Fred J. Biasini, Ph.D.
Lisa Grupe, M.A.
Lisa Huffman, Ph.D.
Norman W. Bray, Ph.D.
Department of Psychology
University of Alabama at Birmingham

To appear in S. Netherton, D. Holmes, & C. E. Walker, (Eds.), Comprehensive Textbook of Child and Adolescent Disorders. New York: Oxford University Press, in press.

Mailing address: Department of Psychology and Civitan International Research Center, SC 313, University of Alabama at Birmingham, Birmingham, AL 35294. Phone: (205) 934-9768, FAX: (205) 975-6330. mailto:bray@cis.uab.edu

Mental retardation is an idea, a condition, a syndrome, a symptom, and a source of pain and bewilderment to many families. Its history dates back to the beginning of man's time on earth. The idea of mental retardation can be found as far back in history as the therapeutic papyri of Thebes (Luxor), Egypt, around 1500 B.C. Although somewhat vague due to difficulties in translation, these documents clearly refer to disabilities of the mind and body due to brain damage (Sheerenberger, 1983). Mental retardation is also a condition or syndrome defined by a collection of symptoms, traits, and/or characteristics. It has been defined and renamed many times throughout history. For example, feeblemindedness and mental deficiency were used as labels during the later part of the last century and in the early part of this century. Consistent across all definitions are difficulties in learning, social skills, everyday functioning, and age of onset (during childhood). Mental retardation has also been used as a defining characteristic or symptom of other disorders such as Down syndrome and Prader-Willi syndrome. Finally, mental retardation is a challenge and potential source of stress to the family of an individual with this disorder. From identification through treatment or education, families struggle with questions about cause and prognosis, as well as guilt, a sense of loss, and disillusionment about the future.

The objective of this chapter is to provide the reader with an overview of mental retardation, a developmental disability with a long and sometimes controversial history. Following a brief historical overview, the current diagnostic criteria, epidemiological information and the status of dual diagnosis will be presented. Comprehensive assessment and common interventions will also be reviewed in some detail.

Historical Perspective

The plight of individuals with developmental disabilities has been dependent on the customs and beliefs of the era and the culture or locale. In ancient Greece and Rome, infanticide was a common practice. In Sparta, for example, neonates were examined by a state council of inspectors. If they suspected that the child was defective, the infant was thrown from a cliff to its death. By the second century A.D. individuals with disabilities, including children, who lived in the Roman Empire were frequently sold to be used for entertainment or amusement. The dawning of Christianity led to a decline in these barbaric practices and a movement toward care for the less fortunate; in fact, all of the early religious leaders, Jesus, Buddha, Mohammed, and Confucius, advocated human treatment for the mentally retarded, developmentally disabled, or infirmed (Sheerenberger, 1983).

During the Middle ages (476 - 1799 A.D.) the status and care of individuals with mental retardation varied greatly. Although more human practices evolved (i.e., decreases in infanticide and the establishment of foundling homes), many children were sold into slavery, abandoned, or left out in the cold. Toward the end of this era, in 1690, John Locke published his famous work entitled An Essay Concerning Human Understanding. Locke believed that an individual was born without innate ideas. The mind is a tabula rasa, a blank slate. This would profoundly influence the care and training provided to individuals with mental retardation. He also was the first to distinguish between mental retardation and mental illness; "Herein seems to lie the difference between idiots and madmen, that madmen put wrong ideas together and reason from them, but idiots make very few or no propositions and reason scarce at all (Doll, 1962 p. 23)."

A cornerstone event in the evolution of the care and treatment of the mentally retarded was the work of physician Jean-Marc-Gaspard Itard (Sheerenberger, 1983) who was hired in 1800 by the Director of the National Institutes for Deaf-Mutes in France to work with a boy named Victor. Victor, a young boy, had apparently lived his whole life in the woods of south central France and, after being captured and escaping several times, fled to the mountains of Aveyron. At about age 12, he was captured once again and sent to an orphanage, found to be deaf and mute, and moved to the Institute for Deaf-Mutes.

Based on the work of Locke and Condillac who emphasized the importance of learning through the senses, Itard developed a broad educational program for Victor to develop his senses, intellect, and emotions. After 5 years of training, Victor continued to have significant difficulties in language and social interaction though he acquired more skills and knowledge than many of Itard's contemporaries believed possible. Itard's educational approach became widely accepted and used in the education of the deaf. Near the end of his life, Itard had the opportunity to educate a group of children who were mentally retarded. He did not personally direct the education of these children, but supervised the work of Edouard Seguin (Sheerenberger, 1983). Seguin developed a comprehensive approach to the education of children with mental retardation, known as the Physiological Method (Sheerenberger, 1983). Assuming a direct relationship between the senses and cognition, his approach began with sensory training including vision, hearing, taste, smell, and eye-hand coordination. The curriculum extended from developing basic self-care skills to vocational education with an emphasis on perception, coordination, imitation, positive reinforcement, memory, and generalization. In 1850, Seguin moved to the United States and became a driving force in the education of individuals with mental retardation. In 1876, he founded what would become the American Association on Metal Retardation. Many of Seguin's techniques have been modified and are still in use today.

Over the next 50 years, two key developments occurred in the United States: residential training schools were established in most states (19 state operated and 9 privately operated) by 1892, and the newly developed test of intelligence developed by Binet was translated in 1908 by Henry Goddard, Director of Research at the training school in Vineland, New Jersey. Goddard published an American version of the test in 1910. In 1935, Edgar Doll developed the Vineland Social Maturity Scale to assess the daily living skills/adaptive behavior of individuals suspected of having mental retardation. Psychologists and educators now believed that it was possible to determine who had mental retardation and provide them with appropriate training in the residential training schools.

During the early part of the 20th century, residential training schools proliferated and individuals with mental retardation were enrolled. This was influenced by the availability of tests (primarily IQ) to diagnose mental retardation and the belief that, with proper training, individuals with mental retardation could be "cured". When training schools were unable to "cure" mental retardation, they became overcrowded and many of the students were moved back into society where the focus of education began to change to special education classes in the community. The training schools, which were initially more educational in nature, became custodial living centers.

