Quotation from "Hiding the Elephant"
When magicians are good at their jobs it is because they anticipate the way an audience thinks. They are able to suggest a series of clues that guide the audience to the deception. Great magicians don't leave audience thought patterns to chance; they depend on the audience to bring something to the table -- preconceptions or assumptions that can be naturally exploited. That's why, despite what people think, children are often bad audiences for magic. They have little experience and make few assumptions. They might not take for granted that holding your hand in a certain way indicates that it's empty, or that walking around a table in a certain manner indicates that it's just a normal piece of furniture. A magic show is built on these tiny allowances -- children may not grant them.
Alteratively, anyone with a firm system of beliefs, anyone who has been forced to categorise or analyse information, is ripe for skillful deception. This is why there are famous examples of learned men of science being badly fooled by the simple tricks of fake physics.
From Hiding the Elephant by Jim Steinmeyer.