Watch “Oliver Sacks on Five Common Types of Hallucinations” on YouTube
The hallucinations that accompany sleep paralysis, for instance, can be very vivid and visceral, auditory, visual and tactile, with the sense of a malignant presence nearby, and a sense of abject terror.
Visions of monsters with outsized heads are common across time and culture. But even when there isn’t, our brains can be unreliable, as reliant on what we’ve been told as what we’ve seen or thought ourselves. We see spooky things because our brains are spooky things.