Intelligence testing is used to assess the all around effectiveness of an individual's mental processes, especially understanding, reasoning, and the ability to recall information. Tests exist that are appropriate for both childrenand adults. The use of standardized tests to produce a numerical value for these abilities is a very popular tool among educators. Correctly administered, some intelligence tests can also detect learning impairments. The Stanford-Binet Intelligence Scale and the Wechsler Intelligence Scales are the two most widely used standardized intelligence tests. Other tests are available thatattempt to quantify areas such as creativity, personality, and ability or aptitude to perform specific tasks. Many employers, from police departments tothe National Football League, use some form of standardized intelligence testing to evaluate job applicants.
The Stanford-Binet Intelligence Scale
Alfred Binet (1857-1911) was a French psychologist who was interested in thestudy of thinking and mental processes. As the director of physiological psychology at the Sorbonne, he was asked by the French Ministry of Public Instruction to develop a method of identifying children who were too so far below average in intelligence that they could not be educated in ordinary public schools. In 1905, Binet and his colleague, Theodore Simon, developed a series ofgraded tasks that could be performed by children of average intelligence at different ages. During the next six years, until his death, Binet worked to refine this scale to produce a score that represented the mental age of the child.
Meanwhile, in the United States. Lewis Terman was studying the differences between groups of very bright and very dull students on various tests. Terman,who joined the faculty of Stanford University in 1910, adapted the Binet intelligence tests and coined the term IQ for intelligence quotient. This numberrepresented a ratio between the mental age and the chronological age of the child. Terman's modifications of Binet's tests became known as the Stanford-Binet test. This test and its subsequent revisions is the most widely used of all mental tests in the United States. The test is now in its fourth edition,sometimes refereed to as SB-FE (Stanford-Binet-Fourth Edition). It is used totest people between the ages of 2 and 23.
The Stanford Binet test is administered individually, and to be accurate mustbe administered by a trained administrator, usually a psychologist or psychiatrist. It is routinely used as tools in school placement, in suggesting thepossibility of a learning disability or a developmental delay, and in tracking intellectual development.
Although the Stanford-Binet scales have been expanded to include children asyoung as two, the test is not particularly reliable in screening very young children for developmental delays or disabilities. Young children are difficult test subjects because they are often wary of strangers, perform inconsistently in unfamiliar settings, have short attention spans, and are easily distractible. The Sanford-Binet test cannot be used to diagnose mental retardationin children aged three and under, and the scoring design may not detect developmental problems in preschool-age children. For this reason, when evaluatingvery young children, the trend is toward a team assessment with many components rather than relying on a single test or IQ number.
It is no longer thought that IQ remains constant during a child's development. Not until around age five does the test start to distinguish children who are likely to show especially high or low intelligence as adults. However, IQmeasured at age 12 tends to be in line with adult intelligence measures. TheStanford-Binet test does not necessarily predict how well a person will do inschool or daily life. Too many factors besides raw intelligence, such as home environment, interest in learning, quality of school instruction, willingness to stick to a task, and support and mentoring from adults affect how wella person does in school and in future occupations.
The fourth edition of the Stanford-Binet Intelligence Scale that is currentlyin use was released in 1986. It was designed with a larger, more diverse, representative sample to minimize the gender and racial inequities that had been criticized in earlier versions of the test.
The Stanford-Binet is a standardized test, meaning that norms, or average values, are established before the test is released for general use by administering the test to a large, representative sample of the prospective test population. The test population for the SR-FE consisted of over 5,000 people between the ages of 2 years and 23 years, 11 months. The test designers attemptedto achieve a balance within the test population by considering geographical region, community size, race, ethnic identity, gender, parental occupation andparental education to address some of the concerns about inequality in earlier versions of the test.
The Stanford-Binet scale tests intelligence across four areas: verbal reasoning, quantitative reasoning, abstract/visual reasoning, and short-term memory.The SB-FE differs from earlier versions of the test because it gives subtestscores in the four areas as well as a single composite IQ score. The areas are covered by 15 subtests, including vocabulary, comprehension, verbal absurdities, pattern analysis, matrices, paper folding and cutting, copying, quantitative, number series, equation building, memory for sentences, memory for digits, memory for objects, and bead memory.
All test subjects take an initial vocabulary test, which along with the subject's age, determines the number and level of subtests to be administered. Total testing time is 45-90 minutes, depending on the subject's age and the number of subtests given. Raw scores are based on the number of items answered, and are converted into a standard age score corresponding to age group.
