Steven Pinker skriver i TIME om medvetandets stora mysterium. Det är inte mycket att säga om artikeln annat än att den är oerhört läsvärd. Att medvetandet är vad hjärnan gör (låter så mycket bättre på engelska; the mind is what the brain does) är allmänt accepterat inom neurologin och det är nog väldigt få vetenskapsmän inom övriga delar av biologin som skulle påstå något annat. Hjärnforskningen har ju gjort det alldeles uppenbart att det vi kallar "jag" är ett resultat av miljoner nervcellers aktiviteter. Svårgripbart, men knappast omöjligt att studera.

Scientists have exorcised the ghost from the machine not because they are mechanistic killjoys but because they have amassed evidence that every aspect of consciousness can be tied to the brain. Using functional MRI, cognitive neuroscientists can almost read people’s thoughts from the blood flow in their brains. They can tell, for instance, whether a person is thinking about a face or a place or whether a picture the person is looking at is of a bottle or a shoe.

And consciousness can be pushed around by physical manipulations. Electrical stimulation of the brain during surgery can cause a person to have hallucinations that are indistinguishable from reality, such as a song playing in the room or a childhood birthday party. Chemicals that affect the brain, from caffeine and alcohol to Prozac and LSD, can profoundly alter how people think, feel and see. Surgery that severs the corpus callosum, separating the two hemispheres (a treatment for epilepsy), spawns two consciousnesses within the same skull, as if the soul could be cleaved in two with a knife.

And when the physiological activity of the brain ceases, as far as anyone can tell the person’s consciousness goes out of existence. Attempts to contact the souls of the dead (a pursuit of serious scientists a century ago) turned up only cheap magic tricks, and near death experiences are not the eyewitness reports of a soul parting company from the body but symptoms of oxygen starvation in the eyes and brain. In September, a team of Swiss neuroscientists reported that they could turn out-of-body experiences on and off by stimulating the part of the brain in which vision and bodily sensations converge.

Förutom att spöket i maskinen är borta har vi även börjat inse att hjärnan är en riktig spindoktor. Det tas inte upp i artikeln, men psykologisk forskning tyder på att våra långtidsminnen är fulla av efterkonstruktioner och rationaliseringar - mycket av det du tror har hänt hände i själva verket aldrig så som du föreställer dig. Det aktiva medvetandet är långtifrån summan av dina samlade intryck, eftersom intrycken är på tok för många för att hantera på en medveten nivå. Hjärnan försöker istället bygga ihop en bild av världen som både hänger ihop logiskt och är till någon nytta.

The brain’s spin doctoring is displayed even more dramatically in neurological conditions in which the healthy parts of the brain explain away the foibles of the damaged parts (which are invisible to the self because they are part of the self). A patient who fails to experience a visceral click of recognition when he sees his wife but who acknowledges that she looks and acts just like her deduces that she is an amazingly well-trained impostor. A patient who believes he is at home and is shown the hospital elevator says without missing a beat, "You wouldn’t believe what it cost us to have that installed."

Många människor skulle förmodligen känna sig obekväma med att inte längre ha någon själ, för att inte tala om hur svindlande tanken är att det vi upplever som vår fria vilja kanske egentligen är en efterrationalisering. En del ser detta som anledning nog att hålla fast vid en mer magisk syn på livet, om inte annat för att skydda det man kallar etik och moral, men Pinker avslutar sin artikel med att förklara varför det inte behöver vara så hemskt trots allt:

In his millennial essay "Sorry, but Your Soul Just Died," Tom Wolfe worried that when science has killed the soul, "the lurid carnival that will ensue may make the phrase ‘the total eclipse of all values’ seem tame."

My own view is that this is backward: the biology of consciousness offers a sounder basis for morality than the unprovable dogma of an immortal soul. It’s not just that an understanding of the physiology of consciousness will reduce human suffering through new treatments for pain and depression. That understanding can also force us to recognize the interests of other beings–the core of morality.

As every student in Philosophy 101 learns, nothing can force me to believe that anyone except me is conscious. This power to deny that other people have feelings is not just an academic exercise but an all-too-common vice, as we see in the long history of human cruelty. Yet once we realize that our own consciousness is a product of our brains and that other people have brains like ours, a denial of other people’s sentience becomes ludicrous. "Hath not a Jew eyes?" asked Shylock. Today the question is more pointed: Hath not a Jew–or an Arab, or an African, or a baby, or a dog–a cerebral cortex and a thalamus? The undeniable fact that we are all made of the same neural flesh makes it impossible to deny our common capacity to suffer.

And when you think about it, the doctrine of a life-to-come is not such an uplifting idea after all because it necessarily devalues life on earth. Just remember the most famous people in recent memory who acted in expectation of a reward in the hereafter: the conspirators who hijacked the airliners on 9/11.

Think, too, about why we sometimes remind ourselves that "life is short." It is an impetus to extend a gesture of affection to a loved one, to bury the hatchet in a pointless dispute, to use time productively rather than squander it. I would argue that nothing gives life more purpose than the realization that every moment of consciousness is a precious and fragile gift.

Andra bloggar om: biologi, neurologi, medvetande, hjärnan, hjärnforskning, själen