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DIGITAL PEOPLE

fine movements such as the changes in eyes and mouth that animate human faces.

Kismet, the robot built by Cynthia Breazeal at MIT to explore humanrobot interactions, shows to great effect the importance of small-scale movements. Much of Kismets impact on people comes from the humanlike motion of its head and face. Kismet, says Breazeal, could actually make eye contact with you. Its night and day when something looks into your eyes versus at your face or just at you. Eye contact is profound.Kismets head movement and changes in expres- sion are accomplished by approximately two dozen servos.They drive, for instance, its lips, which are sufficiently flexible to show different expressions, but are not meant to reproduce the versatility of natural human lips.

What is important about Kismet is its demonstration of the power of a social component in humanrobot relationships, even though the robot is not a human replica. The social connection might be en- hanced, however, with robots whose facial and bodily movements appear natural, and this objective might call for a different system than motors and mechanical linkages. An alternate approach that shows promise for simulating natural movement comes from new classes of smart materials,which change their properties according to exter- nal stimuli or environmental conditions. For example, the plastics called electro-active polymers (EAP) change length or shape under electrical voltage, mimicking what natural muscles do under neural control. EAP materials date to the late nineteenth century, but they came under serious study only in the 1990s. In one type, electrons in the material set up an electric field that causes stretching or shrinkage. In another, which usually operates in a liquid environment, the mo- tion of charged atomsionsmakes the material bend.According to the Jet Propulsion Laboratorys Yoseph Bar-Cohen, a leading re- searcher in the area,the main attractive characteristic of EAP [mate- rials] is their operational similarity to biological muscles, particularly their resilience.

Along with Bar-Cohen, researchers around the world are explor- ing these materials. One dramatic example of these efforts can be seen

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