6. CHILDREN WITH LOW INTELLIGENCE Children with low intelligence are often classified in many ways and the novice can become confused with such different terms as feeble-minded, mentally deficient, dementia, amentia, slow learner, mentally handicapped, mentally retarded, idiot, imbecile, moron, oligophrenia, exogenous, endogenous, educable, educable mentally retarded, trainable, totally dependent, and custodial. Although psychologists, psychiatrists, social workers, educators, and others have had a difficult time finding a satisfactory definition for mental retardation, a close analysis of the problem reveals many reasons for the difficulty. The difficulty of finding a generally satisfactory definition is obvious when one tries to define a heterogeneous group consisting of different types and degrees of many factors on a continuum. Tredgold (1937), one of the early medical authorities, defined mental deficiency as : A state of incomplete development of such a kind and degree that the individual is incapable of adapting himself to the normal environment of his fellows in such a way as to maintain existence independently of supervision, control, or external support (p. 407). Edgard Doll (1941) furnished a more complex definition of mental deficiency. He asserted that a mentally deficient person is: (1) socially incompetent, that is socially inadequate and occupationally incompetent and unable to manage his own affairs at the adult level; (2) mentally subnormal; (3) retarded intellectually from birth or early age; (4) retarded at maturity; (5) mentally deficient as a result of constitutional origin, through heredity or disease; and (6) essentially incurable. These early definitions proved to be limiting in nature, providing the educator with little hope of ever impacting on the life of the mentally deficient child. Heber (1961) proposed the following definition for the American Association on Mental Deficiency which eliminated some of the hopelessness found in the first two: Mental retardation refers to subaverage general intellectual functioning which originates during the developmental period and is associated with impairment in adaptive behavior (p. 499). Subaverage intellectual function in this definition refers to one standard deviation below the general population mean on a standard intelligence test. Impairment in adaptive behavior refers to deficiencies in (1) maturation, (2) learning, and (3) social adjustment. Children with low intelligence are classified educationally into four groups: (1) the slow learner (IQ 80-90); (2) the educably mentally retarded (IQ 50-55 to 75-90); (3) the trainable mentally retarded (IQ 30-55 to 50-55); and (4) the totally dependent or profoundly mental retarded (IQ below 25-30). An educably mentally retarded child is one who, because of subnormal mental development, is unable to profit sufficiently from the program of a regular elementary school, but who is considered to have potentialities in three areas: (1) educability in academic subjects of the school at a minimum level, (2) educability in social adjustment to a point where he can get along independently in the community, and (3) minimal occupational adequacies to such a degree that he can later support himself partially or totally at the adult level (Kirk, 1972, p. 164). The trainable mentally retarded child is one who is not educable in the sense of academic achievement, ultimate social adjustment independently in the community, or independent occupational adjustment at the adult level. This is what Kirk (1972) described as the differentiation between the trainable mentally retarded and the educable mentally retarded child. The trainable mentally retarded child has potential to learn: (1) self-help skills; (2) social adjustment in the family and in the neighborhood, and (3) economic usefulness in the home, in a residential school, or in a sheltered workshop (p. 165). The totally dependent or custodially mentally retarded child is one who, because of severe mental retardation, is unable to be trained in total self-care, socialization, or economic usefulness and who needs continued help in taking care of his personal needs. Such a child requires almost complete care and supervision throughout his life, since he is unable to survive without help (Kirk, 1972, p. 166). Classification of children based on intelligence scores leaves much to be desired. Class placement according to IQ alone does not consider intraindividual differences which are more relevant to educational needs than are levels of intelligence. Two children classified as educable mentally retarded, both having IQ's in the 70's, may differ widely in their educational needs. There are many children whose IQ's classify them as mentally retarded and are placed in classes for the mentally retarded. Some of these come from minority groups; some are children with learning disabilities. Jensen (1970) studied differences between what he calls familial and cultural retardation. His research indicated that some children labeled mentally retarded are not retarded on paired-associate learning and digit repetition. These children tend to come from lower socio-economic areas. The familial retarded perform poorly on paired-associate learning and digit repetition, even though they have similar IQ's to the culturally deprived. In many of the larger cities there appears to be a proportionately higher number of culturally deprived children. Bijou (1968), applying a behavioristic model to mental retardation, rejected the concept that mental retardation is a symptom of "defective intelligence," "clinically inferred brain damage," or "familial factors." He considered mental retardation as a form of limited behavior that has been shaped by the past events in a child's life. These past events are responsible for the delay in development of adequate ways of interacting with the environment. Environment is defined as the biological milieu the child carries with him all the time, as well as the social, cultural, and physical conditions that influence the child's life. The retardation in development, according to behavioral theory, is related to the lack of quality and quantity of opportunities for contracts. The more specific factors that contribute to such retardation are (1) abnormal anatomic structure and functioning, (2) insufficient reinforcement (reward) and discrimination history, (3) reinforcement of undesirable behavior, and (4) severe aversive stimulation (punishment) (p. 321). Kirk (1972) noted that the classification according to a global criterion like an IQ has not proved satisfactory. There is increasing effort to approach assessment from