DANGER OF DECLINING INTELLIGENCE 209 



progress without them. The very superior group, I.Q. 140- 

 154, with some help from the superior group, I.Q. 120-139, 

 could probably maintain the present level of our society. 

 Without these two groups and under the exclusive control 

 of the high average people, I.Q. 110-119, our society would 

 suffer some loss and undergo such simpHfications and 

 changes that the economy would finally collapse. 



Now, of course, these speculations mean nothing unless 

 there is some force at work which would limit or eliminate 

 a major portion of the upper intelligence groups. Certainly, 

 such a force was not operating in the early evolution of man 

 as we have already remarked. In fact, a differential against 

 the upper mental groups is unquestionably a modern trend 

 and is tied up with the Industrial Revolution. In early 

 Colonial America people with ability and means had large 

 families (as large or larger than the less fortunate), and 

 more of their offspring survived. It was after 1800 that the 

 rural-urban differentials began to appear, but they did not 

 assume dangerous proportions until the period of increased 

 industrialization and advanced medicine and hygiene of the 

 end of the century. That a differential force is now at work 

 in the population of the United States and in England, and 

 by inference elsewhere in the world, has been suspected 

 since the 1930's when Frank Lorimer and Frederick Osborn 

 in America and Raymond Cattell in Great Britain published 

 their comparative studies of birth rates and intelligence. 

 Lorimer and Osborn's work, summarized in their book 

 Dynamics of Population reached the conclusion that it was 

 a "moral certainty" that the I.Q. average in the United 

 States was declining by an estimated 2 to 4 points per gen- 

 eration. In the two decades since the book appeared there 

 has been nothing conclusive brought forth which would 

 change the conclusion of the authors. On the contrary, the 

 statement has been strengthened by studies made during 

 the intervening years, particularly those in which census 

 data has been analyzed. 



