely considered to be neither accurate nor fair. Controversy exists today over the effect of race and class on scores and whether IQ tests really measure intelligence. Tests of special aptitudes and personality factors are now favored over the pure intelligence test.
Note: The IQ was originally calculated using the ratio of a person's “mental age” (as measured by a standardized test) and chronological age. An IQ between 90 and 110 is considered average; over 120, superior. (See Stanford-Binet scale.) Few tests still include the controversial notion of mental age.