WHAT IS CONSCIOUSNESS? What is this ineffable, subjective stuff—this thing, substance, process, energy, soul, whatever—that you experience as the sounds and sights of life, as pain or as pleasure, as anger or as the nagging feeling at the back of your head that maybe you’re not meant for this job after all. The question of the nature of consciousness is at the heart of the ancient mind-body problem. How does subjective consciousness relate to the objective universe, to matter and energy?
Consciousness is the only way we experience the world. Without it, you would be like a sleepwalker in a deep, dreamless sleep, acting in the world, speaking, having babies, but without feeling anything. You would feel nothing, nada, nichts, rien. Indeed, in the most famous deduction of Western thought, philosopher and mathematician René Descartes concluded that because he was conscious he existed. That was his only unassailable proof that he wasn’t just a chimera. Maybe he didn’t have the body he thought he had, maybe he had fake memories (premonitions of The Matrix), but because he was conscious he must exist.
Yet the questions go on. Are only people conscious? What about a fetus? What about a neurological patient in a persistent vegetative state, such as Terri Schiavo (who died in 2005), who can’t do much more than open and close her eyes? Although many are willing to accord sentience, consciousness, to our beloved cats and dogs, what about apes, monkeys, whales, mice, bees and all the other critters on the planet? Can a fly be conscious? What about artificial consciousness? Is your cool iPhone sentient? Can machines ever become conscious, as is widely assumed in so many science-fiction novels and movies?
Until recently, these questions were purely within the domain of speculative philosophy and fantasy. But over the past decades, science has been making huge strides in exploring the brain. An immense number of psychological, medical, neurobiological and physical stories about consciousness can now be told. Each Consciousness Redux essay will illuminate one facet of one of the most central, enduring and puzzling aspects of the world, subjective feelings.
I am a scientist who seeks rational explanations of ineffable consciousness and of how and why it arises in the brain. But I also realize that our universe is a strange place; there are more things in heaven and earth than are dreamt of in philosophy. So I try to be humble when it comes to one of the most mystifying aspects of this universe—that I wake up each day and find myself conscious, capable of seeing, touching, loving, feeling and remembering. I am not a zombie! Many different traditions besides the modern scientific one have provided answers, and we should not reject them out of hand but listen to them.
As I write these lines, I am flying back from the annual meeting of the Association for the Scientific Study of Consciousness that took place, this year, in Taipei, Taiwan. It’s a gathering of hard-nosed philosophers, neurologists, psychologists and neuroscientists concerned with consciousness. One of its high points is an annual award, named in honor of the father of American psychology. The 2008 William James Prize for Contributions to the Study of Consciousness went to Naotsugu Tsuchiya, a young neurobiologist from the California Institute of Technology. What had he done that caught the attention of the prize committee?
In 2005 Tsuchiya invented a technique, continuous flash suppression, which renders a picture invisible, hiding it from your conscious sight. Yet some part of your brain has access to the image and influences your behavior in untold ways. The way it works is simple. Say Tsuchiya wants to camouflage a picture of an angry male face. With the help of a split computer screen, Tsuchiya projects a faint image of this snarling guy into your left eye. Your right eye sees a rapidly changing set of colored rectangles, one on top of another. If you keep both eyes open, all you see are the ever changing series of colored patches but no angry face. The constantly flickering colors attract your attention in a way that the static portrait does not. As soon as you close your right eye, the face becomes visible. But otherwise you have no inkling that the face is there, even though your left eye has been staring at it for many minutes. You simply do not see it. So what is the big deal?