The American Association on Mental Deficiency (AAMD), in its Journal of Mental Deficiency (1973, p.11) defined Mental Retardation (retardness) as “significantly sub-average general intellectual functioning existing concurrently with deficits in adaptive behaviour, and manifested during the developmental period”.
The American psychiatric Association Journal (1986) defined it as a “subgeneral intellectual functioning, which originates during the developmental period and is associated with impairment of either learning, social adjustment or maturation”.
However, for our own purpose in this text, Mental retardation or retardedness may be defined as a “severe chronic mental or cognitive incapacitation resulting from either physiogenetic or socio-cultural defects or both, which leads to impairment in the learning and adaptive processes of an individual”.
In the United States of America, most states have laws, which provide that individuals with intelligence quotient (I.Q.) below 70 who show clear evidence of social incompetence or disapproved behaviour can be classified as mentally retarded and committed to institution.
Based on I.Q. levels, the American Association of Mental Deficiency in 1973, identified four levels of mental retardation ranging from “mild” to “profound”. Besides the use of the I.Q. level, the adaptive or adjustment capacity of an individual can be used to determine the degree of a person’s mental retardation. The adaptive capacity may include the extent the individual meets the established standards of personal independence and approved social responsibilities within his socio-cultural environment and age group. The following are the brief details of the I.Q. based mental retardation as identified by the AAMD:
1. Mild Mental Retardation (IQ52-68)
Persons within this level of IQ are considered “educable”, and their intellectual capacities as adults are found to compare to that of the average 8 to 11 year old child. Their social adjustment is often approximate to that of the adolescent. However, their reasoning, imagination, creativity and sense of judgement, tend to be far less than that of the normal adolescent. Most of them hardly show any sign of brain pathology or other physical anomalies.
In any result-oriented task, they often require guidance and some degree of supervision due to their limited ability to forsee the outcome of their actions. If diagnosed and identified early enough, most of them, with parental assistance, and special educational programmes, can afford to adjust socially, acquire simple educational and occupational skills, which enable them become self-supporting. It is this class of mental retardates that psychologists formerly classified as Morons.
2. Moderate Mental Retardation (IQ36-51)
Those who come under this category of mental retardation exhibit the mental levels comparable to that of the average child between 4 and 7 years old as adults.
While a good number of them are considered to be “trainable” in simple adaptive activities of life, some of the brighter ones among them can be taught to read and write a little; and others too may manage to achieve a fair command of spoken language. They are generally characterized as being relatively very slow in learning. They usually appear clumsy and unattractive physically and always suffer from bodily deformities and poor motor coordination. They are also emotionally unstable, while a few of them can be hostile and aggressive as children, but at the same time appear lovable and innocent in their action.
With early diagnosis and adequate training opportunities and parental support, most of them can achieve partial independence in daily self-care and economic usefulness. The nature of their adaptive capacity and adaptive home environment determine whether or not they require institutionalization. A friendly home environment is always much better than most of the so-called special institution centres operated in Nigeria. The persons in this category were formerly referred to as “imbeciles”.
3. Severe Mental Retardation (IQ20-35)
The individuals in this category are sometimes referred to as “dependent retardates”. Severe sensory defects and handicap in co-ordination of physical activities are very common among this category of persons. Perceptual and speech development is also severely impaired. To lesson their dependence, they can be helped to develop some limited levels of simple personal hygiene and self-help skills such as washing and changing their clothes, taking birthm evacuation of their faeces, etc. Although, they depend on others for care all their lives, some of them can be trained to some extent to perform some simple occupational tasks under very close supervision.
4. Profound Menatl Retardation (IQ Under 20)
“Life Support” mental retardate is the term sometimes used in referring to the persons in this category of mental retardation. Greater majority of persons in this category are severely and chronically deficient in adaptive behaviour and unable to master any but the simplest rudimentary level. Central nervous system pathology, severe physical deformities and retarded growth, convulsive seizure, deafness and other such physical anomalies, are common characteristics of this category of mental retardates. As such, they remain in custodial care all their lives. Poor health, lowered resistance to diseases, and most often, parental neglect due to frustration and despire, always result to very short life span.
The last three categories of mental retarded cases (moderate, severe and profound cases) are usually diagnosed and identified early enough during infancy because of the physical malformations, grossly impaired motor and sensory development and other obvious symptoms of abnormality associated with them.
