Free will is the ability to make choices without being limited by any number of factors. This is what the definition on Wikipedia tells us. Each of us is convinced that he has it, and some believe that man is the only animal with this feature. Are we really free to make choices or make decisions? Are our choices free, dependent only on us, or is the freedom in making decisions an illusion, because everything is decided for us by processes taking place in the nervous system?
One of the hottest debates in biology revolves around the question of "innate or learned" in relation to the relative importance of genetics and biology as compared to culture and environment for human behavior. The researchers' view is that many human behavior can be explained by reference to the brain's work, genes, and evolutionary history. This point of view raises the fear that such attribution prevents others from being held accountable for their actions.
Currently, neuroscience enables us to study the brain in real time, which is an ideal tool for studying "free will". The first experiments in this field were carried out by Benjamin Libet in the 1980s. He was interested in the detection of the so-called the action potential in the cerebral cortex while the subjects make an apparently arbitrary decision to perform a movement at a given moment. It was already known that this potential would noticeably precede the first muscle movements, but as people were asked to look at the clock all the time and remember the moment in which they decided to act, it turned out that the potential in the brain to prepare for movement appeared until half a second before this decision is realized in consciousness. This confirmed earlier - and probably unknown to Libet himself - philosophical claims that consciousness is only somehow responsible for "leading" a movement or action, while the very existence of "energy" to that which necessarily gets an outlet is a thing belonging to the world of the unconscious. Numerous other experiments of this type have been carried out, proving the possibility of accurately predicting a human decision before the decision-maker knows about it (convinced that he is coming to it and is choosing it), provided that the bioelectric potentials in the brain were observed. One of the most famous experiments is the Kornhuber experiment.
Under certain conditions related to the state of the brain, people are unable to fully control their actions. Although the existence of such conditions does not directly disprove the existence of free will, studying them, similar to e.g. research, has value in developing models of how the brain can produce our experiences of freedom. For example, people with Tourette Syndrome and related tic disorders make unwanted movements and sounds, the so-called tics, even though they would rather not do it when it is not appropriate. Tics are described as "unwanted" or "unwanted" because they are not strictly unwanted: they can be experienced as a wanted response to an unwanted prior urge. Tics are experienced as an irresistible urge and must ultimately take place. People with Tourette Syndrome are sometimes able to hold their tics down for a limited period of time, but doing so often results in tics exploding afterwards. Maintained control (from seconds to sometimes hours) merely delays and exacerbates the subsequent expression of the tic. In foreign hand syndrome, the affected limb produces meaningful behavior without intention. As a result, the diseased limb shows a "will of its own". The impression of control does not arise in connection with the overt occurrence of a deliberate act, although the sense of belonging to the body is preserved. This phenomenon corresponds to the weakening of the premotor mechanism expressed in time by the emergence of the readiness potential, registered on the scalp hundreds of milliseconds before the spontaneous, voluntary movement appears. When using fMRI to study the temporal dimension of cortical network activation associated with voluntary movement in humans, a sequential process of activation "from predecessor to successor" is observed, starting in the so-called an additional motor cortex (SMA) on the medial surface of the frontal lobe and extending into the primary motor cortex and then into the parietal lobe. The sensation of control thus appears to normally coincide with this ordered sequential activation network, involving the premotor association centers along with the primary motor cortex. In particular, the auxiliary movement unit on the medial surface of the frontal lobe appears to activate in front of the primary motor cortex, possibly due to a pre-motor preparation process. In a recent fMRI study, foreign movement was characterized by relatively isolated activation of the primary motor cortex on the opposite side of the foreign hand, while voluntary movement of the same body part was accompanied by activation of motor association centers associated with the premotor process. The standard neurological explanation is that the felt will reported by the speaking left hemisphere does not correspond to the actions performed by the mute right hemisphere, thus suggesting that these hemispheres may have independent sense of will. Likewise, one of the most salient symptoms of schizophrenia is the illusion of being controlled by an outside force. Schizophrenics sometimes report that, despite their own actions in the world, they do not initiate or want specific actions taken by them. Sometimes it is compared to being a robot controlled by someone else. While the neural mechanisms behind schizophrenia are not yet clear, there is an influential hypothesis that there is a failure of the brain's systems to compare movement commands and body feedback (known as proprioception), leading to accompanying hallucinations and delusions (lack of) control. The issue of free will is so complex that it is impossible to say unequivocally whether we have it. In some states, it can be strongly disturbed, but Libet's experiment unequivocally emphasizes the fact that even if free will exists, it is an illusion, and in fact we are only looking at our predefined actions.
Interestingly, in accordance with the intentions of Hans Kornhuber and Lüder Deecke, the Bereitschaftspotential was never intended to be used as an argument in the debate about free will. If anything, the scientists wanted to show that the brain… has free will, or at least to some extent. At the root of the decision to initiate research was the frustration that science approached the brain as a passive machine that only works and produces thoughts in response to the outside world. "Kornhuber and I believed in free will," said Deecke. According to both scientists, Bereitschaftspotential is only an electrophysiological sign of planning and initiating action. However, it is not he who causes this planning, much less he makes decisions about action.
Libet, who died in 2007, had as many defenders as critics. It seemed unlikely to many scientists that our conscious decision was merely an illusion. Nevertheless, in the decades since his experiment, subsequent studies conducted on increasingly sophisticated equipment, including the use of modern technologies such as fMRI, confirmed his discovery.
Jeff Miller and Judy Trevena of the University of Otago organized a similar experiment in 2009 in which they also used electrodes attached to the heads of volunteers. The respondents' task was to press a key, but only after hearing the signal. The researchers assumed that if Libet was right, the potential following the sound should be more pronounced when the volunteer decided to press a key. Meanwhile, it turned out that the readiness potential did exist before the choice was made, but was the same whether or not someone made a move. The conclusion was that such potential was an expression of increased attention and not of decision-making.
In 2010, Aaron Schurger from the Institut national de la santé et de la recherche médicale in Paris studied changes in neuronal activity. At one point, he looked at the screen and saw what looked like Bereitschaftspotential. Perhaps, he thought at the time, it was not a stimulus at all, forcing the brain to make decisions without our knowledge and consent. It was this willingness potential, rather than a will, that seemed to be a side effect. He signaled traffic planning but did not decide on it. Two years later, Schurger and his colleagues Jacobo Sitt and Stanislas Dehaene, after conducting further experiments, offered an explanation. Neuroscientists know that when we want to make any decision, our neurons must gather evidence for each option. A decision is made when a group of neurons accumulates evidence above a certain threshold. According to Schurger, Sitt, and Dehaene, the potential of readiness is the noise of neurons gathering data on the basis of which a person makes an informed decision! It is a sign of the work of neurons, and not a stimulus forcing one or another decision or reaction, the three experimenters conclude. We do this ourselves. On your own responsibility.
Literature:
Pinker, The Blank Slate: The Modern Denial of Human Nature. London: Penguin, 2002, Dawkins, The Selfish Gene. Oxford: Oxford Univ. Press, 1976. Bundick, M. Spinella, Subjective experience, involuntary movement, and posterior alien hand syndrome Journal of Neurology, Neurosurgery and Psychiatry 68 Schneider, Clinical Psychopathology New York: Grune and Stratton,
No comments:
Post a Comment