A study has revealed that the brain makes decisions about 10 seconds prior to a person realises it.
Experts involved in the study said that looking at brain activity while making a decision, they could predict the choices the subjects would make, before they realised that they had made a decision.
Lead researcher John-Dylan Haynes, a neuroscientist at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, said that the new findings called into question the "consciousness" of decisions that people make, and might even challenge ideas as to how "free" people are to make a choice at a particular moment.
"We think our decisions are conscious, but these data show that consciousness is just the tip of the iceberg," Nature magazine quoted him as saying.
Terming the results "quite dramatic", Frank Tong of Vanderbilt University in Nashville, Tennessee, said that 10 seconds is "a lifetime" in terms of brain activity.
During the study, the brains of 14 volunteers were imaged as they performed a decision-making task.
The subjects had two buttons before them, each to be operated by a different hand, which they could press when they felt the urge to. They were simultaneously shown a stream of letters, which appeared on a screen at half-second intervals.
The volunteers had to remember which letter was showing when they decided to press their button.
Upon analysis of the data, the researchers realised that the earliest signal they could catch started seven seconds before the volunteers reported having made their decision.
Given the delay of a few seconds in the imaging, they reckoned that the brain activity could have begun about ten seconds before the conscious decision.
The researchers revealed that the signals were picked up from a region called the frontopolar cortex, which is located at the front of the brain, immediately behind the forehead.
While writing about the observations made during the research in his study report, Haynes said that the frontopolar cortex might be the brain region where decisions are initiated.
He also revealed that the next step in the research would be to speed up the data analysis so as to enable his team to predict people's choices as their brains would make them.