Monkeys can control a robot arm as naturally as their own limbs using only brain signals, a pioneering experiment has shown. The macaque monkeys could reach and grasp with the same precision as their own hand.

"It's just as if they have a representation of a third arm," says project leader Miguel Nicolelis, at Duke University in Durham, North Carolina. Experts believe the experiment's success bodes well for future devices for humans that are controlled solely by thought.