Possible interpretations of UFO reports

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Interpretations of UFO reports include possibilities that, like philosophical thought experiments, may violate established knowledge, consensus reality, or even logic itself. Unlike philosophical thought-experiments, mainstream interpretations of UFO reports suggest they are largely a product of optical illusion, human error, and cognitive bias. [1] [2] [3] [4] [5] [ excessive citations ]

Contents

Overview

Interpretations of UFO reports question whether they are caused by real objects or the human mind. Other interpretations, like magical thinking or Tibetan Buddhism, consider the possibility that physical reality is inherently psychogenic. Possible interpretations of UFO reports - Real vs Psychogenic.png
Interpretations of UFO reports question whether they are caused by real objects or the human mind. Other interpretations, like magical thinking or Tibetan Buddhism, consider the possibility that physical reality is inherently psychogenic.

While the term "possibility" normally refers only to things that could actually happen, in philosophy the term can be broadly-construed to include concepts that seem to violate all mainstream knowledge, the known laws of physics, and even the laws of logic. [6] Famous thought experiments consider such seemingly-absurd possibilities as nothing actually existing, an evil demon capable of complete deception, a disembodied brain spontaneously emerging out of a cloud of particles, and a cat that is neither dead nor alive until observed by a human.[ citation needed ]

Some UFO interpretations are consistent with generally-accepted views of reality. The Psychosocial hypothesis is the mainstream interpretation, suggesting UFO reports are largely a result of human perception based on prior expectations. Meanwhile, the Extra-terrestrial hypothesis, an unsubstantiated fringe theory that is nonetheless generally-consistent with mainstream physics and logic, suggests that alien beings use advanced technology to travel interstellar distances to reach Earth. [7]

Many possible interpretations fall outside the real of realistic possibilities. The Crypto-terrestrial hypothesis is one such philosophical thought experiment questioning whether it would be possible for a superior Earth-based civilization to mask its existence from humans; while the idea contradicts mainstream knowledge, it is still consistent with known laws of physics and logic. In contrast, the Time traveler UFO hypothesis, if true, could violate current understanding of the laws of physics and perhaps even the tenets of logic. Other conceptual possibilities outright posit that reality might not even be logically consistent; philosophers have considered the idea that reality is a dream, a simulation, or a manifestation of human thoughts.[ citation needed ]

During the 20th century, believers connected UFOs to innumerable fringe concepts including astral projection, [8] telepathy, [9] ESP, [10] clairvoyance, [11] spirit photography, telekinetic powers, [12] full trance mediums, [13] the Loch Ness Monster [14] and the theory of Atlantis. [15]

UFOs reports as psychogenic

The most-accepted explanation for UFO reports is the Psychosocial hypothesis, which proposes that UFO reports are best explained as a creation of human minds and behavior. Mainstream explanations range from simple optical illusions and mistaken identifications to UFO hoaxes and deception campaigns.

Known psychogenic causes

Many UFO reports have been attributed to known psychogenic causes.

Illusions and errors

Animation of the parallax effect, where a moving observer perceives differences in velocity between objects at varying distances. An object in the sky directly above the nearest buildings, but mistakenly thought to be above the furthest ones, would be perceived as moving rapidly. Parallax scroll.gif
Animation of the parallax effect, where a moving observer perceives differences in velocity between objects at varying distances. An object in the sky directly above the nearest buildings, but mistakenly thought to be above the furthest ones, would be perceived as moving rapidly.

Some optical illusions might cause UFO reports. eye floaters are sometimes visible deposits within the eye's vitreous humour ("the vitreous"), which is normally transparent, or between the vitreous and retina. They can become particularly noticeable when looking at a blank surface or an open monochromatic space, such as a blue sky. As early as 1903, scientists demonstrated how the supposed Martian canals could arise as an optical illusion. [16] Each retina has a retinal blind spot that is not consciously perceived to the process of filling-in. In the autokinetic effect, stationary lights can appear to move; it was first recorded in 1799 by Alexander von Humboldt who observed illusory movement of a star in a dark sky, although he believed the movement was real. [17] In normal afterimages, illusory perceptions occur after the withdrawing of an image. In palinopsia, disorders like visual snow syndrome or hallucinogen persisting perception disorder lead to abnormal afterimages.

