Washington: In an experiment, researchers from University of Washington (UW) have used a direct brain-to-brain connection to enable participants play a question-and-answer game by transmitting signals from one brain to the other over the internet.
The experiment shows that two brains can be directly linked to allow one person to guess what's on another person's mind.
"This is the most complex brain-to-brain experiment that has been done in humans. It uses conscious experiences through signals that are experienced visually, and it requires two people to collaborate," said lead author Andrea Stocco, assistant professor of psychology at UW.
The experiment was carried out in dark rooms in two labs located almost a mile apart and involved five pairs of participants who played 20 rounds of the question-and-answer game.
Each game had eight objects and three questions that would solve the game if answered correctly.
The first participant, or "respondent", wears a cap connected to an electroencephalography (EEG) machine that records electrical brain activity.
The respondent is shown an object (for example, a dog) on a computer screen, and the second participant, or "inquirer", sees a list of possible objects and associated questions.
With the click of a mouse, the inquirer sends a question and the respondent answers "yes" or "no" by focusing on one of two flashing LED lights attached to the monitor, which flash at different frequencies.
A "no" or "yes" answer both send a signal to the inquirer via the internet and activate a magnetic coil positioned behind the inquirer's head.
But only a "yes" answer generates a response intense enough to stimulate the visual cortex and cause the inquirer to see a flash of light known as a "phosphene".
The phosphene -- which might look like a blob, waves or a thin line -- is created through a brief disruption in the visual field and tells the inquirer the answer is yes.
Through answers to these simple yes or no questions, the inquirer identifies the correct item.
The researchers took steps to ensure participants could not use clues other than direct brain communication to complete the game.
They wore earplugs so they could not hear the different sounds produced by the varying stimulation intensities of the "yes" and "no" responses.
"We took many steps to make sure that people were not cheating," Stocco added.
Participants were able to guess the correct object in 72 percent of the real games, compared with just 18 percent of the control rounds.
"They have to interpret something they are seeing with their brains. It is not something they have ever seen before," noted study co-author Chantel Prat from UW's Institute for Learning and Brain Sciences.
The team is also working on transmitting brain states like sending signals from an alert person to a sleepy one or from a focused student to one who has attention deficit hyperactivity disorder (ADHD).
"Imagine having someone with ADHD and a neurotypical student," Prat said. "When the non-ADHD student is paying attention, the ADHD student's brain gets put into a state of greater attention automatically."
The research was detailed in the journal PLOS ONE.