Alien abduction stories are probably based on sleep paralysis, a condition where you wake up, dream-hallucinate someone in your room, and can’t move
“The room is dark, but she can make out the silhouette of a man at the foot of her bed. She knows he’s not a friend. Her instinct is to fling herself out of bed, to sit up, to kick: anything to make the shadow leave. But as much as she tries, she can’t move.
He places a hand on the bed. Some switch flips in Alina’s brain, and she’s terrified. It’s beyond nervous or scared, even beyond what she normally would be feeling with an intruder in her room. Blood is rushing into her temples, clouding her vision. Pure, unadulterated terror. Her mind cries again to run or fight, but her limbs are weighted down by an unseen force.
The man crawls forward until his face is even with hers. She tries to turn away, but can’t. The man’s eyes lock with hers. They are bright orange-red, radiating like fire, and the pupils are vertical black slits. His mouth opens to reveal rows of jagged teeth, Alina’s brain is screaming too loud to think, she strains against her invisible bonds but they-
Her arms jerk and she gasps. The man is gone. Her panic dissipates like fog in the midday sun.
Alina, like 6% of the population, suffers from sleep paralysis. This condition is essentially an overlap between the waking and REM (rapid-eye movement) states of consciousness. REM is the stage of sleep when we experience dreams. During this phase, our minds operate at a level close to waking, but we perceive a constructed dream world instead of our surroundings. To keep our interactions with the dream world from spilling over into real life, we are almost completely paralyzed while in REM sleep, aside from breathing and eye movement. For most people this is not a problem, since the paralysis ends when they wake up. But during episodes of sleep paralysis, the mind wakes and the eyes open, but the body remains paralyzed. This is sometimes accompanied by dream images, often superimposed on the environment as hallucinations, and a feeling of dread or fear. (1)
This occurs most often in patients with narcolepsy, who experience it as they fall asleep roughly half of the time. Patients without the disorder experience it less frequently, but surveys suggest that at least half of the population will suffer from sleep paralysis at least once in their life. Medical students, workers with strange shifts, and anyone else with sporadic sleep schedules are most susceptible. If occurrences are hypnagogic, meaning they occur at the start of sleep, then they are often forgotten by morning. But if they are hypnapompic, occurring at the moment of waking, the memories can be vivid and disturbing”