An ergonomic pointing device, such as a mouse, is coupled to a computer having a visual display device. As a user rotates a roller associated with the mouse, the mouse generates computer signals that are interpreted by an operating system and software applications running on the computer. The signals generated by the roller, together with a given software application, can be used for spatial navigation. In spatial navigation, a user rotates the roller to cause the computer and the visual display to increase or decrease magnification levels of the document on the display. Other models of spatial navigation allow the user to activate a roller switch, depress special function keys on a keyboard and/or move the mouse to pant, automatically scroll or manually scroll through the document.