Om medvetandets roll i beslutsfattande

Neurofysiologen Benjamin Libets arbeten om den relativa timingen mellan viss slags hjärnaktivitet och det vi subjektivt upplever som beslutsfattande är så överraskande och kontraintuitiva att de kommit att bli närmast ikoniska. Så här skriver Sam Harris i sin lilla pärla till bok Free Will^1,2:

The physiologist Benjamin Libet famously used EEG to show that activity in the brain's motor cortex can be detected some 300 milliseconds before a person feels that he has decided to move. Another lab extended this work using functional magnetic resonance imaging (fMRI): Subjects were asked to press one of two buttons while watching a "clock" composed of a random sequence of letters appearing on the screen. They reported which letter was visible at the moment they decided to press one button or the other. The experimenters found two brain regions that contained information about which button subjects would press a full 7 to 10 seconds before the decision was consciously made. More recently, direct recordings from the cortex showed that the activity of merely 256 neurons was sufficient to predict with 80 percent accuracy a person's decision to move 700 milliseconds before he became aware of it.

These findings are difficult to reconcile with the sense that we are the conscious authors of our actions. One fact now seems indisputable: Some moments before you are aware of what you will do next - a time in which you subjectively appear to have complete freedom to behave however you please - your brain has already determined what you will do. You then become conscious of this "decision" and believe that you are in the process of making it. (Harris, s 8-9.)

Eller, ännu lite slagfärdigare formulerat:

Fotnoter

1) Sam Harris besvarar frågan om den fria viljans existens med ett solklart nej - i kontrast med Daniel Dennett, som i den här på bloggen nyligen hyllade Intuition Pumps och i tidigare böcker besvarar den med ja. Det verkar dock inte finnas några väsentliga skillnader mellan deras respektive uppfattningar i själva sakfrågan om vad som faktiskt försiggår i våra hjärnor, utan det handlar mer om vad vi bör lägga i begreppet fri vilja. Tom Clark artikulerar skillnaden i följande stycke, som Harris återger på s 20-22 i sin bok och som både han och (enligt uppgift) Dennett accepterar som en riktig beskrivning av meningsskiljaktigheten:

Harris is of course right that we don't have conscious access to the neurophysiological processes that underlie our choices. But, as Dennett often points out, these processes are as much our own, just as much part of who we are as persons, just as much us, as our conscious awareness. We shouldn't alienate ourselves from our own neurophysiology and suppose that the conscious self, what Harris thinks of as the real self (and as many others do, perhaps), is being pushed around at the mercy of our neurons. Rather, as identifiable individuals we consist (among other things) of neural processes, some of which support consciousness, some of which don't. So it isn't an illusion, as Harris says, that we are authors of our thoughts and actions; we are not mere witnesses to what causation cooks up. We as physically instantiated persons really do deliberate and choose and act, even if consciousness isn't ultimately in charge. So the feeling of authorship and control is veridical.

Moreover, the neural process that (somehow - the hard problem of consciousness) support consciousness are essential to choosing, since the evidence strongly suggests they are associated with flexible action and information integration in service to behavior control. But it's doubtful that consciousness (phenomenal experience) per se adds anything to those neural processes in controlling action.

It's true that human persons don't have contra-causal free will. We are not self-caused little gods. But we are just as real as the genetic and environmental processes which created us and the situations in which we make choices. The deliberative machinery supporting effective action is just as real and causally effective as any other process in nature. So we don't have to talk as if we are real agents in order to concoct a motivationally useful illusion of agency, which is what Harris seems to recommend we do near the end of his remarks on free will. Agenthood survives determinism, no problem.

Daniel Dennett har för övrigt alldels nyligen författat en lång och mycket läsvärd recension av Harris bok, där han inte lägger några fingrar emellan: han kallar visserligen boken "remarkable [...], engagingly written and jargon-free, appealing to reason, not authority, and written with passion and moral seriousness", men också "a veritable museum of mistakes". Den uppfattning som uttrycks i bildens Steven Kaas-citat, och som Harris i sin bok formulerar gång gå gång, bl.a. med orden...

Did I consciously choose coffee over tea? No. The choice was made for me by events in my brain that I, as the conscious witness of my thoughts and actions, could not inspect or influence.

...har Dennett inte mycket till övers för i sin recension:

Not so. He can influence those internal, unconscious actions—by reminding himself, etc. He just can’t influence them at the moment they are having their effect on his choice. (He also can’t influence the unconscious machinery that determines whether he returns a tennis serve with a lob or a hard backhand once the serve is on its way, but that doesn’t mean his tennis strokes are involuntary or outside his—indirect—control. At one point he says “If you don’t know what your soul is going to do, you are not in control.” Really? When you drive a car, are you not in control? You know “your soul” is going to do the right thing, whatever in the instant it turns out to be, and that suffices to demonstrate to you, and the rest of us, that you are in control. Control doesn’t get any more real than that.)

Harris ignores the reflexive, repetitive nature of thinking. My choice at time t can influence my choice at time t’ which can influence my choice at time t”. How? My choice at t can have among its effects the biasing of settings in my brain (which I cannot directly inspect) that determine (I use the term deliberately) my choice at t’. I can influence my choice at t’. I influenced it at time t (without “inspecting” it). Like many before him, Harris shrinks the me to a dimensionless point, “the witness” who is stuck in the Cartesian Theater awaiting the decisions made elsewhere. That is simply a bad theory of consciousness.

Harris har lovat replikera inom kort - håll utkik på hans blogg!

2) Jag har lyft bort ett par fotnoter från Harris passage, och istället tillfogat några länkar till hans källor.