An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. The term "IQ" comes from the German Intelligenz-Quotient. When modern IQ tests are constructed, the mean (average) score within an age group is set to 100 and the standard deviation (SD) to 15.
"I once thought it possible to create a set of tests of each intelligence - an intelligence-fair version to be sure - and then simply to determine the correlation between the scores on the several tests. I now believe that this can only be accomplished if someone developed several measures for each intelligence and then made sure that people were comfortable in dealing with the materials and methods used to measure each intelligence."
No matter their form or content, tests of mental skills invariably point to the existence of a global factor that permeates all aspects of cognition. And this factor seems to have considerable inﬂuence on a person’s practical quality of life. Intelligence as measured by IQ tests is the single most effective predictor known of individual performance at school and on the job. It also predicts many other aspects of wellbeing, including a person’s chances of divorcing, dropping out of high school, being unemployed or having illegitimate children.
In response to concerns about cultural and ethnic biases in traditional IQ tests, the developmental psychologist Howard Gardner, PhD, popularized the phrase "multiple intelligences" to reflect that fact that intelligence is multi-faceted. Gardner's IQ tests measure not only verbal and mathematical skills but also musical, mechanical, physical, and even social skills.
Overall, experts hold positive attitudes about the validity and usefulness of intelligence and aptitude tests. Tests are seen as adequately measuring most important elements of intelligence, although the tests are believed to be somewhat racially and socioeconomically biased. Problems with intelligence tests are perceived in the influence of nonintellectual characteristics on test performance and in the frequent misinterpretation and overreliance on test scores in elementary and secondary schools.
Does this mean that intelligence tests are in- valid? As so often when you examine a question carefully in psychology, the answer depends on what you mean. Valid for what? Certainly they are valid for predicting who will get ahead in a number of prestige jobs where credentials are im- portant. So is white skin: it too is a valid predictor of job success in prestige jobs. But no one would argue that white skin per se is an ability factor. Lots of the celebrated correlations between so-called intelligence test scores and success can lay no greater claim to representing an ability factor.
Paradoxically, one of the clearest signs of the success of intelligence tests is that they are no longer widely administered. In the wake of legal cases about the propriety of making consequential decisions about education on the basis of IQ scores, many public school officials have become test-shy. By and large, the testing of IQ in the schools is restricted to cases involving a recognized problem (such as a learning disability) or a selection procedure (determining eligibility for a program that serves gifted children).
It is important to understand what remains stable and what changes in the development of intelligence. A child whose IQ score remains the same from age 6 to age 18 does not exhibit the same performance throughout that period. On the contrary, steady gains in general knowledge, vocabulary, reasoning ability, etc. will be apparent. What does not change is his or her score in comparison to that of other individuals of the same age. A six-year-old with an IQ of 100 is at the mean of six-year-olds; an 18-year-old with that score is at the mean of 18-year-olds.
Another major issue is the inconsistent use of these tests. Some school districts rely heavily, or even exclusively, on standardized IQ test scores to identify giftedness, yet other districts may use a multidimensional procedure that views test scores as only one piece of a much larger picture of a child's talents. Indeed, opponents of "IQ-only" identification point out that these tests may assess only a narrow range of ability, neglecting a child's strengths in other areas, such as spatial reasoning or nonacademic talents.
The Wechsler test and the Stanford-Binet Intelligence Scales (SC) are the most standardized and widely used exams. Average test results range from 90 - 110:
A score below 70 indicates mental retardation.
A person who scores 130 or higher is usually considered gifted, although different programs set different levels for this classification.
A person with a score of 145-160 is usually classified as highly advanced or very gifted.
A person with a score of 165 or higher is usually classified a genius.
Since Alfred Binet first used a standardized test to identify learning-impaired Parisian children in the early 1900s, it has become one of the primary tools for identifying children with mental retardation and learning disabilities. It has helped the U.S. military place its new recruits in positions that suit their skills and abilities. And, since the administration of the original Scholastic Aptitude Test (SAT)--adapted in 1926 from an intelligence test developed for the U.S. Army during World War I--it has spawned a variety of aptitude and achievement tests that shape the educational choices of millions of students each year.