Brain game demonstrates telepathic link based on nerve impulses
A question-and-answer game has been conducted by sending brain signals over the internet between two players a mile apart.
The study is thought to be the first to demonstrate a telepathic link based on nerve impulses, allowing one person to guess what is on another's mind.
For the experiment, one participant (the respondent) wears an electrode cap recording brain activity while being shown an object on a computer screen, for instance a picture of a dog.
A second player (the inquirer) has a list of possible objects and associated questions, and sends a series of questions to the respondent by clicking a mouse.
The respondent replies "yes" or "no" to each question by focusing on one of two LED lights flashing at different frequencies.
Both answers send a signal over the internet that activates a neuron-stimulating coil behind the inquirer's head. But only a "yes" signal is intense enough to trigger what appears to be a flash of light behind the eyes.
The flash, or "phosphene", caused by a brief disruption in the brain's visual cortex, tells the inquirer the answer is "yes".
By noting the answers to the questions, the inquirer eventually identifies the object.
Lead scientist Dr Andrea Stocco, from the University of Washington's Institute for Learning & Brain Sciences in the US, said: "This is the most complex brain-to-brain experiment, I think, that's been done to date in humans.
" It uses conscious experiences through signals that are experienced visually and it requires two people to collaborate."
The study was carried out in dark rooms in two university laboratories located almost a mile apart and involved five pairs of volunteers who played 20 rounds of the game.
Steps were taken to ensure participants did not cheat and had to complete the game using direct brain communication.
Inquirers wore earplugs so they could not hear the different sounds produced by the magnetic coil when transmitting a "yes" or "no" signal.
Players were able to guess the correct object 72% of the time. Incorrect guesses were caused by several factors, including uncertainty about whether a phosphene had appeared.
"While the flashing lights are signals that we're putting into the brain, those parts of the brain are doing a million other things at any given time too," said co-author Dr Chantel Prat, also from the University of Washington.
The brain game is described in the online journal Public Library of Science ONE.