 The strait jacket suggests that the Screamer might have been insane (and subsequently bound by some sort of mental institution) prior to being infected.The artificial intelligence of "Left 4 Dead" features a dynamic system for game dramatics, pacing and difficulty called the "Director".Instead of fixed spawn points for enemies, the Director places enemies and items in varying positions and quantities based upon each player's current situation, status, skill and location, creating a new experience for each playthrough.