I’d like to call the following a neurophysiosophical rant, i.e. philosophical rant grounded in neurophysiology. You can use it.
If any of you have studied for the GRE (Graduate Records Examination) within the past several years, chances are you’ve run across a reading passage describing the findings of Benjamin Libet, a neurophysiologist from UC, San Francisco. When I think about it, I’ve actually learned a lot of interesting things from GRE reading passages. But this one in particular has stuck with me, because ever since I read it I’ve been skeptical about the idea of free will.
There is a lengthy (understatement!) Wikipedia page dedicated to this historical debate, but if you aren’t particularly in the mood to tackle an 8,920 word scientific discourse (that’s equivalent to 10% of a full-length novel), this post should suffice (however, if you are, you should seriously read it–it’s pretty cool). Here’s the meat:
Two scientists name Lüder Deecke and Hans Helmut Kornhuber discovered something called readiness potential (RP) in 1964. RP quantifies the ramping up of electrical activity in the motor cortex and supplementary motor area of the brain that precedes a voluntary muscle movement. Benjamin Libet’s contribution in the 1980s was to show through experimentation that this RP signal precedes the conscious will to move. Of course, his methods were a bit ghetto: RP was measured with an electroencephalogram (EEG), movement was detected with an electromyograph (EMG), and first awareness of will to move was noted by the test subject using a fancy oscilloscope timer–as you can imagine, the time of this first will to move would be impossible to record exactly due to the amount of time between urge to act and ability to note the location of the dot on the oscilloscope. Furthermore, if the subject follows Libet’s direct instructions to note when “s/he was first aware of the wish or urge to act,” s/he would not in fact be willfully deciding to move. In this case, perhaps the “urge” felt by the subjects is the RP.
I wouldn’t hang my hat on the results of this study. But a more recent study (2008) repeated the experiment with some modifications and extensions, including the use of fMRI machine learning through multivariate pattern analysis to predict which button, left or right, a test subject would choose to press. The authors write, “We found that the outcome of a decision can be encoded in brain activity of prefrontal and parietal cortex up to 10 seconds before it enters awareness.” However, the accuracy rate was only 60%. Moreover, this experiment still relied on the test subjects noting the time of first awareness of urge to move. In my opinion, the result is therefore more intuitive than the alternative. I would be much more surprised if a person felt an “urge” to move and it was not the result of an electrical signal in the brain. On the other hand–is it even possible to experience will to move in the absence of an urge of any kind? The neural motor default is inhibition, not excitation.
The issue of finding proper controls for a scientific experiment is pervasive and fascinating. This scientific question regarding free will is particularly troublesome because there are so many unanswered questions whose predicted answers necessarily contribute to the premise upon which the experiment is based. Such questions include: How might free will be observed if it does exist? If asked to exercise free will, does this conscious determination to make certain decisions at “random” intervals preclude the ability to act in a truly autonomous manner? (I hypothesize yes.) Under the right circumstances, can RP actually start after conscious will to move (and then, what are these circumstances)? Do different kinds of actions require different kinds of free will? What is free will, anyway?
To the last question, I present the Merriam-Webster definition: “Freedom of humans to make choices that are not determined by prior causes or by divine intervention.” Great–now what do these “prior causes” entail? Where philosophy meets science, the rabbit hole runs deep.
Okay, so here is one sub-question which some scientists, including Libet, have endeavored to answer: Once started, can RP and/or the progression toward movement be stopped? Libet did observe that RP could be initiated without being followed by actual movement, implying that the subconscious decision to move was vetoed. Michael Egnor of Science News thinks that the buck, while perhaps not stopping, brakes to a school-zone appropriate speed here, and Benjamin Libet would agree. According to Egnor, Libet wrote, “This kind of role for free will is actually in accord with religious and ethical strictures. These commonly advocate that you ‘control yourself.’ Most of the Ten Commandments are ‘do not’ orders.” Interestingly, he firmly believed in free will (or at least free won’t), maintaining that the ‘veto’ need not be neurophysiologically predetermined–in his words: “We would not need to view ourselves as machines that act in a manner completely controlled by the known physical laws.” But in my opinion, it’s very likely that there is a separate brain signal that competes with the readiness potential and overrides it. In fact, how could there not be? Our sensory neurons are constantly competing with each other to dominate our awareness, so why should the process of decision-making be any different? I don’t think anyone would argue that consciousness is an entity wholly distinct from the physical wiring of the brain. Thus, the question that I think becomes most pertinent in this debate is: Does the competing “veto” signal exist physically, and if so, where and how does it arise?
Scientists Simone Kühn and Marcel Brass were of the mind that the veto probably also arises subconsciously. In 2009, they sought to answer this question. The premise: If in fact the decision to veto is an act of consciousness, test subjects should be able to distinguish the true permission of movement from mere impulse (as in failure to make a decision at all either way). I won’t go into the methods (read their paper if you’re interested), but the results showed that the volunteers could not make this critical distinction. Thus, the evidence more strongly supports a model in which decision to veto an action also arises subconsciously.
One of the most compelling experiments on this subject for me is a 1990 study by Ammon and Gandevia in which the scientists were able to manipulate test subjects’ perception of their control over decisions. Summary: any given right-handed volunteer would normally choose to move his right hand 60% of the time; however, when the right hemisphere of the brain was stimulated using magnets, he would choose to move his left hand 80% of the time. The incredible part: despite external influence, subjects still believed that their choices regarding which hand to move had been made freely.
After reading all this literature, if I had to say which side I’m leaning to, it’s definitely the one in which all our decisions result from an optimization calculation in the brain. It makes so much sense to me that we would integrate all our nature and nurture–observations, information, training and genetic tendencies–as parameters for some extremely complex multivariate nonlinear regression, in order to make the best possible decision. I mean, I can understand situations in which even suicide might be computed by the brain to be the least negative/painful option.
Am I okay with the idea that I may be no more than a biotic cyborg? I guess so, yea. But there’s still a strong sense of personal responsibility. It’s more important than ever to stay as informed as I possibly can about all issues (moral and otherwise) that might directly affect my life, so that when the need to decide presents itself, my neural networks will make the best decision for me and for those around me.
Discussion Topic: What do you think? Is free will a thing?