Seriously though, read the book "trick of the mind" by Derren Brown which explains how the mind can be manipulated to believe owt. He debunks sprirtualists who say they can speak to the dead and exposes them as charlatans.
The power of suggestion is a powerful thing and he should know what he is talking about with the things he gets people to believe.
Also you can consider how it has been proven that positive thought can help improve medical conditions.
Basically its all in the mind! If you truly think you will see a ghost/ ufo you will.