Membership of the Giga Society is ideally open to anyone outscoring .999999999 of the adult population on at least one of the accepted tests. This means that in theory one in a billion individuals can qualify. Please do not confuse this criterion with popularly published scores on childhood tests (which are mental/biological age ratio I.Q.'s that are not comparable with deviation I.Q.'s and tend to be much higher), estimated I.Q.'s of famous people, or self-claimed I.Q.'s of megalomaniacs. You can not join by simply listing your real-life achievements, diplomas and the like, even though you are of course of greater value to society because of those than you would be because of a high test score.
Main goal of the Giga Society is to further the establishment of mental ability test norms in the very high range. This is done by recognizing high-scoring candidates for their effort in taking the tests (not for being intelligent), Giga Society membership being one of the incentives for test-taking. Into the bargain, this also promotes the general goals of high-range I.Q. testing, as well as the study of creativity and genius in terms of personality features. Inspired by the prospect of membership, many take the tests, thus bringing in much research data. This is explained so explicitly in this paragraph because experience has shown that some otherwise misunderstand the nature of the society, and mistake it for a cult of megalomania.
The society was founded in 1996 by Paul Cooijmans, who has served as its Psychometitor since, and has a journal named Nemesis which appears after every enrolment, the first of which occurred in 1999.