As a result of the disillusionment with residential treatment, advocacy groups, such as the National Association of Retarded Citizens and the President's Commission on Mental Retardation, were established in the 1950's through the 1970's. The Wyatt-Stickney federal court action, in the 1970's, was a landmark class action suit in Alabama establishing the right to treatment of individuals living in residential facilities. Purely custodial care was no longer acceptable. Concurrent with this case, the United States Congress passed the Education for the Handicapped Act in 1975, now titled the Individuals with Disabilities Education Act. This Act guaranteed the appropriate education of all children with mental retardation and developmental disabilities, from school age through 21 years of age. This law was amended in 1986 to guarantee educational services to children with disabilities age 3 through 21 and provided incentives for states to develop infant and toddler service delivery systems. Today, most states guarantee intervention services to children with disabilities between birth and 21 years of age.

Definition/Diagnosis/Classification.

According to Sheerenberger (1983), the elements of the definition of mental retardation were well accepted in the United States by 1900. These included: onset in childhood, significant intellectual or cognitive limitations, and an inability to adapt to the demands of everyday life. An early classification scheme proposed by the American Association on Mental Deficiency (Retardation), in 1910 referred to individuals with mental retardation as feeble-minded, meaning that their development was halted at an early age or was in some way inadequate making it difficult to keep pace with peers and manage their daily lives independently (Committee on Classification, 1910). Three levels of impairment were identified: idiot, individuals whose development is arrested at the level of a 2 year old; imbecile, individuals whose development is equivalent to that of a 2 to 7 year old at maturity; and moron, individuals whose mental development is equivalent to that of a 7 to 12 year old at maturity.

Over the next 30 years, the definitions of mental retardation focused on one of three aspects of development: the inability to learn to perform common acts, deficits or delays in social development/competence, or low IQ (Yepsen, 1941). An example of a definition based on social competence was proposed by Edgar Doll who proposed that mental retardation referred to "social incompetence, due to mental subnormality, which has been developmentally arrested, which obtains at maturity, is of constitutional origin, and which is essentially incurable" (Doll, 1936 p. 38). Fred Kuhlman, who was highly influential in the early development of intelligence tests in the United States, believed mental retardation was "a mental condition resulting from a subnormal rate of development of some or all mental functions" (Kuhlman, 1941 p. 213).

As a result of the conflicting views and definitions of mental retardation, a growing number of labels used to refer to individuals with mental retardation, and a change in emphasis from a genetic or constitutional focus to a desire for a function-based definition, the American Association on Mental Deficiency (Retardation) proposed and adopted a three part definition in 1959. "Mental retardation refers to subaverage general intellectual functioning which originates in the developmental period and is associated with impairment in adaptive behavior" (Heber, 1961). Although this definition included the three components of low IQ (<85), impaired adaptive behavior, and origination before age 16, only IQ and age of onset were measurable with the existing psychometric techniques. Deficits in adaptive behavior were generally based on subjective interpretations by individual evaluators even though the Vineland Social Maturity Scale was available (Sheerenberger, 1983).

In addition to the revised definition, a five level classification scheme was introduced replacing the previous three level system which had acquired a very negative connotation. The generic terms of borderline (IQ 67-83), mild (IQ 50-66), moderate (IQ 3-49), severe (16-32), and profound (IQ <16) were adopted.

Due to concern about the over or misidentification of mental retardation, particularly in minority populations, the definition was revised in 1973 (Grossman, 1973) eliminating the borderline classification from the interpretation of significant, subaverage, general intellectual functioning. The upper IQ boundary changed from <85 to < 70. This change significantly reduced the number of individuals who were previously identified as mentally retarded impacting the eligibility criteria for special school services and governmental supports. Many children who might have benefitted from special assistance were now ineligible for such help. A 1977 revision (Grossman, 1977) modified the upper IQ limit to 70 - 75 to account for measurement error. IQ performance resulting in scores of 71 through 75 were only consistent with mental retardation when significant deficits in adaptive behavior were present.

The most recent change in the definition of mental retardation was adopted in 1992 by the American Association on Mental Retardation. "Mental retardation refers to substantial limitations in present functioning. It is characterized by significantly subaverage intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work. Mental retardation manifests before age 18" (American Association on Mental Retardation, 1992). On the surface, this latest definition does not appear much different than its recent predecessors. However, the focus on the functional status of the individual with mental retardation is much more delineated and critical in this definition. There is also a focus on the impact of environmental influences on adaptive skills development that was absent in previous definitions. Finally, this revision eliminated the severity level classification scheme in favor of one that addresses the type and intensity of support needed: intermittent, limited, extensive, or pervasive. Practically, a child under age 18 must have an IQ < 75 and deficits in at least 2 of the adaptive behavior domains indicated in the definition to obtain a diagnosis of mental retardation.

Educational Classifications. While the medical and psychosocial communities were developing an acceptable definition and classification system, the educational community adopted their own system of classification. Their three level system separated school age children with mental retardation into three groups based on predicted ability to learn (Kirk, Karnes, & Kirk, 1955). Children who were educable could learn simple academic skills but not progress above fourth grade level. Children who were believed to be trainable could learn to care for their daily needs but very few academic skills. Children who appeared to be untrainable or totally dependent were considered in need of long term care, possibly in a residential setting. Some form of this scheme is still in use today in many school systems across the country.

DSM-IV. DSM-IV attempts to blend the 1977 and 1992 definitions put forth by the American Association on Mental Retardation. It adopts the 1992 definition, but retains the severity level classification scheme from the 1977 definition. The upper IQ limit is 70, and an individual must have delays in at least two of the 10 areas outlined in the 1992 definition. In general, the overview of mental retardation in DSM-IV is thorough and easy to follow. However, it should be noted that comprehensive cognitive and adaptive skill assessment is necessary to make the diagnosis; it should not be made on the basis of an office visit or developmental screening.

