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.
Developmental Disabilities is an umbrella term that includes Intellectual Disability but also includes other disabilities that are acknowledged during early childhood. 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.
No. The evaluation and classification Intellectual Disability is a complex issue. 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, professionals must consider such factors as
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:
There are a number of causes of intellectual disability. 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.
AAIDD stresses that the overarching reason for evaluating and classifying individuals with intellectual disabilities 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.
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.
Intellectual Disability is one type of a larger universe of many types of Developmental Disabilities.
Developmental disabilities are defined as 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.
Intellectual Disability encompasses the “cognitive” part of this definition, that is, a disability that are 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.
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 "mental retardation" 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.