Can brain science explain free will? Credit: © Images.com/Corbis
Friday, September 21, 2007

Seeking Free Will in Our Brains: A Debate

By: Mark Hallett, and Paul R. McHughM.D.

Two senior scientists, a neurologist and a psychiatrist, debate the meaning of free will and whether brain science can, now or ever, fully explain it.

Our freedom to choose, to make good or bad decisions about everything from which dessert to select to whether to save a life or commit a crime, seems part of our basic human nature. Long the province of philosophers and theologians, recently free will has become a question that fascinates neuroscientists. Looking for its basis in the brain has led some to argue that free will is only an illusion—a perception not congruent with the unconscious biochemical processes that they see as leading to thought and action. Two senior scientists, a neurologist and a psychiatrist, debate the meaning of free will and whether brain science can, now or ever, fully explain it. Each scientist first wrote a position statement; they then exchanged statements to write rejoinders.

 

Free Will: An Illusory Driver of Behavior

Mark Hallett’s opening statement

My position is that free will is only a perception—our interpretation of how we experience our actions in the world. No evidence can be found for the common view that it is a function of our brains that causes behavior.  I will make my argument based on research about making “voluntary” movements for two reasons.  First, I am a neurologist, specifically a motor physiologist.  Second, movements are easily measured.  While other, more complex decisions, such as what I choose for dinner, also can be viewed as influenced by free will, I suspect that they will turn out to be analogous to movement. Anyway, such decisions often eventually manifest in movement of some kind, perhaps reaching for the cookbook or a take-out menu.

I do not doubt that I feel strongly that I have freedom of choice.  And I suspect most humans have the same feeling as I do, even though I can’t assess this directly.  But, of course, this feeling of free will is the case only when I think about it, since most of the time I just go about my business, more or less on automatic pilot.  My feeling that I have free will is a subjective perception, an element of my consciousness that philosophers call a “quale.”  We do not understand The answers to these questions are easy only for the dualist, who believes in a mind separate from the brain and who thinks that free will comes from the mind.  No evidence for this position can be found, however, and therefore most scientists reject it. the biological nature of consciousness or how awareness is generated, so it is difficult to understand the physiology of any quale, including the perception of free choice.  But we do know that our sense of the world is a product of our brain and that a one-to-one match between reality and that interpretation does not exist.  Our introspection, our sense of what our brain is doing—while clearly useful to us and also valuable as an object of study—can be deceptive.

Looking for Free Will in the Brain

We are constantly making movements.  While we certainly think we choose them freely, do we really? What would it mean if we did?  The physiology of movement has been the object of intense study by scientists, and we now know the drivers of movement.  These drivers include sensory input from the external world, our emotions, our biological drive for homeostasis—for balance of our physiological systems—and our past experience, including rewards and punishments that resulted from previous actions.  Do these fully determine our choice or can we identify another factor, which we call free will? 

The answers to these questions are easy only for the dualist, who believes in a mind separate from the brain and who thinks that free will comes from the mind.  No evidence for this position can be found, however, and therefore most scientists reject it.  The mind (consciousness) is a product of the brain, so if free will can be a driver of movement, we have to be able to find it in the brain.  All the tools of modern neuroscience provide ways of studying this question.

Looking for free will in the brain not only is interesting for its own sake, but it is also important for understanding a number of neurological and psychiatric conditions.1  We can observe in patients with certain disorders that a relationship between movement genesis and a sense of volition is not mandatory.  For example, people with Tourette syndrome often say that they cannot not act out their tics. With psychogenic movement disorders—also called conversion disorders or the old term, hysteria—the movements look voluntary, but patients say they are involuntary.  In schizophrenia, movements also may look normal, but patients might say that these movements are controlled by external agents.  In early Huntington’s disease, the apparently involuntary chorea (rapid jerky movement) is sometimes interpreted as being voluntary. And in anosognosia (a condition in which a person who suffers disability due to brain injury seems unaware of an impairment), patients may think that they have made a movement when they have not. 

Do We Freely Choose to Move?

In general, scientists need to study what we call “simplified preparations” in which it is possible to control all the variables in a situation.  One such experimental situation is making a single movement of the hand or finger.  People can be asked to move whenever they want to; the commonsense view is that a person consciously decides to make a movement and then makes it.  Free choice has preceded the movement. 

