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 indications of mental ability in young children, memory and imagination 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 auditory 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 readiness 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 intellectual advances, but of special study of modes of defining words in terms of other word symbols.
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.