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EVIDENCE OF THE RAPIDLY DECREASING BIRTH RATE IN 



FAMILIES IN WHICH HIGHLY INTELLIGENT 



CHILDREN OCCUR 



MARGARET V. COBB 



Cambridge, Massachusetts 



Scattered studies of the birth rate in special groups show each year more 

 clearly that, in general, the more intelligent the group, the more rapidly 

 the birth rate is decreasing. I wish merely to bring to attention, in proper 

 setting, the evidence from the group of children over 135 Stanford Binet 

 I.Q. (135-190) who were gathered in P. S. 165 Manhattan in 1922. ] Rarely, 

 perhaps never, has so intelligent a group of human beings been drawn to- 

 gether; rarely, perhaps never, has so sharp a decrease in family size or so 

 low a birth rate been reported from a healthy group. (It may be noted 

 that the way in which this group was selected automatically excluded no- 

 children families. The figures for this group are not thereby lowered as, 

 for instance, figures as prepared for college graduates usually are. The 

 low figures for this group are therefore all the more significant.) These 

 figures have already been twice reported, incidentally, in studies whose 

 titles point to other content. They were first mentioned in the Journal of 

 Educational Psychology for January, 1925, in a report by Dr. Leta S. Holling- 

 worth and myself, entitled "The Regression of Siblings of Children Who 

 Test at or above 135 I.Q. (Stanford Binet);" and second, in a report by 

 Miss Grace Allen in the Eugenics Record Office Bulletin No. 25, for May, 

 1926, entitled "The Families Whence High Intelligence Springs." The 

 figures mentioned in the two studies differ a little because the families in- 

 cluded in the two groups, while largely over-lapping, are not identical. In 

 the first study, the number of children per family is slightly under 2; in 

 the families of their fathers and mothers the number had been 6 to 7. In 

 the second study, the decrease from the previous generation to the present 

 is from 6.3 to 2.3 children per family. In the first group, 90 per cent of 

 the families are Jewish; in the second, 70 per cent. The second group was 

 made to include as many non- Jewish families outside the first group as could 



1 This group has been described previously, especially in the Twenty-Third Yearbook 

 of the National Society for the Study of Education, Taylor and Cobb. 



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