Authors: David Eagleman
Incognito (26 page)
While the brain normally emerges from slow-wave sleep into lighter stages, and finally to wakefulness, Kenneth’s electroencephalogram (EEG) showed a problem in which his brain tried to emerge straight from a deep sleep stage directly into wakefulness—and it attempted this hazardous transition ten to twenty times per night. In a normal sleeping brain, such a transition is not attempted
even once in a night. Because there was no way for Kenneth to fake his EEG results, these findings were the clincher that convinced the jury that he indeed suffered from a sleepwalking problem—a problem severe enough to render his actions involuntary. On May 25, 1988, the jury in the Kenneth Parks case declared him not guilty of the murder of his mother-in-law and, subsequently, of the attempted murder of his father-in-law.
13
As with Tourette’s sufferers, those subject to
psychogenic disorders, and the
split-brain patients, Kenneth’s case illustrates that high-level behaviors can happen in the absence of free will. Like your heartbeat, breathing, blinking, and swallowing, even your mental machinery can run on autopilot.
The crux of the question is whether
all
of your actions are fundamentally on autopilot or whether there is some little bit that is “free” to choose, independent of the rules of biology. This has always been the sticking point for both philosophers and scientists. As far as we can tell, all activity in the brain is driven by other activity in the brain, in a vastly complex, interconnected network. For better or worse, this seems to leave no room for anything
other than
neural activity—that is, no room for a ghost in the machine. To consider this from the other direction, if free will is to have any effect on the actions of the body, it needs to influence the ongoing brain activity. And to do that, it needs to be physically connected to at least some of the neurons. But we don’t find any spot in the brain that is not itself driven by other parts of the network. Instead, every part of the brain is densely interconnected with—and driven by—other brain parts. And that suggests that no part is independent and therefore “free.”
So in our current understanding of science, we can’t find the physical gap in which to slip free will—the uncaused causer—because there seems to be no part of the machinery that does not follow in a causal relationship from the other parts. Everything stated here is predicated on what we know at this moment in
history, which will certainly look crude a millennium from now; however, at this point, no one can see a clear way around the problem of a nonphysical entity (
free will) interacting with a physical entity (the stuff of the brain).
But let’s say that you still intuit very strongly that you have free will, despite the biological concerns. Is there any way neuroscience can try to directly
test
for free will?
In the 1960s, a scientist named
Benjamin Libet placed electrodes on the heads of subjects and asked them to do a very simple task: lift their finger at a time of their own choosing. They watched a high-resolution timer and were asked to note the exact moment at which they “felt the urge” to make the move.
Libet discovered that people became aware of an urge to move about a quarter of a second before they actually made the move. But that wasn’t the surprising part. He examined their EEG recordings—the brain waves—and found something more surprising: the activity in their brains began to rise
before
they felt the urge to move. And not just by a little bit. By over a second. (See figure on the following page.) In other words, parts of the brain were making decisions well before the person consciously experienced the urge.
14
Returning to the newspaper analogy of consciousness, it seems that our brains crank away behind the scenes—developing neural coalitions, planning actions, voting on plans—before we receive the news that we’ve just had the great idea to lift a finger.
Libet’s experiments caused a commotion.
15
Could it be true that the conscious mind is the last one in the chain of command to receive any information? Did his experiment drive the nail into the coffin of free will? Libet himself fretted over this possibility raised by his own experiments, and finally suggested that we might retain freedom in the form of
veto
power. In other words, while we can’t control the fact that we get the urge to move our finger, perhaps we retain a tiny window of time to stop the lifting of our finger. Does this save free will? It’s difficult to say. Despite the impression that a veto might be freely chosen, there is no evidence to suggest that it, too, wouldn’t be the result of neural
activity that builds up behind the scenes, hidden from conscious view.
“Move your finger when the impulse grabs you.” Long before a voluntary movement is enacted, a buildup of neural activity can be measured. The “readiness potential” is larger when subjects judge the time of their urge to move (grey trace), rather than the movement itself (black trace). From Eagleman,
Science
, 2004, adapted from Sirigu et al,
Nature Neuroscience
, 2004.
People have proposed several other arguments to try to save the concept of free will. For example, while classical physics describes a universe that is strictly deterministic (each thing follows from the last in a predictable way), the
quantum physics of the atomic scale introduces unpredictability and uncertainty as an inherent part of the cosmos. The fathers of quantum physics wondered whether this new science might save free will. Unfortunately, it doesn’t. A system that is probabilistic and unpredictable is every bit as unsatisfying as a system that is deterministic, because in both cases there’s no choice. It’s either coin flips or billiard balls, but neither case equates to freedom in the sense that we’d desire to have it.
Other thinkers trying to save free will have looked to
chaos theory, pointing out that the brain is so vastly complex that there is no way, in practice, to determine its next moves. While this is certainly true, it doesn’t meaningfully address the free-will problem, because the systems studied in chaos theory are still deterministic: one step leads inevitably to the next. It is very difficult to predict where chaotic systems are going, but each state of the system is causally related to the previous state. It is important to stress the difference between a system being unpredictable and it being free. In the collapse of a pyramid of ping-pong balls, the complexity of the system makes it impossible to predict the trajectories and final positions of the balls—but each ball nonetheless follows the deterministic rules of motion. Just because we can’t say where it’s all going does not mean that the collection of balls is “free.”
