BIOLOGY IN HUMAN AFFAIRS 



mental growth and behavior patterns offer one of the most 

 promising fields for future research. Cretinism, long known 

 for its disastrous effects upon mental development, is prob- 

 ably only one of many such influences, though the most 

 spectacular one in its obvious outcomes. Chemical cor- 

 relates of personality types have been mentioned in an 

 earlier section. Already the clinical psychologist and the 

 physiological chemist are working side by side in the 

 study of problem children. 



Development is more dependent upon natural maturation 

 than upon formal training. Gesell has shown that if 

 one member of a pair of infant twins is for several weeks 

 given frequent practice in a motor activity, such as climb- 

 ing stairs, while the other member of the pair is given 

 no practice, the latter, when later given the opportunity 

 to practice, reaches within a few days the level of skill 

 the other has taken weeks to acquire. Much the same seems 

 to be true of mental acquisitions. The nine-year-old of 

 average intelligence who has not been taught to read can 

 be made ready for the third school grade within a few 

 months. The twelve-year-old of average intelligence 

 who has been deprived of opportunity to learn to read 

 can be made ready for high school by the time he is four- 

 teen. Researches in child psychology have shown that 

 much time is wasted in schools by presenting subject 

 matter prematurely. Many a child agonizes for months 

 over long division who, a couple of years later, would 

 be able to learn it in thirty minutes or an hour. The same 

 is true of every type of curriculum material. Refinement of 

 pedagogical method is often resorted to where timeliness 

 of instruction would be far more economical and effective. 

 Experiments have shown that it takes an extraordinary 

 amount of pedagogical ingenuity to teach a strictly average 

 five-year-old to read as well as first grade children are 

 expected to, but that almost any method works fairly 



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