venerdì 13 agosto 2010

Why We See Spirits and Souls


Why We See Spirits and Soul.

Uunderstanding the neurobiology of religious belief is a far cry from explaining it away.

By Michael Graziano

Scientific anti-theism began, arguably, with Thomas Huxley, the 19th-century champion of the theory of evolution who styled himself “Darwin’s bulldog.” Huxley advocated improving the Bible by removing “statements to which men of science absolutely and entirely demure.” Since then, the view that science should correct people’s mistaken religious beliefs, and even more so that science is fundamentally antithetical to religion, has grown in popularity. It is now championed by influential public figures like Richard Dawkins and Christopher Hitchens.

A primary basis for scientific anti-theism is that much of religion can potentially be explained by science. The philosopher Daniel Dennett sees religious belief as a non-adaptive byproduct of other developments in our evolution. The anthropologist Pascal Boyer finds the foundation of religion in our psychological readiness to accept vivid, memorable tales about the world around us. Even more threatening to traditional understandings of religion is the emerging neuroscience of human consciousness. The molecular biologist Francis Crick (co-discoverer of DNA) argued that human consciousness — and thus the soul, so to speak — is nothing more than an emanation of our neuronal machinery. A more recent analogy holds that the software of the mind cannot exist independently of the physical hardware of the brain. For many advocates of these views, religion thus comes tumbling down, its fundamental tenets “explained away.”

But I’m not so sure. I’m a neuroscientist and also an atheist, but I’m not an anti-theist. I find religion to be a fascinating human psychological and cultural phenomenon and see no reason to try to eradicate it (not that it could be eradicated ). Nor do I believe that science — and neuroscience in particular — can somehow persuade people that religion is nonsense.

To explain something is not the same as to explain it away. Neuroscientists can explain much of gustatory perception. We understand in great detail the interrelated functioning of receptors in the tongue, the neurons that carry the signals, and the centers in the brain that receive the information. But explaining taste has not rendered it obsolete. No one has responded to these discoveries by giving up on delicious food.

Neuroscience can indeed explain, in a general way, some widely shared aspects of religious belief and behavior. Our brains possess specialized machinery that allows us to be socially intelligent: we are primed to think about, believe in, and even “feel” the presence of conscious minds. From this perspective, it is no accident that most religious traditions include a set of beliefs about conscious entities that exist inside of people (the soul) or that exist independently of physical bodies (ghosts, angels, spirits, gods).

Cognitive neuroscientists such as Nancy Kanwisher and Rebecca Saxe at MIT have found that social cognition depends on a set of structures mainly in the right hemisphere of the brain. When we interact with another person, that machinery brings together our prior knowledge with facial expressions, body language, spoken words, and other information to construct a model of the other person’s mind (what neuroscientists call a “theory of mind”). We experience this model as though we are sensing the other person’s emotions and intentions.

Without that specialized machinery, we would be socially blind. We would be oblivious to other people’s conscious minds. With that social machinery in place, we are prone to see minds everywhere — in ourselves, in other people, and floating in the spaces around us as ghosts and spirits. Factually speaking, spirits are projections of the brain. They are, as an anti-theist might say, merely constructs of our social intelligence.

But there is a problem with that “merely.” Consider human consciousness, which is evidently no less a construct of the brain. In my own work, I have proposed that human consciousness is a social perception. Just as we perceive motives and emotions and awareness in other people, so we perceive the same properties in ourselves. The machinery in the brain that is used to understand other minds may be used to understand our own minds as well.

If consciousness is merely a construct of our social machinery, and therefore not a real thing independent of the brain, does that mean we should ignore it and relegate it to the category of nonsense “explained away” by science? Can we dismiss conscious self-awareness from our minds? Perhaps perceptions have a validity of their own, even if they are purely constructs of the brain and do not correspond to a concrete reality.

One of the strangest insights to emerge from neuroscience is the distinction between perception and reality. We experience our perceptions, not reality. Ever since the cortical physiology of color was first explored in the 1960s by David Hubel and Torsten Wiesel, physiologists have understood that color does not exist in any absolute sense. Wavelengths of light exist, but the colors that we perceive as green and blue do not correspond in any simple way to these wavelengths. Color is a relative property. It depends on the eye’s sampling of wavelengths from many surfaces over an entire visual scene and the brain’s comparison of one surface to another. The same wavelength might look green in one visual scene, red in another, gray in a third.

But no one thinks that, on the basis of these findings, color has been “explained away” or shown to be false. When we observe wavelength, we perceive it as color. When we observe a brain actuating a body, we perceive it as a conscious entity. Both have a “real” side and a reconstructed, perceptual side. We live and move and act in the world of our perceptions and must take them as they are.

Much of the modern clash between science and religion focuses on questions about whether God exists independently or is a construct of the brain and whether the soul lives on after the body or ends when the brain dies. Are these crucial religious questions? I would argue that they are not. For the vast majority of people, religion is a way of life. It is about community and music, place and food, comfort and emotional support. It is, like all of human culture and experience, a function of our peculiar neurobiology, and we should try to appreciate it as such.

Michael Graziano is a professor of neuroscience in the psychology department at Princeton University and the author of God, Soul, Mind, Brain: A Neuroscientist’s Reflections on the Spirit World.

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