Concept of IQ
IQ, or Intelligence quotient, is defined originally as the ratio of mental age to chronological age multiplied by 100. On contemporary intelligence tests, the average performance for a given age assigned is assigned a score of 100. For example an average child, whose mental and chronological ages are the same, has an IQ of 100. But an 8-year-old who answers questions as would a typical 10-year-old has an IQ of 125. IQ scores have been shown to be associated with such factors as morbidity and mortality parental social status, and, to a substantial degree, biological parental IQ. While the heritability of IQ has been investigated for nearly a century, there is still debate about the significance of heritability estimates and the mechanisms of inheritance. IQ scores are used as predictors of educational achievement, special needs, job performance and income.
By this point in your life, you've faced dozens of ability tests: course examinations, intelligence tests, driver's license examinations, and college entrance examinations. Scientists classify these tests as either an
Aptitude test: A test designed to predict a person’s future performance; aptitude is the capacity to learn.
Achievement test: A test designed to assess what a person has learned.
The difference between aptitude tests and achievement tests are not so clear. Your achieved vocabulary influences your score on most aptitude tests. Similarly, your aptitude tests for learning and test-taking influence your grades on tests for achievement. Most tests, whether labeled aptitude or achievement, assess both ability and its development. Practically speaking, however, aptitude tests predict future performance and achievement tests assess current performance.
Aptitude test: A test designed to predict a person’s future performance; aptitude is the capacity to learn.
Achievement test: A test designed to assess what a person has learned.
The difference between aptitude tests and achievement tests are not so clear. Your achieved vocabulary influences your score on most aptitude tests. Similarly, your aptitude tests for learning and test-taking influence your grades on tests for achievement. Most tests, whether labeled aptitude or achievement, assess both ability and its development. Practically speaking, however, aptitude tests predict future performance and achievement tests assess current performance.
Today’s most widely used intelligence test, the Wechsler Adult Intelligence Scale (WAIS), was created by psychologist David Wechsler. He developed a similar test for school-age children, called the Wechsler Intelligence Scale for Children (WISC), and still later a test for preschool children. The WAIS consists of 11 sub-tests, and it yields not only an overall intelligence score, but also a separate “verbal” and “performance” (nonverbal) scores. Striking differences between the two scores alert the examiner to possible learning problems.