Intelligence is an abstract concept that is virtually impossible to measure. Intelligence includes not only factual knowledge but also abstract thinking, logic and reasoning. Standard IQ tests attempt to measure intelligence through carefully structured questions. These tests may be useful tools for predicting academic success, but the tests do not measure all aspects of intelligence, nor do they account for variations in social backgrounds.
Definition
IQ stands for intelligence quotient. French psychologist Alfred Binet coined the term in 1904 as a means to classify schoolchildren according to their learning potential, explains the website Audiblox, which specializes in learning programs for gifted children and those with learning disabilities. IQ is a person's mental age divided by his chronological age, multiplied by 100. For example, if a 16-year-old girl had a mental age of 20, her IQ score would be 125, or above average. An IQ of 100 means the person has average intelligence for his age.
Purpose
IQ tests predict academic success, says psychologist Jonathan Rich, a specialist in psychological testing. The tests measure qualities typically considered to be signs of intelligence. IQ tests cannot measure social or interpersonal skills or creativity. Rich notes that academic success does not necessarily equal happiness or success in other areas of life.
Tests
Several standardized IQ tests are used. Binet's original test, which has been revised several times and is now called the Stanford-Binet Test, is typically used for children from 2.5 to 16 years of age, says Rich. The most commonly used tests are the Wechsler tests, which are individualized for ages 2 to 7 years, 6 to 16 years, and 16 to 89 years of age. Although slightly different, all tests are timed and measure similar concepts including factual knowledge, memory and concentration, abstract reasoning, visual-spatial thinking and common sense. The tests include verbal and performance subtests. The verbal portion tests facts, reasoning, and memory. The performance subtests use block arranging, puzzles and pictures to assess the person's ability to mentally rotate images, arrange pictures to tell a story and use reason and logic to duplicate patterns and objects. Nonverbal tests, such as the Leiter Test and Raven's Progressive Matrices Test, are useful for people who are not fluent in English.
Scoring
IQ tests use a derivative score, states Rich. This score compares your score with other people your age. The average score is 100. Variations above or below the average score are expressed as percentile ranks. A percentile rank is your ranking compared with other test takers, or the percentage of people you scored the same as or higher than. For example, if your percentile rank is 95, you scored higher than 95 percent of all those of your age who took the test, explains Audiblox. IQ scores remain relatively stable, says Rich, but an individual's score may vary by five points from day to day or as much as 10 points over the course of years.
Limitations
IQ tests may provide useful information to predict school performance, but test results should be used with caution, suggests Audiblox. All IQ tests measure intelligence relative to a particular culture, says Rich. No test is "culture-free." The tests do not take into account factors that may influence intelligence levels, such as home or community life.
