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You may think you decided to read this story -- but in fact, your brain made the decision long before you knew about it.
In a study published Sunday in Nature Neuroscience,
researchers using brain scanners could predict people's decisions seven
seconds before the test subjects were even aware of making them.
The decision studied -- whether to hit a button with one's left or
right hand -- may not be representative of complicated choices that are
more integrally tied to our sense of self-direction. Regardless, the
findings raise profound questions about the nature of self and
autonomy: How free is our will? Is conscious choice just an illusion?
"Your decisions are strongly prepared by brain activity. By the time
consciousness kicks in, most of the work has already been done," said
study co-author John-Dylan Haynes, a Max Planck Institute neuroscientist.
Haynes updated a classic experiment by the late Benjamin Libet,
who showed that a brain region involved in coordinating motor activity
fired a fraction of a second before test subjects chose to push a
button. Later studies supported Libet's theory that subconscious
activity preceded and determined conscious choice -- but none found
such a vast gap between a decision and the experience of making it as
Haynes' study has.
In the seven seconds before Haynes' test subjects chose to push a
button, activity shifted in their frontopolar cortex, a brain region
associated with high-level planning. Soon afterwards, activity moved to
the parietal cortex, a region of sensory integration. Haynes' team
monitored these shifting neural patterns using a functional MRI
machine.
Taken together, the patterns consistently predicted whether test
subjects eventually pushed a button with their left or right hand -- a
choice that, to them, felt like the outcome of conscious deliberation.
For those accustomed to thinking of themselves as having free will, the
implications are far more unsettling than learning about the
physiological basis of other brain functions.
Caveats remain, holding open the door for free will. For instance,
the experiment may not reflect the mental dynamics of other, more
complicated decisions.
"Real-life decisions -- am I going to buy this house or that one, take
this job or that -- aren't decisions that we can implement very well in
our brain scanners," said Haynes.
Also, the predictions were not completely accurate. Maybe free will
enters at the last moment, allowing a person to override an unpalatable
subconscious decision.
"We can't rule out that there's a free will that kicks in at this late
point," said Haynes, who intends to study this phenomenon next. "But I
don't think it's plausible."
That implausibility doesn't disturb Haynes.
"It's not like you're a machine. Your brain activity is the
physiological substance in which your personality and wishes and
desires operate," he said.
The unease people feel at the potential unreality of free will, said National Institutes of Health neuroscientist Mark Hallett, originates in a misconception of self as separate from the brain.
"That's the same notion as the mind being separate from the body -- and
I don't think anyone really believes that," said Hallett. "A different
way of thinking about it is that your consciousness is only aware of
some of the things your brain is doing."
Hallett doubts that free will exists as a separate, independent force.
"If it is, we haven't put our finger on it," he said. "But we're happy to keep looking."
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