Determined, page 3
Three Hundred Milliseconds
Let’s start off with William Henry Harrison, ninth president of the United States, remembered only for idiotically insisting on giving a record-long two-hour inauguration speech in the freezing cold in January 1841, without coat or hat; he caught pneumonia and died a month later, the first president to die in office and the shortest presidential term.[*],[1]
With that in place, think about William Henry Harrison. But first, we’re going to stick electrodes all over your scalp for an electroencephalogram (EEG), to observe the waves of neuronal excitation generated by your cortex when you’re thinking of Bill.
Now don’t think of Harrison—think about anything else—as we continue recording your EEG. Good, well done. Now don’t think about Harrison, but plan to think about him whenever you want a little while later, and push this button the instant you do. Oh, also, keep an eye on the second hand on this clock and note when you chose to think about Harrison. We’re also going to wire up your hand with recording electrodes to detect precisely when you start the pushing; meanwhile, the EEG will detect when neurons that command those muscles to push the button start to activate. And this is what we find out: those neurons had already activated before you thought you were first freely choosing to start pushing the button.
But the experimental design of this study isn’t perfect, because of its nonspecificity—we may have just learned what’s happening in your brain when it is generically doing something, as opposed to doing this particular something. Let’s switch instead to your choosing between doing A and doing B. William Henry Harrison sits down to some typhoid-riddled burgers and fries, and he asks for ketchup. If you decide he would have pronounced it “ketch-up,” immediately push this button with your left hand; if it was “cats-up,” push this other button with your right. Don’t think about his pronunciation of ketchup right now; just look at the clock and tell us the instant you chose which button to push. And you get the same answer—the neurons responsible for whichever hand pushes the button activate before you consciously formed your choice.
Let’s do something fancier now than looking at brain waves, since EEG reflects the activity of hundreds of millions of neurons at a time, making it hard to know what’s happening in particular brain regions. Thanks to a grant from the WHH Foundation, we’ve bought a neuroimaging system and will do functional magnetic resonance imaging (fMRI) of your brain while you do the task—this will tell us about activity in each individual brain region at the same time. The results show clearly, once again, that particular regions have “decided” which button to push before you believe you consciously and freely chose. Up to ten seconds before, in fact.
Eh, forget about fMRI and the images it produces, where a single pixel’s signal reflects the activity of about half a million neurons. Instead, we’re going to drill holes in your head and then stick electrodes into your brain to monitor the activity of individual neurons; using this approach, once again, we can tell if you’ll go for “ketch-up” or “cats-up” from the activity of neurons before you believe you decided.
These are the basic approaches and findings in a monumental series of studies that have produced a monumental shitstorm as to whether they demonstrate that free will is a myth. These are the core findings in virtually every debate about what neuroscience can tell us on the subject. And I think that at the end of the day, these studies are irrelevant.
It began with Benjamin Libet, a neuroscientist at the University of California at San Francisco, in a 1983 study so provocative that at least one philosopher refers to it as “infamous,” there are conferences held about it, and scientists are described as doing “Libet-style studies.”[*],[2]
We know the experimental setup. Here’s a button. Push it whenever you want. Don’t think about it beforehand; look at this fancy clock that makes it easy to detect fractions of a second and tell us when you decided to push the button, that moment of conscious awareness when you freely made your decision.[*] Meanwhile, we’ll be collecting EEG data from you and monitoring exactly when your finger starts moving.
Out of this came the basic findings: people reported that they decided to push the button about two hundred milliseconds—two tenths of a second—before their finger started moving. There was also a distinctive EEG pattern, called a readiness potential, when people prepared to move; this emanated from a part of the brain called the SMA (supplementary motor area), which sends projections down the spine, stimulating muscle movement. But here’s the crazy thing: the readiness potential, the evidence that the brain had committed to pushing the button, occurred about three hundred milliseconds before people believed they had decided to push the button. That sense of freely choosing is just a post hoc illusion, a false sense of agency.
This is the observation that started it all. Read technical papers on biology and free will, and in 99.9 percent of them, Libet will appear, usually by the second paragraph. Ditto for articles in the lay press—“Scientist Proves There Is No Free Will; Your Brain Decides Before You Think You Did.”[*] It inspired scads of follow-up research and theorizing; people are still doing studies directly inspired by Libet nearly forty years after his 1983 publication. For example, there’s a 2020 paper entitled “Libet’s Intention Reports Are Invalid.”[3] Having your work be important enough that decades later, people are still trash-talking it is immortality for a scientist.
