Philosophy

5

LECTURE: Free will and neuroscience

Neuroscience is the scientific study of the brain and nervous system. It is sometimes claimed that findings in neuroscience have cast doubt on the reality of free will. Alfred Mele, in his book Free: Why Science Hasn’t Disproved Free Will, responds to such arguments. Let’s look at what he has to say in response to the most influential argument of this type.

The Libet experiment

The argument in question rests on a famous experiment carried out by neuroscientist Benjamin Libet (1916-2007). Mele is a contemporary philosopher who has become well known for his work on the topic of free will. Here they are:

Libet Mele

Here is the setup for the experiment. Subjects were asked to flex a wrist whenever they felt like doing so, and then to report on when they had become consciously aware of the urge to flex it. Their brains were wired so that the activity in the motor cortex responsible for causing their wrists to flex could be detected.

Libet found that, while an average of 200 milliseconds passed between the conscious sense of willing and the flexing of the wrist, the activity in the motor cortex would begin an average of over 500 milliseconds before the flexing. To be sure, that’s an extremely short time difference. A millisecond is a thousandth of a second. But the difference is there. Hence the conscious urge to flex seems to follow the neural activity which initiates the flexing, rather than causing that neural activity.

Here’s a chart representing the sequence of events in the experiment:

Awareness of urge: -200 ms

Time

EEG begins to rise: -550 ms Time of action: 0 ms

The reason this is supposed to pose a problem for free will is this. It seems that, if we have free will, the sequence involving the urge to flex, the neural activity, and the act of flexing should look something like this:

conscious urge neural activity flexing of wrist

But instead, Libet says, we have a sequence that looks like this:

neural activity conscious urge flexing of wrist

In other words, it isn’t that the conscious urge is what causes the neural activity that results in the flexing. Rather, it is the unconscious neural activity that causes the flexing and the conscious urge. The conscious urge is just along for the ride. The idea that it is what is causing the behavior is an illusion.

The conclusion many people draw from this is: If free will requires that consciously willing to do something is the cause of doing it, then it seems that we don’t really act freely.

Problems with the argument

So it is claimed. But as Mele and others have pointed out, in fact there are many problems with this argument:

1. Sufficient or merely necessary?

The first problem is that Libet didn’t show that the kind of neural activity he measured is invariably followed by flexing. Given his experimental setup, only cases where the activity was actually followed by flexing were detected. He didn’t check for cases where the neural activity occurred but was not followed by flexing.

So we have no evidence that that kind of neural activity is sufficient for the flexing. It may be that the neural activity is necessary for the flexing, but not by itself enough. Perhaps it leads to flexing (or doesn’t) depending on whether it is conjoined with a conscious free choice to flex. In other words, the actual sequence may be:

conscious urge

neural activity flexing of wrist

That is to say, for all Libet has shown, it may be that the neural activity will be followed by a flexing of the wrist only if there is also a conscious urge, and not if there is no such urge. And if so, then the conscious urge is playing an essential role after all, contrary to what Libet assumes. Libet did not even test for this possibility.

2. Idiosyncrasy of the setup

A second problem is that the sorts of actions Libet studied are far from being a representative sample. They are highly idiosyncratic. The experimental setup required subjects to wait passively until they were struck by an urge to flex. But in general, our actions don’t work like that, especially those we attribute to free choice. When we do the sorts of things that we usually attribute to free choice, they aren’t the result of passively waiting for some random urge to strike us. Instead, they involve active deliberation – the weighing of considerations for and against different possible courses of action.

It’s hardly surprising that conscious deliberation has little influence on what we do in an experimental situation like the one Libet set up, in which the subjects are told not to deliberate actively, but just to sit back and wait for an urge to strike them!

It is also very strange to think that free choice is a matter of letting “urges” strike us. Think of an urge you have to sneeze. Suppose you try to resist the urge but are unable to. Is that what you would normally consider a free choice? If anything, it is the opposite. So why on earth would Libet take acting on passing urges to be a model for all purportedly free actions?

