An over-active imagination, perhaps. I don't know.
One never knows where these things start. I read something once...perhaps it was Stephen King??? I read an interview and he said what got him into scary stories so much was his brother. He said his brother would be so afraid because of this night visitor. It was a white wolf that came into his room at night and would stand by the bed and look at him. And the white wolf would come in walking and standing on its two hind legs like a person. The interviewee said that description was so chilling and unforgettable it spurred on his imagination to horror stories.