The basic Libet finding that you’re kidding yourself if you think you made a decision when it feels like you did has been replicated. Neuroscientist Patrick Haggard of University College London had subjects choose between two buttons—choosing to do A versus B, rather than choosing to do something versus not. This suggested the same conclusion that the brain has seemingly decided before you think you did.[4]
These findings ushered in Libet 2.0, the work of John-Dylan Haynes and colleagues at Humboldt University in Germany. It was twenty-five years later, with fMRIs available; everything else was the same. Once again, people’s sense of conscious choice came about two hundred milliseconds before the muscles started moving. Most important, the study replicated the conclusion from Libet, fleshing it out further.[*] With fMRI, Haynes was able to spot the which-button decision even farther up in the brain’s chain of command, in the prefrontal cortex (PFC). This made sense, as the PFC is where executive decisions are made. (When the PFC, along with the rest of the frontal cortex, is destroyed, à la Gage, one makes terrible, disinhibited decisions.) To simplify a bit, once having decided, the PFC passes the decision on to the rest of the frontal cortex, which passes it to the premotor cortex, then to the SMA and, a few steps later, on to your muscles.[*] Supporting the view of Haynes having spotted decision-making farther upstream, the PFC was making its decision up to ten seconds before subjects felt they were consciously deciding.[*],[5]
Then Libet 3.0 explored free-will-is-an-illusion down to monitoring the activity of individual neurons. Neuroscientist Itzhak Fried of UCLA worked with patients with intractable epilepsy, unresponsive to antiseizure medications. As a last-ditch effort, neurosurgeons remove the part of the brain where these seizures initiate; with Fried’s patients, it was the frontal cortex. One obviously wants to minimize the amount of tissue removed, and in preparation for that, electrodes are implanted in the targeted area prior to the surgery, allowing for monitoring activity there. This provides a fine-grained map of function, telling you what subparts you should avoid removing, if there’s any leeway.
So Fried would have the subjects do a Libet-style task while electrodes in their frontal cortex detected when particular neurons there activated. Same punch line: some neurons activated in preparation for a particular movement decision seconds before subjects claimed they had consciously decided. In fascinating related studies, he has shown that neurons in the hippocampus that code for a specific episodic memory activate one to two seconds before the person becomes aware of freely recalling that memory.[6]
Thus, three different techniques, monitoring the activity of hundreds of millions of neurons down to single neurons, all show that at the moment when we believe that we are consciously and freely choosing to do something, the neurobiological die has already been cast. That sense of conscious intent is an irrelevant afterthought.
This conclusion is reinforced by studies showing how malleable the sense of intent and agency is. Back to the basic Libet paradigm; this time, pushing a button caused a bell to ring, and the researchers would vary how long of a fraction-of-a-second time delay there’d be between the pushing and the ringing. When the bell ringing was delayed, subjects reported their intent to push the button coming a bit later than usual—without the readiness potential or actual movement changing. Another study showed that if you feel happy, you perceive that conscious sense of choice sooner than if you’re unhappy, showing how our conscious sense of choosing can be fickle and subjective.[7]
Other studies of people undergoing neurosurgery for intractable epilepsy, meanwhile, showed that the sense of intentional movement and actual movement can be separated. Stimulate an additional brain region relevant to decision-making,[*] and people would claim they had just moved voluntarily—without so much as having tensed a muscle. Stimulate the pre-SMA instead, and people would move their finger while claiming that they hadn’t.[8]
One neurological disorder reinforces these findings. Stroke damage to part of the SMA produces “anarchic hand syndrome,” where the hand controlled by that side of the SMA[*] acts against the person’s will (e.g., grabbing food from someone else’s plate); sufferers even restrain their anarchic hand with their other one.[*] This suggests that the SMA keeps volition on task, binding “intention to action,” all before the person believes they’ve formed that intention.[9]
Psychology studies also show how the sense of agency can be illusory. In one study, pushing a button would be followed immediately by a light going on . . . some of the time. The percentage of time the light would go on was varied; subjects were then asked how much control they felt they had over the light. People consistently overestimate how reliably the light occurs, feeling that they control it.[*] In another study, subjects believed they were voluntarily choosing which hand to use in pushing a button. Unbeknownst to them, hand choice was being controlled by transcranial magnetic stimulation[*] of their motor cortex; nonetheless, subjects perceived themselves as controlling their decisions. Meanwhile, other studies used manipulations straight out of the playbook of magicians and mentalists, with subjects claiming agency over events that were actually foregone and out of their control.[10]
If you do X and this is followed by Y, what increases the odds of your feeling like you caused Y? Psychologist Daniel Wegner of Harvard, a key contributor in this area, identified three logical variables. One is priority—the shorter the delay between X and Y, the more readily we have an illusory sense of will. There are also consistency and exclusivity—how consistently Y happens after you’ve done X, and how often Y happens in the absence of X. The more of the former and the less of the latter, the stronger the illusion.[11]
Collectively, what does this Libetian literature, starting with Libet, show? That we can have an illusory sense of agency, where our sense of freely, consciously choosing to act can be disconnected from reality;[*] we can be manipulated as to when we first feel a sense of conscious control; most of all, this sense of agency comes after the brain has already committed to an action. Free will is a myth.[12]
Surprise!, people have been screaming at each other about these conclusions ever since, incompatibilists perpetually citing Libet and his descendants, and compatibilists being scornful shade throwers about the entire literature. It didn’t take long to start. Two years after his landmark paper, Libet published a review in a peer-commentary journal (where someone presents a theoretical paper on a controversial topic, followed by short commentaries by the scientist’s friends and enemies); commentators beating on Libet accused him of “egregious errors,” overlooking “fundamental measurement concepts,” conceptual unsophistication (“Pardon, your dualism is showing,” accused one critic), and having an unscientific faith in the accuracy of his timing measurements (sarcastically proclaiming Libet as practicing “chronotheology”).[13]
The criticisms of the work of Libet, Haynes, Fried, Wegner, and friends continue unabated. Some focus on minutiae like the limitations of using EEGs, fMRI, and single-neuron recordings, or the pitfalls inherent in subjects self-reporting most anything. But most criticisms are more conceptual and collectively show that rumors of Libetianism killing free will are exaggerated. These are worth detailing.