A good model for free actions in general?

The problem, then, is that Libet is drawing a sweeping conclusion about all our actions from a small handful of cases that are far from representative. Again, he tells the subjects to wait passively, and to act on an urge. But the sorts of behaviors we attribute to free will are not like that at all. They involve actively thinking through options. It is a fallacy to think that we can draw a conclusion about those cases from the idiosyncratic examples Libet focuses on.

3. A crude model of action

A third problem is that Libet seems to be working with a crude model of human behavior, on which a free action would be one where, with full consciousness, you think “I am now going to do X,” and then carry out this conscious choice. But nobody really thinks of free action that way.

For example, consider what happens when you make a cup of coffee. You don’t explicitly think “Now I will pick up the kettle; now I will pour hot water through the coffee grounds; now I will put the kettle down; now I will pick up a spoon; now I will begin to stir...” and so on. You simply make the coffee. Of course, you are in a general way aware of what you are doing, but you are not bringing to the focus of your consciousness each stage in the process. You might, after the fact, bring to consciousness the various steps you just carried out; or you may not.

But in our ordinary way of thinking about human behavior, we take this sort of action to be the result of free choice either way. We don’t normally think of free choice as requiring some fully conscious act of thinking “I now hereby choose to carry out action X.” If I asked you if you remember pouring the water, you might say “I don’t know, I just did it. I was thinking about something else at the time.” But neither of us would conclude from that that your pouring of the water was not the result of free choice.

“My will isn’t free until I’ve had my morning java!’

But in that case, what does it matter if, in Libet’s scenario, the choice to flex registers in consciousness literally a fraction of a second after the neural activity? Libet seems to be assuming that a free choice has to be something we are fully and explicitly aware of, but this is a straw man. He is criticizing a model of free action that no one is actually defending anyway.

4. Alternative interpretations

A fourth problem is that Libet jumps to conclusions when interpreting the neural activity he measured. He thinks of the neural activity as corresponding to something like an unconscious intention to flex. And since the subject isn’t aware of that intention, he thinks that the brain rather than the subject is what “decides” what to do.

But why interpret the neural activity that way? There are, in fact, several other ways one could interpret it, all of which are consistent with the evidence. For example, one could interpret the neural activity as corresponding to the subject preparing to flex the wrist, without yet having made the choice to do so. Or one could interpret it as corresponding the subject imagining or thinking about flexing, before having decided to do so. And both of these interpretations are consistent with the idea that the conscious choice is also needed for the flexing to happen.

Another alternative is to think of the neural activity as corresponding to a general intention to flex, as opposed to a proximal intention to flex. The idea is this. Imagine you get up at 7 am one morning and decide that you will leave for school at 8 am. That is a “general intention” to leave at 8 am. But of course, you don’t actually leave at the moment you formed that intention. You only leave an hour later. A general intention to carry out some action can come long before the action is actually carried out. Then 8 am arrives, and you think “OK, it’s time, I’d better go.” Now you form a “proximal intention” to leave, the one that actually results in the action of leaving.

So, maybe what is going on in Libet’s example is that the neural activity corresponds to the subject forming a general intention of flexing, and the conscious urge corresponds to a proximal intention to flex. The subject first thinks “I’m going to flex within the next moment” (which corresponds to the neural activity) and then a split second later thinks “Now!” (which corresponds to the conscious urge).

Nothing in Libet’s experiment is incompatible with these alternative interpretations. Again, the experiment simply does not show that free will is an illusion.

Here are some optional YouTube videos on our topic:

The Libet Experiment: Is Free Will Just an Illusion?:

https://www.youtube.com/watch?v=OjCt-L0Ph5o

Mele on Free Will and Neuroscience:

https://www.youtube.com/watch?v=rCM5BFU01YU

Closer to Truth on Is Free Will an Illusion?:

https://www.youtube.com/watch?v=XalpMgP3E94