Wechsler intelligence test

Definition

The Wechsler intelligence tests are a widely used series of intelligence tests developed by clinical psychologist David Wechsler.

Purpose

The Wechsler Intelligence Scales for Children (regular, revised, and third edition) and Wechsler Preschool and Primary Scale of Intelligence are used as tools in school placement, in determining the presence of a learning disability or a developmental delay , in identifying giftedness, and in tracking intellectual development. They are often included in neuropsychological testing to assess the brain function of individuals with neurological impairments.

Description

The most distinctive feature of the Wechsler tests is their division into a verbal section and a nonverbal (or performance) section, with separate scores available for each subsection. All of the Wechsler scales are divided into six verbal and five performance subtests. The complete test takes 60 to 90 minutes to administer. Verbal intelligence, the component most often associated with academic success, implies the ability to think in abstract terms using either words or mathematical symbols. Performance intelligence suggests the ability to perceive relationships and fit separate parts together logically into a whole. The inclusion of the performance section in the Wechsler scales is especially helpful in assessing the cognitive ability of non-native speakers and children with speech and language disorders . The test can be of particular value to school psychologists screening for specific learning disabilities because of the number of specific subtests that make up each section.

The Wechsler Preschool and Primary Scales of Intelligence (WPPSI) have traditionally been geared toward children ages four to six years old, although the newest version of the test extends the age range down to three years and upward to seven years three months. The verbal section covers the following areas: general information (food, money, the body, etc.), vocabulary (definitions of increasing difficulty), comprehension (responses to questions), arithmetic (adding, subtracting, counting), sentences (repeating progressively longer sentences), and similarities (responding to questions such as "How are a pen and pencil alike?"). The performance section includes picture completion, copying geometric designs, using blocks to reproduce designs, working through a maze, and building an animal house from a model.

The Wechsler Intelligence Scale for Children (WISC) is designed for children and adolescents ages six to 16. Its makeup is similar to that of the Preschool Scale. Differences include the following: geometric designs are replaced by assembly of three-dimensional objects; children arrange groups of pictures to tell simple stories; they are asked to remember and repeat lists of digits; a coding exercise is performed in place of the animal house; mazes are a subtest. For all of the Wechsler scales (which also include the Wechsler Adult Intelligence Scale, or WAIS), separate verbal and performance scores, as well as a total score, are computed. These are then converted using a scale divided into categories (such as average and superior), and the final score is generally given as one of these categories rather than as a number or percentile ranking.

The Wechsler Intelligence Scales are standardized tests, meaning that as part of the test design, they were administered to a large representative sample of the target population, and norms were determined from the results. The scales have a mean, or average, standard score of 100 and a standard deviation of 15. The standard deviation indicates how far above or below the norm the subject's score is. For example, a ten-year-old is assessed with the WISC-III scale and achieves a full-scale IQ score of 85. The mean score of 100 is the average level at which all 10-year-olds in the representative sample performed. This child's score would be one standard deviation below that norm.

While the full-scale IQ score provides a reference point for evaluation, it is only an average of a variety of skill areas. A trained psychologist evaluates and interprets an child's performance on the scale's subtests to discover their strengths and weaknesses and offer recommendations based upon these findings.

Risks

The only known risk of the Wechsler intelligence tests is that the results are misused or are given undue weight.

Parental concerns

Results of intelligence tests should not be considered a complete indication of a child's future path. They are most useful in determining children who may need special attention, either because of disability or because of giftedness. Parents should consider the possible consequences carefully if they are considering telling their child the outcome of this or any other intelligence test.

KEY TERMS

Norms —A fixed or ideal standard; a normative or mean score for a particular age group.

Representative sample —A random sample of people that adequately represents the test-taking population in age, gender, race, and socioeconomic standing.

Standard deviation —A measure of the distribution of scores around the average (mean). In a normal distribution, two standard deviations above and below the mean includes about 95% of all samples.

Standardization —The process of determining established norms and procedures for a test to act as a standard reference point for future test results.

Resources

BOOKS

Flanagan, Dawn P., and Alan S. Kaufman. Essentials of WISC IV Assessment. Hoboken, NJ: John Wiley & Sons, 2004.

PERIODICALS

Canivez, Gary L., and Marley W. Watkins. "Long-Term Stability of the Wechsler Intelligence Scale for Children—Third Edition among Students with Disabilities." School Psychology Review 30 (Summer 2001): 438–54.

Caruso, John C., and Norman Cliff. "Increasing the Reliability of Wechsler Intelligence Scale for Children—Third Edition Difference Scores with Reliable Component Analysis." Psychological Assessment 12 (March 2000): 89–97.

Watkins, Marley W., et al. "Factor Structure of the Wechsler Intelligence Scale for Children—Third Edition among Gifted Students." Educational and Psychological Measurement 63 (October 2003): 164–72.

Tish Davidson, A.M. Paula Anne Ford-Martin