The juxtapy of the Libet experiment?
Brain researchers pull closures about the man’s picture. A popular topic is the human decide. In addition to statements about whether the intuition or rational thinking is "smarter", it is also possible to represent a general and provocative thesis: human decide is completely determined by the brain and not of a free will. A new attempt to the Berlin brain researcher John-Dylan Haynes recalls the famous Libet experiment from the 1980s. But whether the results provide a statement about the free of will – appears in nearby examination anything else than likely.
Benjamin Libe’s goods were safe, he had the results of Chun Siong Soon, Marcel Brass, Hans-Jochen Heinze and John-Dylan Haynes may experience: unconscious influence on free decisions in the human brain (Nature Neuroscience 11, 543-545). Libet, a Neurophysiologist’s late year’s last year, was in many ways in many ways. He has not only met the question of consciousness, as hardly any other researcher dared to take the word in his mouth. In the experiments that made him so familiar, he has namely busy with human will-freedom. For this he had derived in an experiment electrical signals from the brain of his subjects, during this spontaneous to move the index finger. You also had to remember on a rough stopwatch, at what time she had made her decision. The evaluation of its results showed that the conscious experience of these decisions has frequently anticipated a so-called standby potential in the brain.
So the brain had already "decided" in advance and the subject afterwards the decision is experienced? It is interesting that Benjamin Libbie himself has never pulled this nearby conclusion in whole rigorously: for him there was still the possibility of a veto, with which people could stop the movement of the showfinger. The embassy is then: there may be no free want, but at least a free not-want. So that the person of their brain activation is not helplessly delivered helpless.
However, this restriction was almost no one taken into account and from all the roofs the message was spoiled: there is no free will, because the decision is already fixed, see standby potential. For example, Wolfgang Prinz, director at the Max Planck Institute for Cognitive and Neuroscience in Leipzig, refers to in this respect for Libete Research. Prince stop the free will for an illusion, a social invention, and likes to compare him with Marty Unicorns.
That the majority of the experiment was understood in the opposite way as the experimentator itself, hardly anyone has noticed today. You have to determine if the experimental data can noise both a claim and your opposite nozzle, then the experiment seems to be well not to be well suited to decide the question for debate. For experienced researchers such as Benjamin Libet or Wolfgang Prinz, one should ame that they are not only in the measurement procedures and data and therefore lead to different results.
"Reward reading" competition
Stephan mucus, author of the book Worse reading – Pioneering work of brain research, which appeared in the Telepolis series, writes a creative competition. For the best imple, as the technical procedures of "thought reading" could be used or misused in the future, attract attractive prices. Closing date is the 21. June 2008. The conditions of participation can be found on the Competition page.
Libet modernized
Now the researchers have published the outcome of their experiment around the study manager John-Dylan Haynes, which reminds of Libete experiments; and also she turns to the question of free will. In contrast to the early experiments, but the imaging methods of modern brain research are available, such as functional magnetic resonance tomography (FMRT). Due to strong magnetic fields, differences can be measured in the oxygen distribution of the brain, which is associated with neuronal activity, ie firing the 100 billion neurons in the brain.
For Chun Siong Soon and his colleagues, 14 test persons have gone to the pipes in which such a tomograph measures brain activation. Your task was to spontaneously print a button with the left or right index finger. In parallel, a random sequence of consonants ran on the screen, which was changed every 500 milliseconds. The moment the subjects for the push of the button had to remember the displayed letter. If Libbe was still the inaccurate Meng with the stopwatch, it would have to look more closely in the brain, at what time references to the decision to find. After the push of the button left or right according to their decision, the subjects had to specify, namely, which letter was just visible when they made the decision.
Haynes’ specialtat are pattern recognition methods to discover differences in the many ten thousand measured data points in the brain, which remain hidden from the most common methods. In this case, point for point as with a searchlight the entire brain can be collected; In all data points, the so-called voxeln, which fall into his light cone, you are looking for a meaningful pattern. This should allow the distinction whether the subjects had chosen the left or right side. However, the time resolution of the FMRT is not so good. Every two seconds, a snapshot of the entire brain is made and one contains only one representative value of the oxygen distribution for this period per voxel.
