ABDUCTED BY ALIENS?, ON PRIMETIME: THE OUTSIDERS, TUESDAY, AUGUST 18 ON ABC

People have often wondered: Are we are living alone in the infinite universe, or are there other intelligent life forms out there in the cosmos? Nearly half of all Americans and millions more worldwide think that we are not alone. And then there are the people who not only believe there are aliens out there, but that they've been abducted during the night by them. From a former U.S. Marine who says he was completely paralyzed when aliens entered his apartment to twin sisters who say they were abducted on a spaceship together, Juju Chang meets people who give extraordinary accounts of encounters with the unexplained. Chang also interviews Harvard scholars who have a medical explanation of how people could believe they are experiencing life with extraterrestrials. The hour examines what these people's testimonials say about the human psyche. "Primetime: The Outsiders" airs TUESDAY, AUGUST 18 (10:01-11:00 p.m., ET) on the ABC Television Network.

Among the people Chang interviews is Stan Romanek, who captured his alleged sightings on video. He says he has more witnesses, documentation and so-called proof of extraterrestrial contact than anyone else. He also shares controversial video that he says shows an alien at his kitchen window and allows "Primetime" access into a hypnotic regression therapy session, which is how he remembers the alleged abductions.

But psychologists say pop culture and media generated images of extraterrestrials can become easily engrained in our subconscious and then vividly re-enacted in our dreams. Could a common disorder called sleep paralysis explain why so many self-proclaimed "abductees" are absolutely convinced what they've experienced is real?

David Sloan is the executive producer of "Primetime: The Outsiders."