The mean, or average, score on the Stanford-Binet test is 100. This means 50percent of people score above 100 and 50 percent score below 100. The actualnumber is calculated by taking the person's mental age as determined by the test results and dividing it by their chronological age then multiplying by 100. For example, if a 14 year old does as well as the average 16 year old, theIQ score is 16/14 x 100 = 114. Scores generally range from about 40 (very low) to 160 (very high). An IQ score of 130 is higher than about 98 percent ofall people tested.
The Wechsler Intelligence Scales
The Wechsler Intelligence Scales consist of several different standardized tests used to evaluate reasoning and intellectual abilities in pre-school children through adults.
David Wechsler (1896-1981) was an American psychologist who began his careerby administering and interpreting mental tests that had been designed for theUnited States Army to assign recruits to army jobs that best suited their abilities. Through these experiences, he expanded the definition of intelligence to include the global capacity to act purposefully, to think rationally, and to deal effectively with the environment. He believed that intelligence wasan aspect of personality, not a separate, isolated quality. Wechsler then developed intelligence tests to measure what he viewed as intelligence.
Like the Stanford-Binet tests, the Wechsler tests are administered individually by a trained test administrator. Because they are easier to administer, these tests are often preferred by school psychologists over the Stanford-Binettests. There are currently three Wechsler Intelligence Scales in use in theUnited States today: The Wechsler Adult Intelligence Scale - Revised (WAIS-R), the Wechsler Intelligence Scale for Children-Third Edition (WISC-III), andthe Wechsler Preschool and Primary Scale of Intelligence - Revised (WPPSI-R).
The Wechsler scales are divided into six verbal and five performance subtests. The complete test takes 60-90 minutes to administer. Verbal and PerformanceIQs are scored based on the results of the testing, and then a composite Full Scale IQ score is computed.
The Wechsler Adult Intelligence Scales are used to determine vocational ability, to assess adult intellectual ability in the classroom, and to determine organic deficits. Both adult and children's Wechsler scales, as well as the Stanford-Binet test, are often included in neuropsychological testing to assessthe brain function of individuals with neurological impairments.
The WAIS-R was revised in 1981 because of a need for a more contemporary normgroup than the original test sample. The test is designed for adults, age 16-74.
To establish the norms, or average values, for the revised version, the testwas given to a sample of 1,180 Americans. The sample included both Whites andpeople of color who were able to speak and understand English. Excluded fromthe sample group were people who were institutionalized for mental retardation, who were brain damaged, who were severely emotionally disturbed, and whohad restrictive physical disabilities. All the Wechsler tests have average orstandard scores of 100. People are compared against others in their age group.
The 11 subtests of the WAIS-R include information, digit span, vocabulary, arithmetic, comprehension, similarities, picture completion, picture arrangement, block design, object assembly, and digit symbol. An example of questions on the subtest of similarities might be: "Describe how the following pair of words are alike or the same--hamburger and pizza." A correct response would be"Both are things to eat."
Wechsler Intelligence Scale for Children, Third Edition subtests include manyof the same categories of subtests as the WAIS-R. In addition, there are twooptional performance subtests: symbol search and mazes. The test is designedfor children ages 6 to 16. The test is divided into two main sections,. Theverbal section measures how well children express themselves in words and howwell they understand what others say to them. The performance section measures non-verbal areas such as spatial relationships. Breaking down the tests into sections related to different kinds of learning is an advantage in helpingpsychologists detect patterns of strengths and weaknesses and in pinpointinglearning disabilities.
Wechsler Preschool and Primary Scale of Intelligence-Revised was released in1989. It is designed to assess the intelligence of children ages 3 through 7years, 3 months. This is an extension of the range of the original test, which was designed for children ages 4 years, 6 months through 6 years. The testis divided into six verbal and five performance subtests. The eleven subtestsare presented in the following order: information, animal house and animal house retest, vocabulary, picture completion, arithmetic, mazes, geometric design, similarities, block design, comprehension, and sentences. As with the other Wechsler tests, the average score is 100, and children are compared against the performance of other children their age.
Other intelligence tests also exist. One is the Slosson Intelligence Test-Revised (SIT-R), also called the "Short Intelligence Test." The revised versionwas issued in 1991. This test can be used from infancy through age 27, and contains items similar to the Wechsler scales. One advantage is that the test does not have to be administered by a trained test giver. The disadvantage isthat there are statistical and interpretive limitations on the data that comes out of the testing process.
Other Types of Intelligence Testing
Other tests are designed to be given in groups. These include the Cognitive Abilities Test (CAT) and the School and College Abilities Tests (SCAT). Thesetests can be given by untrained test administrators and are computer scored.
Intelligence testing is just one snapshot of a person's abilities. The information from the test does not predict one's success in life. It should be taken as just one factor in a complete neurological or psychiatric evaluation.