SINGLE TESTS AND SERIES OF TESTS 19 



important than such a special scrutiny of single tests 

 is the laying of emphasis upon a general critical 

 position : no single test, no matter how good it may 

 be, should ever be made the instrument for testing 

 the intelligence of an individual. 5 



Because the single test tests on the one hand more, 

 and on the other hand, less than it really ought to 

 test. 



More, because the mental activity that is aroused 

 in a subject by an experimental task, a test-question, 

 or the like, is the fused resultant of quite varied an- 

 tecedent conditioning factors: and we do not know 

 what share that particular conditioning factor that 

 we call intelligence played in the performance. In 

 this equivocal nature of the object under investiga- 

 tion lies the too often little noted distinction between 

 tests and laboratory experiments. If I arrange an 

 investigation of memory in the laboratory, I know 

 that I am actually examining memory and not some- 

 thing else, because in numerous single experiments 

 I vary in a measurable way certain conditions only 

 of the function of memory while I keep all the other 

 conditions constant. But when, on the contrary, I 

 administer a test of learning or a test of immediate 

 memory by itself to a person, the outcome is affected 

 by the real capacity of retention, understanding of 

 the material, attention, interest, etc., all without con- 

 trol and this quite regardless of the disposition 

 of the subject at the time. Or, take another exam- 



8 Cf. Binet (36, p. 201) : "One test has no meaning, but five or 

 six tests do mean something. * * * The attention of psy- 

 chologists must, then, be called especially to this principle of the 

 multiplicity of tests," 