Causes Of Mental Retardation
Causal Factors: The causes of mental retardation can be broadly classified into two:
1. Organic Factors
2. Socio-cultural Defects or Deprivation.
Organic Factors
Among the organic related mental retardations, we have the following causative factors:
1. Genetic Chromosal Defects
Mental retardation inherited through genetic tranfer tends to run in families. Thus, mental retardation of this nature is organic. It is also recognized that poverty and socio-cultural deprivation tend to run through families, and with early and continued exposure to such deprivative conditions, even the inheritance of average intellectual potential may not guarantee normal intellectual functioning. In the same way, genetic defects leading to poor metabolic activities result in many other anomalie, besides mental retardation.
2. Infection And Toxic Agents
The fetus of a pregnant mother with certain virus diseases such as German measles, may suffer brain damage just in the same way as that of a mother with syphilis and HIV/AIDS. Brain damage may result from infections occuring after birth due to viral encephalitis.
Besides, some toxic agents like carbon monoxide and lead, may cause damage to the brain during the developmental stage of the fetus or after birth. Certain drugs taken by the mother during pregnancy may lead to congenital malformations, or an overdose of drugs administered to the infant after birth may resul in toxicity and brain damage. Similarly, immunological agents, such as antitietanus serum or typhoid vaccine, may result to brain damage. Any of the above may lead to impaired mental development of the child so affected.
3. Prematurity and Trauma
Follow-up studies on children both prematurely who weigh less than 1,500 grams at birth showed that there was a high incidence of neurological disorders, including mental retardation (Kennedy, 1963; Rothchild, 1967).
Physical injury at birth due to accident during delivery may lead to brain damage that can result to impaired mental development. Bleeding in the brain area is identified as the most common birth trauma that can bring about brain damage and subsequent mental retardation. Anoxia, that is, lack of sufficient oxygen to the brain caused either by delayed breathing or stuffy birth environment, is another type of birth trauma that can lead to brain damage. Anoxia may also occur after birth as a result of cardiac arrest associated with surgical operations, hearth attacks, etc.
4. Ionizing Radiation
Radiation may act directly on the fertilized ovum or may produce gene mutations in the sex cells of either or both parents, which may lead to either mental or physical retardation or both in an off-spring. Sources of such harmful radiations include high energy X-rays used for diagnosis and therapy; nuclear weapon testing and exposure to other radioactive materials.
5. Malnutrition And Other Biological Factors
Deficiency in protein and other essential nutrients during early embryonic stage can lead to an irreversible physical and mental underdevelopment. Protein deficiencies in the mother’s diet during pregnancy and in the baby’s diet after birth have been identified as potent causes of mental and even physical retardation.
In Nigeria, and in fact, in the entire tropical sub-Saharan Africa, malaria infection of the pregnant mother or severe acute attack of the malaria parasite of the neonate (the new infant), accounts for the greatest number of death and even both physical and mental developmental impairment among children of growing age.
Socio-cultural Defects/Deprivation
It was formerly believed that all mental retardation was the result of faulty genes or of other causes of organic brain pathology. By several studies, it has been established that adverse socio-cultural conditions, particularly those involving a deprivation of minimum level of stimulation at early stages of development, also play primary role in the etiology of mental retardation. Two subtypes of mental retardation fall in this category.
(a) Mental retardation associated with extreme sensory and social deprivation, such as prolonged isolation during early years of development.
(b) Cultural-familial retardation resulting from substandard and inferior quality of interaction within the sub-cultural environment and with the people where the child finds himself.
The children who fall within the category of the cultural-familial mental retardation are usually minor or mild mental retardates. Such children show no identifiable brain pathology and as such, are not easily identified as mentally retarded until they enter school or any other skill acquisition programme when they start having serious problems in learning. Many Nigerian children belong to this category.
As a number of investigations carried out in United States and elsewhere have shown, most of such children come from poverty-stricken, unstable and often disrupted family backgrounds characterised by lack of intellectual stimulation, an inferior quality interaction with others, and general environmental deprivation (Braginsky and Braginsky 1974; Heber, 1970; Tarjan and Eisenbery, 1972).
These findings lend credence tothe critics of the gifted children institutions run in Nigeria, as they argue that such programme is not realistic because it does not have provision for the children who are naturally gifted, but socio-culturally deprived.
