Researchers used a brain-to-brain interface they developed to allow pairs of participants to play a '20 question' style game by transmitting signals from one brain to another over the Internet. Their experiment is thought to be the first to demonstrate that two brains can be directly linked to allow someone to accurately guess what is on another person's mind.
Credit: University of Washington
"This is the most complex brain-to-brain experiment, I think, 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."
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 a it was transmitted to their brain using transcranial magnetic stimulation via a magnetic coil positioned behind their 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.
Image: Architecture of the BBI and “20 Questions” Experiment.
The researchers repeated the experiment over 20 rounds - 10 control games where the brain-to-brain link wasn't working and 10 proper rounds - and took strict precautions to make sure no one could cheat.
The participants were able to guess the objects correctly in 72 percent of the real rounds, compared to only 18 percent of the control rounds. And the team believes many of those incorrect guesses were caused by the inquirers not being able to recognise the phosphene, or visual hallucination, that signalled a 'yes' response.
The results have been published in PLOS ONE.