ICD-10. ICD-10 is the tenth revision of the International Classification of Diseases (World Health Organization, 1993). It is currently in use in some countries around the world but will not be adopted for use in the United States until after the year 2000. ICD-10 differs from ICD-9 in at least two key ways. First, it includes more diagnoses and is, consequently, much larger. The second major change is the coding scheme. The diagnostic codes have been changed from numeric codes to codes that begin with an alphabet letter and are followed by two or more numbers (e.g., mild mental retardation has changed from 317 to F70).

ICD-10 characterizes mental retardation as a condition resulting from a failure of the mind to develop completely. Unlike DSM-IV and the Classification Manual of the AAMR, ICD-10 suggests that cognitive, language, motor, social, and other adaptive behavior skills should all be used to determine the level of intellectual impairment. ICD-10 also supports the idea of dual diagnosis, suggesting that mental retardation may be accompanied by physical or other mental disorders.

Four levels of mental retardation are specified in ICD-10: F70 mild (IQ 50 - 69), F71 moderate (IQ 35 - 49), F72 severe (IQ 20 - 34), and F73 profound (IQ below 20). IQ should not be used as the only determining factor. Clinical findings and adaptive behavior should also be used to determine level of intellectual functioning. Two additional classifications are possible: F78 other mental retardation and F79 unspecified mental retardation. Other mental retardation (F78) should be used when associated physical or sensory impairments make it difficult to establish the degree of impairment. Unspecified mental retardation (F79) should be used when there is evidence of mental retardation but not enough information to establish a level of functioning (e.g., a toddler with significant delays in development who is too young to be assessed with an IQ measure).

Epidemiology

Over the past 50 years the prevalence and incidence of mental retardation have been affected by changes in the definition of mental retardation, improvements in medical care and technology, societal attitudes regarding the acceptance and treatment of an individual with mental retardation, and the expansion of educational services to children with disabilities from birth through age 21. The theoretical approach to determining the prevalence of mental retardation uses the normal bell curve to estimate the number of individuals whose IQ falls below the established criterion score. For example, 2.3% of the population of the United States has an IQ score below 70, and 5.5% has an IQ score below 75. However, this estimate does not account for adaptive behavior skills. Based on empirical sampling, Baroff (1991) suggested that only 0.9% of the population can be assumed to have mental retardation. Following a review of the most recent epidemiological studies, McLaren and Bryson (1987) reported that the prevalence of mental retardation was approximately 1.25% based on total population screening. When school age children are the source of prevalence statistics, individual states report rates from 0.3% to 2.5% depending on the criteria used to determine eligibility for special educational services, the labels assigned during the eligibility process (e.g., developmental delay, learning disability, autism, and/or mental retardation), and the environmental and economic conditions within the state (U.S. Department of Education, 1994). It is estimated that approximately 89% of these children have mild mental retardation, 7% have moderate mental retardation, and 4% have severe to profound mental retardation. In addition, McLaren and Bryson (1987) report that the prevalence of mental retardation appears to increase with age up to about the age of 20, with significantly more males than females identified.

Etiology. There are several hundred disorders associated with mental retardation. Many of these disorders play a causal role in mental retardation. However, most of the causal relationships must be inferred (McLaren & Bryson, 1987). The American Association on Mental Retardation subdivides the disorders that may be associated with mental retardation into three general areas: prenatal causes, perinatal causes, and postnatal causes. For a complete listing of these disorders, the reader is referred to Mental retardation: Definition, classification, and systems of support (AAMR, 1992). It should be noted that some causes can be determined much more reliably than others. For example, chromosomal abnormalities such as Down syndrome can be assumed to be causal with more certainty than some postnatal infections. It should also be noted that mental retardation is both a symptom of other disorders as well as a unique syndrome or disorder.

Causes associated with level of mental retardation. The most common factor associated with severe mental retardation (including the moderate, severe, and profound levels of mental retardation) has been chromosomal abnormality, particularly Down syndrome (McLaren & Bryson, 1987). In approximately 20 to 30% of the individuals identified with severe mental retardation the cause has been attributed to prenatal factors, such as chromosomal abnormality. Perinatal factors such as perinatal hypoxia account for about 11%, and postnatal factors such as brain trauma account for 3 to 12% of severe mental retardation. In 30 to 40% of cases, the cause is reported to be unknown.

The etiology of mild mental retardation is much less delineated. Between 45 and 63% of the cases are attributed to unknown etiology. Fewer cases of prenatal and perinatal causes are reported, with the largest number attributed to multiple factors (prenatal) and hypoxia (perinatal). Very few postnatal causes have been linked to mild mental retardation (McLaren & Bryson, 1987).

Associated disorders. A variety of disorders are associated with mental retardation. These include: epilepsy, cerebral palsy, vision and hearing impairments, speech/language problems, and behavior problems (McLaren & Bryson, 1987). The number of associated disorders appears to increase with the level of severity of mental retardation (Baird & Sadovnick, 1985).

Psychopathology

Studies estimating the prevalence of mental health disorders among individuals with mental retardation suggest that between 10 and 40% meet the criteria for a dual diagnosis of mental retardation and a mental health disorder (Reiss, 1990). The range in prevalence rates appears to be due to varying types of population sampling. When case file surveys are conducted, the prevalence rates are consistently around 10%. The use of psychopathology rating scales in institutional or clinic samples produces the much higher 40% prevalence rate (Reiss, 1990). The actual prevalence may lie somewhere in between these two estimates. This may be the case due to the tendency of mental health professionals to consider behavior disorders in individuals with mental retardation as a symptom of their delayed development. Nevertheless, individuals with mental retardation appear to display the full range of psychopathology evidenced in the general population (Jacobson, 1990; Reiss, 1990). Individuals with mild cognitive limitations are more likely to be given a dual diagnosis than children with more significant disabilities (Borthwick-Duffy & Eyman, 1990).

