* This was painted by a person with a rare and severe mental disorder. He was constantly seeing his own fantasies all around him. He also had a certain phobia (undisclosed).
* His (the poster’s) psychiatry professor showed this painting in a lecture, and said there was one tell-tale sign in it that showed the painter’s insanity.
* The professor didn’t say what that sign was, leaving the students to do the guesswork. The only clues he gave was, “don’t look for small details, look at the whole; if you figure out what the phobia was, you’ve got the answer; ask yourself what could have preceded this scene; think of what the place would look like with all the objects removed“.
* The professor said that during the 15 years of his teaching, only one student had figured it out.
The painting doesn't look scary or anything.
I can't figure this out, what is the sign of insanity?