Man Imagines Moving His Finger, Causes Another Man’s Finger to Move

The Citizen's Guide to the Future
Aug. 29 2013 12:50 PM

Man Imagines Moving His Finger, Causes Another Man’s Finger to Move

University of Washington brain-to-brain experiment
Mind control? Not exactly.

Image courtesy of the University of Washington

It’s tempting to call this telepathy, or mind control, or a Vulcan mind-meld. It isn’t any of those things. But it is still a head-spinning technological stunt, especially if you haven’t been closely following all of the incremental advances that have made it possible.

On Aug. 12, a University of Washington computer science professor sat at a desk looking at a computer game and imagined moving his right hand to hit the “fire” button on a virtual cannon. In another office across campus, a second researcher sat with his hand poised above a keyboard, not looking at his own computer screen. At the moment that the first researcher imagined moving his hand, the second researcher’s finger moved involuntarily, hitting the space bar. One man’s mind moved another man’s body.


The mechanism behind the feat is less magical than you might imagine. As explained in the University of Washington press release, the first researcher, Rajesh Rao, wore an electroencephalography (EEG) cap, which detects electrical activity in the brain. This was hooked up via the Internet to a transcranial magnetic stimulation (TMS) device that was placed on the head of the second researcher, Andrea Stocco. The magnetic coil, designed to stimulate activity in a given part of the brain, was positioned directly above Stocco’s motor cortex. When Rao imagined moving his hand, that triggered the magnetic stimulation of Stocco’s brain, and his finger moved. Stocco compared the feeling to that of a nervous tic.


This is the latest “first” in a field that has been brimming with them. Researchers have been working for decades on ways to read people’s brain signals, with varying success. The most impressive results so far have come from experiments in which electrodes are surgically implanted in the subject’s brain. But most people don’t want brain surgery, which is why the experiments tend to use monkeys or rats. The University of Washington experiment may be the first in which one human’s brain signals triggered another human’s physical response using only non-invasive technologies, like the EEG cap and the TMS coil. 

That’s a significant step. But comparing this to “mind control” obscures a very important limitation of the technology: It can’t actually read anyone’s thoughts, let alone control them. Far from reading people’s minds, EEG caps so far can only crudely detect the general area of the brain in which electrical activity is occurring. Likewise, TMS coils can stimulate activity in a particular area of the brain, but they can’t specify what type of activity it should be. A burst of stimulation was apparently sufficient to make Rocco’s finger move, but if that finger weren’t already poised over the space bar, there’s no way TMS could guide it there. And the setup can’t provide any feedback about Rocco’s brain to Rao’s, so Rocco had no direct way of knowing whether his thoughts actually had any effect. As Rao said in a statement: “This was basically a one-way flow of information from my brain to his. The next step is having a more equitable two-way conversation directly between the two brains.”

Yes, that is the next step—in theory. In practice, given the current limitations of non-invasive brain-reading technology, that next step is a doozy.

Future Tense is a partnership of SlateNew America, and Arizona State University.

Will Oremus is Slate's senior technology writer.



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