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The computer mouse looks like a harmless device: buttons to push and a rolling ball whose movements across a "mouse pad" control a cursor on a screen. But these mice can roar--and bite; they're associated with workplace disabilities like carpal tunnel syndrome and overuse injuries to tendons, muscles, and nerves of the upper extremities. The sheer number of click-and-drag events takes an ergonomic toll on the human body: mice and related pointing devices--like trackballs, touchpads, and pen-and-tablet interfaces--are involved in 30 to 80 percent of the actions humans perform on computers.
Yet so far, no one has really built a better mouse. That may change soon, according to Jack Dennerlein, assistant professor of ergonomics and safety at the School of Public Health, who has been studying the application of "haptic technology"--the creation and use of devices that engage our sense of touch--to computer mice. "Designers and manufacturers have spent a lot of time on visual and audio media like computer graphics and voice response, but not much on other interfaces," he says. "Touch is the next sensory feedback system we can develop."
Dennerlein, who was trained as a mechanical engineer, notes that "'human factors' research in ergonomics is concerned with both preventing injuries and keeping productivity high; that provides an incentive for companies to participate. It's about optimizing the interface of humans and machines." In technology design, he says, "Performance improves as you add more sensory feedback systems. For example, if you are touch-typing at a keyboard and have both tactile and audio feedback, you can type faster with fewer errors." Using a prototype from Immersion Corporation, Dennerlein has compared haptic computer mice to conventional models in performance tests and found that users can point-and-click 25 percent faster with the added sense of touch.
The haptic mouse, which Immersion eventually expects to market for about $100, looks much like a conventional mouse, but differs in several ways. Its pad has raised edges that confine the mouse's movements, and when the cursor hits the edge of the computer screen, the mouse can move no farther. Nor can you lift the haptic mouse off its mouse pad, since it is connected by mechanical linkages to a pair of motors in the pad. These motors enable the mouse to actively resist the user's hand with counterforces like pressure, movement, springiness, and vibration. When moving across a grid of vertical lines on the screen, for example, the user can feel an increased resistance at each line, so that traversing the grid feels like going over a series of speed bumps. Damping in the mouse can simulate the feeling of viscosity when crossing a particular blue circle on the screen. "Attractive basins" make it easier to point to screen icons--when the pointer approaches the icon, a force that feels like magnetism draws the pointer to its icon target. This eliminates much of the fine tuning involved in the point-and-click process, and so speeds up performance.
Haptic technology, including such "force-feedback" systems as Immersion's mouse, often begins in robotics labs. "Robots can carry out tasks in hazardous environments like outer space, underwater, or nuclear power plants," says Dennerlein, "but the robot's human operator needs tactile feedback to do most of these things well." Computer mice, powered by motors and controlled by microprocessors, are in effect simple robots. In a virtual environment, such haptic interfaces can be programmed to produce appropriate sensations. For example, while driving a car in a video game, the user might suddenly encounter a patch of slippery road; a haptic virtual environment can emulate that slippery feeling.
Such possibilities are in their infancy, but corporate and academic research on haptic technologies is proceeding apace in Japan, Canada, the United States, and Europe. These tactile enhancements have unknown ergonomic dimensions, and Dennerlein is one of the few researchers studying their effects on the human operator. "If you add force to the system, what effect will that have on risk factors for muscle and skeletal disorders?" he asks. "We should design devices not simply to resist operators, but to assist them in completing a task. We want to design a guide dog, not a superhero mouse."
~ Craig Lambert