Satellite photograph of a mesa in the Cydonia region of Mars, often called the "Face on Mars" is a famous example of pareidolia. Martian face viking cropped.jpg
Satellite photograph of a mesa in the Cydonia region of Mars, often called the "Face on Mars" is a famous example of pareidolia.

The human visual system also leads to illusions and errors. In parallax, a stationary object can appear to be moving to an observer in motion. Prior expections can influence the visual system, as in "top-down priming" and the observer-expectancy effect. The human brain is prone to finding patterns, especially faces, where none actually exist, as in pareidolia and apophenia. Images can appear larger and smaller than they actually are, as in macropsia and micropsia.[ citation needed ]

Stories and tales

Some ancient legends were re-interpreted as UFOs. Ezekiel's Wheel, described in the biblical book of Ezekiel, was alleged to have been an alien spacecraft in books like The Spaceships of Ezekiel . In some cases, works of fiction became divorced from their original context and mistaken as factual. In 1938, War of the Worlds was mistaken as factual by some listeners. The 1977 mockumentary Alternative 3 discussed a secret space program; Despite it's fictional origin, the work became incorporated into UFO conspiracy theories.

Some stories, or tall tales, were intended to deceive. In 1897, a paper in Aurora, Texas claimed a pilot 'not of this world' had crashed in the town. Residents later recalled the story was written "as a joke and to bring interest to Aurora. The railroad bypassed us, and the town was dying." [18]

Simple hoaxes and pranks

Many UFO reports are revealed to stem from simple hoaxes. In 1947, a hoaxed disc made of cymbals was created by teens in Twin Falls. In 2009, two men perpetrated the Morristown UFO hoax using flares attached to balloons. [19]

Other simple hoaxes are driven not by recreation but as an attempt to profit. In 1949, con-men perpetrated the Aztec UFO hoax as part of a scheme to sell objects supposedly recovered from a crashed flying saucer. [20] In the 1950s, "Contactee" George Adamski provided a series of UFO photos which are widely believed to be hoaxed to promote Adamski's movement. [21] In 1995, a Alien Autopsy film was widely broadcast, with the filmmakers ultimately confessing to the hoax. [22]

Neuropsychiatric states

Many suggest neurological or psychological effects play a central role in UFO reports. Some UFO reports may stem from altered states of consciousness. [23]

Some interpretations of UFO reports suggest a connection to sleep. A dream is a succession of images, ideas, emotions, and sensations that occur involuntarily during certain stages of sleep. In some cases, dreams can occur outside of typical sleep, for example in hypnagogic imagery. In sleepwalking, fully-asleep people become mobile and sometimes awake in unusual locations; Conversely, in sleep paralysis, people awake to find themselves unable to move. Reports of alien abduction have been explained as stemming from sleep paralysis. [24]

A variety of hallucinogens affect perception, belief, and memory in ways potentially relevant to UFO reports. UFO reports have been variously attributed to intoxicants including alcohol, cannabis, ergot, LSD, ketamine, DMT, [25] and uncountable other substances. Temporal lobe epilepsy, perhaps triggered by artificial magnetic fields, has been cited as a cause of alien encounter reports. [23]

In the mid-20th century, psychologists studied how false memories are formed through memory contamination. The note that memories obtained thorough so-called hypnotic regression may be the result of confabulation. False memories have been proposed as an explanation for alien abduction claims. [26] Loss of consciousness, amnesia, derealization, and fugue states can all lead to the experience of "missing time". [27]

A variety of neurological states and conditions can lead to the formation of false beliefs or delusions. Paranoia as well as ideas and delusions of reference and stem from mania, psychosis, schizophrenia, or dementia. Welder Richard Sharpe Shaver reported receiving secret messages about UFOs via his welding gun. [28] : 201 

Authors speculate UFO reports might stem from people seeking attention or outright malingering. Some individuals with fantasy-prone personality may have contributed to UFO and alien reports, [29] while some reports have been attributed to Munchausen's or factitious disorder, as in the Falcon Lake Incident where a psychiatrist diagnosed a Manitoba man's abdominal marks as "obviously factitial" after he reported being burned by a UFO. [30]

Group belief

Group belief can affect the frequency of UFO reports. The 1947 flying disc wave was initially explained as a "mass hysteria". The Psychosocial hypothesis argue UFO reports spread by social contagion. Similarly, UFO belief is often connected to group faith, spirituality, or religion.

