Asking what ghosts eat may seem like a silly question, as the most common belief is that ghosts don't require food. While some cultures actively feed spirits as part of annual celebrations, other cultures are even convinced that some spirits roam fields of crops in the afterlife, eating as they go.

First off, there are those who believe that because ghosts aren't physical beings, their survival does not depend on organic nutrients. Ghosts are believed to be entities composed of energy. They draw the energy required to sustain their existence from the psychic energy of people around them when they experience strong emotions like anger, fear, or depression. Some also say that spirits can draw power from electromagnetic fields caused by electronic devices and sources of heat, such as a fire or candle.

Another way that paranormal researchers believe ghosts "eat" is through possession of a living person. Once a ghost takes...