An intellectual disability (ID, formerly mental retardation) is a specific type of disability. This disability is caused by significant limitations in intellectual functioning (mental abilities). These limitations make it difficult to acquire important life skills. This is called adaptive functioning.
Intellectual functioning is determined by many factors. However, a primary source of this capacity is mental ability or "intelligence." Intelligence refers to the ability to reason, plan, think, and communicate. These abilities allow us to solve problems, to learn, and to use good judgment. One measure of intelligence is called the intelligence quotient, or IQ. There are standard tests that measure IQ. When someone's IQ score is below 70, it's likely they will have some problems. Because of how these tests are designed, 97.5% of the population would score above 70. These tests are discussed here.
Although ID affects learning abilities, it is not the same as another type of disability called learning disability. Learning disabilities are limited to a specific type of learning. This type is called academic learning. These are the sorts of things taught in schools. Therefore, learning disabilities affect reading, writing, and math. In contrast, intellectual disabilities affect three different types of learning. These are academic learning, experiential learning, and social learning. Children with learning disabilities have trouble with one type; academic learning. Children with intellectual disabilities have trouble with all three:
First, intellectual disabilities affect experiential learning. This type of learning occurs through cause and effect. For example, suppose a child touches a hot stove. This experience causes the child to learn to avoid touching a stove. A child with an ID does not learn from this painful experience. She does not understand the stove (the cause) caused the painful burn (the effect).
Second, intellectual disabilities affect social learning. This learning occurs by observing other people in social situations. We learn social customs and rules by watching others. For instance, we might notice it is customary to greet people by shaking hands or offering a hug. Social learning enables us to learn social skills. These skills are needed to get along well with other people. Moreover, social skills are critical to life success.
Third, intellectual disabilities affect academic learning. We learn useful skills and knowledge via formal education. These skills are reading, writing, and math. Thus, learning disabilities differ from ID because learning disabilities are limited to academic skills. In contrast, IDs include many types of learning problems. These learning difficulties make it hard to develop many practical life skills.
In addition to learning problems, limited intellectual functioning affects social and emotional functioning. Many persons with ID function on an emotional and social level far below what is average for their age. Some people consider this emotional immaturity an endearing quality. The child-like innocence, trust, wonder, and sincerity can be quite charming. However, these very same qualities make people vulnerable to victimization and cruelty.