Reblog: German original | LIBET EXPERIMENTS | 2015
A good 30 years ago, the neurophysiologist Benjamin Libet discovered that the brain initiates movements before the person consciously decides to do so. Since then, philosophers and brain researchers have been arguing about the scope of this finding. Recent experiments show: deep doubts about free will were premature!
Author: Amadeus Magrabi is a cognitive scientist and is currently doing his PhD in neuroscience at the Charité Berlin and at the Berlin School of Mind and Brain (in 2015).
When it comes to free will, you almost only hear extreme views. On the one hand there are the neuro-revolutionaries who dismiss our everyday ideas about responsibility and guilt as scientifically proven illusions. On the other hand, there are the traditionalists who are convinced of human freedom and cannot understand what any laboratory experiments should change about it. And now there's a third group, the "annoyed ones," who can no longer hear the seemingly endless debate about it. But a lot has happened: New empirical results seem to rehabilitate free will.
AT A GLANCE
CONSCIOUSLY OR UNCONSCIOUSLY?
- Because processes in the brain pave the way for our actions before we consciously make the decision to do so, some researchers explained free will as an illusion.
- However, recent evidence suggests that neural preparation does not preclude behavior from being based on conscious motives.
- It has not yet been clarified exactly how thinking and acting are intertwined.
A good starting point for many philosophical discussions is our intuitive experience. What do we mean by free will? By that we mean a certain way of making decisions. For example, when I plan my vacation, I look at my options: how much money and time do I have available? Do I rather want to relax or experience something? Am I after the beach, nature or culture? Apparently speaking of free will only makes sense if we have several options in a situation and can decide in favor of one of them by consciously weighing up reasons. If free will exists, the inner monologue we carry with us should guide our choices.
On the other hand, there is the concern that other, unconscious processes control our behavior and that consciousness only constructs justifications afterwards. So the question of free will is: do conscious considerations determine our decisions, or are they caused by unconscious processes?
For a long time philosophers settled such problems among themselves. That changed drastically when University of San Francisco physiologist Benjamin Libet published the results of his laboratory experiments in the early 1980s . Libet gave his subjects the simple task of flexing their hand. However, they should decide for themselves when to do so. The participants then gave a record of the exact time at which they had decided to take part. A clock that they watched during the experiment was helpful.
Neural initiation
Libet compared the time at which the subjects made their decision with their brain activity, which he registered using electroencephalography (EEG). Other brain researchers had previously discovered that before a movement is carried out, a certain activity pattern occurs over the supplementary motor cortex, a so-called readiness potential. Libet asked herself: Which comes first – this potential for readiness or the subjects' decision? Is the hand movement initiated by conscious decision or by unconscious brain processes?
As it turned out, the participants made their decision on average about 200 milliseconds before the movement. However, the readiness potential began about 550 milliseconds before that; it thus occurred 350 milliseconds before the decision to act. This result caused astonishment: Was the decision already made before the person consciously made it? The feeling that our thoughts determine our actions would then probably be an illusion - caused by hidden neuronal processes. It was said that not the ego, but our brain made the decisions. But why do we often think so hard about our actions if they don't have any effect anyway?
The criticism was not long in coming. Some researchers complained that Libet's subjects had no real alternatives because they were only supposed to move their hand or do nothing. In a 1999 EEG study, neuroscientists led by Patrick Haggard from University College London examined what happens when subjects can choose whether they want to lift their right or left finger. The researchers found an activity pattern similar to Libet's, called the lateralized readiness potential, that also occurred prior to the conscious decision.
Free will is one of the strongest human intuitions of all . No wonder, then, that the findings of neurophysiology got heated
In 2008, a team led by John-Dylan Haynes and Chun Siong Soon from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig investigated whether these results could be confirmed using functional magnetic resonance imaging (fMRI). In this series of experiments, too, the subjects had two options to choose from, and again neural activity patterns announced the upcoming decision. While the time span between the start of action-related brain activity and the decision in the EEG studies was still in the millisecond range, Haynes and Soon used fMRI to register activations in the frontopolar and parietal cortex that even preceded the decision by several seconds.
The neurosurgeon Itzhak Fried checked this finding using electrodes that he implanted in the brains of test subjects. Such a method is usually only used in animal experiments, but Fried examined epilepsy patients who needed such electrodes to treat their condition anyway. This procedure also seemed to confirm Libet's results.
Free will is one of the strongest human intuitions of all. So it's no wonder that these findings got heated. Some wanted to save free will at all costs and simply denied the relevance of neuroscientific studies; the others raised themselves up to become prophets of a new, deterministic image of man.
Two arguments keep popping up in this context: On the one hand, the measured brain activity cannot reliably predict the respective actions of the person. The specific patterns only increase the probability of one or the other decision, but do not determine it. The predictive power of the fMRT data in Haynes and Soon's work was around 60 percent, i.e. not very far above the random level. This suggests that the patterns may not reflect the decision itself, but some sub-process or type of preparation that has only some impact.
NNot at all trivial | Even the occurrence of simple hand movements causes neuroscientists and philosophers to have trouble explaining.
