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The Hierarchy of Brain and Mind


Kirschfeld,  K
Former Department Comparative Neurobiology, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Kirschfeld, K. (2006). The Hierarchy of Brain and Mind. Poster presented at 9th Tübingen Perception Conference (TWK 2006), Tübingen, Germany.

The general consensus is that the brain is something different from the mind: it is made of physical substance, and is subject to the laws of physics. The mind, however, cannot be described by physical methods. It is considered to be related to experiences such as perceptions or consciousness. The question of the connection between mind and brain, or that of body and soul, is probably the most profound problem at the interface between the “sciences” and the “arts”. That signals can be emitted by the brain and then enter our consciousness—and thus that the brain influences the mind—is hardly in dispute. Indeed, psychophysics is even capable of specifying a quantitative relationship between a physical stimulus and the sensation it elicits. Opinion is more divided regarding the question of whether the mind can also influence the brain. German criminal law presupposes that it does [1], and the sociologist J¨urgen Habermas shares this view [2].The concept that the brain determines the mind is consistent with the laws of physics. But this does not apply to the opposite concept, that the mind can affect the brain: an ability of the “mind” to modify the activity of nerve cells would contradict the principle of causality. Benjamin Libet [3], however, takes the latter concept as a starting point in one of his much-discussed experiments on the question of conscious free will. He measured how long it takes for us to make a voluntary movement after we become aware of the fact that we want to make it, and found that the delay was about 200 ms. Surprisingly, however, brain potentials that indicated the initiation of the movement were measurable more than 500 ms before the movement occurred. The conclusion: the “will” cannot trigger the movement, because it is evidenced 300 ms too late. If the opposite result had been obtained, so that the will to act was apparent prior to the brain activity, the conclusion would have been that this result is indeed consistent with the notion that the “will” initiated the movement. Furthermore, Libet concludes that “conscious control over the actual motor performance of the acts remains possible”. Another interpretation of his results, which however can be reconciled with the laws of physics, is as follows. Brain activity initiates both the activation of the muscles that produce the movement, and also the perception that one is “willing” to make the movement. Which of these processes first becomes apparent has no implications regarding the causal relationships. As long as one takes it as given that laws of physics apply to the brain, the possibility that the “will” initiates movements is ruled out.