A Brief History of Intelligence Testing
IQ testing as we know it today has evolved from nearly a century of research. In 1905, Binet and Simon first devised a system for testing intelligence. Scoring was based on standardized, average mental levels for various age groups. In 1916, Terman of Stanford University expanded the Binet-Simon Intelligence Scale. The idea that a test could determine a child's "mental age" became enormously popular. Just before the First World War, a German psychologist named Wilhelm Stern suggested a better way of expressing results than by mental age - Stern determined his results by finding the ratio between the subject's chronological age and their mental age. Thus, the IQ (intelligence quotient) was born. Wechsler, creator of the IQ tests most widely used today (WAIS-R and WAIC-R), devised a system of calculating IQ based not on mental vs. actual age, but on how far the score is from the average IQ score of the population. Thus the deviation IQ replaced the ratio IQ.
Plagued by accounts of misuse, the controversies surrounding IQ testing had tarnished its reputation. However, recent studies have found that certain elements found in IQ tests can accurately predict scholastic and professional achievement. Used properly, valid and reliable IQ tests can be used in a variety of useful situations, like identifying children who require extra assistance in school.
What the Classical IQ Test Measures
Humans have hundreds of specific mental abilities. Some of these abilities can be assessed more easily and accurately than others, and can then be used reliably as predictors of achievement in various areas. This test measures mental abilities that are positively correlated with many skills, as well as academic performance. The test-takers' scores will be a strong, though not perfect, indication of their true potential in terms of the underlying abilities.
This IQ test measures several factors of intelligence - logical reasoning, math skills, language abilities, spatial relations skills, knowledge retained and the ability solve novel problems. It doesn't take into consideration social or emotional intelligence. This test does not measure all areas of intelligence, nor can it anticipate a person's true potential - no test can do that accurately.
Since different IQ tests focus on different factors, test-takers' performances can change from test to test. For example, someone who scores 130 on Raven's Progressive matrices or on our Culture-Fair IQ test (both of which measure general intelligence while minimizing cultural and educational influences) can score 115 on the Wechsler scale. The Wechsler scale has both verbal and performance components, the latter of which has been found to be influenced by schooling. The same person may score only 98 on our Verbal IQ test, which is focused purely on verbal