n detail along with persistence
in the main effort, is needed. The too stubborn young child may waste
a lot of time trying with all his might to force the square block into
the round hole, and so make a poorer score in the test, than if he had
given up his first line of attack and tried something else.
Intelligent behavior must perforce {288} often have something of the
character of "trial and error", and trial and error requires both
persistence in the main enterprise and a giving up here in order to
try again there.

Finally, the instinct of _curiosity_ or exploration is evidently a
factor in intelligence. The individual who is stimulated by novel
things to explore and manipulate them will amass knowledge and skill
that can later be utilized in the tests, or in intelligent behavior
generally.

Special Aptitudes

We distinguish between the general factors in intelligence, just
mentioned, and special aptitudes for dealing with colors, forms,
numbers, weights etc. A special aptitude is a specific responsiveness
to a certain kind of stimulus or object. The special aptitudes are
factors in intelligent behavior--as we may judge from the content of
the intelligence tests--only, the tests are so contrived as not to
depend too much on any one or any few of the special aptitudes.
Arithmetical problems alone would not make a fair test for
intelligence, since they would lay undue stress on the special
aptitude for number; but it is fair enough to include them along with
color naming, weight judging, form copying, and word remembering, and
so to give many special aptitudes a chance to figure in the final
score.

There are tests in existence for some special aptitudes: tests for
color sense and color matching, for musical ability, for ability in
drawing, etc.; but as yet we have no satisfactory list of the special
aptitudes. They come to light when we compare one individual with
another, or one species with another. Thus, while man is far superior
to the dog in dealing with colors, the dog is superior in dealing with
odors. Man has more aptitude for form, but some animals are fully his
equal in sense of location and ability to find {289} their way. Man is
far superior in dealing with numbers and also with tools and
mechanical things. He is superior in speech, in sense of rhythm, in
sense of humor, in sense of pathos. Individual human beings also
differ markedly in each of these respects. They differ in these
special direct