JANUAKY 24, 1913] 



SCIENCE 



139 



total group about each of its members, this 

 order would be hardly any truer than the 

 order got by using the combined scores of 

 the tests alone. The two orders would in- 

 deed be practically identical. There is ex- 

 cellent reason to believe that it is literally 

 true that the result of two hours' tests 

 properly chosen from those already tested 

 gives a better diagnosis of an educated 

 adult's general intellectual ability than the 

 result of the judgments of two teachers or 

 friends who have observed him in the ordi- 

 nary course of life each for a thousand 

 hours. 



There might, of course, be amongst this 

 group certain individuals of great but very 

 highly specialized intellectual ability, as in 

 music or military strategy or mathematics, 

 who would be rated much lower by this 

 team of tests than by the general test of 

 life itself. There might also be certain in- 

 dividuals especially able in just the lines of 

 intellect which these eight tests measure, 

 but low in others, so that their rating by 

 these tests would be much too high. How- 

 ever, such extremely specialized intellects 

 seem to be rare, and this team of tests cov- 

 ers a wider range of the various factors to 

 which men assign credit as intellectual abil- 

 ity than a superficial examination reveals. 

 No student of the matter would pretend to 

 diagnose a man 's station amongst other men 

 for total intellect perfectly in two hours, 

 or in twenty ! But we can by these tests 

 measure approximately the general intel- 

 lectual ability of educated men when per- 

 sonal knowledge of them and their achieve- 

 ments is lacking, and can enrich and im- 

 prove on that knowledge, when it is present. 



As a second illustration I choose the very 

 practical case of prophesying how long a 

 pupil will continue in high school. 



Dr. Van Denburg secured certain infor- 

 mation from each of a thousand pupils en- 



tei'ing the public high schools of New York 

 City in February, 1906, and then kept 

 track of the length that each continued in 

 the high school. Consider first the signifi- 

 cance of the pupils' answers to the follow- 

 ing questions, obtainable in ten minutes or 

 so on the very day that a pupil enters the 

 high school : ' ' What do you intend to do for 

 a living ? " "Do you intend to stay in high 

 school four years?" 



If we let a line two inches long represent 

 eight terms or four years, and draw below 

 it the lines representing the median length 

 of stay* in high school of each of the groups 

 of pupils defined by one sort of answer, we 

 get the facts shown in Pig. 4. 



It is the case, of course, that the prophecy 

 made for any individual is only one of 

 probability. A pupil who reports herself 

 as intending to complete the course may 

 stay only a half year and a pupil who re- 

 ports himself as intending not to complete 

 the course may remain for four years. 

 Only in the long run and on the average 

 can we be certain that the latter will stay 

 five times as long as the former. The ex- 

 pectation for the two groups is shown more 



"■ That is, the length of stay that half of the 

 pupils in the group in question stay longer and 

 half not so long. 



