one of the things I’ve seen most often in usability tests is that people form ideas about what things are and how they work which are just wrong. Then they use these first bits of “knowledge” to help interpret everything they see. If their first assumptions are wrong (“This is a site for __”), they begin to try to force-fit that explanation on to everything they encounter. And if it’s wrong, they’ll end up creating more misinterpretations. If people are lost when they start out, they usually just keep getting…loster. This is why it’s so crucial that you get them off on the right foot, making sure that they’re clear on the big picture.