The Libet experiment: does human freedom exist?

This famous experiment has had repercussions in both psychology and philosophy.

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 experiment has contributed to intensify them.

Throughout this article we will discuss the experiment conducted by the neurologist Benjamin Libet, as well as his procedures, his results and reflections, and the controversy surrounding this study.

Who was Benjamin Libet?

Born in the United States in 1916, Benjamin Libet became a renowned neurologist whose early work focused on the investigation of synaptic and postsynaptic responses, and later on the study of neural activity. the study of neural activity and their threshold sensations (i.e., the point at which the intensity of a stimulus generates a conscious sensation of change).

His first relevant research was aimed at establishing the amount of activation that specific brain areas require to release artificial somatic perceptions. As a result of this work, Libet began his famous research on the consciousness of individuals, as well as his experiments linking neurobiology and freedom..

As a result of his studies and reflections on freedom, free will and consciousness, Libet became a pioneer and a celebrity in 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 initiated his well-known experiments, other researchers such as Hans Helmut Kornhuber and Lüder Deecke had already coined the term "bereitschaftspotential", which in our language could be translated as "readiness potential" or "dispositional potential".

This term refers to a dimension that quantifies the activity of the motor cortex and the supplementary motor area of the brain when these are prepared for voluntary muscular activity. That is, refers to brain activity when planning to perform a voluntary movement.. From this, Libet constructed an experiment in which he looked for a relationship between the subjective freedom we believe we have when initiating a voluntary movement and neuroscience.

In the experiment each of the participants was placed in front of a kind of clock, which was programmed which was programmed to make a complete hand revolution in 2.56 seconds. They were then asked to think of a point on the circumference of the watch chosen at random (always the same one) and at the moments when the hand passed by, they had to make a wrist movement and, at the same time, remember where the hand was on the watch at the moment they had the conscious sensation of making that movement.

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

In order to know these M values, each participant was also asked to report the exact moment at which he/she performed the movement. The temporal figures obtained by means of the V and M variables provided information about the time difference between the moment when the person felt the desire to perform the movement and the exact moment when the movement was performed.

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

Results of the experiment

The findings and conclusions made after the measurements were taken and the study was concluded left no one indifferent.

At first, and as expected, the participants of the study placed the variable V (will) before the 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 person's subjective experience.

However, the data that really revolutionized the field were those extracted from the objective recordings. According to these figures the brain potential for readiness appeared before the subject was aware that he or she wanted to move his or her wristThe brain's readiness potential appeared before the subject was aware that he or she wanted to move the wrist; specifically between 300 and 500 milliseconds earlier. This can be interpreted as meaning that our brain knows before we know 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, specific to the field of philosophy, refers to the belief that a person has the power to freely choose his or her own decisions. the power to freely choose his or her own decisions..

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

Nevertheless, 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 place a restriction on the traditional conception of how freedom works. and free will, considering that the latter would not be in charge of initiating the movement but would be in charge of controlling and finalizing it.

Criticisms of this research

The scientific-philosophical debates about whether people are really free when it comes to making decisions or whether, on the contrary, we are subject to a biologicist materialistic determinism, we are subject to a materialistic, biologistic determinism, go back many centuries.The scientific-philosophical debates about whether people are really free to make decisions or whether, on the contrary, we are subject to a materialistic biological determinism, go back many centuries before Libet's experiment and, of course, still continue today. So, as was to be expected, Libet's experiment was not spared from criticism either from philosophy or from neuroscience.

One of the main criticisms made by some thinkers of free will theories is that, according to them, the existence of this brain anticipation need 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 acts or decisions which require prior reflection.

On the other hand, with regard to the evaluation of the procedures carried out in the experiment, the methods of counting and time measurement have been questionedThe methods of counting and measuring times have been questioned, since they do not take into account how long it takes the different brain areas to emit and receive the messages.