THE BLOG

The Spirit Constructed in the Brain

04/29/2011 12:45 pm ET | Updated Jun 29, 2011

For 20 years at Princeton University I studied how the brain processes sensory information and controls movement, but lately I've become interested in a more esoteric question, the big question of neuroscience: the brain basis of consciousness. There is now a conceptually simple theory that in principle can account for consciousness, that has emerged over the past 10 to 15 years, and that in my view is likely to be correct at least in its general outlines, although a great deal of scientific controversy still surrounds the topic. I wrote about this theory in my recent book, God Soul Mind Brain.

This theory of consciousness begins with something called social perception. Humans are social animals, and not surprisingly the human brain has special-purpose machinery that allows us to be socially intelligent -- to reconstruct information about the contents of other people's minds. When I interact with another person, I reconstruct what he might be thinking and feeling. I monitor what he might be aware of or what he might be attending to. All of this information forms a linked, interconnected bundle of data, an informational model of another person's mind, computed inside my own brain. It is a perceptual model of someone else's consciousness, and the study of the brain circuitry that computes this type of perceptual model is called social neuroscience.

Social neuroscience arguably began in the 1960s with experiments on monkeys. Monkeys are social animals, and it was discovered that neurons in a particular brain area carry information of social relevance, such as visual information about faces or about body gestures. The scientist who made these initial discoveries was Charles Gross, my long-time mentor. I worked in his lab for many years.

The findings from monkeys were picked up by many scientists and extended to the human brain, mainly by putting people in MRI scanners and measuring brain activity. It turns out that the human brain contains specific areas, mainly in the right hemisphere, but to some extent on both sides, that emphasize the task of social perception: of building an informational model of another person's mind. Damage to these brain areas can lead to a disability in social perception.

Now I would like to draw a distinction between two items: social perception and social cognition. The terms are used differently by different scientists, and the border between them is not absolute. We understand other people's minds at many different levels, some more cognitive and some more perceptual. But generally speaking, one might think of social cognition as more a process of intellectually figuring out what might be in someone's mind and social perception as more intuitive, more basic.

One of the best examples to get across this distinction is ventriloquism. In ventriloquism, as an audience member looking at the puppet, you know intellectually, cognitively, that there is no conscious mind in its head. But perceptually, you fall for the illusion. That is what makes ventriloquism fun. When a good ventriloquist makes the puppet move in realistic ways, directs its gaze with good timing, makes it react to its environment in a plausible way, the effect pops out. You can't help feeling as if consciousness, awareness, agency were emanating from the puppet. The social machinery in your brain constructs an informational model of a conscious mind that you project onto the puppet. In fact, you build two perceptual models of minds, one that you project onto the performer and the other that you project onto the puppet. Ventriloquists have worked out a set of tricks to enhance this illusion of two separate minds. That is why the puppet always has a different tone of voice and usually argues with the performer.

Ventriloquism is an exotic example, but this tendency to perceive mind in things is something we do every day. How many times have you gotten mad at your car? You know it doesn't have a mind, but you can't help constructing that perceptual model. We do the same thing to our TVs and to our computers. Some people talk to their plants. Children talk to their stuffed animals.

We do the same thing with respect to each other. When I meet a new person, my brain constructs an informational model of a mind, a consciousness, and attributes it to that person. That model allows me to predict the person's behavior, at least to some extent, and to interact more effectively.

According to the theory, I do the same thing with respect to myself. I perceive consciousness in myself. My brain constructs a perceptual model of a mind that thinks this and that, feels this and that and is aware of this and that; the mind is attributed to my own location. That model provides an organized, coherent way for me to understand myself -- to predict and help guide my behavior. It is not always accurate; it is woefully incomplete; but it is a useful model of myself.

This realization that consciousness is a perception is counterintuitive. We think of consciousness as something ghostly that inhabits an object. But according to this neuro-social theory, consciousness is a perception that is attributed to something. Like beauty, consciousness is in the eye of the beholder. Our brains actively paint consciousness onto ourselves and onto the objects around us.

The implications for spiritual belief are rather startling. In this theory, the spirit world is the complex, richly detailed universe of social perception, the perception of mind. We not only perceive consciousness in ourselves and in others, but we perceive it in the objects and spaces around us. Spiritualism is a fundamental mode of perception by which humans relate to the world. In this view, spiritualism is not an incorrect theory; not a misapplication of rational thought; not pseudoscience. One of the reasons why scientific rationalism has such trouble dealing with religion is that spirituality is not generally about rational thought, evidence or logical inference. At root it is a built-in tendency to construct perceptions of mind, project them around us, and then move through and interact with that perceptual world.

I find myself in the end with a theory that does not fit neatly into anyone's political bunker. It is decidedly materialistic and atheistic. Yet according to the theory, spirits exist -- deities, ghosts, souls, the consciousness of other people, one's own consciousness -- as rich perceptual simulations run on the hardware of the brain. That perceptual world has psychological reality and genuine importance to human existence.