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Mental Deficiency: Mental deficiency is also associated with physical growth. The rate of physical growth of mentally deficient boys is slower than that of normal boys, depending upon the degree of the deficiency (45, 1936). Although subnormal boys continue to grow over a longer time than do normal and superior boys, their ultimate size, on the average, is below that of the private-school boys studied. They show retardation not only in height and weight but also in other developmental factors such ^s learning to walk, teething, and the onset of pubescence. Their mortality rate is nearly twice as high as that of the general population.
One of the most exciting advances in nutrition was the greater recognition of the relationship between good nutrition and mental and physical development. It had been proven that nutritional deficiency early in the life cycle, even before birth, could cause permanent retardation of mental development and learning behavior. Equally impressive was the finding that inadequate diets fed to pregnant animals adversely affect not only the rate of growth of the offspring but also their ultimate size, even when the offspring receive normal diets from the time of birth. These studies had far-reaching practical implications for human societies of the future.
Certain types of feeble-mindedness tend to run in families. Low mentality occurs when some factor that ensures normal development is lacking in both parents. Difficulty arises in the diagnosis of true mental deficiency. There is no conclusive evidence that all cases of feeble-minded-ness are clearly hereditary. Some may be congenital, i.e., acquired during prenatal life. At birth severe lack of oxygen may cause brain damage. Other cases may be intensified by an impoverished social environment. |
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