Do you ever click the 'get mail' button a couple times, just to make sure you got all the email, and there's not another, overlooked letter, maybe sitting in the bottom of the virtual mailbag?

In user testing, time and time again reserchers will see a user try to do something with a new interface, and if the system doesn't react, they'll click again, and click harder again until they can't click any harder. Then they give up and try another tactic.

I wonder how interfaces could be designed to use these behaviors. First, we'd need a pressure-sensitive mouse button, then we'd need to reinvent interactive metaphors to better map to the way we work as people.