Force feedback provides a sense of presence in a virtual world, it is also known as force reflection or haptic feedback and gives a physical sensation or representation to the computer user.
Force feedback provides direct tactile perception of three-dimensional objects and directly couples input and output between the computer and user. It acts as a powerful addition to graphics displays for problems that involve understanding of 3D structures, shape perception and force fields. One of the major roles of force feedback is in the area of 3D gaming where the use of force feedback joysticks can give the user the illusion that they are actually experiencing the virtual environment as if it were a physical environment. Also used in gaming situations are force feedback headphones, these headphones pick up low bass rumble produced by the sound of explosions in a game or the music being played and transmit these as vibration to the user. A combination of the visual, tactile and auditory/tactile feedback would provide the user with a more than sufficient force feedback experience.
There are other groups of people however who would benefit from using force feedback devices particularly mice. One such group of computer users are those with hand or upper body tremors such as people with cerebral palsy, Parkinson's disease or stroke. The average mouse used with a computer tends to move too quickly for people with uncoordinated movements. As a result, fine movements such as icon selection often take a long time.
Hwang (2002) found that "gravity wells" were a useful aid for motion-impaired people. A gravity well is situated at the centre of the target and when the mouse approaches the area it is pulled into the gravity well which then enables the user to perform the activating click whilst the cursor is held steady. Dampening of the cursor movement by making the movements feel more viscous was also suggested as a method of in effect calming the spasmodic nature of some motion-impaired peoples' interactions.
Visually impaired computer users are able to explore 3-D objects using force feedback joysticks. Whilst blind users seldom use a mouse when using a computer, the use of the gravity well may be useful to partially sighted users when their level of screen magnification significantly limits how much of the screen they can access at any one time.
When considering the MultiReader project, the use of force feedback to provide emphasis feedback to blind readers may be a possible area for exploration. The use of varying vibration levels could replace the tools available to the sighted reader for creating emphasis in a text such as italics, bold or capitalisation.