Dr. Peter Lamont is a senior lecturer at the University of Edinburgh where he specializes in the history and psychology of magic and the paranormal. It’s an area of study that explores not only why people believe in the supernatural but how we all understand and relate to the world around us. Here, he explains why a belief in ghosts (both the spirits of loved ones and more malevolent poltergeists) has been a consistent part of human experience, shaped by changing religious, social and cultural contexts over thousands of years.

GEORGE UPTON: The earliest depiction of a ghost, carved into a clay tablet in ancient Mesopotamia, dates from the 4th century B.C. Why has it been such a constant in human history? 

Peter Lamont: If you believe in God or the existence of a soul or that there’...