David Wechsler (January 12, 1896 - May 2, 1981) was a leading American psychologist. He developed well-known intelligence scales, including the Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC). Wechsler is also known for establishing the deviation quotient, or DQ, which replaced the use of mental ages in testing an individual’s intelligence. A student of both Karl Pearson and Charles Spearman, Wechsler was also greatly influenced by Edward L. Thorndike. Updated versions of Wechsler’s intelligence tests continue to remain popular in the twenty-first century.
Wechsler viewed intelligence as an effect rather than a cause, and believed former assessments of general intelligence to be too narrow. Instead, he found that non-intellectual factors, such as personality, often contribute to the development of an individual’s intelligence. For Wechsler, intelligence should be regarded not just as the ability to think rationally, although that was a significant component. Equally important in his conception was the ability to act purposefully and effectively in one's environment. Thus, he regarded the measure of intelligence to go beyond intellectual capacity into the realm of activity in the world, a measure that has much greater usefulness. Wechsler's work has significantly increased our appreciation for what makes for a successful individual.
David Wechsler was born into a Jewish family in Lespezi, Romania, and immigrated with his parents to the United States as a child. He studied at the City College of New York and Columbia University, where he earned his master's degree in 1917.
Shortly after the U.S. entered the First World War, Wechsler joined the U.S. Army as an army psychologist to aid in the screening of new draftees. Assigned to Camp Logan, Texas, Wechsler worked alongside prominent intelligence theorists Karl Pearson, Charles Spearman, Edward Thorndike, and Robert Mearns Yerkes. Here, Wechsler scored the Army Alpha Test, one of two tests designed by the U.S. Army to test group intelligence. Following his work with the Alpha Test, Wechsler worked as an individual psychological examiner, administering the Stanford-Binet test to recruits who had performed poorly in the group intelligence testing. In 1918, Wechsler, along with Spearman and Pearson were sent to perform similar research at the University of London.
Following World War I, Wechsler studied at the University of Paris where he undertook extensive research in experimental psychology until 1922. Upon returning to the United States, Wechsler worked as a clinical psychologist at the Bureau of Child Guidance in New York. In 1925, he received a Ph.D. in experimental psychology from Columbia University where he studied under the direction of Robert S. Woodworth.
After short stints at various locations, including five years in private practice, Wechsler became chief psychologist at Bellevue Psychiatric Hospital in 1932. In 1939, Wechsler published The Measurement of Adult Intelligence, following in 1940 by the equally influential Non-intellective Factors in General Intelligence.
He remained on staff at the Bellevue Psychiatric Hospital until 1967. He died in 1981 at the age of 85.
While working at the Bellevue Psychiatric Hospital, Wechsler published various intelligence scales. The renowned Wechsler Adult Intelligence Scale (WAIS) was developed first in 1939 and termed the Wechsler-Bellevue Intelligence Test. From this he derived the Wechsler Intelligence Scale for Children (WISC) in 1949 and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) in 1967. Wechsler originally created these tests to find out more about his patients at the Bellevue clinic; he found the then-popular Stanford-Binet IQ test unsatisfactory.
The Wechsler scales introduced many novel concepts and breakthroughs to the intelligence testing movement. He did away with the “quotient” scores of older intelligence tests, or the Q in "IQ." Instead, he assigned an arbitrary value of 100 to the mean intelligence and added or subtracted another 15 points for each standard deviation above or below the subject’s mean. Rejecting a concept of global intelligence, as propagated by Charles Spearman's Spearman's hypothesis, he divided the concept of intelligence into two main areas: verbal and performance, and further subdivided and tested each area with a different subtest. These conceptualizations continue to be reflected in the Wechsler scales of the twenty-first century; as such, the WAIS continues to remain the most commonly administered psychological test in existence.
Wechsler's full scale test is broken down into 14 sub-tests, comprising the verbal scale, seven verbal sub-tests, the performance scale and seven performance sub-tests. Wechsler's tests provide three scores; a verbal IQ score, a performance IQ score, and a composite IQ score based on the combined scores.
Verbal subtests aim to test general cultural information, abstract comprehension, arithmetic, verbal reasoning, vocabulary, concentration, and memory. Performance subtests include visual perception, visual-motor coordination, spatial perception, abstract problem solving, sequential reasoning, perception speed, and visual analysis.
The Wechsler Adult Intelligence Scale is appropriate throughout adulthood and for use with those individuals over 74 years-of-age. For testing children aged seven to 16, the Wechsler Intelligence Scale for Children is used, while the Wechsler Preschool and Primary Scale of Intelligence is used for testing children aged two-and-a-half to seven. Both tests can be completed without reading or writing.
Wechsler’s intelligence scales are used not only as an intelligence test, but also as a clinical tool. Many practitioners use the Wechsler’s Intelligence Scale for Children (WISC) to diagnose attention-deficit hyperactivity disorder (ADHD) and to detect learning disabilities. This is usually done through a process called pattern analysis, in which the various subtests' scores are compared to one another and clusters of unusually low scores in relation to the others are searched for. David Wechsler himself suggested this in 1958.
The empirical consensus is that the WISC is best used as a tool to evaluate intelligence and not to diagnose ADHD or learning disabled children. However, many clinicians use it to compare a child's cognitive development to his or her actual school or social performance. Using this discrepancy and other sources of data, the WISC can contribute information concerning a child's psychological well-being.
David Wechsler is best known for his many contributions to intelligence theory. He is credited with the creation of various intelligence testing scales, including the renowned Wechsler-Bellevue Scale of Intelligence, the Wechsler Memory Scale, the Wechsler Intelligence Scale for Children, the Wechsler Adult Intelligence Scale, and the Wechsler Primary and Preschool Scale of Intelligence. Many of these tests have remained in circulation into the twenty-first century, most showing only small alteration over time.
Wechsler is also known for his creation of the "deviation IQ," or DQ, which worked to replace mental age in computing IQ scores; this allowed for greater comparison among adult examinees. An author of various influential publications, Wechsler viewed intelligence as an effect rather than a cause, and believed former assessments of general intelligence to be too narrow. Instead, he found that non-intellectual factors, such as personality, often contribute to the development of an individual’s intelligence. When he died at the age of 85, Wechsler was a greatly respected psychologist.
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