It's a lazy Sunday afternoon. Professor Freedman is enjoying the Southern California weather on Professor Domino's patio.
Domino: Will it be Coke or Pepsi, Dr. Freedman?
Freedman: That's an easy choice, Dr. Domino.
Freedman: Yes, but a lot of it's junk.
Domino: Really? Are you aware of the classic experiment carried out by Benjamin Libet and colleagues?
Freedman: Of course! Libet and colleagues designed an experiment to test whether human subjects had free will. Subjects were instructed to press a button whenever the urge took them. A rotating dial served as a clock so that each subject could note the exact time when he or she became conscious of the urge to push the button. While the subject participated in the experiment, EEG electrodes attached to the scalp measured electrical brain activity indicating preparation for movement preceding the subject's conscious decision to press the button by more than a third of a second.
Domino: And so, Dr. Freedman, do the results of this study show that the subjects had a choice? Or were the decisions predetermined by electrical brain activity?
Freedman: There are two problems with Dr. Libet's experiment. First, as the philosopher Alexander Batthyany has pointed out, the subjects were told to passively wait for an urge to press the button. Naturally, a subconscious urge might first manifest as electrical brain activity before rising to the level of conscious awareness. Secondly, as the philosopher and cognitive scientist Daniel Dennett has pointed out, between making the choice and noting the time on the clock dial, there's a shift from inwardly focused to outwardly focused attention. Because it takes time to reallocate neural resources for attention, the 350 millisecond gap can be easily explained.
Domino: Thank goodness we have philosophers watching over our shoulders! But have you considered the work by John-Dylan Haynes and colleagues? This group of researchers showed that metabolic brain activity measured with fMRI can predict which hand a subject will use to press a button several entire seconds before the choice is made!
Freedman: Pfft ... that's an exaggeration. The prediction accuracy of this study was only 60 percent, barely better than chance.
Domino: Still, more often than not, this choice was preordained by the brain activity of the individual up to seven seconds before he or she made the decision!
Freedman: Ok, fine. Just for the sake of argument, let's suppose the prediction accuracy was 100 percent. What else would be determining the subject's choice other than brain activity? I sure hope my brain is making my decisions! And who says that decisions are made instantaneously? It doesn't surprise me that a decision could occur over the course of several seconds.
Domino: Ah, but if you believe in free will, you believe that nothing outside of yourself is determining your decisions. And yet, science shows that your brain is a machine, subject to the laws of nature just like any other machine. Your neurons obey the laws of cause and effect—determinism—whereas they'd need to act in defiance of such laws if you truly had a will of your own.
Freedman: You've just argued that the outcomes of these experiments are irrelevant since free will is, according to you, impossible even in principle. Fine. But, I disagree that free will is incompatible with determinism. To me, free will is simply the idea that I am free to do as I want, regardless of whether my wants are, in turn, determined by something else.
Domino: That doesn't seem like free will to me. A robot programmed to endlessly perform some menial task might have free will in that sense.
Freedman: Well, no task is objectively menial. To an asexual alien from Mars, the task of copulating with beautiful women to produce offspring might appear menial! Let me quote the late science fiction writer Philip K. Dick: "Reality is that which when you stop believing in it, it doesn't go away." If free will is an illusion, it must go away when we stop believe in it. Ever heard of Huntington's disease, Dr. Domino?
Domino: Yes, it's a terrible disease.
Freedman: That's right. Huntington's disease is a neurodegenerative disorder in which individuals undergo involuntary, dance-like movements. And whether I believe in free will or not, I still have a sort of free will that an individual with Huntington's disease does not have.
Domino: Ah, but a patient with Huntington's disease undergoes more than simply involuntary movement! The patient may also experience personality changes, such as hypersexuality. To be truly free, one must not only have control over his or her bodily movements, but also his or her desires. When considering instances such as Huntington's disease, or a brain tumor, we usually recognize that the individual is not responsible for these personality changes. And yet, almost everyone experiences personality changes of a similar sort during puberty. We do not choose our personalities. Human will isn't sovereign and immutable, but instead controlled by biology and genetics.
Freedman: I might have a slightly different personality than I did as a child, but it's not as if puberty took away my free will!
Domino: Then consider the addict who feels compelled against his or her will to continue abusing drugs to the point of losing a job, family, dignity, and perhaps even life. Does this individual have free will?
Freedman: Each time the drug addict relapses, he or she is choosing to satisfy cravings which are subjectively worse than the consequences of relapse.
Domino: That's hardly what I call free will.
Freedman: The philosopher Arthur Schopenhauer once wrote, "Man can do what he wants, but he cannot will what he wills." The drug addict's choice to satisfy a craving is a free choice, but he or she has little control over the cravings.
Domino: Yes, little if any! The cravings are generated by the nucleus accumbens, part of the basal ganglia, a group of subcortical brain structures which have a largely unconscious yet profound influence on human behavior. The neurons of the nucleus accumbens release dopamine which modulates attention and rewards certain behaviors. This dopaminergic modulation is the true motivation for many of our behaviors and can turn strong individuals into hopeless addicts.
Freedman: Ah, but the cerebral cortex—the neural substrate of the conscious self—has top-down projections which modulate the nucleus accumbens. If we equate the cortex with the self, the self can directly influence the activity of the nucleus accumbens and the rest of the brain, which in turn influences the self. For instance, we can change our brains through practices such as mindfulness and meditation to alleviate anxiety and intrusive thoughts. Neuroscientist Michael Gazzaniga has used similar arguments to assert that the self can alter the brain through top-down causation.
