The study raises the controversial question of whether humans actually have free will.
Dr. John-Dylan Haynes led the project at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, in collaboration with the Charité University Hospital and the Bernstein Center for Computational Neuroscience in Berlin.
He told The Local that philosophers, psychologists, legal experts and brain scientists have already shown interest in the "striking finding" of the study, which was written in conjunction with his colleagues Chun Siong Soon, Marcel Brass and Hans-Jochen Heinze and published online by Nature Neuroscience on Sunday.
"The results change the way we think about human decision making because it shows that the brain prepares decisions over longer periods than previously thought possible," Haynes told The Local on Monday. "There is a cascade of unconscious processing steps and only at the end do we reach awareness. By the time we have the feeling that we're making up our mind, the decision has already been made, so there's not much space for the will there."
The six-month study used sophisticated computer programs trained to measure typical brain activity patterns scanned before participants freely decided whether to push a button with their right or left hand. Researchers found they could use these brain signals to predict a subject's decision some seven seconds before he or she consciously made the decision.
Haynes told The Local that there are many real-world applications for the study results, including the possible development of brain-computer interface technology for things like prostheses that predict the user's will of movement.
Other potential applications tread on delicate ethical ground in the legal, forensics and criminology fields, Haynes said. "Here you're in the realm of thought crime," he explained. "Predicting crime before it happens, like in the film 'Minority Report,' raises questions of whether the methodology is right."
The 2002 Tom Cruise film portrays a future in which a flawed criminal justice system predicts and punishes potential perpetrators before they commit an offence.
Because Haynes says the results of the study do not rule out free will, he is interested in pursuing further studies to determine the degree to which a decision is reversible once it has been made. "This is ultimately what it means if you want to rule out free will," he said.
The study, "Unconscious determinants of free decisions in the human brain," cites the 20-year-old findings of American brain scientist Benjamin Libet, who discovered a brain signal he called the "readiness-potential," that occurs just a moment before before conscious decision. Libet's findings rekindled the centuries-old debate over the possibility of free will, which many scientists said believe is illusory if the brain makes choices without the awareness of the conscious mind.
Haynes' study could work to disprove human free will, but he doesn't think that a scientific exclusion of the concept would change everyday life. "I think people cling to the idea," he said. "It might change the way people think about themselves, though."
As to whether such a revelation would change religious beliefs about the human ability to choose between right and wrong, Haynes said: "Religious people don't generally think about their beliefs differently, they just hate the scientists."