Soon and other researchers now went to look as far as possible in the past to moor the distinction between left and right side in the brain. The idea was there: Each would like to see it, before the subject of the subject has decided deliberately decided, the sooner the brain unconsciously prepared the decision. The searchlight paired with the pattern recognition allowed this distinction to seven seconds beforehand in the foremost area of the forehead; Since the signal measured by the FMRT, however, limits the actual neuronal activation in time, the researchers speak of up to ten seconds. Unlike, when you were expected, but the hit rate does not rise all the decision all until the time of the deliberately experienced decision, but then breaks again four to six seconds before.
It is therefore important not only the temporal duration, but also the hit rate – you just have blindly advised, you already came to the random rate of 50 percent. Every second decision could be said correctly before, (almost) as if you were putting on roulette on red or black. The measurement data from the brain increases the hit rate at some times to up to 60 percent and are thus significantly above the blind rates. comment
Is thus reied the topic "will-free"?
If you believe the media reports, you have to ame. Only a few, for example the journalists of SPIEGEL ONLINE, has noticed that 60 percent is not a crazy hit rate. Most others, including the specialist journalists from the magazine Nature Reviews Neuroscience, have simply suppressed the interpretation of Soon and his colleagues and also speak of a "high accuracy."
Overall, the strongness of prediction in recent studies has fallen on. If in the field of visual perception still came to 90 percent, one had to be concealed for concealed intentions, whether a lateral addition or subtraction was carried out (rendering patterns in the brain), already with 70 percent beggue. This will give the suspicion that even the latest methods of pattern recognition are gradually stobbing their limits.
Even 60 percent are still better than nothing. But the amption that the brain "decisions" the matter should, whether to print left or right, already experienced before the conscious? That the conscious decision is falling only at the time t0, in any case, does not mean that there was no conscious advancement for the earlier date, which prepared the decision. If thereby influenced in some cases where you print later, the present data of the researchers were equally well suited. One should not forget that the subjects are not unconscious in the pipes before their push-button. After all, it took more than 20 seconds on average, until the test person made their decision for a passage. In fact, among professionals, there is a controversy about what the subjects actually do when they lie in the brain scanner and apparently do nothing. Therefore, the argumentation of the researchers, they had discovered "unconscious influencing", not completely. For how do you want to distinguish in the brain conscious of unconscious influences from each other?
In addition, Soon and his colleagues had excluded more than half of the subjects in an advance experiment because they did not behave according to their ideas. For example, if you tended too much to one side, so left or right preferred or not spontaneously decided enough, was not allowed in the tomographs. This raises the question of whether the results can be generalized on everyday life decisions – here we often have the impression of consciously controlling our behavior through planning and strategies. The subjects in the scanner, on the other hand, have gotten created, just do not apply strategies; It bothered to print exactly if you are the "penetration gets true to do it."What meaning does it have for a person to find a" urge "to print a left or right knob? This is certainly not a prime example of human decisions. If conscious strategies are forbidden, then it seems succinctly no longer surprising to find a brain activation that is already preparing for one or the other movement in front of the conscious experience, at least tend.
Another council give the measurement data recorded after the conscious experience of the decision. For a long time, in the left and right motor cortex, which lie on the upper external randoms in about the middle of the brain, the movements of the other corporal halves are controlled in the middle of the brain. Thus, the left motor area for the movement of the right finger is conditional and vice versa. By electrical stimulation in these areas you can even exclude unwilling movements. If you use the searchlights from Soon and colleagues for the later time, so, especially in these areas, you have expected a stronger activation. These have also found the researchers – but love their methods CA. Three to four seconds later only with 75 percent hit rate the distinction between left and right side.
But if you want to know that with certainty on the left side a strong signal must have been when the person printed on the right, why does not allow the methods of pattern recognition to grow 100 percent? In early experiments, one could even determine with the Bloben eye on the basis of the signal history in regions, which process, for example, the visual perception of homes or landscapes, with 85 percent hit rate, whether a subject is just a house or landscape; And that not only worked on average, as with Soon and colleagues, but for every single time the participants made this idea. Conclusion
From neuroscientific perspective is the new study by Chun Siong Soon, Marcel Brass, Hans-Jochen Heinze and John-Dylan Haynes sure a high quality and interesting work. However, the interpretation becomes problematic, it deals with "unconscious influence" on a "free decision."Above all, it remains appealing what this data contributes to our understanding of free will and free decisions. As a similar to Benjamin Libets, it has been interpreted unilaterally and superflatable until today, therefore, the new study in future discussions was allowed to drive their spooky. One should expect from the appropriate researchers but first a description of what they understand at a free will before they are looking to refute him.