People often get such terrifying experiences because they seem to have full control over their senses even after they are paralyzed. The condition is sometimes accompanied by the sound of approaching footsteps, strange smells, and visions of weird shadows or sparkling eyes, and a heavyweight on the chest that makes it difficult to breathe, if not impossible. All of the senses of the victim are telling that there's something unusual going around with them. Rather than ghosts or demons, scientists also have an explanation for the condition. They call it - "Sleep paralysis" or sometimes "Isolated Sleep Paralysis".