"The search for artificial intelligence modelled on human brains has been a dismal failure. AI based on ant behaviour, though, is having some success." Now engineers study ant collectives. "Digital ants and birds, then, are good at thinking up solutions to problems, but Dr Dorigo is now working on something that can act as well as think: robots. A swarm of small, cheap robots can achieve through co-operation the same results as individual big, expensive robots—and with more flexibility and robustness; if one robot goes down, the swarm keeps going. ... All this is done without any pre-existing plan or central co-ordination. It relies on interactions between individual robots."