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How does your computer feel today? No, I'm not asking about its state of cybernetic health, but rather about whether it's giving you any tactile feedback or manipulative capability through your fingers.

Touch is the latest to be added to the list of human senses a computer can address. It's called haptics, from the Greek haptesthai, meaning to grasp or touch.

The earliest haptic devices for computers were Braille readers. With them, a blind person can move a finger along a line of metal pins that form a Braille representation of the current on-screen line of text. Although they're very useful, these devices are limited to rendering text.

There are now a few more devices that use haptic technology. Among the earliest, developed a few years ago, were joysticks and similar gaming controls that employed force feedback, offering varying resistance to movement, depending on what was happening on-screen.

Vibrating Mice

The newest devices are haptic mice from Logitech that use a vibration-generating motor to simulate different surface textures and materials. They're relatively simple and inexpensive, employing new technology from Immersion in San Jose.

More than just a frill or a thrill, "the addition of tactile feedback to computer mice can significantly enhance user performance," says Jack Dennerlein, assistant professor of ergonomics at Harvard University. "Our laboratory studies show that people complete basic cursor-targeting tasks faster with tactile feedback."

AVB also recently released a vibrating mouse, although it is primarily intended for use with games. (See "Vibrating Mouse Shakes Up Your Surfing.")

Phantom Arm

But more sophisticated haptic tools are available. Perhaps the best-known is the Phantom from SensAble Technologies. This device employs a moving arm that ends in a stylus for you to hold or a thimble into which you insert a finger. These are used in conjunction with software called the FreeForm Modeling System.

As you move the device's arm, a cursor moves around the screen. Using the device, if one encounters a "solid" object in the on-screen universe, the arm stops. Moving along a surface provides tactile information about the surface's texture, and you can readily and intuitively sense curves and corners and, by exerting more pressure, cause deformation of the object.

Using "digital clay" as a sculpting medium, this system essentially does for clay and foam modeling what the word processor did for typing. The process may not be faster for creating the first object, but once that's captured, it can be manipulated, modified, and rescaled digitally. The artist can copy and reuse model features, control the hardness and surface smoothness of the clay, and mirror and scale objects--and, of course, "undo" is just a keystroke away.

Practical Applications

Haptic devices have many potential practical applications in training people to develop and practice specific motor skills, such as in the field of medicine. One use is for training in surgical procedures. Another is in telemedicine, where a doctor can physically examine and palpate areas on a patient's body, receiving accurate and informative tactile feedback even though the patient and doctor are in different locations.

Haptics is also being investigated as a tool for analyzing data. Just as color and graphical representations have enhanced the ability to manipulate and understand masses of data, haptics may contribute the ability to sense additional dimensions in a single view.

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