David Wechsler

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David Wechsler (born January 12, 1896 in Lespezi , Iași district , Romania ; † May 2, 1981 in New York ) was an American psychologist of Romanian - Jewish origin who dealt with the measurement of intelligence .


Wechsler studied at the City College of New York and then at Columbia University , where, after completing his studies a. a. at Edward Thorndike and James McKeen Cattell its 1917 Master made. In the same year he was employed by the US Army as a psychologist at Camp Logan, Texas. The sent him to further studies at the University of London , where he worked with the psychologist Charles Spearman and the mathematician Karl Pearson . From 1922 to 1925 he was a psychologist in educational counseling (Child Guidance Clinic) of the City of New York. After receiving his doctorate in 1925 under Robert S. Woodworth at Columbia, he was 1925-27 secretary of the Psychological Corporation . From 1932 to 1967 he worked as chief psychologist at Bellevue Psychiatric Hospital in New York. From 1933 he was also professor of clinical psychology at the Medical College of New York University . He also trained in psychoanalysis with Anna Freud .


Wechsler's intelligence concept

From 1917 he helped Edwin Boring to evaluate the data that arose when examining the recruits with the Army Alpha Test and other methods. His observations on the weaknesses of the tests made him question the academic definition of intelligence. He observed total failures in the tests, which coped well with everyday life. Therefore, he developed a broader concept of intelligence that also included non-intellectual aspects of personality.

For him, intelligence is “the composite or global ability of the individual to act purposefully, to think sensibly and to deal effectively with his environment”. His tests are based on the assumption that intelligence is composed of various abilities (for example a verbal-symbolic and a practical group factor, see Louis Leon Thurstone ). At the same time, Wechsler sticks to a summary in a total intelligence to describe a person (see Spearman's two-factor theory of intelligence ).

The variance intelligence quotient

Instead of referring to an intelligence age according to Alfred Binet or the equivalence or age IQ according to William Stern (intelligence age by age × 100), Wechsler proposed in 1932 the determination of the intelligence quotient as a so-called deviation IQ with a mean value of 100 and a standard deviation of 15 in front. The test values ​​achieved (raw values) are compared using a table with the standard values ​​from a representative comparison group. The seemingly arbitrary standard deviation of 15 resulted from the empirical values ​​that resulted from the determination of the age IQ in the tests from the Binet tradition: this value was between 14 and 16. The main reason for the introduction of the deviation IQ was that in adulthood with stable intelligence the division by age becomes meaningless (solved in Stanford-Binet by entering a constant 16 as the age for adults). In addition, the deviations from the mean value can be compared across different age groups. In all intelligence tests commonly used today , in which the result is given as IQ, this means Wechsler's deviation IQ. In addition, all common intelligence tests that do not output an IQ also use deviation measures that are equivalent to the deviation IQ and only have a different standard deviation and usually a different mean value, often standard or T values .

The changer scales

In 1939 he developed a test battery that became known as the Wechsler Bellevue Intelligence Scale (WBIS). Compared to the Stanford-Binet test by Lewis Madison Terman , this scale is characterized by the inclusion of several practical sub-tests, which relativize the preponderance of verbal tasks. Many parts of the test battery were already in use in other contexts: for example, the mosaic test as a block design test by Kohs (1923). This construction makes it possible to look at the individual strengths and weaknesses in addition to an estimate of the overall intelligence. The test was originally designed for clinical use in adults. The test quickly became the most popular intelligence test in the United States. Wechsler revised it for the first time in 1942.

In 1949 he published the Wechsler Intelligence Scale for Children (WISC) (revised 1974). In 1955 he developed another intelligence test for adults, the Wechsler Adult Intelligence Scale (WAIS) , which adopts the same structure as the WBIS, but takes more account of the different groups of the population (e.g. with 10 percent non-whites in the Comparison group). This scale was revised in 1981. His final test, the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) for very young children, was published in 1967.

Curt Bondy transferred WAIS to Germany in 1956 as HAWIE (Hamburg Wechsler Intelligence Test for Adults) and in 1956 WISC as HAWIK (Hamburg Wechsler Intelligence Test for Children). The HAWIE has been used since 2007 as WIE (German-language version of WAIS-III ), the HAWIK since 2007 as HAWIK-IV. The Wechsler Preschool and Primary Scale of Intelligence-III (WPPSI-III, Wechsler 2002) was initially published as a German-language adaptation under the name HAWIVA-III (Hannover-Wechsler-Intelligenztest für das Vorschulalter-III). Since 2009 the German version of the procedure has been available again under its original name WPPSI-III . However, Wechsler's conception was criticized early on in German-speaking countries, especially by Gerhard Dahl, both in terms of statistical processing and in terms of the diagnostic relevance (e.g. degradation diagnostics) of the test scales. The results of statistical investigations have confirmed Dahl's hypothesis that the Wechsler scales do not allow valid differential diagnostic statements and that the test can be shortened considerably without loss of knowledge, which was realized in the development of an independent reduced test form (WIP). As a statistically reliable test for recording general intelligence, the WIP was widely accepted in German-speaking countries, so that a second edition with extensive analyzes and representative standard values ​​was soon required. With the dissolution of the Anton Hain publishing house and the subsequent difficult and ultimately fruitless negotiations with the American copyright holder, further publication of the WIP had to be terminated. However, the criticism of the German versions of the Wechsler scales contained therein has not gone unnoticed, as the adaptation of WAIS-III in Germany shows.

Based on and criticized the Wechsler tests, the Adaptive Intelligence Diagnostics (AID, now AID 3) was developed in Austria by Klaus Kubinger and the Kaufman Assessment Battery for Children (K-ABC, also in German) in the USA . In addition to significant independent developments, both tests still show clear traces of their origin from the Wechsler range.


  • 1935: The Range of Human Capacities Baltimore
  • 1939: The Measurement of Adult Intelligence Baltimore, (3rd edition 1944)
    • German 1956: The measurement of the intelligence of adults. Bern, Stuttgart: Huber (3rd edition 1964)
  • 1958: The Measurement and Appraisal of Adult Intelligence


  1. Dahl, Gerhard : To determine the pathological decline in intelligence in HAWIE with the help of the breakdown quotient. Psychol. Forsch. 28, 476-490 (1965).
  2. ders .: Conformity validity of the HAWIE and development of a reduced test form. 94 S. Hain. Meisenheim. 1968
  3. ders .: WIP. Reduced changeover intelligence test. Application, evaluation, statistical analysis, standard values. 134 S., Hain, Meisenheim, 1972
  4. ders .: WIP. Manual for the reduced changer intelligence test. 2nd completely revised and expanded edition. Hain, Koenigstein 1986

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