Assessment of a child suspected of having a developmental disability, such as mental retardation, may establish whether a diagnosis of mental retardation or some other developmental disability is warranted, assessing eligibility for special educational services, and/or aid in determining the educational or psychological services needed by the child and family. At a minimum, the assessment process should include an evaluation of the child's cognitive and adaptive or everyday functioning including behavioral concerns, where appropriate, and an evaluation of the family, home, and/or classroom to establish goals, resources, and priorities.

Globally defined, child assessment is the systematic use of direct as well as indirect procedures to document the characteristics and resources of an individual child (Simeonsson & Bailey, 1992). The process may be comprised of various procedures and instruments resulting in the confirmation of a diagnosis, documentation of developmental status, and the prescription of intervention/treatment (Simeonsson & Bailey, 1992). A variety of assessment instruments have been criticized for insensitivity to cultural differences resulting in misdiagnosis or mislabeling. However, assessments have many valid uses. They allow for the measurement of change and the evaluation of program effectiveness and provide a standard for evaluating how well all children have learned the basic cognitive and academic skills necessary for survival in our culture. Given that the use of existing standardized instruments to obtain developmental information as part of the assessment process may bring about certain challenges, there does not appear to be a reasonable alternative (Sattler, 1992). Thus, it becomes necessary to understand assessment and its purpose so that the tools which are available can be used correctly, and the results can be interpreted in a valid way.

The four components of assessment (Sattler, 1992), norm-referenced tests, interviews, observations, and informal assessment, complement each other and form a firm foundation for making decisions about children. The use of more than one assessment procedure provides a wealth of information about the child permitting the evaluation of the biological, cognitive, social and interpersonal variables that affect the child's current behavior. In the diagnostic assessment of children, it is also important to obtain information from parents and other significant individuals in the child's environment. For school-age children, teachers are an important additional source of information. Certainly, major discrepancies among the findings obtained from the various assessment procedures must be resolved before any diagnostic decisions or recommendations are made. For example, if the intelligence test results indicate that the child is currently functioning in the mentally retarded range, while the interview findings and adaptive behavior results suggest functioning in a average range, it would become necessary to reconcile these disparate findings before making a diagnosis.

Developmental Delay or Mental Retardation

In diagnosing infants or preschoolers, it is important to distinguish between mental retardation and developmental delay. A diagnosis of mental retardation is only appropriate when cognitive ability and adaptive behavior are significantly below average functioning. In the absence of clear-cut evidence of mental retardation, it is more appropriate to use a diagnosis of developmental delay. This acknowledges a cognitive or behavioral deficit, but leaves room for it to be transitory or of ambiguous origin (Sattler, 1992). In practice, children under the age of 2 should not be given a diagnosis of mental retardation unless the deficits are relatively severe and/or the child has a condition that is highly correlated with mental retardation (e.g., Down syndrome).

Cognitive/Developmental Assessment Tools

Bayley Scales of Infant Development - Second Edition (Bayley, 1993): The Bayley Scales is an individually administered instrument for assessing the development of infants and very young children. It is appropriate for children from 2 months to 3½ years. It is comprised of three scales, the Mental Scale, the Motor Scale, and the Behavior Rating Scale. The Mental Scale assesses the following areas: recognition memory, object permanence, shape discrimination, sustained attention, purposeful manipulation of objects, imitation (vocal/verbal and gestural), verbal comprehension, vocalization, early language skills, short-term memory, problem-solving, numbers, counting, and expressive vocabulary. The Motor Scale addresses the areas of gross and fine motor abilities in a relatively traditional manner. The Behavior Rating Scale is used to rate the child's behavioral and emotional status during the assessment. Performance on the Mental and Motor Scales is interpreted through the use of standard scores (mean = 100; standard deviation = 15). The Behavior Rating Scale is interpreted by the use of percentile ranks. The Bayley Scales were standardized using a stratified sample of 1,700 infants and toddlers across 17 age groupings closely approximating the U.S. Census Data from 1988. The manual includes validity studies and case examples. The Bayley Scales is one of the most popular infant assessment tools. It can also be used to obtain the developmental status of children older than 3 ½ who have very significant delays in development and cannot be evaluated using more age- appropriate cognitive measures (e.g., a 6 year old with a developmental level of 2 years).

The Differential Ability Scales (DAS) (Elliott, 1990): The DAS consists of a battery of individually administered cognitive and achievement tests subdivided into three age brackets: lower preschool (2 ½ years to 3 years, 5 months), upper preschool (3 ½ years to 5 years, 11 months), and school age (6 years to 17 years, 11 months). The cognitive battery focuses on reasoning and conceptual abilities and provides a composite standard score, the General Conceptual Ability (GCA) score. Verbal and Nonverbal cluster standard scores and individual subtest standard scores are also available. The DAS has several advantages over other similar measures. It has a built-in mechanism for assessing significantly delayed children who are over the age of 3 ½ years. It can also provide information comparable to other similar instruments in about half the time. Finally, it is very well standardized and correlates highly with other cognitive measures (i.e., the Wechsler Scales).

Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R) (Wechsler, 1989): The WPPSI-R can be utilized for children ranging in age from 3 years to 7 years, 3 months. Though separate and distinct from the WISC-III (discussed below), it is similar in form and content. The WPPSI-R is considered a downward extension of the WISC-III. These two tests overlap between the ages of 6 and 7 years, 3 months. The WPPSI-R has a mean of 100 and standard deviation of 15, with scaled scores for each subtest having a mean of 10 and a standard deviation of 3. It contains 12 subtests organized into one of two major areas: the Verbal Scale includes Information, Similarities, Arithmetic, Vocabulary, Comprehension, and Sentences (optional) subtests; the Performance Scale includes Picture Completion, Geometric Design, Block Design, Mazes, Object Assembly, and Animal Pegs (optional) subtests. The WPPSI contains 9 subtests similar to those included in the WISC-III (Information, Vocabulary, Arithmetic, Similarities, Comprehension, Picture Completion, Mazes, Block Design, and Object Assembly) and 3 unique subtests (Sentences, Animal Pegs, and Geometric Design). Three separate IQ scores can be obtained: Verbal Scale IQ, Performance Scale IQ, and Full Scale IQ. The WPPSI-R was standardized on 1,700 children equally divided by gender and stratified to match the 1986 U.S. census data. This instrument cannot be used with severely disabled children (IQ's below 40) and, with younger children, may need to be administered over two sessions due to the length of time required to complete the assessment.

