Eight people have reliably used a mind-controlled robotic third arm to do two things at once. The technology could be used give a helping hand when lifting heavy objects or for tasks that require more than two arms.

Participants in the experiment had to learn to control a robotic arm using a brain-machine interface. The robotic arm was placed next to the participants, and they wore two electrodes on the outside of their head to capture  brain activity. The arm was then calibrated to pick up on the differences in brain patterns when participants imagined the arm grasping and releasing a bottle.

To test their skills, participants had perform two tasks simultaneously. The first was to hold and release a bottle using the robotic arm, and the second was to use their two real arms to move a ball around on a tray.

The team found that eight out of the fifteen participants could reliably roll the ball to target points on the tray while grasping and releasing the bottle with the robotic arm, but the other seven struggled and were only successful about half the time.

“The two groups didn’t differ by their ability to control the arm, but probably by their ability to concentrate on multiple tasks at once,” says Shuichi Nishio at the Advanced Telecommunications Research Institute in Kyoto, Japan. In other words, he believes people who were better at the task were simply better at multitasking.

Robotic arms like this could be used for people who work in factories, for example, by helping to lift very heavy objects or just providing an extra hand when needed. This contrasts with other projects that have focused on using robotic arms for prosthetics.

Beyond multitasking, experimenting with a mind-controlled robotic arm could act as a form brain training. The authors propose that practicing with the robotic arm could improve people’s general ability to concentrate on multiple things at once.

Earl Miller at the Massachusetts Institute of Technology agrees that this may improve the ability of participants to concentrate, but no more than any other activity requiring focus.

“Practicing sustained focus, concentration, will make you better at doing it,” he says. It is sort of like meditation, only with a mind-controlled robotic arm.