I've stated before that I have a theory about Atlantis in the Stargate universe. Basically I used to belive that the sources of most of the human, ancient, replicator and other species imbecility came from contact with Atlantis. While their was no evidence outside of empirical observation of Stargate before finding atlantis and of all species having had contact with atlantis making obviously stupid decision and ignoring obvious information. However in the latest episode and with addition observation of the Asgard, the Wraith, the G'aoul and the new traveler species I must revise the sources of this stupidity.
My new theory is that hyperspace radiation is harmful to the cognitive function of the "intelligent" species. This seems to be the only link between all those species and their appears to be a direct link between the use of hyperspace and the decline in human logic abilities. Further proof might be required but the number of species with hyperspace capability demonstrating very poor cognitive skill is indicative of a possible connection between the two.