Intellectual Disabilities

Definition of Intellectual Disability

Intellectual disability is a disability characterized by significant limitations in both intellectual functioning and in adaptive and developmental behavior, which covers many everyday social and practical skills. This disability originates before the age of 18.

Intellectual Functioning

Intellectual functioning refers to general mental capacity, such as learning, reasoning, problem solving, and so on.

Adaptive Behavior

Adaptive behavior is the collection of conceptual, social, and practical skills that are learned and performed by people in their everyday lives. 

Intellectual Functioning and Adaptive Behavior impact the following developmental skills:

  • Conceptual skills—language and literacy; money, time, and number concepts; and self-direction.
  • 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 to avoid being victimized.
  • Practical skills—activities of daily living (personal care), occupational skills, healthcare, travel/transportation, schedules/routines, safety, use of money, use of the telephone.

Age of Onset

This condition is one of several developmental disabilities—that is, there is evidence of the disability during the developmental period, which in the US is operationalized as before the age of 18.

Become a Member Today!

Would you like to be a member of the largest organization in the United States dedicated to
improving the quality of life for people with intellectual and developmental disabilities (I/DD)?

Join Us