A ghost may present itself as an image, sounds, odors, tactile, feelings of cold, a feeling of intruding presence, or any combination of impressions. Some parapsychologists consider ghosts and poltergeists separate phenomena. In this case the viewer experiences what amounts to an hallucination, but its ultimate source is outside him. Animals, with senses more acute than man's, are supposed to be able to see or sense the presence of ghosts, even if humans on the scene sense nothing unusual. Folklorists generally distinguish two types of mythical ghost, the spectre-ghost or apparition, frightening but harmless, and the hungry ghost, which actively preys upon the living.
Vampires are a form of the hungry ghost.
Even today in the industrialized world, belief in ghosts and hauntings, or at least allowing their possibility, is widespread and held by many people, including the educated. Proving or disproving the existence of ghosts as true paranormal entities is difficult, amounting to trying to show the existence or non-existence of things that may or may not exist in a material sense. Psychical researchers have offered what they consider evidence in the form of photographs, videos and sound recordings, but none of these are convincing and all would be easy to fake. Other known phenomena can explain ghosts. People may hallucinate or misidentify, influenced by wishful thinking, grief and loneliness.