You Guys Proclaim the Death of Free Will, Based on Spontaneous Finger Movements?
The Libetian literature is built around people spontaneously deciding to do something. In the view of Manuel Vargas, free will revolves around being future oriented, enduring an immediate cost for a long-term goal, and thus “Libet’s experiment insisted on a purely immediate, impulsive action—which is precisely not what free will is for.”[14]
Moreover, what was being spontaneously decided was to push a button, and this bears little resemblance to whether we have free will concerning our beliefs and values or our most consequential actions. In the words of psychologist Uri Maoz of Chapman University, this is a contrast between “picking” and “choosing”—Libet is about picking which box of Cheerios to take off the supermarket shelf, not about choosing something major. Dartmouth philosopher Adina Roskies, for example, views Libet-world picking as a caricature of real choice, dwarfed even by the complexity of deciding between tea and coffee.[*],[15]
Does the Libet finding apply to something more interesting than button pushing? Fried replicated the Libet effect when subjects in a driving simulator chose between turning left and turning right. Another study merged neuroscience with getting out of the lab on a sunny day, checking for the Libet phenomenon in subjects just before they bungee-jumped. Did the neuroscientists, clutching their equipment, jump too? No, a wireless EEG device was strapped to the jumpers’ heads, making them look like Martians persuaded to bungee-jump by frat bros after some beer pong. Results? Replication of Libet, where a readiness potential preceded the subjects’ believing they had decided to jump.[16]
To which the compatibilists replied, This is still totally artificial—choosing when to leap into an abyss or whether to turn left or right in a driving simulator tells us nothing about our free will in choosing between, say, becoming a nudist versus a Buddhist, or becoming an algologist versus an allergologist. This criticism was backed by a particularly elegant study. In the first situation, subjects would be presented with two buttons and told that each represented a particular charity; press one of the buttons and that charity will be sent a thousand dollars. Second version: two buttons, two charities, push whichever button you feel like, each charity is getting five hundred dollars. The brain was commanding the same movement in both scenarios, but the choice in the first one was highly consequential, while that in the second was as arbitrary as the one in the Libet study. The boring, arbitrary situation evoked the usual readiness potential before there was a sense of conscious decision; the consequential one didn’t. In other words, Libet doesn’t tell us anything about free will worth wanting. In the wonderfully sarcastic words of one leading compatibilist, the take-home message of this entire literature is “Don’t play rock paper scissors for money [with one of these free will skeptic researchers] if your head is in an fMRI machine.”[17]
But then, the revenge of the free will skeptics. Haynes’s group brain-imaged subjects participating in a nonmotoric task, choosing whether to add or subtract one number from another; they found a neural signature of decision coming before conscious awareness, but coming from a different brain region than the SMA (called the posterior cingulate / precuneus cortex). So maybe the pick-your-charity scientists were just looking in the wrong part of the brain—simple brain regions decide things before you think you’ve consciously made a simple decision, more complicated regions before you think you’ve made a complicated choice.[18]
The jury is still out, because the Libetian literature remains almost entirely about spontaneous decisions regarding some fairly simple things. On to the next broad criticism.
60 Percent? Really?
What does it mean to become aware of a conscious decision? What do “deciding” and “intending” really mean? Again with semantics that aren’t just semantic. The philosophers run wild here in subtle ways that leave many neuroscientists (e.g., me) gasping in defanged awe. How long does it take to focus on focusing on the second hand on a clock? In her writing, Roskies emphasizes the difference between conscious intention and consciousness of intention. Alfred Mele speculates that the readiness potential is the time when, in fact, you have legitimately freely chosen, and it then takes a bit of time for you to be consciously aware of your freely willed choice. Arguing against this, one study showed that at the time of the onset of the readiness potential, rather than thinking about when they were going to move, many subjects were thinking about things like dinner.[19]