This was put to the test first in the classic experiments in the 1970s by Benjamin Libet, Ph.D., and colleagues at the University of California, San Francisco.2  In these experiments, study participants sat in front of a clock-like timer, with a ball moving around the periphery once every 3 seconds. They were told to perform a simple motor task, such as flexing a finger or wrist, whenever they wanted to and, afterwards, tell the investigator where the ball was (that is, what time it was) when they decided to move.  An electroencephalogram (EEG) recorded their brain activity, while electromyography (EMG) recorded the electrical activity of their muscles. 

What Libet learned was that participants in the study had the first conscious sense of willing the movement (called “time W”) about 300 milliseconds before the onset of muscle activity (as measured by the EMG).  But the EEG Consciousness can be deceptive, so is it possible that our sense of willing a movement is incorrect in regard to when it actually happened in the brain?  showed brain activity in the motor cortex beginning about 1,000 milliseconds before movement could be measured—in other words, earlier than conscious awareness of the intention to move. This early brain activity measured by the EEG probably takes place in the supplementary motor area and premotor cortex in preparation for initiating  movement.  This experimental result, which has been duplicated many times, appears to indicate that the movement begins unconsciously. This does not jibe with our ordinary sense of how we operate.

Can the data from the Libet experiment be interpreted in other ways?  Libet himself argued that we still have free choice, but it is confined to the ability to veto actually making a movement after the intention to move becomes conscious.  This is not a strong argument, however, since the veto could also be initiated subconsciously long before the act. 

Another whole set of issues revolves around the problem of the timing of subjective events.  Consciousness can be deceptive, so is it possible that our sense of W, of willing a movement, is incorrect in regard to when it actually happened in the brain?  A number of experiments have explored this.  The results show that, first, W is not strongly linked to the time of movement onset, so whatever is going on in the brain at time W cannot be responsible for movement genesis.1  Moreover, the brain event of W may even be later than we subjectively report.  This should not be a complete surprise since humans “live in the past”—certainly perception of a real-world event has to be subsequent to its actual occurrence, since it takes time (albeit very little time) for the brain to process sensory information about the event.  A recent experiment showed that it was possible to manipulate the conscious awareness of willing a movement by delivering a transcranial magnetic stimulus to the area of the brain just in front of the supplementary motor area after the movement had already occurred.3  This suggests that the brain events of W may occur even after the movement. 

If free will does not generate movement, what does?  Movement generation seems to come largely from the primary motor cortex, and its input comes primarily from premotor cortices, parts of the frontal lobe just in front of the primary motor cortex.   The premotor cortices receive input from most of the brain, especially the sensory cortices (which process information from our senses), limbic cortices (the emotional part of the brain), and the prefrontal cortex (which handles many cognitive processes).  If the inputs from various neurons “compete,” eventually one input wins, leading to a final behavior.  For example, take the case of saccadic eye movements, quick target-directed eye movements.  Adding even a small amount of electrical stimulation in different small brain areas can lead to a monkey's making eye movements in a different direction than might have been expected on the basis of simultaneous visual cues.4  In general, the more we know about the various influences on the motor cortex, the better we can predict what a person will do. 

In humans, various areas of the frontal cortex appear to be more active when movements are made with free choice as opposed to being triggered by sensory stimuli.  A number of experiments have used neuroimaging to evaluate movements made at freely chosen times, as opposed to times indicated by sensory stimuli (for example, a sound or light).  Other experiments have compared movements chosen freely from a menu, contrasted with a specifically instructed movement.  These areas of the frontal cortex need more study, but their operation does not seem different in principle from that of the primary motor cortex.

From Movement to Thinking to Consciousness 

The initiation of simple movement appears to be good for experimental analysis of free will. As I have described, we can understand the physiology of this process without invoking unknown forces, and our sense of volition is deceptively I expect that what happens in our brain when we initiate and process a thought will likely be similar to what happens with a movement.  And, up to now, no experiment involving “free will” has identified a factor other than the routine operation of different parts of the brain. placed by our consciousness just before the movement occurs.  This certainly gives rise to the feeling that we are freely choosing to move.  But could this experimental paradigm be misleading? 

