What is the main symptom of the psychological disorder called "Boanthropy"?

Boanthropy is a rare psychological disorder that causes a human being to believe they are a cow.

King Nebuchadnezzar II of the Neo-Babylonian Empire is sometimes attributed with boanthropy based on the description in the Book of Daniel which says that he "was driven from men, and did eat grass as oxen". Psychologists generally group Boanthropy, along with other forms of zoanthropy, into the diagnosis of Clinical lycanthropy. Other conditions frequently, but not universally, found in patients include schizophrenia, psychotic depression, and bipolar disorder.

Dreams may also play an important part. Jung for example records how a stubborn woman 'dreamed she was attending an important social occasion. She was greeted by the hostess with the words: "How nice that you could come. All your friends are here, and they are waiting for you." The hostess then led her to the door and opened it, and the dreamer stepped through – into a cowshed!'.

Freud had long since noted 'cases in which a mental disease has started with a dream and in which a delusion originating in the dream has persisted'.

R. D. Laing offers an autobiographical account of a brief reactive psychosis in which the protagonist had a 'real feeling of regression in time...I actually seemed to be wandering in a kind of landscape with – um – desert landscape – as if I were an animal, rather – rather a large animal..a kind of rhinoceros or something like that and emitting sounds like a rhinoceros'.