Last Friday I gave a presentation to the participants of Picture Australia on the redesign I have been working on. I always get a little nervous before a talk, but then once I start talking the nerves disappear and everything is fine.Today I had a bad start to the presentation. I was standing in front of the lectern with a mouse and my powerpoint presentation ready to go. I click the mouse to start the presentation & what appears on the screen, but the right click menu! Why is it that as soon as the mouse is taken away from the context of the computer, it is so easy to make a mistake like this. The mental model for the mouse becomes a previous/next series of buttons. To move to the next slide, the natural mapping is to click the right mouse button, bringing up the dreading menu & grinding the presentation to a halt. I wasn’t the only presenter who had problems with this, at least a third of the presenters made the same mistake.Maybe it was just the way that things were set up, the laptop was out of reach. Maybe if it had been closer to the lectern the relationship with the mouse would have been there and things would have gone smoothly.