Individual intelligence tests
There are two major types of intelligence test, those administered to individuals and thsoe administered to groups.
The two main individual intelligence tests are the:
- Stanford-Binet Intelligence Test
- Wechsler tests, i.e. WISC for children and WAIS for adults
Some of the content of these tests is clearly culture-loaded, hence there is the:
- Kaufman Assessment Battery for Children - a more recent test which attempts to minimize cultural bias. The test also attempts to separate crystallized and fluid intelligence.
Group-administered intelligence tests involve a series of different problems and are generally used in mass testing situations such as the military and schools. Examples of group tests are:
- Multidimensional Aptitude Battery
- The Cognitive Abilities test
- Scholastic Assessment Tests
Part of the reason for shifting away from verbal-based tests, in particular, is the issue of culture-loading.
Advantages of group tests:
- can be administered to very large numbers simultaneously
- simplified examiner role
- scoring typically more objective
- large, representative samples often used leading to better established norms
- examiner has less opportunity to establish rapport, obtain cooperation, and maintain interest
- not readily detected if examinee tired, anxious, unwell
- evidence that emotionally disturbed children do better on individual than group tests
- examinee’s responses more restricted
- normally an individual is tested on all items in a group test and may become boredom over easy items and frustrated or anxious over difficult items
- individual tests typically provide for the examiner to choose items based on the test takers prior responses - moving onto quite difficult items or back to easier items. So individual tests offer more flexibility.
Intelligence Tests
Intelligence is often defined as a measure of general mental ability. Of the standardized intelligence tests, those developed by David Wechsler are among those most widely used. Wechsler defined intelligence as “the global capacity to act purposefully, to think rationally, and to deal effectively with the environment.” While psychologists generally agree with this definition, they don't agree on the operational definition of intelligence (that is, a statement of the procedures to be used to precisely define the variable to be measured) or how to accomplish its measurement.
Test construction. To be useful, tests, including intelligence tests, must be constructed using the established criteria of standardization, reliability, and validity.
- Standardization is the process of making uniform and objective both testing procedures and scoring procedures in order to obtain meaningful scores. Scores on standardized tests are interpreted in reference to scores obtained from a standardization sample, that is, scores from a comparable group of subjects tested under appropriate conditions.
- The term reliability refers to the consistency of results. Reliability of a test is determined by one of the following methods.
- test and retest reliability: comparison of original test scores with retest scores
- alternate form reliability: comparison of scores obtained on alternate forms of a test
- split-half reliability: comparison of scores obtained on two halves of tests (such as scores on odd- versus even-numbered questions)
- The term validity refers to the extent that a test measures what it is supposed to measure. Types of validity include
- content validity: the extent to which a test reflects a sample of the behavior to be measured
- predictive validity: the extent to which a test can predict a person's behavior in another situation
- face validity: how appropriate a test “appears” to be, just from the way the items read
- construct validity: how well a test assesses the construct (for example, intelligence) for which it was designed
- concurrent validity: how well the results of a test agree with those of a new test or a different form of the test measuring for the same construct (for example, intelligence)
Measures of intelligence
- Sir Francis Galton, a pioneer in the measurement of individual differences in late nineteenth-century England, was particularly concerned with sensory responses (visual and auditory acuity and reaction times) and their relationship to differences in ability.
- Several individual tests have been used to test intelligence.
- The Binet-Simon intelligence scale, developed by French psychologists Alfred Binet and Theodore Simon, was administered to children to evaluate their performance ( mental age) at a given chronological age. The mental age/chronological age measure, called a mental quotient, was used to evaluate a child's learning potential.
- Lewis Terman of Stanford University revised the Binet scale in 1916. The revised scale, called the Stanford-Binet intelligence scale, although it retained the concept of mental and chronological ages, introduced the concept of the intelligence quotient (IQ) arrived at by the following widely used formula, which allows comparison between children of different ages.
The 1986 revision of the test, the latest of several, varies the calculation so that the test is useful for adults as well as for children. An individual's score for correct answers is compared to a table of scores of test takers of the same age (with the average score always scaled to 100). Scores between 90 and 110 are labeled as “normal,” above 130 as “superior,” and below 70 as mentally deficient, or “retarded.” The distribution of IQ scores approximates a normal (bell-shaped) curve (Figure 1 ).
Figure 1 / The Normal IQ Distribution- David Wechsler developed the Wechsler Adult Intelligence Scale (WAIS) in 1939, revised as the WAIS-R. Wechsler also developed the Wechsler Intelligence Scale for Children (WISC), revised as the WISC-R. The revised forms of these scales are still widely used. They contains two sub-scales, verbal and performance, which provide a verbal IQ and a performance IQ; the subscales are combined for the total IQ. Test score combinations may reveal other strengths and weaknesses to a skilled examiner.
Tests of aptitude and achievement. Group tests (such as the California Achievement Tests and the SAT, the Scholastic Assessment Test) are often used to measure aptitude, the capacity to learn (including both verbal and performance aptitudes) and achievement, what has been learned.
Ranges of intelligence scores. The two extremes of levels of intellectual functioning are known as developmentally disabled and gifted.
- Those identified as mentally retarded (sometimes described as developmentally disabled) have IQ scores of 70 or below. Severity of disability and corresponding IQ scores are mild (50 to 70), moderate (35 to 50), severe (20 to 35), and profound (below 20). Some, but not all, of the causes of mental retardation are known and include Down syndrome, a genetic disorder; phenylketonuria, a metabolic disorder; and developmental disability due to anoxia (lack of oxygen) during gestation.
- The gifted usually fall within the upper 2% to 3% of the IQ score distribution (between 130 and 145). Louis Terman's well-known longitudinal study of the gifted, which will not be complete until 2010, found that gifted children are generally superior to average-IQ peers in health, achievement, and adjustment to life stresses. Currently, gifted children are identified not only by IQ but also by superior potential in any of six areas: general intelligence, specific aptitudes (math, for example), creativity, leadership, performing arts, and athletics.