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WASHINGTON, Sept. 23 (Xinhua) -- U.S. researchers have successfully performed a mindreading-like question-and-answer experiment via a direct brain-to-brain connection, with one player able to send brain signals over the Internet to allow a fellow player a mile away accurately guess what's he or she is thinking about.
"This is the most complex brain-to-brain experiment, I think, that's been done to date in humans," lead author Andrea Stocco, an assistant professor of psychology and a researcher at University of Washington's Institute for Learning & Brain Sciences, said in a statement.
The experiment, detailed Wednesday in the U.S. journal PLOS ONE, used conscious experiences through signals that are experienced visually and it required two people to collaborate.
One participant, or "respondent," wore a cap connected to an electroencephalography machine that records electrical brain activity, and was shown an object, for example, a dog, on a computer screen.
A second participant, or "inquirer," had a list of possible objects and associated questions, and sent a series of questions by clicking a mouse.
The respondent answered "yes" or "no" to each question by focusing on one of two flashing LED lights attached to the monitor, which flashed at different frequencies.
A "no" or "yes" answer both sent a signal to the inquirer via the Internet and activated a magnetic coil positioned behind the inquirer's head. But only a "yes" answer generated a response intense enough to stimulate the visual cortex and caused 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 -- was created through a brief disruption in the visual field and told the inquirer the answer was "yes." Through answers to these simple "yes" or "no" questions, the inquirer identified the correct item.
The experiment was carried out in dark rooms in two university 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 researchers took steps to ensure participants couldn't use clues other than direct brain communication to complete the game. For example, inquirers wore earplugs so they couldn't hear the different sounds produced by the varying stimulation intensities of the "yes" and "no" responses.
The results showed that participants were able to guess the correct object in 72 percent of the games.
Incorrect guesses in the games could be caused by several factors, the most likely being uncertainty about whether a phosphene had appeared, they said.
"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 Chantel Prat, also associate professor of psychology of the University of Washington.
In 2013, the same team performed what they believe is the first direct brain-to-brain connection between humans, during which they used noninvasive technology to send a person's brain signals over the Internet to control the hand motions of another person.
Other scientists have connected the brains of rats and monkeys, and transmitted brain signals from a human to a rat, using electrodes inserted into animals' brains.
