Neuroscientist Michiko Kimura Bruno shares her thoughts on the famous experiments by Benjamin Libet that challenge the concept of free will.
Two decades ago, while interning at the National Institutes of Health, I worked in a lab focused on studying the control of human motor functions. The process of using electrical devices to study the physiology of movements sometimes seemed complex and confusing to me. However, one of the tests was quite simple: recording the readiness potential (RP) using an electroencephalogram (EEG).
The traditional understanding of voluntary actions describes the process as a sequence: a person becomes aware of their intention, after which the brain sends a command to execute it. This led us to an important question: is there a brain signal that precedes activity in the motor cortex and other areas responsible for movement? Perhaps this signal is a precursor to the intention to move?
During the experiment, we connected EEG electrodes and asked participants to voluntarily contract the same muscle, for example, by squeezing their fingers. The EEG records noticeable activity, such as spasms, so a single finger squeeze did not cause significant changes in the recording. But after we summed the data from 100 attempts, we noticed that a slow negative signal began to accumulate in the motor cortex and supplementary motor area one to two seconds before the actual movement. This signal, although difficult to interpret, was named the readiness potential.
Libet's Experiments
In 1983, Benjamin Libet conducted a series of experiments aimed at exploring the connection between our intention and the readiness potential. He asked participants to spontaneously flick their fingers while monitoring a special clock that made a full rotation in 2.6 seconds. Participants were asked to report when they first became aware of their intention to flick. Libet referred to this moment as the time of "willing" (W-willing).
As expected, the readiness potential was recorded before the onset of movement. However, what was even more intriguing was that it began to manifest earlier than the time of willing recorded in the experiment, by several hundred milliseconds. Libet interpreted this finding as evidence that the brain begins to initiate voluntary actions before we make a conscious decision, which sparked significant debate among philosophers and in the media regarding the nature of free will. Libet's experiment became an argument in favor of the theory that free will may be merely an illusion.
Critical Analysis
Libet's argument is based on temporal indicators: the readiness potential precedes the intention. However, both concepts require deeper analysis. Let's consider several counterarguments.
1. Is the time of willing truly the moment of intention? Awareness of intention may not coincide with its formation. Describing the moment of willing requires subjective interpretation and may be distorted by memory and attention processes, making it difficult to measure accurately.
2. Do the results of these experiments reflect the reality of decision-making? Libet's experiments focus on voluntary actions, such as flicking a finger, rather than on conscious choices based on reasons. Later studies have shown that the neural mechanisms of voluntary and conscious decisions may differ. The readiness potential is clearly recorded during voluntary actions but not during more conscious decisions, such as choosing a charity to donate to.
3. What does the readiness potential actually represent? Its presence before an action does not prove that it is the cause. Since the readiness potential is defined by averaging many attempts only after the action has been performed, there is a likelihood of errors in the data: we only record accumulation in cases where movement has occurred. We cannot average neural activity in cases where movements do not happen.
In fact, new research suggests that the readiness potential may not be a separate signal. It may simply reflect random fluctuations in neural activity that sometimes reach a sufficient level to trigger movement.
Aaron Shurger and his team used a battery model of random factors to demonstrate that spontaneous movements occur when the level of background noise in motor areas exceeds a certain threshold. Thus, the readiness potential represents a statistical "averaged" form of such fluctuations. Further research has shown that even after the onset of early motor activity, participants are capable of blocking the intended movement.
As a child, I often played similar games where I pretended to choose one option and then changed my mind at the last minute. But does this really prove free will? Probably not. Interestingly, researchers continue to explore these questions under controlled conditions.
Thus, the modern scientific paradigm asserts that movement arises from the probabilistic accumulation of neural activity rather than from a single "decision signal." Conscious intention actively interacts with these processes, modifying and shaping actions.
Reflections on Free Will
There is a common misconception that to assert the existence of free will, one must be aware of every intention. However, many routine actions, such as opening doors, brushing teeth, or driving a car, are performed semi-automatically. We possess consciousness as a whole, but we do not always recognize every small decision. Nevertheless, if asked, we can assert that these actions are carried out through our choice and free will.
In other words, what we perceive as conscious intention (i.e., the intention underlying free will and actions) differs from the awareness of intention at the moment before action. Moreover, simple awareness of intention is not equivalent to having an intention that reflects our free will and values. Neurobiology can only partially measure the former and come close to the latter to a small extent.
I am also struck by how often intention and action diverge: missed free throws, easy goals, double faults. In everyday life, we drop objects, spill drinks, and make slips of the tongue. In other cases, movements occur without any awareness of intention at all. This variability makes the idea of random neural activity quite appealing.
Ultimately, Libet's experiments do not resolve the debate about free will but deepen it. They show that the mechanisms governing our actions are more dynamic and complex than we had assumed. Nevertheless, they also emphasize that conscious intention is not a singular moment. It is a broad and multifaceted phenomenon shaped by experience, values, memory, and reflection. Science reminds us that human will exists in a constant interplay between automatic processes and the choices we make over time. And this space—chaotic, noisy, and beautiful, inherent to humanity—remains the place where free will manifests.
Source
