A game of Simon Says is even more fun when you can lead without actually saying anything at all. With a low-cost gadget from DIY neuroscience company Backyard Brains and an iPad, controlling another person's arm with your brain is as easy as connecting a few wires — no superpowers required.

In a new video from TED, Backyard Brains co-founder and neuroscientist Greg Gage demos the "human-human interface," a colorful, fist-sized device with knobs, lights and ports. It also features exposed electronics, presumably to make you feel like even more of a mad scientist. Powered by a simple 9-V battery, the human-human interface allows you to "take away [someone else's] free will" over a part of their body, Gage says.

Essentially, all the users need to do is stick a couple of adhesive electrodes in the right spots on their arms, clamp some wires to the electrodes and plug the wires into the interface. In this demonstration, Gage positions the electrodes along the both volunteers' ulnar nerves, which run along the back of the forearm and up to the fingers. The ulnar nerve, like every other nerve in the body, causes actions to happen via the electrical signals that it conducts. When you curl your fingers toward your palm, your brain sends electrical signals down through your spinal cord and out to your ulnar nerve, which carries the signal to fingers and triggers the muscles to carry out the action.

The electrodes are there to pick up that signal in the arm of the person calling the shots — let's call her Simon — and transmit it into the arm of her partner. Once the electrodes are in place, they pick up on the electrical signals in Simon's ulnar nerve every time she curls her fingers and send a corresponding electrical signal down through the wire and into the human-human interface. That signal then flows back out through the wires attached to electrodes on the partner's arm, stimulating his ulnar nerve with the electric signal and causing his fingers to curl toward his palm too. In effect, Simon is saying what she wants to her partner to do through electricity rather than words.

Anyone can purchase a human-human interface kit at the Backyard Brains online store for less than $300, though the iPad is not included. This device is marketed toward teachers in the hopes of inspiring young future neuroscientists, but as the audience's reactions attest, it can make adult jaws drop, too.

Photo: Fenn | Flickr