Prevention And Treatment Of Mental Retardation
Both prevention and treatment of mental retardation aim at alleviating the identifiable physiogenic and environmental defects associated with the causes of mental retardation and then exploring and maximizing the learning and adaptive potentials and capacities of the mentally retarded.
In Nigeria, however, there have not been known properly co-odinated efforts or programmes both by the government and non-governmental organizations to prevent or even alleviate the causes of mental retardation in the country. Emphases are placed more on institutionalization of the affected children. Even then, there are hardly enough institutions to accomodate and care for such persons.
Up to the present century, there has not been any official statistical information on the number or percentage of mentally retarded persons in the country on the basise of which proper and co-ordinated curative plans can be affected. This text is therefore basing its recommendations on the studies carried out elsewhere, particularly in the United States.
1. For the Mild Mental retardates who are considered relatively educable, emphasis should be laid on maximizing their intellectual capacities to master basic school subjects and the development of occupational skills to enable them become independent, self reliant and productive members of their community.
2. As for the moderate and severe types of mental retardation, new techniques, materials and specially trained teachers, have produced good results. Operant conditioning methods, (reward motivated learning) are used to teach a wide variety of skills. Emphases are placed on improvement in personal grooming, social behaviour, basic academic skills and occupational skills. The type of skills and training given are based on the peculiar need and capacity of the individual. Such trainings are based on step-by-step progression in which correct adaptive behaviours are properly reinforced (rewarded).
3. Studies indicate that mentally retarded children are generally likely to show better emotional and mental development in relatively caring and reasonably favourable home situations than in an institution (Gold & David, 1974).
Consequently, institutionalization is not recommended where the retarded child makes a satisfactory adjustment at home and in any special class or training school that he may attend on regular basis.
4. The outcome of institutionalization on a mentally retarded child depends greatly on the facilities available in the institution, the training of the staff and the peculiarities of the child himself.
Understandably, many of the mental retardates come from families, which are not capable to take care of them. This is where the community care for the needy, whiich Nigerians are noted for can be put to test because no other persons deserve such care than the mentally retarded and their families.
In United States and Britain, the mentally retarded children from such families are placed in foster homes specially developed for the purpose and carefully supervised.
Prevention Of Mental Retardation:
The problems of mental retardation and its prevention has to do with general human development involving both the human physiogenic processes and his socio-cultural environment. It concerns the question of genetic factors as well as a wide rage of biochemical, neuro-physiological and socio-cultural conditions of the human system.
Before the last twenty-five years, the main approach to the prevention of mental retardation was by rountine health checks for pregnant women and correction of identified pathology, where possible. However, several works in genetics have revealed the role of genetic defects in faulty development. Tests have been devised to identify parents with faulty genes likely to affect the mental and physical development of their offsprings. In United States, there are over 300 clinics offering genetic counselling services to such parents identified as having faulty genes. There are also such clinics in Britain, France, Germany and even India.
Another preventive measure involves the alleviation of socio-cultural conditions that deprive children of the needed stimulation, motivation and opportunity for normal learning and balanced mental and physical development. It was the late American President, John F. Kennedy who set the stage for this new socio-cultural preventive approach in his country in 1963; in his report, part of which reads thus:
“Studies have demonstrated that large numbers of children in urban and rural slums, including pre-school children, lack the stimulus necessary for proper development in their intelligence. Even when there is no organic impairment, prolonged neglect and a lack of stimulus and opportunity for learning can result in the failure of young minds to develop. Other studies have shown that, if proper opportunities for learning are provided early enough, many of these deprived children can and will learn learn and achieve as much as children from more favoured neighbourhoods. The self-perpetuating intellectual blight should not be allowed to continue”.
This report made by the American President befor his assassination some years later directed the attention of that country to the tragic and overwhelming problem of mental retardation. Few years after his death, specificall in 1970, the President’s committe on Mental Retardation, the American Psychological Association and other concerned organizations in that country, stressed the necessity for a “broad spectrum” approach which gave impetus for the implementation of essential measures for the prevention of mental retardation.
The spectrum approach focused on three key measures, which included:
1. Application of existing knowledge
2. Community services and
3. Research on all phases of the problem.
In fact, Nigeria can also borrow a leaf from this approach whereby each state of the federation can be given legal and legislative and the financial backings to develop stimulating socio-cultural conditions in high risk urban and rural slums.

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