[Footnote 1: These, in large part, deal with words and ideas and are, therefore, weighted in favor of abstract intelligence, and put at a discount individuals whose experience and whose intelligence are predominantly social or mechanical in character. Some of the tests are fairly adequate for mechanical intelligence, but no good tests have been devised for social intelligence. These tests, however, as used in the army and for appraising college entrants, as at Columbia University, have been demonstrated to be fairly good indices of general intelligence.] Individual differences are, therefore, seen to be not simply differences with respect to given mental traits, but differences with respect to general mental capacity. Experimental investigation points to a graded difference in mental capacity, ranging from idiocy to genius, the largest group being normal or average, the size of the group diminishing with further deviation from the average in either direction. Certain important correlations, furthermore, have been found between the level of intelligence and the level of character. The great in mind, it may be said briefly, are also great in spirit. "General moral defect commonly involves intellectual inferiority. Woods and Pearson find the correlation between intellect and character to be about .5.... General moral defect is due in part to a generally inferior nervous organization."[1] [Footnote 1: Thorndike: _Educational Psychology_ (1910), p. 224.] One other important correlation must be noted. While gifts and capacities are specific, superiority in a given trait commonly involves superiority in most others. Exceptional talent in one direction in most cases involves exceptionality in many other respects. While talents are not indiscriminately transferable from one field to another, the same complex of traits which makes a person stand out preeminently in a given field, say law, would make him stand out in any one of half a dozen different fields into which he might have gone. There seems to be no evidence that extraordinary capacity in one direction is balanced by extraordinary incapacity and stupidity in others. The fact that individuals differ not only in specific traits but in general mental capacity has, also, certain obvious practical consequences. It means that there are present in society, in the light of recent tests in the army, an unexpectedly large number of individuals below the level of normal intelligence. One in five hundred, Thorndike estimates, is the "frequency of intellectual ability so defective as to disturb the home, resist school influence, and excite popular derision." These are clearly liabilities in the social order. On the other hand, there is a large number above the level of average intelligence. The importance of this group for human progress can hardly be overestimated. As we have seen in other connections, progress is contingent upon variation from the "normal" or the accustomed, and such variation