;588 THE MAINTENANCE OF THE INDIVIDUAL 



Sultan chewed the smaller stick down into a wedge and then, inserting 

 it into the larger hollow stick, proceeded to get the fruit. This is a 

 degree of intelligence such as might be seen in primitive cave men who 

 chipped stones to make weapons, or hollowed out trees to make canoes. 



Intelligence in Man 



Man, however, is a long step above the ape because he not only 

 can do things that the ape can, but in addition, he has memory 

 which enables him to make complex abstractions and to think of 

 objects and things which are not present. This ability to form com- 

 plex abstractions and to use them in thinking are things that an ape 

 never could do. As Herrick^ has well said, "The chimpanzee does 

 not know the meaning of F- = 2 PX, and he never can find out J' 

 In addition, man has a tool which the apes cannot use, and that is 

 language. One ape has been taught a very few words, but it is 

 doubtful whether these words have any meaning to him. The reader 

 of these lines not only can see the printed word, but can understand 

 the meaning of the symbols employed and can express it in terms of 

 speech. He has traveled a long way further than the apes because 

 he can read, write, and speak. 



The Measurement of Intelligence 

 Most young people today hear a good deal about "I. Q's." Nu- 

 merous tests have been devised which are supposed to measure the 

 intelligence of the human being. The experts who prepared the tests 

 have established norms, or average scores, for different ages. The 

 I. Q., or intelligence quotient, is found by establishing a ratio between 

 the mental age (M. A.) and the chronological age (C. A.) of the subject. 

 If, for example, a child's chronological age is 9 and he makes a score 

 which is that of a child of 10, his I. Q. is found by dividing his mental 

 age (M. A.) by his chronological age (C. A.) and multiplying by 100. 

 In this case he would have ^ X 100, or an I. Q. of 111. An I. Q. 

 of from 90 to 1 10 is about normal. If a person has over 140 I. Q. 

 he is considered to be a genius, only about 1 per cent of all persons 

 falling in this group. A glance at the chart shows the normal dis- 

 tribution of intelligence as foimd by testing large numbers of people. 

 While the tests now used are far from perfect, testing factual knowledge 

 rather than ability to think, they do indicate in most cases intelligence 

 with reference to the subject tested, and so fulfill a practical purpose. 



' Herrick, C. J., Brains of Rats and Man. Univ. of Chicago Press, 1925. 



