It looks enough like a rat to fool real rats, but Atsuo Takanishi's creation is actually a miniature robot. In a recent trial, he and his colleagues at Waseda University in Japan placed rat and rat-bot together in an enclosure and programmed the robot to head straight for a dish of food. Soon the rat began chasing its doppelganger as if it were a real animal and reached the food much faster than it would have on its own. Next, Takanishi plans to see what happens when rats live with rat-bots for an extended duration. "Will the rats become lazy or selfish if the robots make things too convenient for them?" he wonders. He wants to figure out how to avoid such behavioral changes before humans begin interacting with personal robots.