Mental retardation refers to significantly below-average intelligence. Mental retardation is categorized according to scores on tests that determine intelligence quotient (IQ) and other tests.

• Mild mental retardation (IQ = 50 to 70): Mild mental retardation may not be obvious.
  • Children who are mildly mentally retarded usually learn to walk, talk, and do other activities of daily living, but at a slower pace than children who are not retarded.
  • They can learn to read, write, and do basic math.
  • As adults, they usually are able to live independently and provide for themselves with some assistance.
• Moderate mental retardation (IQ = 35 to 55): Children who are moderately retarded develop much slower than children who are not retarded.
  • They usually do not progress beyond a second grade education level. However, they can learn routine tasks and talk in simple sentences.
  • As adults, they can function in well-supervised work situations and can live in group homes. They can live independently.
• Severe mental retardation (IQ = 20 to 35): Children who are severely retarded have difficulty learning self-care activities, such as feeding themselves.
  • They develop few communication skills, but they can understand and respond to what other people say.
  • They usually can do things that a 2- to 3-year-old can do, such as feed themselves, use the bathroom, and dress themselves.
  • As adults, they may not be able to live alone.