It may well be, as Thorndike suggests, that if higher functions were studied, more striking differences would be revealed. But up to date we can simply say that experimental psychological methods have revealed no far-reaching differences in the mental processes of the several races. Even the Igorrote and Negrito deficiency may be due, Woodworth suggests, to their habits of life rather than to their native endowment. Since exact methods tell us nothing of those higher operations we are most eager to know about, it might be deemed advisable to fall back on general estimates by the most competent observers. Unfortunately, the personal equation enters here to an extent that completely nullifies the value of individual judgments. Travelers in foreign lands are likely to make quite unusual demands on the capacities of the natives with whose aid they are working, and in this way too frequently arrive at an unfair conclusion as to their mental characteristics. In a corresponding test Europeans might do little better. It is, at all events, remarkable that unbiased observers who are fairly sympathetic and remain in long contact with a primitive people usually entertain a rather favorable opinion of their powers. Thus, Prince Maximilian of Wied-Neuwied, expresses the view that, whether other varieties of mankind differ or not, the American aborigines are not inferior to the whites,[2] and corresponding estimates have been made of other races. Still, these are merely personal opinions and we must turn to our second method for possibly more objective, if indirect, evidence on the subject. Are, then, cultural differences necessarily the result of racial differences? In thus investigating the relations between race and civilization we may fruitfully employ the method of variation. Making the racial factor a constant, we may inquire whether culture, too, is thereby made a constant, and whether a change in racial propinquity is correlated with a proportionate change of culture. On the other hand, we may start with culture as a constant and inquire whether each form or grade of culture is the concomitant of definite racial characteristics and whether a change in culture is accompanied by a corresponding change of race.