Shrewbot is the size of a small dog, can move its head around, runs on batteries, and has omnidirectional wheels—and no eyes. Its only sense is touch, from its plastic whiskers. Its snout has 18 of them, which move back and forth five times a second. (Real shrews whisk twice as fast.) When a whisker touches something, it bends backward, pushing a magnet at its base. A magnetic sensor detects the displacement and sends it to Shrewbot's computer processor. Shrewbot uses these touch signals to create a picture of its environment and distinguish shapes and textures.