Tactile and Haptic Displays

The somatosensory system provides us with information about our soma (Greek for body) contact with the outside world and our own movements and body position within it. The somatosensory system is comprised of the following:

• Tactile - Touch, pressure, pain, vibration, shape, texture,
• Temperature - Perception at skin surface,
• Kinesthetic - Limb/joint movement and position and muscle contraction state,
• Pain - Extreme temperature, intense pressure, burning chemicals.

Displays that capitalize on the user's sense of touch are termed tactile, tactual, or cutaneous displays. The most familiar and well known tactile display is braille. It can be considered purely tactile in that a braille character can be identified just as well if the fingers are stationary and the braille pattern moved over them as when the fingers move over the pattern. However, few displays are purely tactile, most require some kinesthetic or movement input.

Displays that combine somatosensory modalities such as tactile and kinesthetics are termed haptic displays. Haptic refers to "active touch" to emphasize the importance of movement/kinesthetics when exploring an object by touch. To determine an object's size, shape, and texture, one must move the hand or fingertips over it.

Haptic displays are characterized by providing both tactile and kinesthetic/force feedback to the user. Most tactile and haptic displays are designed for the hand or fingers, as these areas have the most numerous and sensitive touch receptors.

Braille is an example of a purely tactual display. In this illustration, braille floor numbers help visually impaired users of an elevator.	Game controllers capitalize on "touch" to distinguish buttons by size, shape, texture, and movement direction.