No extended discussion of what "general intelligence" is will be undertaken in these pages, as it would not be germane to the purposes of this monograph. It will be sufficient to refer to the concept which Binet had in mind in standardizing his scale (4): "It seems to us that there is a fundamental faculty, the alteration or the lack of which is of the utmost importance for practical life." It is this "fundamental faculty" which Binet named "judgment" that is the variable upon which rests the extreme position of the children who are to be studied herein. The quantitative methods which make possible the study of the status of these children when they have reached adulthood are those developed in recent years by Thorndike (30) and his students. As the children identified years ago by Binet's method grew to adulthood, there were developed in the various laboratories of Columbia University methods of measuring the intelligence of superior adults, based on the fundamental principles which are the same for mental measurement at all periods of development. Methods have thus been made available for making quantitative statements of the status of these individuals both during development and at maturity. THE RANGE OF INTELLECT ABOVE 180 IQ It is pertinent to inquire what are the limits of variation in terms of standard use in respect to human intelligence. How far superior to the average person are the most highly intelligent individuals currently produced? Galton's (9) X grade of man was defined in terms of incidence as "one in a million." But this X man was not a product of one variable. Galton's X man resulted from an intellect _in combination_ with "zeal and power of working." The incidence of this _combination_ of traits would probably be less than the incidence of intellect alone in degree sufficient for X. Our purpose in this chapter will be to consider investigations, made by direct methods, of the origin and development of children of a type extremely rare in occurrence, incidence being based on one variable only; i.e., intelligence measured in terms of IQ (S-B). For this purpose the line might be drawn at any point farther than +7 PE or +8 PE from the mean. A choice of 180 IQ (S-B) as a minimum insures a degree of plus deviation very rarely found even in metropolitan cities and their suburbs, as is clear from the reports of mental surveys conducted during the present century. The choice of 180 IQ (S-B), instead of 179 or 181 or some other amount of IQ in the extreme upper range, is obviously arbitrary and is adopted merely for the purpose of defining a point at and above which there are very few children who score.