Enabling fisheye effect

I got my MBP yesterday and was trying to enable the fisheye effect for the dock but could not do so. Fisheye effect is enabled on the MBPs that you see in any Apple store where when you move your mouse over the icons on the dock, they expand and then recede. I just could not find that option and my icons simply sit in the dock and nothing happens when I move the mouse over icons. Does anyone know how to enable that option? Thanks. Any help is greatly appreciated.