Intelligence is a trait or set of traits on which individuals differ. To determine intelligence, they sought to examine items that were correlated with high teacher ratings in terms of the child"s mental level (also referred to as mental age) From this they developed the binet-simon test of intelligence, which gave a score. Iq = mental age/chronological age *100, but all modern tests now use deviation iqs. Tests include both verbal and nonverbal (performance) measures. While the results from these tests no longer measure the relative mental age vs. physical age, their score is still reported as iq results (although for children, it still has an age component) Iq now means the relative performance of an individual compared to the average. These tests were eventually modified in the u. s. a. to become the stanford-binet test function of the mental age of the child divided by their actual physical age. Adult version is the wais-iii, child version is the wisc-iii.