Domino: I understand Gazzaniga's arguments. However, if the universe is deterministic, then my actions are predetermined and there is no room for free will. Have a look at the cellular automata in John Conway's Game of Life. These lifelike beings run about as if possessing a will of their own, yet their behaviors are entirely predetermined by the initial conditions of the grid on which the game is played.
Freedman: Yes, but cellular automata are just an abstract model.
Domino: But the same determinism applies to our universe! Consider a thought experiment conceived by the French mathematician Pierre-Simon Laplace: a demon knows the position and momentum of every particle in the universe. With this knowledge, the demon can predict the future of the entire universe according to Newtonian physics. Where is there room for choice in such a predetermined world?
Freedman: Yet today, we know that at the level of subatomic particles, nature behaves randomly.*
Domino: That's true, but the 'quantum indeterminacy' you're referring to doesn't allow for free will either. If my choices are made by rolling dice, how does this make me free?
Freedman: Touché. I don't deny that, at the level of biology, the universe is deterministic. If you define free will to mean freedom from determinism, then no, free will just doesn't exist.
Domino: You admit defeat!
Freedman: Hold on a minute. Daniel Dennett, whom I mentioned earlier, makes the distinction between this sort of free will and the kind of free will "worth wanting." In a lecture addressed to the Santa Fe Institute in 2014, he compares free will to magic. Real magic, in the sense of conjuring spells, is obviously fake, whereas fake magic, in the sense of slight of hand tricks, is real. Similarly, real free will is fake, and fake free will is real. The sort of free will worth wanting is the sort of free will you and I have which a Huntington's disease patient lacks.
Domino: Hmm, this free will is still just an illusion. Your actions are still predetermined, you simply enjoy your predetermined behavior in a way that the Huntington's disease patient does not. You still can't will what you will, as Schopenhauer would say. Even with meditation and top-down mental causation, there are only so many levels to how far you can control your will. Say you want to change your feelings for someone. Your feelings for that person are a primary will, but perhaps you have a secondary will to change them. Your primary will shall change as a function of your secondary will. But what determines your secondary will, your desire to change these feelings? That will had to come from somewhere, right? So there must be a tertiary will determining your secondary will. But if you are completely free, that tertiary will must bow to a quaternary will ... And so forth, ad infinitum. Free will is an incomplete concept!
Freedman: Yes, I have already conceded that that sort of free will is a logical impossibility. At any given moment, only one future is possible. That the brain decides according to some algorithm does not diminish my capacity to choose; on the contrary, this algorithm allows me to choose. How else could a decision be possible if not according to some computational procedure? We've already established that rolling dice is not a free choice. Now, say I'm given some choice in an experiment. If each trial is repeated exactly the same way, then in principle I should decide the same way each time. In practice, this is impossible, because after the first trial, I'd have the memory of the previous trials, which might influence my next decision. The fact that I can integrate previous decisions into my current decision and take a different path, this is all the free will "worth wanting," as Dennett would say.
Domino: But isn't it your brain deciding for you? How is this a real choice?
Freedman: I am my brain, or at the very least my cerebral cortex. That's the basis of monism, the idea that brain and mind are one substance. To say that the brain decided for me is to take a dualist approach based on the idea that the mind is some fundamentally different substance than the brain. Once I abandon the idea of dualism, the accusation of the brain deciding for me disappears.
Domino: But you didn't choose your brain when you were born! And given that there are differences between the brains of sociopaths and normal individuals, how can you really say that you would've made different choices, had you been born as Jack the Ripper?
Freedman: That's a meaningless question. To ask if I would have still murdered if I were Jack the Ripper is like asking if a car would fly if it were an airplane. Of course it would fly, it would no longer be a car! Would an electron be positively charged if it were a proton? I suppose so!
Domino: Although I strongly believe that free will does not exist... I suppose I see your argument.
Freedman: One more point. Researchers have shown that, after reading a passage from a book arguing against the existence of free will, subjects are more likely to subsequently cheat on a task they must perform to earn money than subjects who read a neutral passage. This work underscores the importance of believing in free will for exercising self-control. As Daniel Dennett has argued, telling people that neuroscience leaves no room for free will might not only be jumping to conclusions, but also irresponsible.
Domino: Interesting... Even though I think free will is an illusion, I'll admit that it's an important illusion.
Freedman: Finally, something we can agree on! Now, how abut that Pepsi?
Originally published on Knowing Neurons.
* Further objections to Laplace’s demon would include chaos theory and Heisenberg’s uncertainty principle. Chaos theory states that infinitely small changes in initial conditions may have very large effects. Heisenberg’s uncertainty principle states that infinitely precise measurement of both the position and momentum of a particle is impossible even in principle. Nonetheless, Domino’s argument that the macroscopic world is deterministic still holds.
Libet, Benjamin, et al. "Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential)." Brain 106.3 (1983): 623-642.
Dennett, Daniel C. Freedom evolves. Penguin UK, 2004.
Batthyany, Alexander: Mental Causation and Free Will after Libet and Soon: Reclaiming Conscious Agency. In Batthyany und Avshalom Elitzur. Irreducibly Conscious. Selected Papers on Consciousness, Universitätsverlag Winter Heidelberg 2009, p.135ff.
Soon, Chun Siong, et al. "Unconscious determinants of free decisions in the human brain." Nature neuroscience 11.5 (2008): 543-545.
Gazzaniga, Michael. Who's in Charge?: Free Will and the Science of the Brain. Hachette UK, 2012.
Dennett, Daniel. “Is Free Will an Illusion? What Can Cognitive Science Tell Us?” Santa Fe Institute. James A. Little Theater, Santa Fe, NM. 14 May 2014. Lecture.
Vohs, Kathleen D., and Jonathan W. Schooler. "The value of believing in free will encouraging a belief in determinism increases cheating." Psychological science 19.1 (2008): 49-54