Benjamin Libet
Researcher in the physiology department of the University of California, San Fransisco. Pioneer in the study of human consciousness.
In the 1970's, Libet researched neural activity and sensation thresholds. His initial research involved determining how much activation at specific sites in the brain would trigger artificial somatic sensations, relying on routine psychophysical procedures. Libet's work soon crossed into the realm of investigation of human consciousness, and his most famous and controversial experiment seems to imply that brain physiology precludes free will.
The Experiment
Libet utilized a number of tools in his research. The first of these was the oscilloscope, typically used to graph amplitude and frequency of sound waves. With a few adjustments, however, the oscilloscope could be made to act as a timer. Instead of displaying a series of waves, the output was a single dot that could be made to travel in a circular motion. This timer was set so that the time it took for the dot to travel between each set of marks was approximately forty-three milliseconds. As the angular velocity of the dot remained constant, any change in distance could easily be converted into the time it took to travel that distance.
Additionally, Libet used an electroencephalogram, or EEG, to monitor brain activity. Developed in 1936 by British scientist Walter Grey Walter and inspired by work done in 1929 by Hans Berger, a German psychologist, the EEG uses small electrodes placed at various points on the scalp that measure neuronal activity in the cortex, the outermost portion of the brain, which is associated with higher cognition. The transmission of electrical signals across regions of the cortex causes differences in measured voltage across EEG electrodes. These differences in voltage, known as Event Related Potentials, or ERPs, can be used reliably to show activity in specific areas of the cortex.
Researchers carrying out Libet’s procedure would ask each participant to sit at a desk in front of the oscilloscope timer. They would affix the EEG electrodes to the participant’s scalp, and would then instruct the subject to carry out some small, simple motor activity, such as pressing a button. Additionally, the subject would be asked to note the position of the dot on the oscilloscope timer when “he/she was first aware of the wish or urge to act.” Pressing the button marked the end of the trial, and the position of the dot on the timer was noted again, this time electronically. From these two data points, the position of the timer when the subject gets the urge to push the button and the position of the timer when the button is pushed, researchers were able to calculate the total time of the trial from volition to action. On average, approximately two hundred milliseconds elapsed between the first appearance of conscious will and the act of pressing the button. Researchers also analyzed EEG recordings for each trial with respect to the timing of the action. Here, brain activity involved in the initiation of the action, primarily centered in the secondary motor cortex, occurred, on average, approximately five hundred milliseconds before the trial ended with the pushing of the button. That is to say, researchers recorded brain activity for the pushing of the button as many as three hundred milliseconds before subjects reported the first awareness of conscious will to act.
Implications of Libet's Work
If the brain is the initiator of volition, as Libet's experiments suggest, then what room is left for free will? On the surface, none. If the brain has already taken steps to initiate an action before we are made aware of it, the causal role of conscious volition is all but eliminated.
It would be useful to pause for a moment and consider just what free will actually is. It could be said that will is internal, and that as long as our decisions are internal and not influenced by outside forces, our volitions are free. Psychology as a whole has actually denied this interpretation for quite some time. The two most prominent behavioral theories of the twentieth century, genetics and behaviorism (in other words, nature vs. nurture) are deterministic in nature. One says that our personalities are determined from conception and are based on our genes. The other says that our current personalities are the sum of our memories and experiences. Current thinking blends the two, but the conclusion is still the same: our actions are the product of outside forces. The only way these views make sense is if we consider only the neuronal physics of the brain. Therefore, if we assume that will to act occurs at the level of the brain, then we necessarily assume that neural connections are formed based on simple physics as a result of genetics and experience, and that our actions are determined by outside forces. Thus, in order for free will to exist, it must occur at the level of the mind. This is why Libet's findings are deadly for free will. The mind is left out of the loop while the brain takes orders from the outside world.
Libet himself attempts to reinsert free will into the equation, even in the light of his research. He begins by saying that perhaps the brain generates many more readiness potentials than are actually acted upon, and that the conscious mind is responsible for vetoing those actions it does not want to carry out. He then goes on to talk about "consciousness fields," and other seemingly mystical explanations, but these explanations raise more questions than they answer, as Libet himself now has a Homunculus problem by stating that there is a mechanism in the brain which can veto unconscious urges to act.
At this point, it would be very easy to give up on free will and consciousness all together. Our subjective view of our existence, that consciousness and free will do in fact exist, could be completely wrong. It has been suggested that consciousness is merely a side-effect of neuronal function, an epiphenomenon of the way the brain works. Considering Libet’s research, this interpretation is entirely likely.
Source: Libet, Benjamin, Anthony Freeman & Keith Sutherland, ed. (1999). The Volitional Brain: Towards a neuroscience of free will. Exeter, UK: Short Run Press, Ltd.
--Jason Pfleiger 172.169.7.148 08:36, 12 Jun 2005 (UTC)