Some have argued that this situation is artificial, that everything is really controlled by the experimenter, and that the free choice occurs earlier.  So could it be that while the proximate initiation of movement is actually unconscious, the real free will can be found earlier?  Could it be manifest in the thinking that we do before getting to the movement situation?  For example, we decide, when sitting at the dinner table, that we want to eat rather than talk, and thus our hand “automatically” brings the fork to our mouth. 

We don’t know much about thinking, so more research is needed. But thinking will likely not be much different in principle from moving. That is to say, I expect that what happens in our brain when we initiate and process a thought will likely be similar to what happens with a movement.  And, up to now, no experiment involving “free will” has identified a factor other than the routine operation of different parts of the brain. 

A more detailed understanding of free will is stymied by our not understanding consciousness.  Consciousness is called the “hard problem” by philosophers; it is so difficult that we do not even have a full vocabulary with which to talk about it.  The best we can say now is that consciousness is awareness, and this awareness appears to be composed largely of perceptions and “qualia.” Only if further research shows that free will is also a force that drives behavior can it actually be what we all naively think it is.   While scientists must remain open-minded, since we have no evidence for a force of free will at the present time, I must take the position that free will exists only as a perception.

 

Endorsing the Obvious

Paul R. McHugh’s opening statement

The editors of Cerebrum invited me to consider a philosophical issue—specifically that feature of the human psyche to which the expression “free will” is attached. I took them to mean that sense of responsibility felt during active choices and decisions by people aware of how, through these actions, they affect themselves and their world. The editors asked whether this “felt experience” rests upon a realistic, authentic judgment or whether this feeling of freedom is an illusion or misconception of people who are unaware that hidden factors drive them towards one choice rather than another and so render “freedom” nugatory and inoperative.

When I say this is a philosophical issue, I mean free will is a problem philosophers like to debate. Ancient and modern philosophers (and not a few undergraduate amateurs) have offered opinions and provided reasons for affirming, denying, or qualifying the existence of freedom in the sense that we mean here. It remains a philosophical matter even though in the contemporary era neuroscientists and neuropsychologists have weighed in on the issue—mostly, and for me dishearteningly, tending to claim that free will is one of the many illusions about mental life that advancing science will put aside, much as science put paid to the “flat earth” and the “rising sun.” Hence this invitation to me to present an opinion on the issue. 

Why Ask a Psychiatrist?

Two questions occurred to me when deciding (freely, I presume) to accept the editors’ challenge.

First: the project seemed rhetorically backward. Should I be carrying the burden of proof here? The conscious mind and Neuroscientists challenging the concept of freedom may need more help than they realize, given the limited tools they have at hand. all the mental experiences tied to freedom of the will—choosing, deciding, hoping, deliberating, fearing, and cooperating with others—seem as self-evident as the five senses. No one asks us to prove them “real,” especially before hearing evidence that would claim they are not. Here, though, editors rule and authors follow.

Second: why ask a psychiatrist rather than a philosopher to tackle the issue? Neuroscientists challenging the concept of freedom may need more help than they realize, given the limited tools they have at hand. But, on reflection, perhaps psychiatric work may sit closer to that of neuroscientists and thus a psychiatrist may grasp their claims more sympathetically than a philosopher, even while offering evidence of a kind that, speaking to their experience, they would be less likely to ignore.

To this point, psychiatrists work with patients who fall into two great families, and the distinctions between those families do reveal matters relevant to the issue of free will. The first group encompasses all those patients whose mental difficulties derive directly from material causes (genes, infections, traumas, and so on) that change their brains. These are the patients with Alzheimer’s disease, Huntington’s disease, schizophrenia, and the like. In every respect, psychiatrists think about these patients in the same way neurologists think about patients with epilepsy, cardiologists about heart failure, gastroenterologists about peptic ulcer. They see the patients as object/organisms afflicted by some physical disruption of their bodies, brains, and minds. Their pathologies constrain their freedom of thought and action in ways that can be put right if and when that pathology is “cured.”

The other family of psychiatric patients encompasses those who provide “reasons” for their mental distress. They work under ill-fated assumptions that through “reasoning” lead them to regrettable goals. This family includes the anorexics, the dependent, and the demoralized. Although not denying that the brain is involved, their psychiatrists do not regard them as object/organisms afflicted by a pathological change in the brain but as subject/agents responding to the distressing differences between what they want and what life delivers. Their freedom is not lost but misused, and treatments customarily amount to a subtle (and occasionally not so subtle) conflict of wills between them and physicians who are striving to persuade and guide them to better ways of action by such methods as cognitive behavioral therapy. 

