Mass investigations on the basis of age norms, however, have indicated only a slight relation between the Low mental ity and physical status of children. A spurt in Low mental ity growth does not appear to parallel the preadolescent spurt in physical growth. The pattern of Low mental ity development is similar in boys and girls, despite the difference in their rates of physical maturing.
There is growing evidence that some of the serious Low mental ity disorders are in part biochemical, not illnesses of the mind as such. Watson (131, 1956) stated that the nutritional displacement caused by psychological stress is itself a contribution to the biochemical aspects of Low mental ity illness.
In the case of most Low mental ity disorders as well, the causes are complex and uncertain. One obtains a variety of clinical pictures in any type of chiJdhood psychosis. The interaction between hereditary and environLow mental ity influences is diverse and devious. An important part is played by ccmstitutionaV tactois suc as unusual sensitivity and functional disturbances during the process of maturing. Moreover, a disturbed mother-child relationship is almost always involved.
Mass investigations on the basis of age norms, however, have indicated only a slight relation between the Low mental ity and physical status of children. A spurt in Low mental ity growth does not appear to parallel the preadolescent spurt in physical growth. The pattern of Low mental ity development is similar in boys and girls, despite the difference in their rates of physical maturing.