Note: subsequent to my writing of this post, an excellent scientific paper has been published that makes many of the same arguments, but does it much better. The paper is by Brass et al., 2019, and I highly recommend reading it if you are interested in this topic. You can find it [here]. They also present a very interesting model of decision-making that I'm sure will be the topic of some future posts!
As I
discussed in my previous post on this topic, it seems that free will should be
observable in the neuron and therefore should be testable. I’m not the only one to think that way, and
in the last few years a few researchers have attempted to design experiments
that would test this concept. I find the
experiments to be very interesting and creative, but, unfortunately they fall
short of the goal. I think it is worth
discussing here what some of the difficulties are in some detail. This post is going to have to be longer than
most.
The most
commonly referenced paper on this topic is Libet et al. from 1983, but I would
rather review in detail a more recent paper:
Soon et al., 2013 “Predicting free choices for abstract intentions.” It’s an interesting experiment and
illustrates many of the basic principles and basic difficulties with this type
of experiment.
The basic
principle that is put forth in these papers is that there is activity in the
brain that precedes the conscious
awareness of “free will” decisions that we make. The implication is that freely made decisions
are not really free – rather, they are the result of earlier unconscious
processes in the brain that determined the decision. Ultimately, what these researchers would like
to say is that our decisions are made unconsciously and therefore determined by
other brain processes, thus supporting the idea that free will is only an
illusion.[1] Of course the popular press loves that, and
is quick to jump to conclusions about the meaning of the research. Well, I don’t think it means what they think
it means!
First, I’m
going to have to explain the methods used in the paper in a bit of detail so
that my comments make sense. The paper
itself is freely available at Pubmed, and if you have interest in this topic,
it is worth reading the original paper.
The attempt
in this research was to try to get subjects to make a “freely made decision”
involving abstract thought. Previous
published experiments of this nature usually involved a task that required
physical movement. Movements involve a
certain amount of pre-planning in the brain and the investigators wanted to
separate the abstract decision from the brain activity involved in movement.
In the
experiment, subjects were shown a screen with a few numbers on it and one
letter in the center. The screen changed
once every second to a new set of numbers and a new letter. As the screens would move past, the subject
was to randomly decide at some point that, in the subsequent screen, they were
going to either add or subtract in the screen that followed. They had to remember the letter that was on
the screen when they consciously decided they were going to add or
subtract. The next screen gave them the
first number (a single digit) and then the third screen gave them the second
number along with four answers and they had to pick the correct one that
corresponded to either the addition or subtraction problem. Then, a fourth screen appeared that had four
letters to choose from and they had to pick the letter that was on the screen
when they decided to either add or subtract.
That completed one test, and then the process started over again. One annoying thing for me is that I could not
find anywhere in the paper that described how many trials each subject did. Knowing the number of samples is critical in
trying to understand the detailed results and the statistics presented. Maybe I missed it somewhere in the paper –
otherwise it seems like a pretty glaring omission that peer-review would have
caught.
There was a screening
process for subjects to make sure they met certain criteria (more on that
later) and then 22 subjects completed the real test. They were positioned in an MRI machine that
could scan their brain activity every two seconds. I won’t go into the details, but there is a
method of brain scanning developed a few years ago that shows the areas of the
brain with the highest relative activity.
So, the researchers searched across the entire brain to see if there were
regions of the brain that had activity related to the decision to add/subtract
and the timing of that decision. Then,
since they knew when the subjects were conscious of their decision (based on
the design of the test), they looked at brain activity up to eight seconds
prior to the conscious decision point.
It’s a fairly
complicated procedure to determine whether activity is correlated with the
decision made, but in the end they found two areas of the brain that had
activity that predicted the impending decision with around 59% accuracy. Practically, this means that you could query
this area of the brain and ask “is the person going to make a decision to
add/subtract?” and the activity of the area could be analyzed to predict yes or
no with respect to an upcoming decision in 59% of the cases. Note that if you knew nothing you should be
able to predict decision or no decision with 50% accuracy. Nonetheless, 59% is statistically
significant, meaning that it is highly probable that the predicted activity really
was correlated with the decision and didn’t just happen by chance. This predictive activity occurred 2-4 seconds
before the person was conscious of their decision. The implication is that some area of your
brain knew of the decision before “you” did, thus showing that the decision was
not really “free” but was determined by unconscious brain activity.
I will quote
their conclusion here just for completeness before diving into my review of
this paper: “To summarize, we directly
investigated the formation of spontaneous abstract intentions and showed that
the brain may already start preparing for a voluntary action up to a few
seconds before the decision enters into conscious awareness. Importantly, these
results cannot be explained by motor preparation or general attentional
mechanisms. We found that frontopolar and precuneus/ posterior cingulate
encoded the content of the upcoming decision, but not the timing. In contrast,
the pre-supplementary motor area predicted the timing of the decision, but not
the content.”
First, I’m
going to make three general statements and explain their impact on the
understanding of the results of this experiment and similar experiments, then I
have a few specific comments that would be more like comments I would have made
if I had been a reviewer of this paper.