Organized deception

Some UFO reports have been linked to organized deception campaigns from con-men, racketeers, military, and intelligence agencies. [31]

The 1947 Maury Island incident is widely viewed as a hoax perpetrated by Fred Crisman, perhaps to discredit initial "flying saucer" witness Kenneth Arnold. Astronomer Morris K. Jessup was contacted by elements in the US Navy, who furnished him with copy of his book elaborately annotated by multiple alleged non-humans. [32] In the 1970s Travis Walton incident, two members of a forestry crew allegedly staged a hoax alien abduction with the aid of a third person operating a lookout tower spotlight. In the 1980s, Paul Bennewitz was targeted by Air Force personnel and fed disinformation that led to his hospitalization for paranoia. UFOlogist Bill Moore later confessed to misleading Bennewitz and others, while Bill Cooper was given corroborating disinformation by John Lear. [28] : 111– 

Purported psychogenic causes

A number of fringe explanations have been used to suggest UFOs are psychogenic. Believers in reincarnation have claimed that memories from previous lives can be recovered in subsequent lives. Prior to modern understandings of genetics, some people falsely believed memories could be passed on genetically to offspring. Spiritualists claimed the ability to communicate mentally or to perceive things though a "sixth sense". Fringe theories have variously alleged UFO reports might be linked to past-life experience, [1] race memory, [33] the collective unconscious, [34] clairvoyance, [11] or telepathic contact. [9]

Some worldviews, such as magical thinking and the so-called Law of Attraction, claim that reality is inherently psychogenic. Tulpas, a supposed paranormal entity created by human thought, have been invoked to explain UFOs. [35] Psychogenic reality is an element in the 1956 film Forbidden Planet and the 1986 Michael Crichton novel Sphere . [36]

UFOs as extant phenomenon

In this mode of thinking, some UFO reports are caused by something outside the human mind. In late 1947, Air Force General Nathan Twinning became one of the early proponents of this view when he signed off on a report which concluded that UFO reports were "not visionary or fictitious". [37]

Known phenomenon

Venus is often visible to the naked eye in daytime, as seen just prior to the lunar occultation of 7 December 2015. Lunar Occultation of Venus (NHQ201512070001).jpg
Venus is often visible to the naked eye in daytime, as seen just prior to the lunar occultation of 7 December 2015.

Natural

"No single object has been misinterpreted as a 'flying saucer' more often than the planet Venus"

Jacques Vallee, quoted by Phillip Klass in UFOs Explained (1975) [38]

Optical effects have led to UFO reports and photographs, including mirages, Fata Morgana, imaging artifacts, bokeh, and lens flare. [39] Other UFOs has been attributed to astronomical objects like stars, Venus [40] [39] or other planets, the moon, [39] comets, and the milky way. UFOs has be purported be caused by atmospheric objects and lights, including meteors, [39] auroras, lightning, st. elmo's fire, Ball lightning, [39] swamp gas and will-o-the-wisp, sprites, temperature inversions, ice crystals, lenticular clouds, [39] sun dogs, and others.

Some point to chemical reactions or radioluminescence, while bioluminent lifeforms in their air, land, and water. Flocks of birds have generated radar signatures, while swarms of insects were theorized to be a cause of UFO reports, a theory popularized in the X-Files episode War of the Coprophages. [41]

Technological

Artificial lighting including lighthouses and beacons, light pollution, spotlights and searchlights, [39] projected images, lasers and laser pointers have been linked to UFOs. Similarly phosphoresent chemicals, including radioactive or UV paints, enriched or manufactured radioactive elements, can create visual effects. [42]

A wide array of aerial objects have been linked to UFOs: fireworks and rockets, balloon and sky lanterns, [39] aircraft and contrails, [39] missiles, flares, [39] chaff, smokescreens, ICBMs, satellites, [39] space vehicles, rocket exhaust, [39] the International Space Station, [39] space debris, [39] drones, [43] stealth aircraft [44] Similarly, radar glitches, false blips, thermal inversions, and spoofing have been known to give rise to UFO reports. [45] [46]