Wechsler Intelligence Scale for Children-III (WISC-III) (Wechsler, 1991): The WISC-III can be utilized for children ranging in age from 6 years through 16 years of age. It is the middle childhood to middle adolescence version of the Wechsler Scale series. It contains 13 subtests organized into two major areas: the Verbal Scale includes Information, Similarities, Arithmetic, Vocabulary, Comprehension, and Digit Span (optional) subtests; the Performance Scale includes Picture Completion, Picture Arrangement, Block Design, Object Assembly, Coding, and the optional subtests of Mazes, and Symbol Search. Three separate IQ scores can be obtained: Verbal Scale IQ, Performance Scale IQ, and Full Scale IQ. Each of these separate IQ's are standard scores with a mean of 100 and a standard deviation of 15, with scaled scores for each subtest having a mean of 10 and a standard deviation of 3. The WISC-III was standardized on a sample of 2,200 American children selected as representative of the population on the basis of 1988 U.S. census data.

Wechsler Adult Intelligence Scale - Revised (WAIS-R) (Wechsler, 1981): The WAIS-R covers an age range of 16 years, 0 months to 74 years, 11 months. The revised version contains about 80% of the original WAIS and was modified mainly due to cultural considerations. There are 11 subtests: Verbal Scale - Information, Similarities, Arithmetic, Vocabulary, Comprehension, and Digit Span; Performance Scale - Picture Completion, Picture Arrangement, Block Design, Object Assembly, and Digit Symbol. The WAIS-R was standardized in the 1970's on a sample of 1,880 white and non-white Americans equally divided among gender. The WAIS-R has a mean of 100 and a standard deviation of 15 with the scaled scores for each subtest having a mean of 10 and a standard deviation of 3.

Stanford-Binet:Fourth Edition (SB: FE) (Thorndike, Hagen, & Sattler, 1986): The SB: FE is appropriate for use on individuals ranging in age from 2 to 23. It is comprised of 15 subtests, though only 6 (Vocabulary, Comprehension, Pattern Analysis, Quantitative, Bead Memory, and Memory for Sentences) are used in all age groups. The other 9 subtests (Picture Absurdities, Paper Folding and Cutting, Copying, Repeating Digits, Similarities, Form-Board Items, Memory for Objects, Number Series, and Equation Building) are administered on the basis of age. Unlike previous editions, the SB: FE uses a point scale similar to that of the Wechsler Scales, is more culturally sensitive, and includes some new items in the areas of memory for objects, number series, and equation building.

Once administered, the SB: FE yields three types of scores: age scores (or scaled scores), area scores (general intelligence, crystallized intelligence and short-term memory, specific factors, and specific factors plus short-term memory), and a Composite Score (similar to the Full-Scale IQ of the Wechsler). The SB: FE Composite Score has a mean of 100 and a standard deviation of 16 (unlike the Wechsler's standard deviation of 15).

Overlap between the WISC-III and the Stanford-Binet:Fourth Edition: The WISC-III is appropriate between the ages of 6-16, while the Stanford-Binet: Fourth Edition is appropriate between the ages of 2 and 23. While the child is between 6 and 16, either test is appropriate. Correlations range from .66 to .83 between the WISC-R Full Scale IQ and the Fourth Edition composite. Results from Thorndike, Hagen, and Sattler (1986) show that while the two tests yield approximately equal scores, they are not interchangeable. This is partly due to the fact that they operate on different standard deviations (Sattler, 1992).

Overlap between the WAIS-R and the Stanford-Binet:Fourth Edition: Results for individuals with and without mental retardation are similar in that the WAIS-R yields higher scores than the Stanford-Binet Fourth Edition.

Special Note: Assessment Tools for Individuals with Mental Retardation. The Stanford-Binet: Fourth Edition and the Wechsler Scales are useful instruments in assessing mild mental retardation; however, neither is designed to test individuals with severe/profound mental retardation. In addition, due to the high floor on the Wechsler Scales the publisher recommends that a child obtain raw score credit in at least 3 subtests of the Verbal Scale and the Performance Scale before assuming they provide useful information. Raw score for 6 subtests, 3 Verbal and 3 Performance are recommended for a valid Full Scale IQ.

McCarthy Scales of Children's Abilities (McCarthy, 1972): The McCarthy Scales can be used with children between the ages of 2 ½ years and 8 ½ years. It contains six scales: Verbal Scale, Perceptual-Performance Scale, Quantitative Scale, Memory Scale, Motor Scale, and General Cognitive Scale. In addition to yielding a General Cognitive Index (GCI), the McCarthy Scales provide several ability profiles (verbal, non-verbal reasoning, number aptitude, short-term memory, and coordination). The overall GCI has a mean of 100 and a standard deviation of 16 and is an estimate of the child's ability to apply accumulated knowledge to the tasks in the scales. The ability profiles, in particular, make the McCarthy Scales useful for assessing young children with learning problems. The GCI is not interchangeable with the IQ score rendered by the Wechsler Scales; therefore, caution is advised in making placement decisions based on the GCI, especially in the case of children with mental retardation (Sattler, 1992).

