Intellectual Disability

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Frequently Asked Questions on Intellectual Disability

What is intellectual disability?

Intellectual disability is a disability characterized by significant limitations both in intellectual functioning (reasoning, learning, problem solving) and in adaptive behavior, which covers a range of everyday social and practical skills. This disability originates before the age of 18.

Is intellectual disability the same as mental retardation? Why do some programs and regulations still say mental retardation?

The term intellectual disability covers the same population of individuals who were diagnosed previously with mental retardation in number, kind, level, type, duration of disability, and the need of people with this disability for individualized services and supports. Furthermore, every individual who is or was eligible for a diagnosis of mental retardation is eligible for a diagnosis of intellectual disability.

While intellectual disability is the preferred term, it takes time for language that is used in legislation, regulation, and even for the names of organizations, to change.

Is intellectual disability the same as developmental disabilities?

"Developmental Disabilities" is an umbrella term that includes intellectual disability but also includes other disabilities that are apparent during childhood.

Developmental disabilities are severe chronic disabilities that can be cognitive or physical or both. The disabilities appear before the age of 22 and are likely to be lifelong.Some developmental disabilities are largely physical issues, such as cerebral palsy or epilepsy. Some individuals may have a condition that includes a physical and intellectual disability, for example Down syndrome or fetal alcohol syndrome.

Intellectual disability encompasses the “cognitive” part of this definition, that is, a disability that is broadly related to thought processes. Because intellectual and other developmental disabilities often co-occur, intellectual disability professionals often work with people who have both types of disabilities.

Is intellectual disability determined by just an IQ test?

No. The evaluation and classification intellectual disability is a complex issue. There are three major criteria for intellectual disability: significant limitations in intellectual functioning,  significant limitations in  adaptive behavior,  and onset before the age of 18.

The IQ test is a major tool in measuring intellectual functioning, which is the mental capacity for learning, reasoning, problem solving, and so on. A test score below or around 70—or as high as 75—indicates a limitation in intellectual functioning.

Other tests determine limitations in adaptive behavior, which covers three types of skills:

  • Social skills—interpersonal skills, social responsibility, self-esteem, gullibility, naïveté (i.e., wariness), social problem solving, and the ability to follow rules, obey laws, and avoid being victimized

AAIDD publishes the most advanced scientific thinking on this matter in the 11th edition of its manual, Intellectual Disability: Definition, Classification, and Systems of Supports. In defining and assessing intellectual disability, AAIDD stresses that, in addtion to an  assessement of intellectual functioning and adaptive behavior, professionals must consider such factors as

  • community environment typical of the individual’s peers and culture
  • linguistic diversity
  • cultural differences in the way people communicate, move, and behavior

What causes intellectual disability?

There are a number of causes. Our understanding of the causes of intellectual disability focuses on the types of risk factors (biomedical, social, behavioral, and educational) and the timing of exposure (prenatal, perinatal, and postnatal) to those factors.   

What is the most modern thinking about how to help people with intellectual disability?

The overarching reason for evaluating and classifying individuals with intellectual disability is to tailor supports for each individual, in the form of a set of strategies and services provided over a sustained period.

Our goal is to enhance people’s functioning within their own environment in order to lead a more successful and satisfying life. Some of this enhancement is thought of in terms of self-worth, subjective well being, pride, engagement in political action, and other principles of self-identity.   

What role has AAIDD played in defining intellectual disabilty?

AAIDD, the world’s largest and oldest organization of intellectual disability professionals, has played a major role in evolving ideas about and approaches to intellectual disability. In fact, the Association, founded in 1876, has published 11 editions of its definitional manual between 1908 and 2010, each edition containing the latest scientific understanding of the condition.

The first definitions of the condition focused on a failure to adapt socially to the environment. Later definitions added a medical approach that considered heredity and pathology and called for individuals with intellectual disability to be segregated. Then the rise of the cognitive testing movement brought an emphasis on measuring intellectual functioning by IQ test. The IQ test became the way to define the group and classify the people within it.

In its 1959 definition and classification manual, AAIDD first attempted a dual-criterion approach: a definition that mentioned both intellectual functioning and “impairments in maturation, learning, and social adjustment.” In its 1961 manual, AAIDD folded the “impairments” description into the phrase “adaptive behavior,” a term still used today. The definition was refocused in 1992 to reflect a new way of understanding and responding to the condition.. AAIDD moved away from a diagnostic process that identified deficits solely on the basis of an IQ score, and began considering social, environmental, and other elements as well. Most crucially, the emphasis shifted from providing programs to people with intellectual disability to designing and delivering support tailored to each individual to help them reach their highest level of functioning.

The third element of the definition involves age of onset. Early definitions mentioned “the developmental period.” AAIDD’s 2002 definition clarified that the disability originates "before the age of 18.”

It is important to note that the 1992 definition was the first to view intellectual disability as a condition that could be enhanced by provision of supports, rather than as a static, lifelong disability.

Since 1992, the Association has worked to further develop and refine this paradigm shift. The approach is more fully fleshed out in the Association’s 11th and most recent manual, Intellectual Disability: Definition, Classification, and Systems of Supports, published in 2010.