an intraindividual point of view and to approach treatment behaviorally. An assessment of a child's functioning level, by diagnostic tests, by learning tests, or by functional analysis of behavior, leads to the organization of the environment in a way that will help him make a more adequate adaptation to the surrounding milieu (p. 172). Causes of Mental Retardation. There are many conditions, diseases, and situations that can cause mental retardation. The five major causes are: (1) genetic, (2) prenatal, (3) perinatal, (4) postnatal, (5) cultural. Waisman and Gerritsen (1964) stated that there are now nearly ninety diseases that can be traced to inborn errors of metabolism and that these are transmitted genetically by means of a hereditable trait. They asserted: This implies a defect in some gene which controls a certain enzyme system necessary for the normal function of a body issue. Thus, the intimate relationship between genes and enzymes underlines the significance of biochemistry and genetics in those diseases which are associated with mental deficiency (p. 308). The most common chromosomal abnormality is found in Down's Syndrome, or mongolism. This condition was described by Langdon Down about one hundred years ago. It was originally called Down's Disease, but because of the appearance of slanting eyes it was termed "mongolism." Other chromosomal aberrations have been found which affect intelligence. Gottesman (1963) stated: The majority of evidence accumulated so far with respect to chromosomal aberrations suggests that practically all parts of chromosomes are capable of affecting measured intelligence and that any upset in the general genetic balance has harmful effects on both the physical and mental traits (p. 248). In the early 1940's, it was discovered (Swan et al., 1946) that German Measles (Rubella) contracted by the mother during the first three months of pregnancy may result in congenital defects in the child, including mental retardation. Fraser (1964) showed that only 17 to 24 percent of the children are defective, and that many mothers who contract Rubella during the first trimester of pregnancy do not have defective children. In 1940, Landsteiner and Wiener (1946) reported the study of a condition involving the presence of agglutinin in the blood of rabbits. Among humans, the RH positive factor is found in the blood of 86 percent of individuals. The blood of the remaining 14 percent of human beings does not contain this RH factor and is said to be RH negative. RH positive blood and RH negative blood are incompatible and when occurring in the same blood stream, produce agglutinin which causes blood cells to clump together. This produces immature blood cells due to their failure to mature in the bone marrow. Yannet and Lieberman (1944) and Snyder et al. (1945) found a relationship between the presence of RH incompatible blood and mental retardation. The writers indicated that when the fetus inherits an RH factor which is incompatible with that of the mother, the child is apt to be mentally retarded. One perinatal cause resulting in mental retardation is asphyxia, which is caused by lack of oxygen to the brain during the period of birth. Frederick Schreiber (1939) studied this problem extensively and presented evidence that mental defects in children are sometimes the result of what he termed "cerebral anoxia." According to Schreiber, the brain cannot function without an adequate supply of oxygen. When the oxygen supply to the brain is blocked for more than a few minutes, irreparable damage to the brain cells results. Masland et al. (1958) reviewed the literature concerning the relationship of mental retardation and found that investigators do not all agree. Although many children with anoxia at birth die in infancy and some are defective later, there are also many who develop normally. They stated: "Important changes in the chemistry of the body occur during conditions of asphyxia," but the "newborn infant is capable of tolerating a relatively severe degree of oxygen deprivation." Studies on prematurely born children have shown a relationship between prematurity and mental retardation. Alm (1953) studied 999 premature boys and compared them statistically with 1,002 boys who were not born prematurely. He found that there were more epileptics, cerebral palsied, and mentally deficient among the premature. Of those who lived, the height and weight was less for the prematurely born at age 20 and more of them had disorders of some kind. Wortis (1961) reported that in the Soviet Union the rate of premature births per 100 population in Kiev was 4.7. In New York, at that time, the rate was 9.4 per 100, and in the poorer districts, 16 per 100. It appeared that the incidence of prematurity was greater in lower socioeconomic areas than in higher levels. This could be due to lack of adequate medical prenatal treatment, to poor nutrition, or to other factors. In addition to genetic, prenatal, and perinatal conditions that can cause mental retardation, there are some conditions and diseases that can result in mental retardation when they occur in infancy and early childhood. Encephalitis refers to an inflammation of the central nervous system caused by a particular virus. The term encephalitis refers to a variety of disorders of early childhood, the most familiar is encephalitis lethargica, which sometimes occurs as an epidemic disease and has been fatal to many children. Meningitis has caused deafness and blindness in children, and has been recognized as a possible cause of mental retardation (Kirk, 1972, p. 177). Cultural factors in the etiology of mental retardation refer to causative factors in the social environment. The relationship of experience to intelligence was explored by many researchers. Hunt (1961) discovered that adequate early experience is effective in accelerating mental growth. Haywood (1970) presented considerable information on the positive relationship of early deprivation or intervention to intelligence. Clarke and Clarke (1965), in a section on the genetic and environmental studies of intelligence stated: It may be assumed that heredity plays an essential part in determining the limits of intellectual development, but these limits are considerably wider than was formerly thought. With moderate uniformity of environment, individual differences result largely from genetic variations. The feeble-minded (educably mentally retarded), however, more than any other group in western culture have been reared in the most adverse circumstances, followed in many cases by further lengthy periods of residential schools and institutions, with all that this