So despite all our hopes and intuitions about free will, there is currently no argument that convincingly nails down its existence.
The question of free will matters quite a bit when we turn to culpability. When a criminal stands in front of the judge’s bench having recently committed a crime, the legal system wants to know whether he is
blameworthy
. After all, whether he is fundamentally responsible for his actions navigates the way we punish. You might punish your child if she writes with a crayon on the wall, but you wouldn’t punish her if she did the same thing while sleepwalking. But why not? She’s the same child with the same brain in both cases, isn’t she? The difference lies in your intuitions about free will: in one case she has it, in the other she doesn’t. In one she’s choosing to act mischievously, in the other she’s an unconscious automaton. You assign culpability in the first case and not in the second.
The legal system shares your intuition: responsibility for your actions parallels volitional control. If
Kenneth Parks was awake when he killed his in-laws, he hangs. If asleep, he’s acquitted. Similarly, if you hit someone in the face, the law cares whether
you were being aggressive or if you have hemiballismus, a disorder in which your limbs can flail wildly without warning. If you crash your truck into a roadside fruit stand, the law cares whether you were driving like a maniac or instead were the victim of a heart attack. All these distinctions pivot on the assumption that we possess free will.
But do we? Don’t we? Science can’t yet figure out a way to say yes, but our intuition has a hard time saying no. After centuries of debate, free will remains an open, valid, and relevant scientific problem.
I propose that
the answer to the question of free will doesn’t matter
—at least not for the purposes of social policy—and here’s why. In the legal system, there is a defense known as an
automatism
. This is pled when the person performs an automated act—say, if an epileptic seizure causes a driver to steer into a crowd. The automatism defense is used when a lawyer claims that an act was due to a biological process over which the defendant had little or no control. In other words, there was a guilty act, but there was not a
choice
behind it.
But wait a moment. Based on what we’ve been learning, don’t such biological processes describe most or, some would argue, all of what is going on in our brains? Given the steering power of our genetics, childhood experiences, environmental toxins, hormones, neurotransmitters, and neural circuitry, enough of our decisions are beyond our explicit control that we are arguably not the ones in charge. In other words, free will
may
exist—but if it does, it has very little room in which to operate. So I’m going to propose what I call the
principle of sufficient automatism
. The principle arises naturally from the understanding that free will, if it exists, is only a small factor riding on top of enormous automated machinery. So small that we may be able to think about bad decision making in the same way we think about any other physical process, such as diabetes or lung disease.
16
The principle states that the answer to the free-will question simply does not matter. Even if free will is conclusively proven to exist
one hundred years from now, it will not change the fact that human behavior largely operates almost without regard to volition’s invisible hand.
To put this another way,
Charles Whitman, Alex the sudden pedophile, the frontotemporal shoplifters, the gambling Parkinson’s patients, and
Kenneth Parks all share the common upshot that acts cannot be considered separately from the biology of the actors. Free will is not as simple as we intuit—and our confusion about it suggests that we cannot meaningfully use it as the basis of punishment decisions.
In considering this problem,
Lord Bingham, Britain’s senior law lord, recently put it this way:
In the past, the law has tended to base its approach … on a series of rather crude working assumptions: adults of competent mental capacity are free to choose whether they will act in one way or another; they are presumed to act rationally, and in what they conceive to be their own best interests; they are credited with such foresight of the consequences of their actions as reasonable people in their position could ordinarily be expected to have; they are generally taken to mean what they say. Whatever the merits or demerits of working assumptions such as these in the ordinary range of cases, it is evident that they do not provide a uniformly accurate guide to human behaviour.
17
Before moving into the heart of the argument, let’s put to rest the concern that biological explanations will lead to freeing criminals on the grounds that nothing is their fault. Will we still punish criminals? Yes. Exonerating all criminals is neither the future nor the goal of an improved understanding.
Explanation does not equal exculpation
. Societies will always need to get bad people off the streets. We will not abandon punishment, but we will refine the
way
we punish—as we turn to now.
The study of brains and behaviors finds itself in the middle of a conceptual shift. Historically, clinicians and lawyers have agreed on an intuitive distinction between
neurological disorders (“brain problems”) and
psychiatric disorders (“mind problems”).
18
As recently as a century ago, the prevailing attitude was to get psychiatric patients to “toughen up,” either by deprivation, pleading, or torture. The same attitude applied to many disorders; for example, some hundreds of years ago, epileptics were often abhorred because their seizures were understood as demonic possessions—perhaps in direct retribution for earlier behavior.
19
Not surprisingly, this proved an unsuccessful approach. After all, while psychiatric disorders tend to be the product of more subtle forms of brain pathology, they are based, ultimately, in the biological details of the brain. The clinical community has recognized this with a shift in terminology, now referring to mental disorders under the label
organic disorders
. This term indicates that there is indeed a physical (organic) basis to the mental problem rather than a purely “psychic” one, which would mean that it has no relation to the brain—a concept that nowadays makes little sense.