Photo by Bohdan Bohdanov.

Psychologists usually attribute belief in conspiracy theories and finding a conspiracy where there is none to a number of psychopathological conditions such as paranoia, schizotypy, narcissism, and insecure attachment, or to a form of cognitive bias called “illusory pattern perception”. However, the current scientific consensus holds that most conspiracy theorists are not pathological, precisely because their beliefs ultimately rely on cognitive tendencies that are neurologically hardwired in the human species and probably have deep evolutionary origins, including natural inclinations towards anxiety and agency detection. Many conspiracy theories relate to clandestine government plans and elaborate murder plots. Conspiracy theories usually deny consensus or cannot be proven using the historical or scientific method, and are not to be confused with research concerning verified conspiracies. In principle, conspiracy theories are not always false by default and their validity depends on evidence just as in any theory. However, they are often discredited a priori due to the cumbersome and improbable nature of many of them. This is a list of conspiracy theories that are notable.

Aliens: Among the foremost concerns of conspiracy theorists are questions of alien life; for example, allegations of government cover-ups of the supposed Roswell UFO incident or activity at Area 51. Also disseminated are theories concerning so-called ‘men in black’, who allegedly silence witnesses. Multiple reports of dead cattle found with absent body parts and seemingly drained of blood have emerged worldwide since at least the 1960s. This phenomenon has spawned theories variously concerning aliens and secret government or military experiments.

Illuminati: Conspiracy theories concerning the Illuminati, a short-lived 18th-century Enlightenment-era secret society, appear to have originated in the late 19th century, when some conservatives in Europe came to believe that the group had been responsible for the French Revolution of 1789–1799.Hoaxes about the Illuminati were later spread in the 1960s by a group of American practical jokers known as the Discordians, who, for example, wrote a series of fake letters about the Illuminati to Playboy.

Flat Earth: Flat Earth theory first emerged in 19th-century England, despite the Earth’s spherical nature having been known since at least the time of Pythagoras. It has in recent years been promoted by American software consultant Mark Sargent through the use of YouTube videos. Flat-earther conspiracy theorists hold that planet Earth is not a sphere, and that evidence has been faked or suppressed to hide the fact that it is instead a disc, or a single infinite plane. The conspiracy often implicates NASA. Other claims include that GPS devices are rigged to make aircraft pilots wrongly believe they are flying around a globe.

Reptilians: Reptilians – also called reptoids, archons, reptiloids, saurians, or draconians– are supposed reptilian humanoids, which play a prominent role in fantasy, science fiction, ufology, and conspiracy theories. The idea of reptilians was popularized by David Icke, a conspiracy theorist who claims shape shifting reptilian aliens control Earth by taking on human form and gaining political power to manipulate human societies. Icke has stated on multiple occasions that many world leaders are, or are possessed by, so-called reptilians. Critics of the conspiracy theory disparagingly refer to alleged reptilians as lizard people.

Story by Martina Goulding.