VARIABILITY IN INTELLIGENCE 



515 



It will be noted that among these 905 children the 

 intelligence quotients cover the range from below 60 to 

 above 140, that is, from feeble-mindedness to a very high 

 degree of superiority. The brightest child in the group 

 is as far above the average as the dullest of the group is 

 below. It will also be noted that as we go from the 

 average toward either extreme the number of cases de- 

 creases gradually. There are far more cases just above 



5'6-65 66-75 76-85 86-95 96-105 106-115 116-115 116-135 136-145 

 .33% 2.3% 8.6% 20.1% 33.9% 23.1% 9.0% 2.3% .55%, 



Fig. 149 



(Reproduced from Terman, The Measurement of 

 Intelligence.) 



the borderline of feeble-mindedness than in the same 

 range just below it, and more cases of moderate than of 

 extreme brightness. There is no sharp dividing line 

 between any two grades of mental ability. The entire 

 range of human intelligence is from profound idiocy, 

 which is represented by an intelligence quotient of less 

 than 10, to a degree of superiority represented by an 

 intelligence quotient of 180 or 190. The greatest ex- 

 tremes of intelligence were not found in this group of 

 905 children. 