These latter patients provide the first challenge that psychiatrists offer to those who would hold free will to be an illusion. Come see these patients where choices are the problem and where they defend their choices with arguments that frustrate their recovery. Freedom they have in abundance; it’s wisdom they lack. 

From experiences with both sets of patients, I concluded that freedom of the will exists in just the way consciousness itself can exist—powerful or weak, present or absent. It is far from an illusion but a basic fact of human nature on which many other facts and judgments depend. 

Tying Mind to Brain

Certain philosophers and some of their neuroscience students reject this naturalistic defense of freedom by noting that it rests on descriptions of mental experiences. But, say they, brain material produces all mental phenomena, including consciousness and its expressions. These psychological “effects” emerge from the complex, mechanistic, causal apparatus that is the brain. Therefore, like all “effects” in nature, they must be lawfully determined by their “causes.” What people do—and believe they choose to do—is inexorably determined by brain conditions present and past. A new predestination is born, as all psychological freedom, sensed or supposed, is illusionary.

On hearing this argument (and some form of it is far from original or even contemporary, given that Spinoza argued in similar ways), I’m struck by how it is built on presumptions rather than on a body of fact or neuroscientific discovery. We have no grasp of any aspects of the elements underlying consciousness that can through their nature be tied to the anatomy or physiology of neurons, receptors, or brain systems. Much is correlated, particularly as brain imaging technology has grown, but nothing is explained. Its champions presume that eventually, given the steady progress that they anticipate, neuroscientists will know all about the brain and see how mental productions are like all other productions of the body. This argument dismisses as simply a matter of the moment our present vast ignorance of just how the brain relates to mental phenomena.

But compare the difference between what we know about the way the kidney produces urine and what we know of the brain’s role in producing conscious mental life. This exercise reveals that it’s not just our ignorance of facts that inhibits the latter account, it’s the lack of any conception of how mechanisms and products relate in it.

With urine, we have a clear grasp of how the anatomical construction and physiological actions within the nephron produce and permit a sequence of glomerular filtration of water from blood and selective reabsorbing of water and solutes in the tubule. We have an equally clear grasp of the physical characteristics of water as an ideal solvent, capable of carrying minerals and other substances through these mechanisms so as to clear the body of them. We even know, because of the work of Nobelist Peter Agre, the molecular structure and genetic construction of the aquapore in membranes that permits water to pass through them. What is mechanism, what is pathway, what is medium, and how they all interrelate for life’s benefit is clear.

We know nothing of a similar kind tying brain to mind or mind to brain. We have no idea of how neural systems—distributed, modular, and parallel as various ones are—can generate anything of a subjective nature such as any element of consciousness or consciousness itself. Likewise, we have no grasp of any aspects of the elements underlying consciousness that can through their nature be tied to the anatomy or physiology of neurons, receptors, or brain systems. Much is correlated, particularly as brain imaging technology has grown, but nothing is explained. And therefore hoping that what works in describing how organs like the kidney produce urine will work to explain the relation of brain to mind amounts to fantasy. It does epitomize the propensity of investigators to work happily away within the idiom of their successes, while ignoring issues that may demand reasoning with new idioms carrying new implications.

Scientists rightly claim that the brain is necessary for consciousness and that manipulations of the brain affect consciousness—witness anesthesia. But correlating brain events and conscious events does not explain consciousness and certainly not the vital, first-person (that is, “my”) experience of consciousness on which choice and freedom rest.  

As far as anyone can tell, mental “reasons” (and decisions from amongst them) are real aspects of nature brought into being by consciousness and, as claimed by their subjects, “free” in principle. I look for the time when neuroscientists will turn to explain how the material world can evoke these wonderful characteristics of human beings and will abandon any thought of them as illusionary.

For Freedom, Not Predestination                                        

The answers to the philosophical question of freedom lie in the subjective realm of human life, beyond contemporary Ultimately in a choice between freedom and predestination, I’m for freedom and the proposition it entails—that we’re responsible for making the world what it is. scientific capacities to explain or predict. Subjects are not the same as objects.  Reasons are not the same as physical causes. Freedom is an expression of reasoning by subjects who realize that their choices determine what they make of themselves and are ready to accept the responsibility for what they fashion. To think otherwise is to give oneself over to predestination. 

