Libet's experiment: does human freedom exist?

Are we really masters of our actions or, on the contrary, are we conditioned by a biological determinism? These doubts have been widely debated throughout the centuries of philosophy and psychology, and Libet's experiment it has contributed to intensify them.

Throughout this article we will talk about the experiment carried out by the neurologist Benjamin Libet, as well as its procedures, its results and reflections, and the controversy that surrounds this study.

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Who was Benjamin Libet?

Born in the United States in 1916, Benjamin Libet became a renowned neurologist whose early work focused on investigating synaptic and postsynaptic responses, then focused on the study of neural activity and of the threshold sensations of these (that is to say, the point in which the intensity of a stimulus generates a conscious sensation of change).

His first relevant investigations were aimed at establishing the amount of activation that certain

brain areas concrete needs to release artificial somatic perceptions. As a result of these works, Libet began his famous investigations on the conscience of the people, as well as his experiments linking neurobiology and freedom.

As a result of his studies and reflections on freedom, free will and conscience, Libet became a pioneer and a celebrity within the world of neurophysiology and philosophy. Despite all these, his conclusions have not been without criticism from researchers in both disciplines.

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Libet's experiment

Before Libet began his well-known experiments, other researchers such as Hans Helmut Kornhuber and Lüder Deecke already coined the term “bereitschaftspotential”, which in our language we could translate as “potential of preparation” or “potential of provision".

This term refers to a dimension that quantifies the activity of the motor cortex and supplementary motor area of ​​the brain when they are preparing for voluntary muscular activity. Namely, refers to brain activity when planning to perform a voluntary movement. From this, Libet built an experiment in which a relationship was sought in the subjective freedom that we believe we have when starting a voluntary movement and the neurosciences.

In the experiment, each of the participants was placed in front of a kind of clock which was programmed to make a full turn of the hand in 2.56 seconds. Next, he was asked to think of a point on the circumference of the clock chosen at random (always the same) and the moments when the hand passed there, He had to make a movement of the wrist and, at the same time, remember where the hand was on the watch at the moment of having the conscious sensation of going to perform that movement.

Libet and his team called this subjective variable V, referring to the person's willingness to move. The second variable was coined as variable M, associated with the actual moment in which the participant performed the movement.

To find out these M-values, each participant was also asked to report the exact moment in which they had made the movement. The temporal figures obtained through the variables V and M provided information about the time difference that existed between the moment in which the person felt the desire to perform the movement and the exact moment in which the movement was performed movement.

To make the experiment much more reliable, Libet and his collaborators used a series of objective measurements or records. These consisted of measuring the readiness potential of brain areas related to movement and an electromyography of the muscles involved in the specific activity that was asked of the participants.

Experiment results

The discoveries and conclusions made once the measurements had been made and the study concluded did not leave anyone indifferent.

At first, and as expected, the study participants placed variable V (will) before variable M. This means that they perceived their conscious desire to perform the movement as prior to it. This fact is easily understood as a correlation between brain activity and the subjective experience of the person.

Now, the data that really brought about a revolution were those extracted from the objective records. According to these figures, the brain's readiness potential appeared before the subject was aware that he wanted to move his wrist; specifically between 300 and 500 milliseconds earlier. This can be interpreted as that our brain knows before we ourselves that we want to perform an action or movement.

The conflict with free will

For Libet, these results conflicted with the traditional conception of free will. This term, typical of the field of philosophy, refers to the belief that the person has the power to freely choose your own decisions.

The reason was that the desire to perform a movement considered free and voluntary is actually preceded or anticipated by a series of electrical changes in the brain. Therefore, the process of determining or wanting to make a move begins unconsciously.

However, for Libet the concept of free will continued to exist; since the person still retained the conscious power to voluntarily and freely interrupt the movement.

Finally, these discoveries would imply a restriction on the traditional conception of how freedom works and free will, considering that this would not be in charge of starting the movement but of controlling and ending it.

Criticisms of this research

The scientific-philosophical debates about whether people are really free when making decisions or whether, on the contrary, we are subjected to a materialistic biological determinism, they go back many centuries before the Libet experiment and, of course, they still continue today. So, unsurprisingly, Libet's experiment did not escape criticism from either philosophy or neuroscience.

One of the main criticisms made by some thinkers of free will theories is that, According to them, the existence of this cerebral advance should not be incompatible with this belief or concept. This brain potential could be a series of automatisms linked to a state of passivity of the person. For them, Libet would not be focusing on what is really important, the most complicated or complex actions or decisions which require prior reflection.

On the other hand, regarding the evaluation of the procedures carried out in the experiment, counting and timing methods have been questioned, since they do not take into account how long it takes for different brain areas to emit and receive messages.