DR. JOSH BONGARD

When a person stubs his toe, he compensates by favoring his other leg. More dramatically, if he loses use of both his legs, he can still crawl to get from point A to point B. Now a robot shaped like a four-legged starfish can do the same. Designed at Cornell University, the nine-piece device can advance toward a goal even after incurring damage. In a paper published in this week's Science, the researchers describe the algorithm by which this mechanical beast can assess its own condition.
 
"The main advance here was not just the diagnosis and recovery, but how the robot does that, which is to build a model of itself," explains Josh Bongard, a computer scientist now at the University of Vermont. In the past, robots attempting to recover from damage would have attempted upward of hundreds of thousands of movements in an inefficient trial-and-error process designed to overcome injury. But if these robots are to become "the next generation of planetary rovers," Bongard points out, "you can't assume that this robot can perform hundreds of thousands of trials. It may damage itself further or fall off a cliff." So, Bongard, along with his colleagues Victor Zykov and Hod Lipson, programmed their robot to carefully select its actions so that it makes as few movements as possible.