Ultimately in a choice between freedom and predestination, I’m for freedom and the proposition it entails—that we’re responsible for making the world what it is. Indeed, this proposition organizes and justifies the therapies that psychiatrists direct.

 All forms of predestination tend to disregard—and some practically disavow—the world of subjects. They shroud personal responsibility beneath foreordaining mechanisms, as Edmund in King Lear pointed out in his scornful but poetic rejection of astrology:

This is the excellent foppery of the world, that when we are sick in fortune, often the surfeits of our own behavior, we make guilty of our disasters the sun, the moon, and stars; as if we were villains on necessity; fools by heavenly compulsion; knaves, thieves, and treachers by spherical predominance; drunkards, liars, and adulterers by an enforced obedience of planetary influence; and all that we are evil in, by a divine thrusting on. An admirable evasion of whoremaster man, to lay his goatish disposition on the charge of a star.

   —King Lear I, ii, 128–139

I believe that we’ve hardly begun to grasp just what the existence of mind and freedom means. They certainly are products of the material world, but their existence tells us that material “stuff” counts in ways we’ve tended to ignore. There is a real presence of freedom in material, given that flesh and spirit exist together within the mystery of brain/mind. This is the deepest mystery of our kind. It is not to be denied. 

Rebuttal to Paul R. McHugh

Mark Hallett

Obvious. McHugh calls his understanding of free will “Endorsing the Obvious.”  It does seem “obvious” to me that the earth is flat and that the sun goes around the earth.  Yet I don’t believe these things.  We have sufficient scientific information that gives better explanations, and I believe those.  It is also “obvious” that something cannot be a particle and a wave at the same time, but—even though I can’t say that I understand it completely—I still believe that light can be so.   I agree that it is “obvious” that we have freedom of choice.  It is a common, if not completely universal, phenomenon, and I would even like it to be so.  However, all “obvious” facts need to have scientific examination to see if they are really true.

What can we say about the human “obvious meter”?  The human brain is very good, even incredible, at many things.  Yet it is subject to illusion.  The information from introspection is interesting and important, yet must be taken with a grain of salt.  So, if we want to understand the situation, if we want to verify our obvious impression, we need some objective information. 

McHugh challenges us with the anorexic patient.  He thinks such patients have all the freedom of choice that they need; they are just lacking in wisdom, making the wrong choices.  Psychiatrists tell them what to do, but the advice falls on The topic of free will is not solely a philosophical issue anymore.  It is possible to gather objective data about it.  Moreover, it is important to do so, because the consequences are moral, social, medical, and legal.  deaf ears.  If only they were smarter.  I do agree that the “talking cure” can be effective; ideas can certainly influence behavior.  However, in my view it is likely that anorexia is not solely a matter of misused freedom.  Taking the medical model of disease (that something is also the matter with their brains, similar to the schizophrenic) might also be helpful with these patients.

McHugh agrees that the mind is a product of the brain.  This is important, because, as I noted before, no basis for discussion can be found with anyone who believes that mind and brain are separate.  So, what is the consequence?  It seems clear that we need to study the brain to understand “mind” phenomena such as consciousness and free will. 

Are we ready to understand scientifically all the aspects of “free will”?  I am not so sure, and in this McHugh and I do agree.  We must confront a big barrier, the understanding of consciousness itself.  However, I believe that we can make a start on the issue of free will, and it may well be that such a start will be helpful in understanding consciousness as a whole.

Philosophers can be useful in the search for answers.  Indeed, we need all the help we can get from any serious line of investigation about the nature of the physical world.  Physicists, for another example, should also be helpful. The topic of free will is not solely a philosophical issue anymore.  It is possible to gather objective data about it.  Moreover, it is important to do so, because the consequences are moral, social, medical, and legal.  Let’s take our heads out of the sand, and be willing to accept the facts as they are exposed.  Even if it does not make for good poetry.  

Rebuttal to Mark Hallett

Paul R. McHugh

Neurologists and psychiatrists collaborate as specialists studying and treating human disorders arising from the brain. But like competitive siblings, they tend to vie for attention, particularly over who has the better—more scientific, enlightened, “grown-up”—approach to ultimate questions of human mind and nature. 

