Mental Retardation

The Nature of Mental Retardation

Mental retardation is a disability or impairment in intellectual and social skills. It's a condition of incomplete or immature intellectual development that adversely affects the capacity to cope successfully with the challenges of daily existence. Its most general effect is to increase the degree of dependence in meeting those challenges.

According to the most recent AAMR definition of the disability, the 10th edition of Mental Retardation (Luckasson et al., 2002). This review examines each of its three elements — intelligence, adaptive behavior, and age of onset — as these are described and amplified in the AAMR model. Here is the 2002 definition:

“Mental retardation is a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills. This disability originates before age 18.”

Reference has been made to the effect of mental retardation on “adaptive behavior.” Its most general consequence, at any age, is to limit the mastery of the developmental skills appropriate to that age and thereby to increase the degree of dependency on others for their performance. In childhood and adolescence this means a greater dependence on parents and caregivers than is typical for that age. For some, though, since mental retardation varies so widely in its severity, the prolongation of dependency may be largely limited to the pre-adult years.

The individual with mental retardation will be delayed in the acquisition of age-related developmental skills in all adaptive domains, and his or her behavior, in comparison to that of the normally developing person, will appear “childlike” — that is, more appropriate to a younger age.

To behave in a fashion befitting an age younger than one’s own is, by definition, to behave “immaturely,” and in this sense, mental retardation is regarded as a disorder of chronic intellectual and emotional immaturity. This immaturity is most often apparent in the social and emotional realms, especially in persons with more severe degrees of intellectual impairment. In persons less severely affected, where the level of intellectual impairment is not more than “mild,” the immaturity is more evident in the cognitive realm.

The “chronic” nature of the disorder stems from the limitations set by biology on the period when the brain develops, during which there is corresponding growth of intellectual abilities. Formal measures of intelligence have represented this period as from infancy to about age 17 (e.g., Stanford-Binet IV: Thorndike, Hagen, & Sattler, 1986).

Table X | Levels of Mental Retardation & Capabilities of School-Age Children

Level of Mental Retardation (IQ Range)Percentage of Cases Capabilities of School-Age Children
Mild (50-70)85%Able to acquire reading and arithmetic skills to about a sixth-grade level and can later function relatively independently and engage in productive work
Moderate (35-49)10%Able to learn simple communication and manual skills, but have difficulty acquiring reading and arithmetic skills
Severe (20-34)3-4% Capable of basic speech and may be able to learn repetitive tasks in supervised settings
Profound (below 20)1-2% Severe delays in all areas of development, but some may learn simple tasks in supervised settings

Low IQ scores alone are not sufficient to determine mental retardation. In addition to having an IQ score of approximately 70 or below, the person must have difficulty coping with the tasks appropriate to his or her age and life situation. The educational and support services needed by children with mental retardation depend to a large extent on the severity of the retardation. Table X shows the capabilities of school-age children according to levels of mental retardation.

Most individuals with mental retardation fall in a mild range of severity and are capable of meeting basic educational challenges, such as reading and solving arithmetic problems. Many children with mild retardation are placed in regular classrooms, a practice mainstreaming. Those with severe intellectual deficits require more supportive programs, which may include institutional placement, at least until the person can function in less restrictive settings in the community.

The causes of mental retardation involve biological and environmental factors (Canfield et al., 2003). Biological causes include genetic or chromosomal disorders, brain damage, and exposure to lead. The most common environmental cause is a deprived family environment, one lacking in verbal interactions between the child and the parents, and also lacking in intellectually stimulating play activities.

People at the upper end of the IQ spectrum (typically about 130 or higher) are generally classified as intellectually gifted. As children, they may benefit from enriched educational programs that allow them to progress at a faster pace than standard programs.

Today, the concept of giftedness includes not only children with high IQ scores but also those with special talents, such as musical or artistic ability &mash; skills not typically assessed by standard IQ tests. Gifted children may play musical instruments as well as highly trained adults or solve algebra problems at an age when their peers have not yet learned to carry numbers in addition.

The systematic study of intellectually gifted children began with the work of Lewis Terman, the developer of the Stanford-Binet Intelligence Scale. Many of the intellectually gifted children he studied — the “little geniuses,” as they were originally called — became successful executives and professional and are credited with authoring 90 books and holding more than 100 patents (Feldhusen, 2004). But others in the group worked in occupations that failed to measure up to their intellectual potential.

The high achievers were more likely than the low achievers to have personality traits such as persistence in pursuing goals and a desire to excel. The lesson we can draw from this is that while intelligence may contribute to success, other factors enter the equation.

related literatures:
  1. Mental Retardation: Education and Rehabilitation Services By G. Lokanadha Reddy
  2. What is Mental Retardation?: Ideas for an Evolving Disability in the 21st, edited by Harvey N. Switzky, Stephen Greenspan