Assessing Adaptive Behavior

Adaptive behavior is an important and necessary part of the definition and diagnosis of mental retardation. It is the ability to perform daily activities required for personal and social sufficiency (Sattler, 1992). Assessment of adaptive behavior focuses on how well individuals can function and maintain themselves independently and how well they meet the personal and social demands imposed on them by their cultures. There are more than 200 adaptive behavior measures and scales. The most common scale is the Vineland Adaptive Behavior Scales (Sparrow, Balla, & Cicchetti, 1984).

Vineland Adaptive Behavior Scales (VABS) (Sparrow, Balla, & Cicchetti, 1984): The VABS is a revision of the Vineland Social Maturity Scale (Doll, 1953) and assesses the social competence of individuals with and without disabilities from birth to age 19. It is an indirect assessment in that the respondent is not the individual in question but someone familiar with the individual's behavior. The VABS measures four domains: Communication, Daily Living Skills, Socialization, and Motor Skills. An Adaptive Behavior Composite is a combination of the scores from the four domains. A Maladaptive Behavior domain is also available with two of the three forms of administration. Each of the domains and the Composite has a mean of 100 and a standard deviation of 15. Three types of administration are available: the Survey Form (297 items), the Expanded Form (577 items, 297 of which are from the Survey Form), and the Classroom Edition (244 items for children age 3-13). The Survey and Expanded Forms were standardized on a representative sample of the 1980 U.S. census data including 3,000 individuals ranging in age from newborn to 18 years, 11 months. There are norms for individuals with mental retardation, children with behavior disorders, and individuals with physical handicaps. The Classroom Edition was standardized on a representative sample of the 1980 U.S. census data including 3,0000 students, ages 3 to 12 years, 11 months. Caution is advised when using this scale with children under the age of two because children with more significant delays frequently attain standard scores that appear to be in the low average range of ability. In this case more weight should be placed on the age equivalents that can be derived.

The American Association on Mental Retardation (AMMR) Adaptive Behavior Scale (ABS): The ABS has two forms which address survival skills and maladaptive behaviors in individuals living in residential and community settings (ABS-RC:2; Nihira, Leland, & Lambert, 1993) or school age children (ABS-S:2; Lamber, Nahira, & Leland, 1993). It is limited in scope and should be used with caution. A new scoring method has recently been devised that can generate scores consistent with the 10 adaptive behavior areas suggested in the 1992 definition of mental retardation (Bryant, Taylor, & Pedrotty-Rivera, 1996). The results of this assessment can be readily translated into objectives for intervention.

Achievement Tests

Intelligence tests are broader than achievement tests and sample from a wider range of experiences, but both measure aptitude, learning, and achievement, to some degree (Sattler, 1992). Achievement tests (such as reading and mathematics) are heavily dependent on formal learning, are more culturally bound, and tend to sample more specific skills than do intelligence tests. Intelligence tests measure one's ability to apply information in new and different ways, whereas achievement tests measure mastery of factual information (Sattler, 1992). Intelligence tests are better predictors of scholastic achievement contributing to the decision-making processes in schools and clinics, and they are a better predictor of educability and trainability than other achievement tests because they sample the reasoning capacities developed outside school which should also be applied in school.

To determine if learning potential is being fully realized, results from an IQ test and standardized tests of academic achievement can be compared. If there is a significant difference between IQ and achievement, the child may benefit from special assistance in the academic area identified.

Achievement Assessment Tools That Can Be Used With Children With Mild Learning Disorders.

Woodcock-Johnson Psycho-Educational Battery - Revised (Woodcock & Johnson, 1990): The Woodcock-Johnson is comprised of 35 tests assessing cognitive ability (vocabulary, memory, concept formation, spacial relations, and quantitative concepts) and achievement (reading, spelling, math, capitalization, punctuation, and knowledge of science, humanities, and social studies). Though the test batteries can be used with individuals from age 2 through adulthood, not all tests are administered at every age. The Cognitive Ability Battery and the Achievement Battery each have a recommended standard and supplemental batteries. The Achievement Battery can be used with preschool children (4 or 5 year olds) through adults. They each provide scores which can be converted into standard scores with a mean of 100 and a standard deviation of 15. By comparing the Tests of Cognitive Ability and the Tests of Achievement, the Woodcock-Johnson allows for the assessment of an Aptitude/achievment discrepancy. The discrepancy reflects disparity between cognitive and achievement capabilities. The Woodcock-Johnson was standardized on a representative sample of 6,359 individuals ranging in age from 2 to 95 from communities throughout the United States.

The Wide Range Achievement Test - Revised (WRAT-R) (Jastak & Wilkinson, 1984): The WRAT-R is a brief achievement test and contains three subtests: Reading, Spelling, Arithmetic. The WRAT-R is divided into two levels: Level One (ages 5 years, 0 months to 11 years, 11 months), and Level Two (ages 12 years, 0 months to 74 years, 11 months). The WRAT-R has a mean of 100 and a standard deviation of 15. It also provides T scores, scaled scores, grade-equivalent scores, and percentile ranks. It was standardized on a sample of 5,600 individuals in 28 age groups (5-74 years).

A variety of other achievement tests are available for assessing academic performance. These include, but are not limited to, the Kaufman Test of Educational Achievement (Kaufman & Kaufman, 1985) and the Wechsler Individual Achievement Test (1992).

Other Assessment Tools

Peabody Picture Vocabulary Test - Revised (PPVT-R) (Dunn & Dunn, 1981): The PPVT-R is appropriate for individuals between the ages of 2½ and adulthood and measures receptive knowledge of vocabulary. It is a multiple choice test requiring only a pointing response and no reading ability, thus making it useful for hearing individuals with a wide range of abilities, particularly children with language based disabilities. The revised edition is more sensitive to gender-based stereotypes and cultural issues; in fact only 37% of the original items were retained. The PPVT-R has two forms, L and M, with 175 plates in each form in ascending order of difficulty. Each plate consists of four clearly drawn pictures, one of which is the correct response to the word given by the experimenter. Standard scores have a mean of 100 with a standard deviation of 15. The PPVT-R was standardized on a national sample of 4,200 children (2½ - 18) and 828 adults (19 - 40) equally divided among gender and based on 1970 U.S. census data. The PPVT-R was designed to assess breadth of receptive vocabulary and not as a screening tool for measuring intellectual level of functioning. PPVT-R scores are not interchangeable with IQ scores obtained via the Stanford-Binet: Fourth Edition or the Wechsler Tests.

