I got interested in illusions & ilussionists years ago and even built a couple of stage illusions. I wasn't a performer but I just loved the effects and as I learned "how it's done" I started watching the audiences for their reactions. Once you learn how a trick is done it ceases to be magic more often than not and the most amazing things are usually so simple (in principle). This goes for card tricks, stage shows, psychics...all of it.
At the state fair here in Dallas two years ago, me and my g/f were walking about and saw this large group of people watching some kind of act. The looks on these people's faces were a mix of disgust, horror and bewilderment! When we got to where I could see the stage I couldn't help but laugh out loud and the people around us were mortified that I was laughing!
On the stage was a guy with no lower torso and HE was making all kinds of wise cracks about his condition (like "can you guess who wears the pants in MY family?") so I joined in making fun of him too. That only egged him on and it was fun but people were getting mad at me! Even my g/f couldn't believe what I was doing so I had to let her in on how it was done. I had actually made a version of this illusion so I knew exactly how it worked but this was the first time I had seen it in a show and I was amazed at how real it looked
The point being that the majority of this audience were completely fooled by a simple trick. It's ALL in the presentation and THAT is what makes a psychic's act work also. There's no box on a stage so you don't tend to think about the possibility of any gimmicks being used but there usually is. They're good actors but that's ALL they are.