Purported causes

Natural

It has been suggested that UFO reports might somehow be a natural result of atomic energy. On July 6, 1947, media nationwide claimed that the ongoing "flying saucer" craze was linked to "transmutation of atomic energy", though experts later dismissed that claim as gibberish. In 1968, Air Force debunker J. Allen Hynek, still reeling from public derision over his claim that a UFO report was caused by swamp gas, similarly floated the suggestion that reports might be tied to atomic phenomenon. [47] [48]


Space animal hypothesis proposes that UFO reports might be caused by an unknown form of life indigenous to air or space. In 1923, paranormal author Charles Fort mused, "It seems no more incredible that up in the seemingly unoccupied sky there should be hosts of living things than that the seeming blank of the ocean should swarm with life." [49] [50] During the 1947 flying disc craze, a fan of Fort's writings named John Philip Bessor became the first modern proponent of the hypothesis when he authored a letter to the Air Force suggesting that discs might be "animals bearing very little likeness to human beings". [50] [51] In 2024, scientists argued UFO reports stem from plasma in the upper atmosphere that, though not actually alive, could move and behave in ways that might appear like a rudimentary form of life. [52] Cryptids—a mythological natural being claimed to be associated with supernatural effects, have been linked to UFO reports. [53]

Technological

Human

During World War Two, unidentified lights were thought to be secret German aircraft. The Kenneth Arnold sighting that ignited the 1947 flying disc craze, was initially suspected to be a top secret US craft. Other speculation held the craft might be Soviet or privately held technology. [54]

More fringe ideas held that UFOs might be held by a secret human or super-human Earth-based society. Such a society was imagined to live in lost continents like Atlantis and Lemuria, inside a Hollow Earth, atop the mountains of Tibet, or at the Earth's poles. Over time, stories considered lunar Nazi bases or other "Secret space program|Secret Space Programs". [55]

"Alien"
Contrary to the conjunction fallacy, adding extra details to an interpretation actually makes it less likely. Possible interpretations of UFO reports - con.png
Contrary to the conjunction fallacy, adding extra details to an interpretation actually makes it less likely.

As early as 1947, UFO reports were linked to possible interplanetary or extraterrestrial beings. Even before, authors had speculated about crypto-terrestrials from inside a hollow earth. Others speculated that UFOs might be "interdimensional" in nature, visitors from an "etheric plane". More modern variants argue UFOs can travel through solid matter. Others suggest that UFOs are "alien reproduction vehicles" human craft made using alien technology. [56]

Time and Multiverse travel

Mainstream scholarship devotes serious consideration to interstellar, intergalactic, and potentially even interdimensional travel or "warp drive". In contrast, going "backwards in time" or jumping between "parallel universes" would seem to violate not only known physics, but potentially the laws of logic itself. Backwards time travel is an element in the Michael Criton UFO novel Sphere . [57] [ better source needed ]

Supernatural and folklore

Fantastical or folkloric explanations for UFOs included pixies, fairies, sprites, elves, gnomes, brownies, and little people. [2] Spiritualism included ghosts, spirits, phantoms, specters, and shades as possible interpretations.

Religious interpretations of UFOs include angels, demons, god(s), devil(s), saints [58] and spirits. In the 2002 film Signs, green alien invaders may actually be demonic. [59]