Columbia Mental Maturity Scale: The Columbia Mental Maturity Scale (Burgemeister, Blum, & Lorge, 1972) is a test of general reasoning ability that can be used with children who have significant physical limitations. It is appropriate for children between the ages of 3 ½ years and 9 years, 11 months. The Columbia has a mean of 100, a standard deviation of 16, and can be interpreted using age equivalents. When used in conjunction with the Peabody Picture Vocabulary Test - Revised, it can provide reasonably accurate cognitive status information comparable to the more common intelligence tests.

Leiter International Performance Scale: The Leiter International Performance Scale (Leiter, 1948) is a nonverbal assessment of intelligence. Although the norms are dated, it provides useful information about the cognitive status of children with hearing impairments or severe language disabilities. It can be used with children aged 2 through adults. It is currently under revision and will likely be a useful tool in the future (Roid & Miller, 1997).

For a description of a wide range of other specialty tests, the reader is referred to the Assessment of Children by Jerome Sattler (1992).

Dual Diagnosis

Appropriate assessment of psychopathology in people with dual diagnosis is important because: a) it can suggest the form of treatment; b) it may ensure access to and funding for special services; and c) it can be used to evaluate subsequent interventions (Sturmey, 1995). Brain damage, epilepsy and language disorders are risk factors for psychiatric disorders and are often associated with mental retardation (Rutter, Tizard, Graham, & Whitmore, 1976; Sturmey, 1995). Social isolation, stigmatization, and poor social skills put individuals with mental retardation at further risk for affective disorders (Reiss & Benson, 1985). The relationship between emotional disorders and mental retardation has been noted by many researchers (Bregman, 1991;Menolascino, 1977; Reiss, 1982). Rates of emotional disorders are more prevalent in children with mental retardation than children without mental retardation (Bregman, 1988; Lewis & MacLean, 1982; Matson, 1982, Russell, 1985). As noted previously, epidemiological studies of psychiatric disorders in individuals with mental retardation show that this population experiences higher rates of psychopathology (Corbett, 1985; Gostason, 1985). Though children with mental retardation are diagnosed with psychiatric disorders more often than children without mental retardation, they are usually diagnosed with the same types of disorders. However, uncommon psychiatric disorders may be found in children with severe and profound levels of mental retardation (Batshaw & Perret, 1992).

An additional problem is the application of DSM-IV criteria to individuals with mental retardation. Though the DSM has proven useful in diagnosing individuals with mild or moderate mental retardation (especially when the criterion are modified in some way, leading to problems in clearly operationalized definitions), many psychologists and psychiatrists rely more on biological markers, observable signs, and patterns of family psychopathology to diagnose individuals with severe and profound mental retardation thus implying that the DSM may not be as useful with this population (Sturmey, 1995). The mismatch between behaviors scripted in the DSM-IV and psychopathology presented in individuals with mental retardation can lead to under diagnosing of these individuals (Sturmey, 1995). Because the DSM is so widely used by psychiatrists, psychologists, health insurance companies, and because of the way it is coordinated with the International Classification of Diseases (ICD), it will continue to be the main diagnostic source. Practitioners should take care not to modify the DSM criteria for their own use and instead should use the criteria as they are prescribed and document cases where the criteria are inadequate to make a comprehensive diagnosis (Sturmey, 1995).

Most psychologists in the mental health field have little exposure to individuals with mental retardation and are sometimes uncomfortable treating these individuals; in fact, many professionals seem unaware that this group can experience mental health problems (Reiss & Szyszko, 1983). Mental health and mental retardation systems have been separated in this country for many years making it difficult to administratively serve people with both mental retardation and mental health disorders (Matson & Sevin, 1994). Recently, there has been a heightened awareness of need to pursue behavioral-psychiatric assessment, diagnosis, and treatment of people with mental retardation and mental health problems (Bregman, 1991; Eaton & Menolascino, 1982; Reiss, 1990).

A variety of behavioral assessment tools are available and provide key information for practioners in this area. A few of the commonly used measures or checklists include: the Child Behavior Checklist (Achenbach & Edelbrock, 1986), the Conners Parent (or Teacher) Rating Scale (Conners, 1990), the Revised Behavior Problem Checklist (Quay & Peterson, 1987), and the Social Skills Rating System (Gresham & Elliott, 1990). These measures are only as reliable as the parent, guardian, or teacher completing them. However, they can provide useful information about the nature of the behavioral problems or competencies of the child. All of the scales noted above focus primarily on behavioral difficulties with the exception of the Social Skills Rating System which includes items that address prosocial behaviors.

Interdisciplinary Approach

Because children with mental retardation often have other problems, it is necessary to involve a team of practitioners from different areas (e.g., child psychiatrist, social worker, child psychologist, special education teacher, speech and language specialist, and community agencies), in the comprehensive diagnosis. This type of interdisciplinary team approach is relatively new but is considered to be imperative for comprehensive assessment, treatment, and management of children with mental retardation (Lubetsky, Mueller, Madden, Walker, & Len, 1995). A natural extension of the interdisciplinary approach is the involvement of the family in the decision-making process. In fact, recent government and educational initiatives such as Public Law 99-457 and Public Law 102-119 require the involvement of parents and professionals in early intervention services (Lubetsky et al, 1995). A family-centered interdisciplinary approach begins with an assessment of the child (including school history, obtained from parents and school records), family (family marital and parenting history), and community resources. Medical, developmental and psychiatric histories are obtained. Behavioral analysis, psychoeducational, speech and language testing are completed. Medical and neurological assessments are performed. The team presents these results to the parents who are actively involved in evaluating and implementing treatment recommendations (Lubetsky, et al, 1995).

