The Giga Society is open to anyone outscoring .999999999 of the adult population on any of the below tests. This means that ideally 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 IQs that are not comparable with deviation IQs and tend to be much higher), estimated IQs of famous people or self-assumed IQs of megalomaniacs. You cannot join by simply listing your real-life achievements, diplomas and the like, even though you are of course of much greater value to society because of those than you would be because of a test score.
Main goal of the Giga Society is to further the study of high intelligence, in particular the establishment of norms for the very high range. This is done by rewarding high-scoring testees for their effort in taking the tests (Giga Society membership being one of the rewards). The society was founded in 1996 by Paul Cooijmans (not a member), who has served as its Administrator since, and has a journal named Nemesis which appears after every new enrollment.
Many think the Giga Society can only have six members as a result of its admission level and the size of the world population. This is false. The top six are not the same individuals at each moment but are being replaced constantly. And because existing members are not expelled, any number of members is possible over time.
Some think the Giga Society's members must be proportionally divided over the continents. This fallacy results from the prejudice that average and spread of intelligence are identical everywhere in the world. These people stand on their prejudice and say "the facts are wrong because they don't fit my prejudice". But the Giga Society has no prejudice, goes exclusively by test scores, and is blind to the candidate's continent of origin. As an aside, the member list is not public, so those speaking about the origin of the members may be misinformed to begin with.
Study of statistics regarding intelligence in the world and of received test submissions has led me (Administrator) to conclude that the actual level of one in a billion of the world population occurs between IQ 180 and 185 (on a scale with 15 points per standard deviation), rather than at the theoretical 190. This is so because the world average IQ, expressed on this scale, is not 100 but somewhat below 90, probably between 85 and 90.
For consistency though I have decided to keep the pass level at its original height rather than lowering it to its correct value. This means the admission requirement is much more stringent than originally claimed by the society, and the current members have met this more stringent requirement. In fact, this admission level lies well outside the range of scores that can be statistically expected given the world intelligence distribution (the world's highest IQ is probably somewhat under 185). But since the norms at this very top of the range are tentative - sometimes too high, sometimes too low, searching for their true value - it can be expected every now and then a candidate will qualify. To date (April 2008), 7 have qualified out of approximately 2300 who in total took about 3100 tests.
The uncertainty in the norms at this range means that the world's most intelligent persons are not necessarily found in the Giga Society; for data about the truly most intelligent - that is, the highest scorers based on the best norms and best tests according to the most recent insights - see the report Statistics of the top scorers.
These are ALL of the accepted tests, so please do not send messages asking "is the ... test accepted too?". Most of the tests can be found on or through GliaWeb. Required is a score at or above .999999999 of the adult population. Retest scores are not accepted.
Do realize that the qualification information provided on this page is clear and complete, and that not understanding it - that is, applying without a qualifying score - is not compatible with the intelligence level claimed by applying, and naturally disqualifies the applicant.