References

  1. 1 2 Handbook of UFO Religions. BRILL. March 8, 2021. ISBN   978-90-04-43553-7 – via Google Books.
  2. 1 2 Lewis, James R. (December 1, 2000). UFOs and Popular Culture: An Encyclopedia of Contemporary Mythology. Bloomsbury Publishing USA. ISBN   978-1-57607-375-9 – via Google Books.
  3. ↑ After the Flying Saucers Came: A Global History of the UFO Phenomenon. Oxford University Press. 2024. ISBN   978-0-19-086987-8.
  4. ↑ The Psychology of Public Belief in Unexplained Phenomena: Close Encounters, Extraterrestrials and UFOs. Taylor & Francis. 19 December 2025. ISBN   978-1-040-61231-6.
  5. ↑ How UFOs Conquered the World: The History of a Modern Myth. Quarto Publishing Group USA. 14 May 2015. ISBN   978-1-78131-472-2.
  6. ↑ Norman Swartz and Raymond Bradley, Possible Worlds — An Introduction to logic and its philosophy, 1979, Hackett Publishing company, inc., ISBN   0-631-16130-9. pp. 329–330
  7. ↑ Wall, Mike (28 July 2014). "Want to Colonize an Alien Planet? Send 40,000 People". Space.com. Retrieved 24 February 2021.
  8. ↑ Lewis, James R. (December 1, 2000). UFOs and Popular Culture: An Encyclopedia of Contemporary Mythology. Bloomsbury Publishing USA. ISBN   978-1-57607-375-9 – via Google Books.
  9. 1 2 Tumminia, Diana (May 17, 2007). Alien Worlds: Social and Religious Dimensions of Extraterrestrial Contact. Syracuse University Press. ISBN   978-0-8156-0858-5 – via Google Books.
  10. ↑ Lorenzen, Coral E.; Lorenzen, Jim (January 14, 1976). Encounters with UFO Occupants. Berkley Publishing Corporation. ISBN   978-0-425-03093-6 – via Google Books.
  11. 1 2 "Resurfaced secret CIA documents reveal details of 'two alien bases' that are hidden on Earth". Yahoo News. May 2, 2025.
  12. ↑ Spielberg, Steven; Mathison, Melissa (March 12, 2002). E.T.: The Extra-Terrestrial From Concept to Classic: The Illustrated Story of the Film and Filmmakers. HarperCollins. ISBN   978-1-55704-504-1 – via Google Books.
  13. ↑ https://www.google.com/books/edition/Encyclopedic_Sourcebook_of_Ufo_Religions/sNIQAQAAIAAJ
  14. ↑ Williams, Jerry (September 21, 2013). Monsters of the UFO: The paranormal link between monsters and UFOs. Jerry Williams. ISBN   978-1-4848-5661-1 – via Google Books.
  15. ↑ Davis, S. Peter (January 14, 2013). Occam's Nightmare. Lulu.com. ISBN   978-1-304-03018-4 – via Google Books.
  16. ↑ Evans, J.E.; Maunder, E.W. (1903). "Experiments as to the actuality of the 'canals' observed on Mars". Monthly Notices of the Royal Astronomical Society (abstract). 63 (8): 488. Bibcode:1903MNRAS..63..488E. doi: 10.1093/mnras/63.8.488 .
  17. ↑ Handbook for the Amateur UFO Investigator. Lulu.com. 6 July 2017. ISBN   978-1-387-08300-8.
  18. ↑ "Close Encounters of a Kind". Time. 1979-03-12. Archived from the original on 2012-09-14. Retrieved 2007-04-12.
  19. ↑ "How We Staged the Morristown UFO Hoax". eSkeptic. Skeptics Society. April 1, 2009. Retrieved April 16, 2009.
  20. ↑ Cahn, J. P. Cahn (September 1952). "The Flying Saucers and the Mysterious Little Men" (PDF). True. Archived from the original (PDF) on June 22, 2023. Retrieved June 22, 2023.
  21. ↑ "The Queen & the Saucers". Time . 1 June 1959. Archived from the original on 13 July 2007. Retrieved 27 April 2007.
  22. ↑ Levy, Michael M; Mendlesohn, Farah (2019). Aliens in Popular Culture. Santa Barbara, California: ABC-CLIO. ISBN   9781440838330.
  23. 1 2 Hitt, Jack. "This Is Your Brain on God". Wired– via www.wired.com.
  24. ↑ "Alien Abduction? Science Calls It Sleep Paralysis (Published 1999)". The New York Times . July 6, 1999.
  25. ↑ "Taking DMT Can Lead to Experiences Similar to Those Reported by People Who Claim to Have Been Abducted by Aliens, Study Shows - Newsweek". Newsweek.
  26. ↑ Cromie, William J. (February 20, 2003). "Alien abduction claims examined".