1. It’s
not clear to me that “consciousness” and “will” are the same things. The key assumption in these types of
experiments is that we are conscious of the will’s decision at the moment it is
made. I’m not certain that such an
assumption is valid. I don’t have any
data to prove the correlation one way or the other, but since free will and
consciousness are both somewhat nebulous and hard to define, it seems like a
bit of a leap to think that they must be perfectly correlated in time. Isn’t it possible that your will begins to
act on your brain before you are conscious of it?
About the
only example I can bring up here is to consider the common phrase “go with your
gut.” What do people mean when they say
that? Physiologically it doesn’t make a
lot of sense, yet we all know what is meant by that phrase because we
experience it. Sometimes we know what we
need to do right away – almost unconsciously it seems – and yet sometimes we
are hesitant. So people say “go with
your gut” because there are times where it almost seems like working through a
conscious calculated decision is just not warranted or can even lead us to make
the wrong decision. To me, this
indicates that sometimes our will is active before we are conscious of it. Of course, for those of you who are
determinists, you’ll say that this common phrase is as close as we usually come
to realizing that every decision we make is pre-determined by our ongoing brain
activity. Possibly. The point is – who knows? And until we know, I find it hard to draw
firm conclusions from these types of experiments about free will. To be fair, I don’t think the authors of
these papers make this direct connection in their papers – I think it is
usually the things written later about the article that make this claim because
such a claim is a bit more sensational.
Along with
this issue is that it seems to me that it is particularly difficult to pinpoint
when you are conscious of a decision.
Subjects in these studies have to have some way of marking the time
point when they are conscious they are making a decision. I find that conceptually difficult. How do you really know? How accurate can you really be? Seems to me that an error of a few seconds is
certainly possible.
2. The
tasks in these experiments are basically random, not necessarily decisions of
the will. To be honest, I’m not sure
how else they could do these experiments.
But I would say that the influence of free will in the human mind and
brain is fundamentally different than making random decisions. I tried to illustrate that a bit with my
entry on the “Turing Test with Numbers”.
The difference between a random number series and a series determined by
the “will” is hard to identify. Further,
how do human beings make random decisions anyway? My hypothesis is that the process for picking
random numbers is different than the normal process for making decisions. I would not expect our free will to be
involved in the selection of truly “random” decisions or actions. I kind of figure that we must pick random
numbers in a manner similar to the way computers pick random numbers – they
have to find some kind of electronically noisy process that has apparent
randomness in it. If so, then we would
use some neurons who are tuned to fire or not fire based on small differences
in the random fluctuation of ions at the nerve membrane. I don’t know if this is true or not, but I
really don’t see why we need our free will to make a random decision. If our random decisions are really
pre-determined by various brain circuits, that would not bother me at all. And it has no impact on what I consider free
will.
3. The
will is a weak force. When
determinists argue against free will being a separate influence on the brain,
they seem to imply that the will takes over all of the brain’s activity and is
the overwhelming influence over what happens.
I don’t see it that way. I think
most of what we do, and most of what the brain does, is essentially composed of
physical, material reactions and responses to various sensory inputs. Essentially, I would say that we are
primarily acting on complex reflexes that are fine-tuned by the will. I
think we can go through our day pretty mindlessly doing the things we need to
do without involving the will much. In
many cases, I would say that the will’s influence is very subtle. Frequently I
think our will is entirely masked by these reflexes. Why do we do things that we say we don’t want
to do? We intend to do good things, but
then we make bad decisions. Sometimes in
these cases I would say we are driven by our habits and passions, and the will
is completely pushed aside.[2]
The
implication of the will being a weak force is that when we try to
experimentally identify it, it is very difficult. We end up trying to measure a very small
signal riding on top of a huge signal, and that is very hard to do. We are trying to pick out subtle neural
activity in the midst of huge networks of coordinated neurons being driving by
prior neural inputs. Fundamentally, this
is why I think an experiment demonstrating whether or not we really have free
will is extremely difficult to conduct.
Related to
this issue is the method used to identify brain activity. fMRI is used to identify this activity based
on a parameter called BOLD. This
parameter correlates to the use of energy within the neurons. When neurons are more active, they use more
energy than they usually do, and that can be measured. But this type of measurement requires that
there are a large number of neurons in a specific region of the brain that
become highly active during any specific time period. You can’t pick out the activity of a few
neurons with this method. Subtle changes
would be lost. Also, unique activity in
broad regions of the brain would not show up here either. An analogy might be trying to determine where
I work by observing the rush hour traffic patterns in Cleveland. That might predict where a lot of people
work, but I happen to work south of downtown (usually). Others might not even go to work during rush
hour times. The BOLD parameter only
picks up major activity and if, as I suggest, the will is a subtle force, it
won’t appear in the tests being done using that method. There are other testing methods used by other
investigators, and I may get into those in the future.
Now for some more detailed considerations of this particular paper.
4.