Psychoeducational Intervention

As a result of federal legislation developed with the aid and encouragement of a number of advocacy groups (i.e., the Individuals with Disabilities Education Act; Public Law 94-142, Public Law 99-457, and Public Law 102-119), children and adolescents with mental retardation or related developmental disorders are entitled to free and appropriate intervention. Appropriate intervention should be based on the needs of the child as determined by a team of professionals, address the priorities and concerns of the family, and be provided in the least restrictive most inclusive setting (i.e., where they have every opportunity to benefit from interacting with nondisabled peers and the community resources available to all other children).

Infant/Toddler Services

Services to infants and toddlers can be home-based, center-based, or some combination of the two. The nature of the services should be determined based on the results of the child assessment and family priorities for the child. These should be used to develop an Individual Family Service Plan for the child which includes all parties participating in the intervention and is coordinated by a Services Coordinator (case manager) who is available and acceptable to the family. The services may include assistive technology, intervention for sensory impairments, family counseling, parent training, health services, language services, nursing intervention, nutrition counseling, occupational therapy, physical therapy, case management, and transportation to services.

Preschool and School Services

Services to preschool children, ages 3 through 5, and school-aged children, 6 through 21, can be home-based, but are more frequently center-based. As in the case of infants and toddlers, a team evaluation and parent input is used to develop an intervention plan. This plan, the Individualized Education Plan (IEP), details the objectives for improving the child's skills and may include family or parent focused activities. Services may include special education provided by a certified teacher and focused on the needs of the child, child counseling, occupational therapy, physical therapy, language therapy, recreational activities, school health services, transportation services, and parent training or counseling. These services should be provided in the most inclusive least restrictive setting (e.g., a regular preschool program, Headstart Center, child's home).

Social/Interpersonal Intervention

Social and interpersonal interventions can be both preventative and therapeutic. As noted above, children with mental retardation are at an increased risk for behavioral disorders. Therefore, a variety of group social and recreational activities should be included in the child's educational program. These activities should include nondisabled peers and may include participation at birthday parties, attending recreational activities such as ball games and movies, participating in youth sports activities, and visiting community sites such as the zoo. The goal of these activities should be to teach appropriate social skills relevant to group participation and building self-esteem.

Parents also may benefit from prevention activities. Respite care provided by trained individuals can afford parents the opportunity to address their own needs (e.g., personal time, medical appointments, socializing with peers, etc.). They can be much more effective in parenting when their own needs have been met. Social or parent support groups can also be an outlet for parents to discuss their feelings with individuals who have similar experiences. These groups may be syndrome specific (e.g., Parent Advocates for Down Syndrome) or more generic in nature.

Therapeutic interventions with the children and families may include family therapy, individual child behavior therapy, parent training, and group therapy with mildly mentally disabled children and adolescents focusing on developing appropriate social skills. Child behavioral interventions can be used to teach self-care, vocational, leisure, interpersonal, and survival skills (e.g., finding a public restroom). Disruptive behaviors such as tantrumming, self-injury, noncompliance, and aggression toward others can also be addressed through behavioral techniques. The most frequent form of behavioral intervention for problematic behavior involves differential reinforcement of incompatible and/or other behaviors (Batshaw & Perret, 1992).

Psychopharmacological Intervention

Treatment specifying the use of medication should only be considered when a particular psychiatric condition know to benefit from a particular drug coexists with the mental retardation or developmental disability. This may take the form of a severe depression, obsessive-compulsive disorder, attention deficit-hyperactivity disorder, or a variety of other psychiatric disorders. There are few well controlled studies of drug treatments with children who have mental retardation. It should also be noted that the use of medication as a form of chemical restraint should be avoided. In addition, when drug treatment is used, it should only be one component of an overall treatment approach (Batshaw & Perret, 1992).

An invaluable resource in evaluating and treating children with mental retardation is the child's family. Consequently, including the families of children with or at-risk for disabilities in every phase of intervention, from identification to planning to implementation through monitoring should be considered. However, including families in decisions about the treatment or management of their children's problems presents new challenges. Nevertheless, trying to understand and include families in the decision-making process can ultimately be rewarding and beneficial for all involved.

Level of Family Involvement

How and when should families be included in decision making? There is no standard formula for answering this question. Families, like individuals, vary tremendously. Nevertheless, there are some issues that must be considered when involving families in team decisions about their child with a disability. First, the team must be receptive to including families in the decision-making process. This involves some effort on the part of the non-family team members to encourage family participation. In addition, the team must decide what child and family concerns are related to enhancing the development of the child. These should be the focus of generating family-oriented service delivery alternatives.

Second, the team must consider the level of knowledge and understanding of the family related to the disability of the child and/or the service/treatment options. If families are to participate in the decision-making process they must have the knowledge necessary to select appropriate alternatives. It is unfair to assume that families will not understand or cannot make appropriate decisions about the care of their child. They are the consumers and need to be given the chance to make an informed choice.

Finally, once the family has an adequate understanding of the condition and service/treatment alternatives, they may need to be nurtured through the team decision-making process. Most families have never been faced with participating as a member of a team of professionals and may initially be reticent or nonparticipatory in discussions unless they are specifically invited to do so. Certainly, as a primary care provider the parent or family member has more at stake than the other team members. Over time, however, the cautious or reticent family member may become an active and vital team member.

Encouraging Parent Participation

Health and education professionals who participate as team members must actively pursue parent-professional partnerships in the decision-making process. The logical first step is to acknowledge the value of the parent-professional relationship. Parents should be viewed as equal partners who can make important and necessary contributions in the planning, decision-making, process. If professionals are reluctant to or refuse to acknowledge parents as partners in the process, they run the risk of alienating them resulting in a lack of interest or participation in necessary services. Once the non-family team members accept the parents or other relevant family members as equal partners in the planning process, strategies to encourage continued active participation should be developed and implemented.

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