Intelligence scales are used to measure intelligence. Intelligence scales and tests which are individually administered include the Stanford-Binet Intelligence Scale and the Wechsler Intelligence Scale for Children. Intelligence tests in educational settings are typically administered by a school psychologist or other trained examiner. Intelligence tests are widely used in the assessment of learning disabilities for special-education services and in the identification of gifted students. Statistical analyses are commonly conducted to analyze and evaluate intelligence-test scores. Intelligence tests have advantages in that they are highly regarded by both educational researchers and school personnel. Research has demonstrated the benefits of cross-battery intelligence- test assessment to measure and compare theory-based cognitive factors.
Standardized intelligence scales are tests used as assessment instruments to measure the intelligence of individuals. Although there are group intelligence tests, this article will be concerned primarily with individually administered measures of intelligence. The most widely used and educationally applied intelligence scales are the Stanford-Binet Intelligence Scale and the Wechsler Intelligence Scale for Children.
Generally speaking, an individual's intelligence is dependent on general mental abilities involved in processes such as learning, using language, reasoning, classifying, making calculations, and adjusting to novel situations. Intelligence is related to an individual's performance on intelligence tests that include items requiring various tasks--verbal, mathematical, perceptual, and problem-solving, for example. The performance of individuals on intelligence tests is compared with others of the same age group and/or level of ability. Thus, intelligence quotients (IQs) are based on an individual's norm group (Gage & Berliner, 1988; Weber, 1991).
The mean intelligence scale or intelligence test IQ score is defined as 100. IQs above 130 are generally considered as superior. Scores between IQ 85 and 115 are considered to be within the average range of intelligence (Lewis & Doorlag, 1987). Scores between IQ 70 and 85 are considered low average. IQ measures can be thought of as tests of mental age. High scores on intelligence tests mean that children are developing more rapidly than their age-mates. The environment in which a child develops is critical in enhancing intelligence, particularly fluid intelligence. Environmental and emotional factors during childhood and adolescence can cause IQ scores to vary moderately (Kirk & Gallagher, 1989; Lewis & Doorlag, 1987; Piaget, 1981; Roid, Shaughnessy, & Greathouse, 2005).
In 1905, the French educator Alfred Binet (1857-1911) and Theophile, or Théodore, Simon (1873-1961) developed tests to use in classifying students for entrance and appropriate grade placement in a new nationwide French public school system. Binet and Simon sought to develop the most diverse tests possible to determine the frequency of success of students as a function of age. The original Binet-Simon Scale of Intelligence consisted of 30 subtests of age-graded items--questions to answer, problems to solve, and tasks to perform--which children of different ages should be able to do. These tests were the precursors of all later intelligence tests (Piaget, 1981; Weber, 1991).
The Binet-Simon Scale
Based on the Binet-Simon Scale of Intelligence, a child who can answer questions that average nine-year-olds can answer are assigned a mental age (MA), of nine (Weber, 1991). The child's MA, as measured by the intelligence test, is then compared to his or her actual chronological age (CA). The German psychologist William Stern concluded that simple comparisons between MA and CA are insensitive to degrees. Stern advocated using a ratio of MA to CA to measure intelligence. However, in Stern's historic formula, he multiplied the initial quotient by 100 in order to eliminate the decimal point. Thus, Stern's formula for this intelligence quotient (IQ) is: MA ÷ CA x 100 = IQ. Examples of the calculation of three different intelligence quotients is shown in Table 1. In Case 1 of Table 1, where a child's CA exceeds his or her mental age, the child is classified as "slow" and is assigned to a lower grade level. In Case 2 where a child's MA equals his or her chronological age, the resulting IQ is 100, the mean IQ level. In Case 3 where a child's MA exceeds his CA, the child is classified as "bright" and is resultantly assigned to a higher grade level (Weber, 1991).
Table 1 The Calculation of IQs from Mental Age
Case Mental Age (MA) Chronological Age (CA) IQ Calculation: MA ÷ CA x 100 Resulting IQ 1 9 12 9 ÷ 12 x 100 75 2 9 9 9 ÷ 9 x 100 100 3 9 6 9 ÷ 6 x 100 150 Modified from Weber, 1991.
The Stanford-Binet Scale
In 1916, Lewis Terman (1877-1956), a Stanford University psychologist, revised the original Binet-Simon Scale of Intelligence. The revised Binet-Simon Scale, titled the Stanford-Binet Intelligence Scale, was restandardized on new populations of children and published by the Houghton Mifflin Company. Terman was also well known for his work with gifted children. In 1920, he began a longitudinal study that was to continue for more than 50 years in which he followed over 1500 gifted children into maturity and old age (Dallman, Rouch, Char, & DeBoer, 1982; Kirk & Gallagher, 1989; Weber, 1991).
The Stanford-Binet Intelligence Scale is the traditional intelligence scale and cognitive intelligence test battery. It is perhaps the best known of the individually administered measures of intelligence, and is more suitable for testing children than late adolescents and adults (Borg & Gall, 1989).
There are newer versions of the Stanford-Binet that are linked to older, previous editions, including the original version. There are full-scale or complete cognitive batteries of the regular Stanford-Binet and abbreviated batteries (Glutting, 1989). A well-known earlier edition of the instruments representing the third revision is the Stanford-Binet Form L-M version published in 1960, comprised of two scales serving different purposes. Unfortunately, the Stanford-Binet Form L-M has less power to measure IQs at the high end of intelligence and has norms that discriminated against gifted students (Silverman & Kearney, 1992). The fifth edition of the Stanford-Binet Intelligence Scale, or SB5, was introduced in 2003.
