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Two humans link their brains to play 20 Questions

A noninvasive brain-to-brain interface successfully let two people in separate locations share thoughts.

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Michelle Starr Science editor
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
3 min read

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University of Washington graduate student Jose Ceballos wearing the EEG cap to transmit answers. University of Washington

If you could eschew the telephone, and instead wear a cap that allowed you to share your thoughts with someone else, very far away, would you? It may be a moot point now, but there may come a time in the not-too-distant future when it isn't, largely due to the work of Andrea Stocco and his team at the University of Washington's Institute of Learning & Brain Sciences.

In this latest round of Stocco's research, two people were successfully able to transmit their thoughts to each other over the Internet, completing a game of questions-and-answers.

"This is the most complex brain-to-brain experiment that's been done to date in humans," Stocco said. "It uses conscious experiences through signals that are experienced visually, and it requires two people to collaborate."

As with previous experiments conducted by Stocco and his team, the experiment takes place between people in separate locations.

One person, the responder, was shown an image on a screen. The other participant, the inquirer, then sent yes or no questions by clicking on them with a mouse. The responder, wearing an EEG cap that monitors, captures and translates brain activity, answered by staring at one of two flashing LEDs attached to the monitor, which flashed at different frequencies.

These answers were captured, translated and sent via the Internet to the inquirer, where they were transmitted to the brain using transcranial magnetic stimulation via a magnetic coil positioned behind the head. By using TMS to stimulate the visual cortex, the inquirer was able to see a flash of light known as a phosphene for "yes" answers. For "no" answers, the inquirer sees nothing and is therefore able to proceed.

The experiment was conducted in two dark rooms almost a mile apart, with five pairs of study participants, each of whom played 20 rounds of the game: 10 real games and 10 control rounds. Each game consisted of eight objects, with three questions for each object that would solve the game if answered correctly. For the control games, an undetectable plastic spacer was placed between the magnetic coil and the inquirer's head to block the TMS.

Making sure to correct for any possible means of cheating, such as blocking the test subjects' hearing, and repositioning the magnetic coil for each round, the participants were able to successfully guess the correct object for 72 percent of the real games, compared with 18 percent of the control games.

There were several reasons for the incorrect guesses in the real games, the most likely of which was interpreting the phosphene as something not seen with the eyes, but the brain. Other errors could be chalked up to hardware problems, the responder focusing on both flashing lights rather than one, or the responder not knowing the answers.

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University of Washington postdoctoral student Caitlin Hudac seated in front of the TMS coil. University of Washington

With a $1 million grant awarded to the team last year, they have been able to broaden their research. Another area they are looking into is transmitting brain states, such as from an awake person to a sleepy one, or from a focused student to one who has ADHD.

"Imagine having someone with ADHD and a neurotypical student," said co-author Chantel Prat, a faculty member at the Institute for Learning & Brain Sciences and a UW associate professor of psychology. "When the non-ADHD student is paying attention, the ADHD student's brain gets put into a state of greater attention automatically."

This also feeds into the notion of "brain tutoring," which the team is also exploring. This could be simply transferring information from teacher to student, but it also could involve transferring signals from a healthy brain to one that is developmentally impaired, or affected by a stroke.

"Evolution has spent a colossal amount of time to find ways for us and other animals to take information out of our brains and communicate it to other animals in the forms of behavior, speech and so on. But it requires a translation. We can only communicate part of whatever our brain processes," Stocco said.

"What we are doing is kind of reversing the process a step at a time by opening up this box and taking signals from the brain and with minimal translation, putting them back in another person's brain."

The paper on this latest round of experiments can be found online, published this week in the journal PLOS One.