Here's one of my favorite psychology studies of all time. You bring people into the lab, and you ask them, "Do you know how a toilet works?" And they say "Uhh yes, I'm not an idiot." And then you go "Okay, could you please write down, step by step, how a toilet works." And then you ask them to explain something that requires knowledge of toilets, like "How does pressing the lever on the side of the toilet cause the bowl to empty and then refill again to a certain level?"
What participants learn in this study is that, to their horror, they don't really know how a toilet works, at least not nearly as well as they thought they did. This isn't specific to toilets—you can get it with everything from spray bottles to helicopters.
Alles wat Jan bezighoudt, interesseert en irriteert... en ook een beetje onzin...