For example, if you could tell from my brain activity that I like Vietnamese food, that would certainly help predict my restaurant visits. You would also find out that I actually visit Vietnamese restaurants more often than other restaurants. But that does not mean that this preference is the only relevant factor for my actions. Other things like the price or the friendliness of the service also play a role - and sometimes make me decide differently. Similarly, the brain activity in Libet's experiments and the follow-up studies could reflect an influencing factor, without the decisions being fixed by it and the persons concerned not being able to act differently.
The second criticism is that the laboratory scenarios were not real decisions at all. Imagine you are asked to choose a right or left index finger motion. Which side would you choose? There doesn't seem to be any good reason why you should move one finger and not the other. The decision has no special consequences or anything to do with your personal values or desires. You will certainly not regret it later and think: crap, if only I had used the other finger! In comparison with real decisions in everyday life – for example, which job vacancy we want to apply for or who we want to marry – an important quality is missing here: personal relevance, which makes it necessary to weigh different reasons against each other.
Coincidence is involved
According to Aaron Schurger and Stanislas Dehaene of the National Research Institute INSERM in Paris, even random fluctuations in brain activity can swell into an impulse that triggers the action in question in weakly motivated movements. For such "pseudo-decisions" as in Libet's experiments, a conscious act of will is possibly not required at all. Actual action is likely to be neuronally initiated in a different way. In addition, investigations by a research team led by Alexander Schlegel from 2013 and 2015 showed that readiness potentials can occur even without a conscious impulse to act.
Taking these concerns seriously, there isn't much left that the Libet experiments and their successors can tell us about free will. However, psychological behavioral studies that do not require brain scans and electrode measurements are increasingly being included in the current debate. One example is the work of Yale University social psychologist John Bargh.
In one of his experiments, subjects first had to solve a language task. They were presented with a number of words and asked to sort them in such a way that grammatically correct sentences came out. For example, "finds", "immediately", "it", "he" becomes the sentence "he finds it immediately". The subjects were told that they wanted to test their language talents - but in fact the experimenters divided the participants into three groups: the first group was given words related to politeness, the second group those related to impoliteness, and the third group got neutral words.
The subjects were then asked to contact the experimenter. But they were just talking and didn't stop when the participants had been waiting for a long time. The study measured how many people interrupted the researchers' conversation within ten minutes.
Studies show that conscious considerations determine our decisions only to a limited extent. There is also evidence of an unconscious influence
You can probably guess what came out: Two out of three participants who had previously read rude words interrupted the experimenters; in the group with the polite expressions, however, only 16 percent. And the neutral group was in between at 38 percent. As a later survey revealed, none of the subjects had recognized a connection between the language task and their decision to interrupt the experimenter.
There are almost countless experiments that have yielded similar results. What does that tell us? According to such studies, if free will means that conscious considerations alone determine our decisions, that is not the case. Finally, there is a proven unconscious influence: whether or not we interrupt other people's conversations should be based on our values, our self-image and our assessment of the situation - but a completely irrelevant language test?
We spontaneously feel uncomfortable with the thought that such trifles guide our decisions without us even realizing it. Of course, that doesn't mean that our thinking doesn't play a role in decision-making. But there is some evidence that actions are not entirely controlled by conscious processes.
Is it so important for free will that we are always aware of everything? It all depends on the relationship between conscious and unconscious processes. If the latter opposes conscious intentions, we would say that it restricts our free will. But if the unconscious is to be seen more as the executive organ of conscious decision-making and both are rowing in the same direction, so to speak, free will does not seem to be endangered.
Unconsciously out of habit
In everyday life, conscious thoughts play a greater role when we find ourselves in situations that are new to us. We then turn our attention to the decision problems and weigh all the arguments against each other to make the best possible choice. On the other hand, when we are in familiar situations, unconscious processes take over and our actions become automatic. It could be that our conscious thoughts partially prepare the unconscious and thus help determine how we behave. Consequently, decisions that are unconscious could also be viewed as consciously controlled in a broader sense.
But how the conscious relates to the unconscious and how both interact with each other, no one knows exactly. Consciousness remains one of the greatest mysteries in science because it is difficult to find an objective and reliable way to measure it. For the time being, strong statements about free will are therefore difficult.
In all of this, one should not forget that there are many intuitive notions about free will that are scientifically untenable. For example, we have the subjective impression that we are "uncaused polluters", which means: We could indeed set causal chains in motion with our decisions, but our decisions themselves are virtually not caused by anything. According to this, decisions would have to take place in a kind of abstract space, detached from the laws of nature. For science, on the other hand, the causal principle applies, according to which everything has a cause and an effect. Therefore, from this point of view, decisions must also have causes.
On closer inspection, it is not at all desirable that decisions have no cause. After all, we want our actions to be based on good arguments and not just fall out of the blue.
In addition, a free choice is sometimes required not to be influenced by upbringing, childhood experiences, or genetic predisposition. Here, too, one can say from the perspective of research: We most likely do not have this kind of freedom. But even if free will means that conscious considerations determine our decisions, then this question is far from settled.
Given the complexity of the situation, one should not expect a simple either/or answer to the question of free will. Instead, a concept would be appropriate in which one gradually speaks of more or less freedom. Thus, when we are wide awake and thinking well, we achieve a greater degree of free will than when we are tired, stressed, or drunk.
The situation remains tricky, as with so many philosophical questions. Studies suggest that unconscious processes are more involved in our decisions than it appears. Nor are they always consistent with our conscious intentions. But what role consciousness plays in decision-making remains unclear for the time being.
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