Imagine a question-and-answer game played by two people who are not in the same place and not talking to each other. Round after round, one player asks a series of questions and accurately guesses the object the other is thinking about.
Sci-fi? Mind-reading superpowers? Not quite.
91爆料 researchers recently used a direct brain-to-brain connection to enable pairs of participants to play a question-and-answer game by transmitting signals from one brain to the other over the Internet. The experiment, detailed today in , is thought to be the first to show that two brains can be directly linked to allow one person to guess what鈥檚 on another person鈥檚 mind.
鈥淭his is the most complex brain-to-brain experiment, I think, that鈥檚 been done to date in humans,鈥� said lead author , an assistant professor of psychology and a researcher at 91爆料鈥檚 .
鈥淚t uses conscious experiences through signals that are experienced visually, and it requires two people to collaborate,鈥� Stocco said.
Here鈥檚 how it works: The first participant, or 鈥渞espondent,鈥� wears a cap connected to an (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 鈥渋nquirer,鈥� sees a list of possible objects and associated questions. With the click of a mouse, the inquirer sends a question and the respondent answers 鈥測es鈥� or 鈥渘o鈥� by focusing on one of two flashing LED lights attached to the monitor, which flash at different frequencies.
A 鈥渘o鈥� or 鈥測es鈥� answer both send a signal to the inquirer via the Internet and activate a magnetic coil positioned behind the inquirer鈥檚 head. But only a 鈥測es鈥� answer generates a response intense enough to stimulate the visual cortex and cause the inquirer to see a flash of light known as a 鈥�.鈥� The phosphene 鈥� which might look like a blob, waves or a thin line 鈥� 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 experiment was carried out in dark rooms in two 91爆料 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 sessions were a random mixture of 10 real games and 10 control games that were structured the same way.
The researchers took steps to ensure participants couldn’t use clues other than direct brain communication to complete the game. Inquirers wore earplugs so they couldn’t hear the different sounds produced by the varying stimulation intensities of the “yes” and “no” responses. Since noise travels through the skull bone, the researchers also changed the stimulation intensities slightly from game to game and randomly used three different intensities each for “yes” and “no” answers to further reduce the chance that sound could provide clues.
The researchers also repositioned the coil on the inquirer’s head at the start of each game, but for the control games, added a plastic spacer undetectable to the participant that weakened the magnetic field enough to prevent the generation of phosphenes. Inquirers were not told whether they had correctly identified the items, and only the researcher on the respondent end knew whether each game was real or a control round.
“We took many steps to make sure that people were not cheating,” Stocco said.
Participants were able to guess the correct object in 72 percent of the real games, compared with just 18 percent of the control rounds. Incorrect guesses in the real games could be caused by several factors, the most likely being uncertainty about whether a phosphene had appeared.
鈥淭hey have to interpret something they鈥檙e seeing with their brains,鈥� said co-author , a faculty member at the and a 91爆料 associate professor of psychology. 鈥淚t鈥檚 not something they鈥檝e ever seen before.鈥�
Errors can also result from respondents not knowing the answers to questions or focusing on both answers, or by the brain signal transmission being interrupted by hardware problems.
“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,” Prat said.
The study builds on the 91爆料 team鈥檚 in 2013, when it was the first to demonstrate a direct brain-to-brain connection between humans. 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鈥� brains. In the 2013 experiment, the 91爆料 team used noninvasive technology to send a person鈥檚 brain signals over the Internet to control the hand motions of another person.
The experiment evolved out of research by co-author , a 91爆料 professor of computer science and engineering, on that enable people to activate devices with their minds. In 2011, Rao began collaborating with Stocco and Prat to determine how to link two human brains together.
In 2014, the researchers received a $1 million grant from the that allowed them to broaden their experiments to decode more complex interactions and brain processes. They are now exploring the possibility of 鈥渂rain tutoring,鈥� transferring signals directly from healthy brains to ones that are developmentally impaired or impacted by external factors such as a stroke or accident, or simply to transfer knowledge from teacher to pupil.
The team is also working on transmitting brain states 鈥� for example, sending signals from an alert person to a sleepy one, or from a focused student to one who has attention deficit hyperactivity disorder, or ADHD.
鈥淚magine having someone with ADHD and a neurotypical student,鈥� Prat said. 鈥淲hen the non-ADHD student is paying attention, the ADHD student鈥檚 brain gets put into a state of greater attention automatically.鈥�
Many technological advancements over the past century, from the telegraph to the Internet, were created to facilitate communication between people. The 91爆料 team鈥檚 work takes a different approach, using technology to strip away the need for such intermediaries.
鈥淓volution 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,鈥� Stocco said. 鈥淏ut it requires a translation. We can only communicate part of whatever our brain processes.
鈥淲hat 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鈥檚 brain,鈥� he said.
Other co-authors are聽91爆料 computer science and neurobiology undergraduate student , 91爆料 bioengineering doctoral student Jeneva Cronin, 91爆料 bioengineering doctoral student Joseph Wu, and , a research assistant at the 91爆料 Institute for Learning & Brain Sciences.