Whether or not we have free will is a question philosophers have been debating for millennia. In the early 1980s, there was a brief moment when it appeared the debate may finally have been settled.
The potential solution came not from philosophy, but neuroscience.
The answer, somewhat depressingly, was that free will didn’t exist. Experiments carried out by the neuroscientist Benjamin Libet appeared to show decisions being made in the brain before people were even aware of them.
It was as if science had finally revealed the strings of the puppet master controlling our thoughts and actions.
To even casual observers of the history of inquiries into free will, this pronouncement felt premature. Thankfully, they were right.
Scientists today are much more sceptical not only of the idea that free will doesn’t exist, but also of the notion that brain scans will ever definitively prove or disprove its existence. But why?
How you make a decision
Ultimately, the question of free will may be best left to philosophers, but that doesn’t mean it’s a topic neuroscientists should ignore.
Experiments into how the human brain makes decisions have led to important insights into neurology and psychology, and have expanded our understanding of the brain’s inner workings.
Those experiments include the ones Libet conducted in the 1980s, which, although viewed in a more critical light now, paved the way for decades of innovative research.
The experiments were simple. Libet attached volunteers to an electroencephalogram (EEG) machine to monitor their brain activity, then placed a button in front of them and asked them to decide when they wanted to press it.
While they were deciding, they had to watch a timer, consisting of a dot moving around the inside of a circle (like a second hand on a clock). Each volunteer had to note the dot’s position when they decided to press the button.
With the EEGs, Libet was looking for something called a readiness potential, a build-up of activity in the brain’s motor cortex that precedes a muscle movement.
He was hoping to see how a volunteer’s awareness of their decision to move (their noting of the dot’s position) lined up with their readiness potential.
The distinct pattern of readiness potentials turned up in the volunteers’ EEGs around 200 milliseconds earlier than their decisions to press the button. In other words, their brains were preparing to press, before they were aware of having decided to press.
The interpretation was that “unconscious processes precede and determine our intentional actions,” says Prof Marcel Brass, a cognitive neuroscientist at the Humboldt-Universität zu Berlin.
“In principle, people have taken that as evidence that we don’t have free will, or at least not conscious free will.”
It’s an existentially bracing finding, if true. But, as Brass notes, subsequent researchers have critiqued both Libet’s methodology and conclusions.
For example, the study relies on volunteers’ judgment of when they made a decision – hardly a sure thing. The experiment also looked at very simple, almost instinctual decisions. Would it hold for more complex decisions, like deciding whether to take a new job, or to get married?
Other scientists have argued that, while Libet found a signal of the brain preparing to act, those preparations could still be overridden.
Indeed, later experiments suggested that it might be possible – people could countermand the actions indicated by the readiness potentials (although further experiments indicate there may not actually be enough time to do so).
Brass believes that what Libet saw wasn’t the brain beginning to carry out an action, but rather the brain formulating a decision about what to do.
“People accumulate evidence for a specific decision and then, when this hits a threshold, they make the decision,” he says. “That means the brain activity reflects the decision process, but it’s not deterministic.”
More recent work looking at what’s called lateralised readiness potentials, which compare both hemispheres of the brain, bears this theory out.
When participants are asked to make a simple yes or no choice, researchers see activity predicting both ‘yes’ and ‘no’, building on separate sides of the brain. When activity on one side crosses a threshold, the brain makes a choice.
Experiments like this have convinced Brass that neuroscience has yet to disprove the concept of free will. It’s also just common sense, he says.
“If there [were a] process in our brains that determines what we’re going to do, we would be extremely inflexible,” Brass says. “In principle, we must be able to redesign or change our course of action on a relatively short-term basis.”
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A counterpoint
Not everyone agrees that free will exists. Speaking on the BBC Science Focus podcast, Prof Robert Sapolsky, a primatologist and neuroscientist from Stanford University, in the US, argues that our conscious experience of free will is an illusion created by our minds.
“It comes down to the fact that all we are is biology, over which we have no control, interacting with the environment, over which we have no control. There’s nothing else there,” he says.
It’s an argument grounded in the determinism of physics, where actions follow clearly defined laws: molecules don’t decide whether to react or not; objects don’t decide whether to obey the law of gravity.
If our biology comes down to nothing more than chemistry and physics, we may also be bound to the laws that govern them.
Even complex decisions stem from the same neural circuitry, Sapolsky argues, meaning that your decision to move to London next year, or to take up pickleball, stems from the same deterministic circuitry that governs your decision to move your hand away from a hot stove.