  27. ↑ https://www.google.com/books/edition/Aliens_and_UFOs_Physical_Psychic_or_Soci/tfzTEAAAQBAJ
  28. 1 2 Michael Barkun (4 May 2006). A Culture of Conspiracy: Apocalyptic Visions in Contemporary America. University of California Press. pp. 86–. ISBN   978-0-520-24812-0. Archived from the original on 26 June 2014. Retrieved 18 October 2012.
  29. ↑ "Fantasy-prone psyche may lie behind strange 'abductions' - UPI Archives". UPI.
  30. ↑ https://scholarsbank.uoregon.edu/server/api/core/bitstreams/268df944-835f-48c7-b4c0-ee4d944452c6/content
  31. ↑ Pilkington, Mark (2010). Mirage Men. Constable & Robinson. p. 320. ISBN   9781845298579. Archived from the original on 29 September 2010. Retrieved 1 October 2013.
  32. ↑ "Solving a UFOlogical 'Murder': The Case of Morris K. Jessup | Skeptical Inquirer". August 26, 2021.
  33. ↑ https://research-repository.uwa.edu.au/files/3221216/Hall_Karen_Peta_2008.pdf [ bare URL PDF ]
  34. ↑ Mehrtens, Susan (September 26, 2012). "Jung On Signs in the Skies: A Jungian Perspective on UFOs".
  35. ↑ Gershon, Livia (February 6, 2024). "Where Tulpas Come From".
  36. ↑ Huberman, Jeffrey Howard; Pope, Brant L.; Ludwig, James (January 14, 1997). The Theatrical Imagination. Harcourt Brace College Publishers. ISBN   978-0-15-503024-4 – via Google Books.
  37. ↑ Nicaise, Alexander (March 3, 2020). "General Nathan F. Twining and the Flying Disc Problem of 1947 | Skeptical Inquirer".
  38. ↑ Klass, Philip J. (January 14, 1975). UFOs Explained. Random House. ISBN   978-0-394-49215-5 – via Google Books.
  39. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 "17 things commonly mistaken for UFOs". BBC Sky at Night Magazine. March 25, 2025.
  40. ↑ Powell, Corey S. "UFO? No, It's Venus". Discover Magazine.
  41. ↑ Callahan, P. S.; Mankin, R. W. (November 1, 1978). "Insects as unidentified flying objects". Applied Optics. 17 (21): 3355–3360. Bibcode:1978ApOpt..17.3355C. doi:10.1364/AO.17.003355. PMID   20203984.
  42. ↑ "Police Report: Stefen Michalak UFO Report - Case Reopened" (PDF). www.bac-lac.gc.ca. 1967-08-10. Archived (PDF) from the original on 2025-08-24. Retrieved 2026-01-09.
  43. ↑ The Week UK (January 11, 2025). "The New Jersey 'UFO' drone scare". The Week.
  44. ↑ Viswanatha, Joel Schectman and Aruna (7 June 2025). "The Pentagon Disinformation That Fueled America's UFO Mythology". WSJ.
  45. ↑ "Flying Saucers Called Mirages". Green Bay Press-Gazette. 1952-06-02. p. 6. Retrieved 2024-11-24– via Newspapers.com.
  46. ↑ Ruppelt 1955 , p. 109
  47. ↑ Peebles, Watch the Skies "Swamp Gas" pp. 203–207
  48. ↑ "UFOs May be Unknown Phenomenon from Nuclear Energy, Expert Declares". The Miami Herald. 24 March 1967. p. 138.
  49. ↑ New Lands, 1923, ch 17
  50. 1 2 "Who 'Discovered Space Animals'?", Civilian Saucer Intelligence of New York Newsletter, (December 15, 1957)
  51. ↑ Richard Toronto, "On the Track of the Gelatinous Meteor: What if UFOs are not extraterrestrial machines, but strange atmospheric life-forms?"
  52. ↑ Knapton, Sarah (February 2, 2024). "We know what 'foo fighters' that buzzed Second World War pilots really were, say scientists". The Telegraph– via www.telegraph.co.uk.
  53. ↑ Clark, Jerome (2000). Extraordinary Encounters: An Encyclopedia of Extraterrestrials and Otherworldly Beings. Santa Barbara, California: ABC-Clio, ISBN   1-57607-249-5, pp. 178–179.
  54. ↑ Examples of Russian speculation:
  55. ↑ Levine, Art (May 29, 2024). "Pentagon Strikes Back Against Claims of Alien Invaders". Washington Spectator . Retrieved May 27, 2025.
  56. ↑ Mirage Men, p.250, 275
  57. ↑ https://www.google.com/books/edition/The_Mammoth_Encyclopedia_of_Science_Fict/JtvABAAAQBAJ
  58. ↑ Miracle of the Sun, 1917
  59. ↑ "Wrestling the Twister: An Interview With M. Night Shyamalan". somethingawful.com.
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