The Stanford-Binet can be administered in long-form or full-scale, or in short-form via any of a number of subtests that represent designated areas such as:
* Verbal Reasoning,
* Abstract-Value Reasoning,
* Quantitative Reasoning, and
* Short-Term Memory (Weber, 1991).
The Stanford-Binet measures of intelligence quotients or IQs yield standard-age, full-scale/long-form, test-composite or total-composite scores and short-form area scores. The Verbal Reasoning Subtest, for example, provides a verbal IQ score.
The Wechsler Scales
The individual intelligence tests that are most often administered are the Wechsler tests, originally dubbed the Wechsler-Bellevue Intelligence Scales, which were developed by David Wechsler, and were published by the Psychological Corporation of San Antonio, Texas (Dallman et al., 1982; Weber, 1991).
The Wechsler Intelligence Scale has also published a number of versions. The Wechsler Intelligence Scale for Children-Revised (WISC-R) is administered to school-age children. It is a "downward extension" of the Wechsler Adult Intelligence Scale or WAIS and is appropriate for use in testing children between the ages of 5 and 17 (Borg & Gall, 1989; Lewis & Doorlag, 1987; Weber, 1991). The fourth version of the scale, or WISC-IV, was introduced in 2003. The Wechsler Intelligence Scale for Children-Fourth Edition maintains many of the features of prior editions (Mayes & Calhoun, 2007).
Another version of the Wechsler that was published for younger children was the Wechsler Preschool and Primary Scale of Intelligence, or WPPSI. It was designed to test children between the ages of 4 and 6 and a half (Borg & Gall, 1989; Field, 1987). The Wechsler Adult Intelligence Scale-Revised or WAIS-R is administered to individuals over age 16 and is suitable for use in testing late adolescents and adults (Borg & Gall, 1989; Weber, 1991). There are also editions that are published in languages other than English (e.g., Japanese, Spanish, French, and Hebrew).
The Wechsler can be implemented in full-scale/full-form and also in abbreviated or split-half short forms making use of various individual subtests of interest. The Wechsler scale has two subscales: a verbal scale and a performance scale. Each edition of the Wechsler has a somewhat variant number of verbal and performance subtests. The verbal subscale includes questions and tasks that involve information, arithmetic, vocabulary, comprehension, similarities, and "digit span." The Digit Span subtest is a measure of short-term memory. The verbal subtests require students to listen to questions and to reply orally. The performance scale is made up of visual-motor tasks and includes several subtest short forms. The subtests are:
* Coding or Mazes,
* Picture Completion,
* Picture Arrangement,
* Object Assembly, and
* Block Design (Axelrod & Paolo, 1998; Comninel & Bordieri, 2001; Lewis & Doorlag, 1987; Lynn et al., 2005; Nicholson & Alcorn, 1993; Weber, 1991; Wyver & Markham, 1998).
The Wechsler scales have achieved increasing prominence in the field of intelligence testing due in part to the fact that they yield a number of useful subscores in addition to an overall IQ score. WISC-R yields total-test scores called full-scale IQ (FSIQ) scores, which are comprehensive measures of intelligence, and two other global scores--a Verbal IQ (VIQ) and a Performance IQ (PIQ) (Borg & Gall, 1989; Lewis & Doorlag, 1987). The VIQ is calculated by adding the scaled scores of all of the verbal subtests except Digit Span. The PIQ is obtained from five of the performance subtest scale scores (Nicholson & Alcorn, 1993).
The WISC-R also yields factor-based scores on four different indices:
* Verbal Comprehension Index or VCI,
* Perceptual Organization Index or POI,
* Freedom from Distractibility Index or FDI, and
* Processing Speed Index or PSI (Calhoun & Mayes, 2005).
In addition, a test of memory impairment yields the Wechsler Memory Scale Memory Quotient (WMS MQ) (Prifitera & Barley, 1985).
Other Intelligence Scales
There are a variety of other intelligence scales that are sometimes used in intelligence testing. These include:
* The Kaufman Brief Intelligence Test or K-BIT,
* The Leiter International Performance Scale and the Leiter International Performance Scale-Revised,
* The Merrill Palmer Developmental Scale-Revised,
* The Fagan Test of Infant Intelligence or FTII, and
* The Bayley Scales of Infant Development.
Standardized intelligence scale instruments require special training for their administration and interpretation. The tests are typically administered individually by a school psychologist or other trained examiner. The examiner is usually involved in the selection of tests that are administered and in the general approach for administration. The experience level of the examiner in the facilitation of tests is important in avoiding examiner and administration errors. The use of the same examiner can minimize the factor of errors arising from administration, possible bias, and/or influence. Some intelligence tests have advantages and disadvantages in the relative ease or difficulty of accurate administration (Avant, 1987; Dallmann et al., 1982).
Administration may involve a full battery or a short-form procedure. Any of a number of subtests can be administered as a screening device when complete administration is not feasible (Haynes, 1985).
Because the performance of students may be influenced by the conditions of administration, the tests may be administered more than once. Students may suffer the effects of anxiety or have problems with seating or other physical arrangements in a first administration that make a second administration necessary. An examinee's scores from different administrations, previous and current, can be compared.
The measurement of an individual school-aged child's intelligence provides information about his or her overall or global intellectual ability and the specific factors of intelligence. The measurement of the child's higher or lower levels of cognition include his or her...
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