Still, others believe that locating the (non-)existence of free will in our biology may not be fully accurate. While it’s a contentious theory, some scientists believe free will may emanate from a far smaller scale: the quantum realm.
According to quantum theory, particles can be held in a superposition of two states, which eventually resolves to one or the other (fascinatingly, this often happens as soon as someone tries to measure them). This process is often held to be random, meaning it can’t be predetermined.
Some researchers are exploring the ways that quantum interactions are at work in our brains, where they could influence how neurons function.
Though it’s far from certain, it could be that random quantum fluctuations play a role in shaping our decisions, lending an element of indeterminacy and, hence, perhaps free will, to our actions.
Dr Danko Georgiev, a biochemist at Bulgaria’s Medical University of Varna, has even gone so far as to calculate the amount of free will derived from random quantum fluctuations in our brains’ cortical synapses: 0.934 bits of free will per synapse each time a neuron fires.
Sapolsky doesn’t buy the quantum argument, saying he believes it’s only relevant on scales too small to influence biology. What’s more, he argues it’s wrong to confuse randomness with free will.
If your decisions come down to the random fluctuations of atoms, they wouldn’t be your decisions at all, but rather statistical noise.
Yet, Sapolsky doesn’t believe in a predetermined Universe, either. Even if you do believe that our decisions can be reduced to the deterministic laws of physics, it’s not a reason to think that the entire future is known.
Sapolsky says that random events still happen all the time; it’s our reactions to them that are predetermined by the way our brains are wired.
Leave it to the philosophers
As the biological study of decision making has progressed, it’s led many scientists to ask if neuroscience is the right tool to answer the question of free will.
While researchers have made great strides in examining what it looks like to hold intentions, make decisions and initiate actions on a neurological level, it hasn’t done so in a way that has any bearing on the concept of freedom, argues neuroscientist and philosopher Prof Adina Roskies of the University of California, Santa Barbara.
“None of those is directly investigating the question of freedom itself, which I think needs to be philosophically addressed before you understand even what would constitute freedom,” she says.
What, indeed, would ‘freedom’ look like in the brain? Roskies thinks scientists may never agree – definitive definitions of freedom are slippery and may vary from one person to the next.
For her part, Roskies offers a philosophically rigorous version:
“Do the things that we do happen in such a way that we think that we’re the authors of our actions, or in such a way that we’re controlled, constrained or determined in ways that [make it impossible to consider] those actions to be freely willed?”
It’s a definition likely to give most people a headache, but it points to the philosophical depth of the question.
That disconnect between popular conceptions of free will and its complex reality has muddied the debate about free will in the past, Roskies says.
“I often think that when [neuroscientists] make proclamations about how their data bears on the problem of free will, they do it without really understanding the philosophical landscape,” she says.
Today, she says, most neuroscientists frame their work more narrowly, focusing on things like volition and decision making – things important to our understanding of free will, but which have a basis in the real world.
For Roskies, the science points toward the existence of a spectrum of free will, which varies depending on the person and context.
“My view of free will is that it’s dependent on having a constellation of capacities to do things and that some things may have more capacities than others and maybe some people have more capacities than others,” she says.
Some experiments align with this thinking, such as a 2019 study by researchers in the US and Israel that looked at more complex decisions.
Participants were asked to make two decisions involving donations to nonprofit groups.
In the first, they could decide which of two nonprofits to donate $1,000 to, while in the second they were told that each nonprofit would get $500 no matter which button they pressed.
The researchers found a readiness potential only for the second group, where there was no real decision to be made. In the first group, asked to decide where their donation went, it was absent.
The authors say it’s a rebuttal of the notion that the readiness potential underlies all of our actions, and evidence that cognitive state affects how decisions play out in our brains.
For decisions that involve deeper considerations, like those of morality or worthiness, our thinking processes, and perhaps also our freedom to choose, may look different.
In another version of this type of button-pressing experiment, Brass and his colleagues found they could predict which button a participant would press a full ten seconds before they made the decision. But their predictions weren’t perfect, Brass points out, barely beating random guesses.
“You can’t deterministically predict what people are going to do until very close to their decision,” he says.
Though science hasn’t been able to give us a definitive answer about the existence of free will, these kinds of experiments are still valuable.
Not only do they reveal how the brain works as it mulls decisions, but research into the factors guiding our decisions has important ramifications for the justice system, where juries are asked to decide how culpable a defendant is for a crime.
Understanding what capacities are necessary to will an action freely, and how those capacities can be undermined by damage or dysfunction, could change how we think about crime and punishment, Roskies says.
So if neuroscience can’t definitively say we’re not free, perhaps the question we should be asking is just how free can any of us think we really could be?
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