Chapter 4

Mental Retardation

Definitions of Mental Retardation

• AAMR’s 1983 definition in IDEA – Significantly subaverage intellectual functioning– Deficits in adaptive behavior– Manifested during the developmental period

• AAMR’s new definition based on needed supports– Significant limitations in both intellectual functioning and conceptual,

social, and practical adaptive skills; the disability originates before age 18

• Intensity of supports:– Intermittent - As needed, short-term supports– Limited - Consistent support for limited time– Extensive - Consistent support in some settings– Pervasive - Consistent, high intensity support in most settings

Identification and Assessment

Assessing Intellectual Functioning • Standardized tests are used to assess intelligence

– A diagnosis of MR requires an IQ score at least 2 standard deviations below the mean (70 or less)

• Important considerations of IQ tests: – IQ is a hypothetical construct– IQ tests measure how a child performs at one point in time– IQ tests can be culturally biased– IQ scores can change significantly– IQ testing is not an exact science– Results are not useful for targeting educational objectives

• Results should never be used as the sole basis for making decisions regarding special education services

Normal Curve

Assessing Adaptive Behavior

• Adaptive behavior is the effectiveness or degree with which the individual meets the standards of personal independence and social responsibility expected of his age and social group

– Measurement of adaptive behavior has proven difficult because of the relative nature of social adjustment and competence

– Adaptive Behavior Scales (ABS-S) – Observational scale. Part 1 – independent functioning Part 2-Maladaptive behavior

– Vineland – Informant assessment– Scales of Independent Behavior-Provides a comprehensive

assessment of 14 areas of adaptive behavior and 8 areas of problem behavior

Prevalence and Causes

Prevalence• During the 2000-2001 school year, approximately 1% of the total

school enrollment received special education services in the MR category

• Mild MR cases make up about 85% of all persons with MR

Causes• More than 750 causes of MR have been identified• For approximately 50% of mild MR cases and 30% of severe MR, the

cause is unknown

Biological Causes

• Prenatal causes include: – Chromosomal disorders– Inborn errors of metabolism– Developmental disorders– Toxic exposure through maternal substance abuse

• Perinatal causes include:– Intrauterine disorders– Neonatal disorders

• Postnatal causes include:– Head injuries– Infections– Degenerative disorders– Malnutrition

Chromosomal and Genetic Causes

• Tuberous sclerosis – Tumors in nervous system

• Phenylketonuria (PKU) – inability to metabolize enzyme phenylalanine

• Hurler Syndrome – Inability to break down various carbohydrates

• Tay-Sachs disease – abnormal buildup of lipids within body tissue

• Fragile X – Triplet, repeat mutation on the X chromosome

• Down Syndrome -21st set of chromosome is a triplet

Environmental Causes

• Toxoplasmosis – Protozoic infection

• Rubella – German measles infection

• Radiation – Exposure to radiation in utero

• Malnutrition – Pre- and post-natal lack of adequate nutrition

• Drug abuse – exposure in utero

• Blood type incompatibility

• Mosquito bite - encephalitis

• Anoxia – loss of oxygen (umbilical cord around neck)

Environmental Causes

• Biggest preventive strike was the development of the rubella vaccine

Prevention

• The biggest single preventive strike against MR was the development of the rubella vaccine in 1962

• Toxic exposure through maternal substance abuse and environmental pollutants are two major causes of preventable MR that can be combated with education and training

• Advances in medical science have enabled doctors to identify certain genetic influences

• Although early identification and intensive educational services to high-risk infants show promise, there is still no widely used technique to decrease the incidence of MR caused by psychosocial disadvantage

Characteristics of Students with MR• Mild MR

– Usually not identified until school age– Most students master many academic skills– Most able to learn job skills well enough to support themselves

independently or semi-independently

• Moderate MR– Most show significant delays in development during the

preschool years– As they grow older the discrepancies in age related adaptive

and intellectual skills widens

• Severe MR– Usually identified at birth– Most have significant central nervous system damage– Likely to have health care problems that require intensive

supports

Wild Boy 1800

–Dr. Jean Marc Itard was the first to develop a individualized educational procedure. He developed a student centered approach.

–Wild Child

– Itard, J.M.G. (1962). The wild boy of Aveyron. (G. Humphrey & M. Humphrey, Trans.). New York: Appleton-Century-Crofts. (Original works published 1801 and 1806).

Educational Approaches

Curriculum Goals• Functional curriculum

– A functional curriculum will maximize a student’s independence, self-direction, and enjoyment in school, home, community, and work environments

• Life skills– Skills that will help the student transition into adult life in the

community

• Self-determination– Self-determined learners set goals, plan and implement a

course of action, evaluate their performance, and make adjustments in what they are doing to reach their goals

Characteristics of Effective Instruction

• Explicit and systematic instruction • Task analysis

• Direct and frequent measurement of student performance

• Active student response

• Systematic feedback provided by the teacher

• Transfer of stimulus control from prompts to task

• Generalization and maintenance

Educational Placement Alternatives

• Some children with MR attend special schools• Most are educated in their neighborhood schools

– Special classes– Regular class with support– Resource room

• The extent to which a student with MR should be included in the regular classroom should be determined by the student’s individual needs

Current Issues and Future Trends

• Some concerns of the current definition of MR include:– IQ testing will remain the primary means of assessment– Adaptive skills cannot be reliably measured with current

assessment methods– The levels of need supports are too subjective– Classification will remain essentially unchanged in practice

• Acceptance and membership– An especially important and continuing challenge is moving

beyond the physical integration of persons with MR in society to acceptance and membership that comes from holding valued roles