This week, and unexplainable. We've got enough space for the air freshener. And some big questions too. Why do think they see ghosts, and how should they deal with the experience? Chris thinks a lot about these questions, because he isn't just a t v ghost sceptic. I'm a professor ameritus in the psychology department at goldsmith's university of london. He's essentially dedicated his career to understanding why people see ghosts - even though he doesn't necessarily think they're real.