Mental Retardation Defined (page 3)

Two different definitions of mental retardation are used in the United States today. Most states follow IDEA '04, the federal definition (Muller & Markowitz, 2004). However, many professionals prefer the one adopted in 2002 by the American Association on Mental Retardation (AAMR) because it is more detailed and allows for a clearer understanding of the supports the individual needs at school, at home, and in the community.  Accompanying the AAMR definition (the tenth definition this professional organization has developed and supported since 1921), and expanding on how it should be applied, are five assumptions:

1. Limitations in present functioning must be considered within the context of community environments typical of the individual's age peers and culture.
2. Valid assessment considers cultural and linguistic diversity as well as differences in communication and in sensory, motor, and behavioral factors.
3. Within an individual, limitations often coexist with strengths.
4. An important purpose of describing limitations is to develop a profile of needed supports.
5. With appropriate personalized supports over a sustained period, the life functioning of the person with mental retardation generally will improve. (Luckasson et al., 2002, p. 1)

Both the current AAMR definition and its predecessor, which was in effect between 1992 and 2002, have a positive orientation. Before then, definitions used a deficit perspective and described only the limitations of the individual. The more modern view conceptualizes mental retardation in terms of the levels of supports needed for the individual to function in the community as independently as possible (Polloway, 1997). Definitions following the deficit perspective used expressions such as: "significantly subaverage general intellectual functioning," "deficits in adaptive behavior," and "deficits in intellectual functioning." The two recent AAMR definitions-the 1992 and the 2002 definitions—changed to a positive orientation that addresses the interplay among capabilities of individuals; the environments in which they live, learn, and work; and how well each person functions with various levels of support. The needs of people are planned for by thinking about the intensity of supports (intermittent, limited, extensive, or pervasive) that they need in specific areas to function. The 2002 AAMR definition includes a cautious use of IQ scores but stresses concepts of adaptive behavior and systems of supports.

The condition of mental retardation is described and defined by AAMR in terms of three major components:

1. Intellectual-functioning
2. Adaptive behavior
3. Systems of supports

Across each of these components, mental retardation varies along a continuum. Most individuals with mental retardation have mild cognitive disabilities, have adequate adaptive behavior to live and work independently in the community, and usually require few supports. Typically, individuals with moderate to severe mental retardation require considerable supports. Let's examine each of these components in turn.

Intellectual Functioning

In its explanation of the 2002 AAMR definition, the organization stresses that individuals with mental retardation have intellectual functioning "significantly below average," or below levels attained by 97 percent of the general population. This level of functioning may be determined by clinical judgment or by a score on a test of intelligence. If a standardized test is used, the individual must score at least two standard deviations below the mean for the test. On IQ tests, intelligence is regarded as a trait that is distributed among people in a predictable manner. This statistical distribution can be represented as a bell-shaped curve, called the normal curve. In this curve the majority of a population falls in the middle of the bell, at or around an intelligence quotient (IQ) score of 100, and fewer and fewer people fall to either end of the distribution, having very low or very high intelligence. IQ level is then determined by the distance a score is from the mean, or average, score.

The 2002 AAMR definition uses IQ scores to partially explain mental retardation by using a cutoff score of about 70 and below. This definition also codes intellectual abilities to express levels of severity in the following ways:

• Mild mental retardation: IQ range of 50 to 69
  Outcomes: Has learning difficulties, is able to work, can maintain good social relationships, contributes to society
• Moderate mental retardation: IQ range of 35 to 49
  Outcomes: Exhibits marked developmental delays during childhood, has some degree of independence in self-care, possesses adequate communication and academic skills, requires varying degrees of support to live and work in the community
• Severe mental retardation: IQ range of 20 to 34
  Outcomes: Has continuous need for supports
• Profound mental retardation: IQ under 20
  Outcomes: Demonstrates severe limitations in self-care, continence, communication, and mobility; requires continuous and intensive supports