Imagine sitting in a chair, flexing your wrist at random. As far as you know, you decide to flex your wrist, and then you flex it. Decide, flex. Decide, flex.

But what if you found out that while you're sitting peacefully, not planning your next movement, your brain is ahead of the game? What if, in fact, our decisions are made in our subconscious before our conscious mind ever becomes aware of them?

Those are ideas raised by studies stretching back into the 1980s — studies that have led many in the neuroscience community to argue that free will is nothing but an illusion. Our actions, according to this line of thought, are determined mostly subconsciously. When we become conscious of our intentions, we can usually give a reasonable explanation for our choices, but that's all retrospective. There is no "ghost in the machine" swooping in to make decisions against our brain activity — how could there be, when we are the sum of our brain activity?

But don't sound the death knell for free will just yet. Despite tantalizing evidence that our brains are doing much more than we're aware of, free will may still exist. It just hasn't been proven yet.

Goodbye, free will?

The idea that we might need to prove something as self-evident as free will probably seems odd. As humans, we feel with certainty that we're making conscious choices about our day-to-day lives.

In fact, though, we can conduct a wide array of activities without consciousness at all.

"Most of what our brains do is unconscious," said Thalia Wheatley, a neuroscientist at Dartmouth University. "I'm not conscious about every word I'm about to say … I'm not conscious of the fact that I'm pacing around my kitchen right now and my feet aren't tripping."

But these are the activities we do with a brain on autopilot. What about the things we intentionally attend to and decisions we make explicitly? A series of experiments carried out in the 1980s by psychologist Benjamin Libet suggest that even our "conscious" choices may not be so conscious, after all. Libet asked subjects to watch a clock face with a spinning dial, and to occasionally, and randomly, flex a wrist (later experiments were also done with pushing a button and other similarly simple actions).

The participants were then told to gauge, as best they could, where the dial on the clock was pointing when they made the decision to move. All of this was done while the researchers monitored the electrical activity of the participants' brains with electroencephalography (EEG).

Typically, Libet found, people reported making the decision to move about 200 milliseconds before they actually did. Surprisingly, though, the electrical activity in the motor areas of the brain began ramping up about 550 milliseconds before the movement — some 350 milliseconds prior to the conscious decision to move.

"It was seen as like the brain version of determinism," said John-Dylan Haynes, a neuroscientist at the Bernstein Center for Computational Neuroscience in Berlin. "The brain prepares a decision for you, then when it comes to you making up your mind consciously, the dice have already been cast."

Predicting the future

In 2008, Haynes and his colleagues published a study that pushed back the throw of the dice even further. In this study, participants had their brains scanned by functional magnetic resonance imaging (fMRI) while they were given a choice between pushing a button with their left hand or a button with their right hand. The researchers wanted to know what sort of brain activity might be going on in areas beyond just the motor-planning regions studied in Libet's work.

The researchers found that two regions became more active (as measured by an uptick in blood flow to those areas) before a person became conscious of their button-pushing choice. One was Brodmann area 10, which is at the very front of the prefrontal cortex, behind the forehead, and is generally used in executive control. The other active region was part of the parietal cortex, in the upper middle region of the brain. The parietal cortex is involved with sensory integration.

Most striking of all, though, was when those regions became active: at least 7 seconds prior to making a conscious choice to move — a gap 20 times larger than the previously measured 350 milliseconds in the motor-planning regions. What's more, fMRI imaging includes a slight time delay, so that means the activity could have started as much as 10 seconds before the conscious decision point.

The researchers could even predict the choice of button the person would make with about 60 percent accuracy based on the brain activity alone — hardly a crystal ball, but better than pure chance.

The free will debates

These experiments don't bode well for free will, but don't go robbing a liquor store and blaming your subconscious just yet.

The implications of these studies are hotly contested. Many, like neuroscientist Sam Harris, believe that our choices are entirely opaque to us, driven by the complex interaction of our genes and environment, and thus out of our control. "You can do what you decide to do, but you cannot decide what you will decide to do," Harris writes in his book, "Free Will" (Free Press, 2012).

Wheatley, too, doubts that true free will could exist, given what we know about the brain.

"You are your neurons," she said. "There's nothing else up there. When you really think about the brain, the physical system, it becomes very difficult to think about where choice comes in, where free will comes in."

Even consciousness, Wheatley notes, doesn't guarantee free will. You can be conscious of a choice, but could you have truly made another decision, given the brain activity that led to that choice?

Others are not so convinced. No experiment done so far rules out free will, argues Alfred Mele, a philosopher at Florida State University and author of "Free: Why Science Hasn't Disproved Free Will" (Oxford University Press, 2014).

There are two ways to think about free will, Mele said. One is that if a person is sane, rational and uncoerced, and they can make a decision, then they have free will. This is the definition on which our court system is based.

"It's clear that most people, some of the time, do make such decisions, so they would have free will, according to this conception of it," Mele said.

The free will most neuroscientists are discussing is a bit more nuanced. The idea is that, given everything leading up to a conscious choice — external influences, brain activity, prior experiences — people can still make a different choice.

"It could all be shaped, and probabilities could be influenced by the environment and so on, but when you make your decision, there are different possible ways you could go," Mele said.

Even when measuring very trivial decisions with the most accurate technology (electrodes actually inserted into the brain, as part of treatment for severe epilepsy), researchers can only predict decisions based on brain activity about 80 percent of the time. It could be that the equipment isn't good enough to yield perfect predictions, Mele said. Or it could be that there is a certain amount of randomness present in the brain – randomness that represents free will.

It's clear that a decision process begins in the brain far before we're aware of it, Haynes said. But what isn't as clear is whether that process can be stopped, and thus it isn't clear that these experiments rule out free will.

"Can you interfere with this process at any point in time? What are your chances of stopping this process?" Haynes asked. He and his colleagues are in the process of submitting a paper to a peer-reviewed paper on just this subject.

"All I can say is that the data we have at the moment suggests that people can control this process all the way right until the end," Haynes said.

Why free will matters

Free will or not, we are built to assume agency over our actions. It's not surprising to feel a need to solve the mystery of whether something that feels so intertwined with our being is actually real. But all of this free will debate also matters because it turns out people behave very differently when they think they're not accountable for their behavior.

In 2008, psychologists Kathleen Vohs and Jonathan Schooler published a study in the journal Psychological Science in which they asked people to take a math test on a computer. Because of a computer glitch, the participants were told, the answers to the questions would appear onscreen unless they quickly pressed the space bar before each question. Prior to the test, some of the participants read articles telling them that science had disproven free will.

Those participants, primed to disbelieve free will, were more likely to cheat by not pressing the space bar. Similar studies showed other bad behavior. A 2009 study by Florida State University psychologist Roy Baumeister found that when people were told they had no free will, they became more aggressive towards others, giving them spicy hot sauce even after being told they disliked spicy food.

On the other hand, the belief that there is no free will can also make people less punitive and less likely to seek vengeance, according to a 2014 article published in the journal Psychological Science.

"When you confront people and say, 'Oh, you don't have free will,' they can act badly," Wheatley said. But that's not the whole story, she said. "They can also become more compassionate."

The next step for neuroscience, Wheatley said, should be to investigate ever-more complicated decisions. The criticism of work like Libet's and Haynes' tends along the lines of "so what?" she said, because the choices are so primitive. Haynes' recent work, she said, has been delving into more complex choices.

"These decisions are still no 'where to go to college' or 'who to marry,' but they're getting more interesting," she said.