It’s really hard to design an experiment that involves human behavior
when you want to give them complete freedom to make a decision. Experiments need to be well-controlled in
order to draw conclusions, while free will decision-making is anything but well-controlled! So, in this experiment they had to create
some artificial constraints on people’s decision-making. The primary way they did this was to have a
screening test in which subjects performed the test (without the MRI) and their
spontaneous performance had to meet certain criteria. This means that the subject population that
was studied was a selectively biased population. Specifically, subjects had to “spontaneously”
select about the same amount of addition and subtraction tasks. The researchers needed reasonable numbers of
both types of activity, but how do you guarantee that kind of distribution and
still allow people to be “free”? I don’t
think the paper ever said whether the selected subjects continued to pick
similar numbers of addition and subtraction tasks when they were in the MRI,
but I assume that in general they did.
They do mention that they threw out the data for one subject who never
selected a subtraction task in one run.
Obviously, they weren’t really free to choose!
The other thing that I think is
even more problematic is that they only selected subjects who averaged at least
10 or more screens before they made a choice.
Thus, subjects who were naturally highly decisive were excluded from
this study. Thus, only subjects who
pondered things a bit before “freely deciding” were selected. Is it possible that “ponderers” have to mull
things over before making a decision, thus partially explaining why they had
brain activity before they were conscious of their decision? The bottom line is that they had to evaluate
a biased population.
5. The best prediction accuracy was about 59%,
which is fairly weak and barely above statistical significance, given that by
chance the accuracy should be 50%. But,
for an experiment such as this, 59% isn’t terrible. But there’s some missing information that
makes it difficult to judge this predictive ability. Specifically, the average time for subjects
to make a spontaneous decision was 17.8 sec with a standard error of 1.8
sec. Thus, it seems to me that as time
drags on, you can kind of predict about when a decision is going to be
made. Is it really spontaneous in that
case? It seems to me that I made be able
to make a 59% prediction just by knowing which screen number the subject was
on. If my brain can predict it, then so
can the subject’s!
6.
The activity predicts that a decision is going to be made (fairly
poorly), but does not predict what the decision is actually going to be – add
or subtract. The individual is not
really free to decide whether to make a decision – the rules of the experiment
require that they eventually decide and the rules of practicality essentially
require that the decision is made somewhere around 10-20 seconds after the
start of each series of screens. What
seems much closer to spontaneous is add or subtract, but that wasn’t predicted
by the brain activity. Again, to be
fair, you’d think this would be a pretty subtle activity in the brain and hard
to pick out with fMRI methodology.
7.
The subjects had to remember the letter on the screen when they made a
decision. In my opinion (as one who has
a bad memory) the anticipation of having to remember something requires brain
activity. In other words, you have to
know before you see (or hear) something that it is something you’re going to
have to remember. Otherwise, you immediately
forget it (at least that’s how my brain works).
Therefore, I think subjects would have had to do some preparatory brain
work prior to seeing the screen where they made a decision, so that their brain
was ready to store that letter in memory for about 3 seconds. So, one hypothesis might be that the regions
of the brain they identified were involved in preparatory memory activities,
not necessarily in decision-making. I
know they compared the focused activity to general attention mechanisms, but it’s
not clear to me that preparation for specific memory is the same as general
attention.
8.
One thing this paper does show
is that the decision itself and the timing of the decision appeared in separate
parts of the brain. If the will acts at
the level of neurons as I propose, this may suggest that the will acts in
different areas in the brain and then those areas ultimately need to come
together elsewhere in order for a decision to actually be made. I relate these things to my personal
experience (where, in these cases, I’m assuming that I experience what everyone
else in the human race experiences).
Sometimes I’ve made up my mind about something, but I’m not ready to
actually decide, so nothing happens “until I’m ready.” The results of this paper might lend some
weak credence to that…maybe.
Well, there’s a lot more to be
discussed in the various papers in the literature. The point is, disproving free will and
proving determinism is going to be pretty difficult because the experimental
design is conceptually very difficult. I
try hard not to be someone who critiques the work of others without offering an
acceptable alternative. I will have to
present those ideas in a future entry.
But I hope, at the very least, that this helps you not get carried away
by the headlines that say “scientists prove that free will is an illusion.” They haven’t – and they never will![3]
References
Libet B, Gleason
CA, Wright EW, Pearl DK (1983) Time of conscious intention to act in relation
to onset of cerebral activity (readiness-potential). The unconscious initiation
of a freely voluntary act. Brain 106(Pt 3):623–642.
Soon CS, He AH,
Bode S, Haynes JD. Predicting free choices for abstract intentions. Proc Natl
Acad Sci U S A. 2013 Apr 9;110(15):6217-22. doi: 10.1073/pnas.1212218110. Epub
2013 Mar 18.
[1] I
know: researchers are supposed to be
unbiased on not have anything they “would like to say.” So far, every researcher I’ve met is a human
being and, therefore, biased. That
includes me.
[2]
Who “pushes the will aside?” The will –
what else could it be? It’s not that weak of a force!
[3]
Although it’s a little hard for me to prove that something will never happen!
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