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Another semantic problem in the etiology of mental retardation pertains to the use of the word "heredity." Not just the lay public but large numbers of professionals once held the belief that mental retardation to a large extent was directly inherited as a condition present in either the paternal or maternal side. To counteract this there has been a tendency in more recent years strongly to deny altogether the significance of hereditary factors. However, others presently use the term "hereditary" as synonymous with "genetic" (i. e. , transmittal through the germ plasm independent of the trait's manifestation in the parent). Used in this fashion, a statement "heredity plays a significant part in the causation of mental retardation" is not inaccurate.

Within the framework of this brief paper, it is not possible to present a detailed analysis of the many diseases known to produce the symptom we describe as mental retardation. Suffice it to say that besides the genetic factors (classified as endogenous) we may identify three main categories of environmental diseases and injuries (classified as exogenous and ordered according to the time -- before, during, or after birth -- when they are operative); prenatal (e. g. , infection of mother, vitamin deficiency); perinatal (e.g. , hemorrhage during delivery, irregular oxygen supply); and postnatal (e.g. , meningitis, lead poisoning).

Classification

As indicated earlier mental retardation varies in degree; from those so severely impaired as to require permanent full-time nursing care, to those who manage to "get on" in a life situation with minimum demands, but who lack the intellectual resources to face new and more challenging situations.

The introduction of the intelligence tests facilitated originally a seemingly exacting classification of the mentally retarded into three groupings: the moron (IQ of 70-75 down to 50-55); the imbecile (IQ of 50-55 down to 25-30); the idiot (IQ below 25-30). Later, because of the unhappy connotations these words had assumed in the vernacular, the terms mildly, moderately, and severely retarded were introduced.

In the mid-fifties the terms marginally independent, semidependent, and totally dependent came into usage. At the same time, the educators tried to develop a terminology reflecting prevailing concepts of educative capacities of the retarded, and introduced the term educable corresponding to moron or marginally dependent, and trainable corresponding to imbecile or semidependent.

All these diverse efforts concentrated too much on the factor of intellectual inadequacy (in their dependence on the intelligence tests) and did not sufficiently consider the equally important factor of social adjustment or adaptive behavior. Furthermore the static concept of a classification based solely on intelligence test performance proved more and more inadequate as evidence accumulated that a given child might indeed substantially improve his rating on the intelligence test as a consequence of specific education and training or a generally enriched life experience.

Therefore, the new concepts of a behavioral classification combining "Levels of Adaptive Behavior" with "Measured Intelligence" developed in the Manual of Terminology and Classification in Mental Retardation published by the American Association on Mental Deficiency in 1959 must be considered as a real milestone. (1)

Unfortunately, however, the procedure suggested in the manual for implementing these new concepts can only create new confusion because it assigns the entire subaverage group to the realm of mental retardation including what in the past have been known as the slow learners, the borderline, and dull normal groups.

Obviously the challenge for the next decade will be to test out and develop further this new type of classification in order to provide a terminology which is conceptually sound as well as adequate to encompass prevailing programs and practices in the field

Whose Responsibility?

The problem of proper identification and classification does not just pertain to the individual afflicted with the condition but to the condition itself.

Not infrequently mental retardation is seen for instance simply as a mental health problem.

The comprehensive knowledge available today should make it clear that such unilateral identification will interfere with sound program developments -- whether in practice, teaching, or research. Educators, psychologists, social workers, sociologists, rehabilitation workers, and other professions are needed in the field of mental retardation along with the medical and paramedical personnel. The extent of their respective contribution hardly can be expressed in a generic rank order -- it depends on the given situation and the type of case under consideration. If we think of biologically conditioned mental retardation the psychiatrist has but little to offer compared with what the biochemist or obstetrician brings to prevention or the pediatrician to early diagnosis. But conversely the biochemist or obstetrician lacks the psychiatrist's competence to deal with adjustment problems of the retarded adolescent. Development of life skills in the severely retarded -- specific training in speech or perceptual skills, in reading or word recognition, in work training or play activities -- these are areas where the educator's skills are needed rather than the physician's. Similarly with regard to causation we have areas where the sociologist would be the prime investigator and interpreter.