SINGLE TESTS AND SEEIES OF TESTS 15 



than the less intelligent, then it was assumed that 

 the method would answer for testing intelligence. 



Nearly all the methods that were familiar to the 

 psychological experimenter have been tested out in 

 this way, especially in the earlier periods of in- 

 vestigation by mental tests, e. g., measurements of 

 reaction-time, determinations of the threshold of 

 differential sensitivity in the different modalities, 

 optical illusions, experiments on motor skill or 

 strength, association experiments, tachistoscopic ex- 

 periments, learning of syllables, etc. In some cases, 

 it is true, numerous results of interest were secured, 

 but it must be admitted that a good deal of energy 

 has been expended to little avail in these experi- 

 ments. 



(b) A significant advance was made when it was 

 finally recognized that this blind probing about 

 could not lead us farther, that, on the contrary, tests 

 of intelligence must be definitely selected on the 

 basis of certain presuppositions that were to be 

 made concerning the nature of intelligence. Investi- 

 gators, therefore, sought then for exact methods of 

 experimentation that would bring intelligence into 

 direct and manifest operation. To be sure, the prob- 

 lem was at first conceived of in a still too simple 

 form, in that intelligence was thought to be exhibited 

 as a definite clean-cut mental phenomenon and the 

 plan of testing was directed to the examination of 

 this assumed special phenomenon. 



The best-known instance of this is the so-called 

 1 combination method ' of Ebbinghaus, now better 

 designated as the ' completion method ' (5). In Eb- 

 binghaus ' view, every true instance of intellectual 



