With iRobot Corp. reporting sales of more than 2 million Roombas, the robotic vac is more than a curiosity. Users have even established Roomba Web sites and Yahoo discussion groups. As part of a National Science Foundation-sponsored study to explore the social impact of robots, Forlizzi selected six families in Pittsburgh and Harrisburg and gave them either Roombas or a handheld stick vacuums with similar cleaning capacities. She asked family members keep diaries, take photos and check in with researchers periodically over the course of a year. "The surprising thing to me was how much the Roomba changed the way that people cleaned," said Forlizzi, who presented her findings at the Human-Robot Interaction conference in Washington, D.C. in March. Changing lives The robot changed who did the cleaning, involving more men and more younger members of the families, often working in pairs.