Two weeks ago, I wrote about the big question of Free Will in Our Intuition of Choice. In that essay, I introduced the debate around the existence of free will and pondered whether our view of free will should change our feelings on moral responsibility. Many fields of study, including philosophy and the social sciences, have a lot of important things to say about the existence of free will but today we are going to examine one contribution of neuroscience to the debate of whether free will exists.
In this context, not having free will means that one’s decisions are made unconsciously and therefore outside of our domain of influence. If we are to believe that a decision correlates with brain activity (and I believe we have good reason to believe so), then one way of finding out whether decisions are made unconsciously is to look for brain activity about a decision that occurs before one is aware that decision took place.
This is exactly what the pioneering scientist Benjamin Libet did in the 1970s and 80s.
Libet’s experiment in unconscious decision-making
Participants in Libet’s experiment were asked to watch a dot traveling in a circular motion on an instrument that resembled a clock-face and perform a simple motor task such as pushing a button.
After pushing the button, the participants were asked to report the position of the dot when they decided to push the button. While this was happening, Libet used an EEG to record the brain activity of the participants to look for spikes in brain activity that might precede either the button pushed or the decision to do so. By comparing the dot’s position when the participant reported they made the decision to push the button and when the button was actually pushed, Libet was able to map the timing of a conscious decision and its action.
If the moment the button was pushed is treated as “time zero” then Libet found that, on average, the participants reported making the decision 200 milliseconds before the button was pushed. Surprisingly, the EEG showed a spike in brain activity about 330 milliseconds before that decision. That is, Libet found that there was a spike in unconscious brain activity about a half of a second before the button was pushed. Below is a timeline of these events:
Because the brain activity rose before the participant even knew that a decision was made, many people have used this as evidence that our decisions are not free but are actually controlled by brain impulses that occur unconsciously.
So does this evidence leave room for free will?
Does neuroscience leave room for free will?
While Libet’s experiments are fascinating, there are reasons to believe that they do not in fact “disprove” free will. First, Libet himself actually sees his experiments as completely compatible with the notion of free will. In a later experiment, Libet used skin electrodes to detect when the muscle used to push the button was actually activated and found that it occurred 50 milliseconds before the button was pushed. This leaves 150 milliseconds between the conscious urge to push the button and the pushing of the button—enough time that Libet argues leaves room for a “conscious veto” or “Free Won’t” of the urge to push the button.
Beyond this “window of opportunity”, I think there is good reason to question the usefulness of Libet’s experiments in the context of the kind of free will that we all care about—to what extent are we in control of our life trajectory over the long run? In Libet’s experiments, the participants were explicitly told to not think too much about their thinking and to let their impulses arise naturally. This kind of decision-making feels a lot like, for example, the decision about which jar of pasta sauce to grab off the shelf—inconsequential, random, and unconscious. Should we care if free will exists in these contexts?
Overall, I don’t know if Libet’s experiments tell us anything about our free will during conscious deliberation over important choices such as which college to attend or whether to accept a job offer. This is the kind of free will worth fighting for and debating about. Even so, I think we can’t have a conversation about free will without considering Libet’s seminal neuroscience experiments in this area, and it’s an interesting phenomenon nonetheless.
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📆 Upcoming Schedule
With the holidays rapidly approaching I wanted to let all of you know that the Synapse newsletters going out on December 27th and January 3rd are going to be a little different.
On December 27th, I’m going to send out a special “Synapse Feedback” edition in which I present and respond to a lot of the amazing feedback and thoughts I’ve received on the last few newsletters. If you have any new questions or feedback you want to talk about, now is your chance to get in touch!
On January 3rd, there won’t be any original content, but there will be a “Synapse Year-end Review” in which I reflect on the essays I’ve written this year, the threads that connect them, and give you new subscribers a chance to catch up on any essay you might have missed!
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