- mental retardation
a developmental disorder characterized by a subnormal ability to learn and a substantially low IQ.[1900-15]
* * *Subaverage intellectual ability that is present from birth or infancy and is manifested by abnormal development, learning difficulties, and problems in social adjustment.A standardized intelligence test is a common method of identification. Individuals with IQ scores of 53–70 are usually classified as mildly retarded and are able to learn academic and pre-vocational skills with some special education. Those with scores of 36–52 are classified as moderately retarded and are able to learn functional academic skills and undertake semiskilled work under supervised conditions. Those in the severe (21–35) and profound (below 21) ranges require progressively more supervision or full-time custodial care. Mental retardation can be caused by genetic disorders (such as Down's syndrome), infectious diseases (such as meningitis), metabolic disorders, poisoning from lead, radiation, or other toxic agents, injuries to the head, and malnutrition.
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