Mental Retardation

  • Hugo W. Moser
Part of the Readings from the Encyclopedia of Neuroscience book series (REN)


The American Association on Mental Deficiency recommends that mental retardation be defined as “significantly subaverage general intellectual functioning resulting in or associated with concurrent impairments in adaptive behavior and manifested during the developmental period.” While at first glance this definition may appear to be self-evident and innocuous, it was arrived at only after a great deal of discussion and takes into account biological, psychological, social and even economic factors. Particularly important points are the insistence that general intellectual function must be significantly subaverage. Intellectual function here is operationally defined as the results obtained by assessment with one or more individually administered standardized general intelligence tests. With these tests the average IQ is set at 100, and the standard deviation has been found to be 15. Significantly subaverage intellectual function is defined as that which is more than 2 standard deviations below the mean IQ, that is, 70 or below. This upper limit of 70 is meant to be a guideline, and depending upon circumstances it can be extended to 75. Another significant aspect of the definition is that for a person to be classified as mentally retarded, the significantly subaverage intellectual function must be accompanied by impairment in adaptive behavior. This requirement is added in order to avoid inappropriate reliance on, or tyranny of, an IQ number. It is well known that IQ tests may underrepresent a person’s potential, such as when a North American IQ test is administered to a person who has been educated in another language or culture. Impairment in adaptive behavior is defined by Grossman as “significant limitations in an individual’s effectiveness in meeting the standards of maturation, learning, personal independence and/or social responsibility that are expected for his or her age level and cultural group, as determined by clinical assessment and, usually standardized scales.” The developmental period is defined as the period of time between conception and the 18th birthday. The definition of mental retardation is restrictive because we have learned that the inappropriate label of mental retardation may have serious consequences. Simon Olshansky has written: “To schools the category of mental retardation is a way of classifying some students with learning problems; to the person so labeled the categorization is an attack from which recovery is rarely complete.”


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Further reading

  1. Crome L, Stern J (1972): Pathology of Mental Retardation, 2nd ed. Edinburgh: Churchill LivingstoneGoogle Scholar
  2. Grossman HJ (1983): Classification in Mental Retardation. Washington DC: American Association on Mental DeficiencyGoogle Scholar
  3. Hagberg B, Kyllerman M (1983): Epidemiology of mental retardation: A Swedish survey. Brain Dev 5: 441–449CrossRefGoogle Scholar
  4. Olshansky S (1970): Work and the retarded. In: Diminished People, Bernstein NR, ed. Boston: Little, Brown, pp 29–46Google Scholar
  5. Moser HW (1977): Mental retardation. In: Horizons of Health, Wechsler H, Gurin J, Cahill GF Jr, eds. Cambridge: Harvard University PressGoogle Scholar
  6. Moser HW, Ramey CT, Leonard CO (1983): Mental retardation. In: Principles and Practice of Medical Genetics, Emery AL, Rimoin DL, eds. Edinburgh: Churchill Livingstone, pp 352–366Google Scholar

Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

  • Hugo W. Moser

There are no affiliations available

Personalised recommendations