nce of the individuals. Discussion of the question how to
test intelligence in general would quickly lead us into as yet
unsettled controversies. It is a chapter of the psychology of tests
which, especially in the service of pedagogy but to a certain degree
also in the service of medicine, has been more carefully elaborated
than any other. Often it has been contested whether we have any right
to speak of one general central intelligence factor, and whether this
apparently unified activity ought not to be resolved into a series of
mere elementary processes. The newer pedagogical investigations,
however, speak in favor of the view that besides all special
processes, or rather, above all of them, an ability must be recognized
which cannot be divided any further, and by which the individual
adjusts his knowledge, his experiences, and his dispositions to the
changing purposes of life. The grading of the pupils in a class
usually expresses this differentiation of the intelligence; and while
the differences of industry or of mere memory and similar secondary
features may sometimes interfere, it remains after all not difficult
for an observant teacher to grade the pupils of his class, whom he
knows well, according to their general intelligence. The psychological
experiments carried on in the schoolroom have demonstrated that this
ability can be tested by the measurement of some very simple mental
activities. The best method would be the one which would allow the
experimenter, on the basis of a single experiment, to grade the
individuals in the same order in which they appear in the record of
the teacher. Among the various proposed schemes for this purpose the
figures suggest that the most reliable one is the following method,
the results of which show the highest agreement between the rank order
based on the experiments and the rank order of the teachers.[14] The
experiment consists in reading to the pupils a long series of pairs of
words of which the two members of the pair always logically belong
together. Later, one word of each pair will be read to them and they
have to write down the word which belonged with it in the pair. This
is not a simple experiment on memory. The tests have shown that if
instead of logically connected words simply disconnected chance words
are offered and reproduced, no one can keep such a long series of
pairs in mind, while with the words which have related meaning, the
most intelligent pupils can m