Most ghostly experiences can be explained as people’s imagination getting the better of them. But not all. Sometimes there’s more to the story.
The workings of our own brains can generate powerful illusions of ghostly apparitions. For example, ghosts are perhaps most frequently seen by people who are tucked into bed. That’s no coincidence! Scientists know that people sometimes hallucinate during the dreamy twilight periods at the beginning and end of their sleep. An extreme version is the experience of “sleep paralysis.” This is a fairly common sleep dysfunction in which people regain wakeful consciousness of their surroundings but find themselves briefly unable to move. Victims of sleep paralysis often feel a suffocating feeling of pressure on their chest. They may also experience hallucinations of a presence in the room, such as a ghost. Thankfully these episodes only last a minute or two.
This happened to my mother when I was a boy. She woke up one night to an apparition of a man choking her and holding her down on the bed. She was terrified! No one in my family had ever heard of sleep paralysis. How else could we explain her experience? We jumped to the seemingly obvious but incorrect explanation that she had been attacked by a spirit.