Slight though these differences are, they are not to be disregarded, for sometimes the resulting habits are important.  For instance, girls should be better spellers than boys.  Boys should excel in physics and chemistry.  Women should have more tact than men, whereas men should be more impartial in their judgments.  With the same intellectual equipment as women, men should be found more often in positions of prominence because of the strength of the fighting instinct.  The geniuses of the world, the leaders in any field, as well as the idiots, should more often be men than women.  That these differences do exist, observation as well as experiment prove, but that they are entirely due to essential innate differences in sex is still open to question.  Differences in treatment of the sexes in ideals and in training for generation after generation may account for some of the differences noted.

What these differences mean from the standpoint of practice is still another question.  Difference in equipment need not mean difference in treatment, nor need identity of equipment necessarily mean identity of training.  The kind of education given will have to be determined not only by the nature of the individual, but also by the ideals held for and the efficiency demanded from each sex.

Another cause of the differences existing between individuals is difference in race inheritance.  In causing differences in physical traits this factor is prominent.  The American Indians have physical traits in common which differentiate them from other races; the same thing is true of the Negroes and the Mongolians.  It has always been taken for granted that the same kind of difference between the races existed in mental traits.  To measure the mental differences caused by race is an extremely difficult problem.  Training, environment, tradition, are such potent factors in confusing the issue.  The difficulty is to measure inborn traits, not achievement.  Hence the results from actual measurement are very few and are confined to the sensory and sensorimotor traits.  Woodworth, in summing up the results of these tests, says, “On the whole, the keenness of the senses seems to be about on a par in the various races of mankind....  If the results could be taken at their face value, they would indicate differences in intelligence between races, giving such groups as the Pygmy and Negrito a low station as compared with most of mankind.  The fairness of the test is not, however, beyond question."[14] The generality of this conclusion concerning the differences in intelligence reveals the lack of data.  No tests of the higher intellectual processes, such as the ability to analyze, to associate in terms of elements, to formulate new principles, and the like, have, been given.  Some anthropologists are skeptical of the existence of any great differences, while others believe that though there is much overlapping, still differences of considerable magnitude do exist.  At present we do not know how much of the differences existing between individuals is due to differences in remote ancestry.