Both work with patients and thus may not know as much about the healthy mind as they think! But psychiatrists attending to the way patients behave ask “why?” whereas neurologists attending to the way patients move ask “how?”  These questions represent the “top-down” as against the “bottom-up” approach to the mind/brain mystery. Free will surfaces with deliberation, not impulse. And, by definition, deliberation lies in consciousness, where matters riding on a decision are grasped. The answers inform and enhance the study of human activity, but they bring about differing professional emphases and distinct clinical experiences that probably explain the differing notions on free will revealed in this friendly epistolary debate.

No psychiatrist, though, would think that the experiment of Benjamin Libet that Hallett mentions constitutes a test of human free will. That experiment—seen as a meritorious “simplified preparation” by Hallett—would seem to most of us psychiatrists as simpleminded in every sense of that term. It misses the point at issue by assuming that all “voluntary” motor actions deserve to be considered examples of free will. 

Hallett describes what the experimental subjects were told to do: They were to “flex a finger or wrist whenever they wanted to.” But this simply translates into “move when the impulse grabs you.” Given these instructions, surely no one should be surprised that neurophysiologic techniques can pick up traces of the emerging and unopposed impulse before it strikes the subjects’ consciousness. What else would one expect when studying a capricious act with neither consequence nor significance to the actor?

Free will surfaces with deliberation, not impulse. And, by definition, deliberation lies in consciousness, where matters riding on a decision are grasped. The experience of deliberation is a perception (as Hallett notes), but it’s a complex perception of implications tied to choices and responsibility.

Bottom-up neuroscientists find consciousness a “hard problem,” as my colleague also notes. But nonetheless, consciousness is where the action is with free will. What to identify as a function of consciousness divides us in this debate.

I, thinking “top down,” hold that with consciousness nature brings freedom into animal life.  And nature has done so progressively and evolutionarily. Individuals survive and flourish when they can pull together a presenting situation and past experience under the light of consciousness before deciding what to do.

Humans carry this natural freedom beyond issues of individual survival. Human reflections and the choices they engender encompass judgments that sustain communities—deliberating as humans and no other creatures do on matters of right and wrong, good and bad, “me” and “not-me.” From these perceptions and the actions they evoke, personal integrity, cultural reliability, and truth that matters grow exponentially.

Percy Bysshe Shelley asserted, correctly I believe, that “poets are the unacknowledged legislators of the world.” Poets can play that role because they are the most conscious of our kind, and, as the ultimate top-down thinkers, they identify how the freedom embedded in our consciousness transforms us, gives dignity to our fellow man, and charges us with responsibilities to choose the better courses of action in our lives.

In deliberating over what we can notice and how we should respond, poets exhibit more open-mindedness than many neuroscientists. These latter folk, laboring under a metaphysical obsession with dualism that hampers their bottom-up reasoning, can miss—or, as here, dismiss—what we all know about our mental experience and its yield. Indeed, neuroscientists sometimes take up positions, strike postures, and tout experiments that sell us humans short—all of us, themselves included.  

 

References

1. Hallett M. Volitional control of movement: The physiology of free will. Clinical Neurophysiology 2007;118:1179–1192.

2. Libet B, Gleason CA, Wright EW, Pearl DK. Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain 1983;106:623–642.

3. Lau HC, Rogers RD, Passingham RE. Manipulating the experienced onset of intention after action execution. Journal of Cognitive Neuroscience 2007;19:81–90.

4. Cohen MR, Newsome WT. What electrical microstimulation has revealed about the neural basis of cognition. Current Opinion in Neurobiology  2004;14:169–177.



About Cerebrum

 
Bill Glovin, editor
Carolyn Asbury, Ph.D., consultant

Scientific Advisory Board
Joseph T. Coyle, M.D., Harvard Medical School
Kay Redfield Jamison, Ph.D., The Johns Hopkins University School of Medicine
Pierre J. Magistretti, M.D., Ph.D., University of Lausanne Medical School and Hospital
Robert Malenka, M.D., Ph.D., Stanford University School of Medicine
Bruce S. McEwen, Ph.D., The Rockefeller University
Donald Price, M.D., The Johns Hopkins University School of Medicine

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