implies. Thus, the feeble-minded in such conditions seem likely to be functioning towards the lower end of their spectrum of potentialities, while normals under ordinary conditions of life approximate more closely to their upper limits (pp. 133-134). Skeels and Dye (1939) reported on the effects of earlier environmental intervention. They took 13 children from an orphanage and placed them in a state institution for the mentally retarded. These children were under 3 years of age and had an average IQ of 64, their initial IQ's ranging from 35 to 89. Each was placed in a different ward of the institution with older patients so that they would receive a great deal of individual attention from older girls and attendants. A year and a half later, their IQ's measured by the Kuhlmann Test of Mental Development had increased on the average of 27.5 points. As a contrast group, Skeels and Dye used 12 babies who were retained in the orphanage. These 12 children had an initial IQ of 87.6 ranging from 50 to 103. After thirty months, this group, who remained in the orphanage under a nonstimulating environment, dropped in IQ on the average of 26.2 points. Skeels made two follow-up studies of these 25 children. One was made three years after the original study, and the other twenty-one years later. Skeels (1942) found that after three years the experimental children retained their accelerated rate of development in foster homes, while the orphanage children retained their decreased intellectual performance. In the second study, Skeels (1966) followed up the 25 children twenty-one years after the initial testing when they were between 25 and 35 years of age. Every one of the 25 subjects was located and all but one (who had died) were interviewed. Skeels found: 1. The 13 children in the experimental group were self- supporting, and none was a ward of any institution, public or private. 2. In the contrast group of 12 children, one died in adolescence following residence in an institution for the mentally retarded, and four were wards of institutions. 3. The median grade in school completed by the 13 experimental children was twelfth grade. The median grade for the contrast group was less than third grade (pp. 54-55). Skeel's study is one of the rare longitudinal studies of children examined at an early age and followed up when the children had become adults. It demonstrated that differential stimulation at the age of one to two years displaces the rate of mental development upwards or downwards with children who do not reveal any pathology. It also demonstrated that the gains or losses made at an early age are maintained at later ages. Kirk (1972) concluded from these data that when intervention is not introduced at the preschool level, children from inadequate homes tend to retain their rate of development or drop in rate of development as they grow older. When society (as in the form of the Head Start Program) offers compensatory education in the form of preschool, or preschool and change of home, a reversal of this development is accomplished. From the experiments of Skeels and others, there is strong evidence that early intervention with psychologically deprived children will accelerate mental, social, and educational development and that lack of intervention will tend to interfere with development. Bloom (1964) stated that 50 percent of intellectual development takes place between conception and age 4, about 30 percent between ages 4 and 8, and about 20 percent between ages 8 and 17. If this conclusion is substantiated, prevention of cultural mental retardation will require the establishment of home training (Head Start), adequate nursery schools, and kindergarten for all children in low socioeconomic areas. The question of whether mental retardation is hereditary or environmental can only be answered by, "It is both" (Kirk, 1972). The concept of the norm of reaction as used by genetics, helps to clarify the controversy. The norm of reaction was proposed by Dobzhansky (1955) to explain that each child is born with a range of potential ability - his genotypic potential. The point to which he actually develops (his phenotypic behavior) lies somewhere within this range and is determined by his environment. The concept of the norm of reaction does not ask the question of whether heredity is more important than environment. Rather, it asks the questions of whether we are providing maximum environments for children - environments which will help them develop to the top of their ranges of potentiality as determined by the genetic endowment of each individual (p. 182). Prevalence of Children with Low Intelligence The numerous surveys of various populations to determine the prevalence of children with low intelligence have shown a wide range of estimates. One reason for the divergence is the fact that different investigators used different criteria for the groups they called "mentally retarded." Farber (1968) reported on the studies of prevalence rates by various authors in the United States, England, and European countries and on the methods and criteria used in making studies of prevalence. It is obvious that the prevalence rates depend on the cut-off point used by the investigator. If the investigator used intelligence tests he would obtain a higher prevalence if he took a cut-off point of 79 IQ than he would if he took a 69 IQ cut-off point. For example, Farber reported that Akkeson in Sweden used a 79 IQ limit and found 17.9 out of 1000 as mentally retarded. Lofthus, in Norway, used a 75 IQ limit and obtained 38 mentally retarded in 1000. Most surveys use a census method to determine prevalence. Farber concluded that there is considerable uniformity between the studies in the United States in prevalence rates and that the best generalization that can be made is that two to three percent of school children are mentally retarded. The major variables that affect prevalence in most of the studies relate to (1) socioeconomic level, and (2) degree of retardation. Heber (1970) reported an estimated prevalence of IQ's below 75 of white children and found about 7.8 percent to be mentally retarded. Birch and Dye (1970) found similar data in a study in Aberdeen, Scotland. Although children below 50 IQ had the same prevalence figures for both high and low social class, children between IQ's of 60 to 75 were markedly more prevalent in the lower social classes. All the studies to that date, indicated some correlation between lower social economic status and mental retardation, but no specific reasons were given for the results. More research is needed to determine just what correlates contribute to this condition.