1 62 POPULAR SCIENCE MONTHLY 



however, that persons who do well in one subject often do poorly in 

 others and that success in life after school bears little relation to 

 success in school. It has recently been shown by Dr. Thorndike that 

 entrance examinations bear little relation to college marks. 



From the side of experimental psychology, no accurate measure of 

 intellectual ability has been established in spite of many persistent 

 and painstaking researches. The various tests used are found to be 

 special in their character. There are also indications that what are 

 good tests at one age or stage of development may have no significance 

 at another stage. Sensory and motor tests are probably valuable in- 

 dications of mental ability in young children, memory and imagina- 

 tion tests in older children and reasoning tests in youths. 



The function of the nervous system is to respond in an appropriate 

 way to the various phases of the stimulating environment. The most 

 common phase of environment to which human beings respond is the 

 word environment, first to auditory words by movements, then to audi- 

 tory and visual words by images and concepts. The number of words 

 that are known by any person depends upon two factors, the variety in 

 his word environment, auditory and visual, and his own readiness to 

 respond to the various elements of this environment. It is perfectly 

 natural therefore that children who are surrounded by intellectual 

 people or who read a great deal should have large vocabularies and yet 

 that the size of individual vocabularies should vary with their readi- 

 ness to respond to this word environment. The accuracy of response 

 or quality of knowledge can be judged not by the number of words 

 but by the accuracy of definitions or use of words. 



The question naturally arises whether size of vocabulary and ability 

 to define and use words is not a sufficiently accurate measure of the 

 intellectual ability of youths to justify the use of vocabulary tests in 

 examinations for entrance to college. College work is supposed to be 

 general in its character, demanding general ability, of which the 

 vocabulary test ought to give an indication. Of course if students 

 should devote their time to a special study of the dictionary, the test 

 would become special and valueless, since size of vocabulary would not 

 then be an accompaniment and indication of experiences and intel- 

 lectual advances, but of special study of modes of defining words in 

 terms of other word symbols. 



Ill 



A study of the kind of definitions given by persons of different 

 ages is an interesting indication of the sources of word knowledge and 

 of the modes of thought at different ages. 



The first words are of course obtained from direct association with 

 acts and objects and this continues to be a source of vocabulary growth. 



