Physician and biologist, director of the Neurosciences Institute in San Diego
"William James, the great psychologist and philosopher, said consciousness has the following properties: It is a process, and it involves awareness. It’s what you lose when you fall into a deep, dreamless slumber and what you regain when you wake up. It is continuous and changing.
"There is every indirect indication that a dog is conscious—its anatomy and its nervous system organization are very similar to ours. It sleeps and its eyelids flutter during REM sleep. It acts as if it’s conscious, right? But there are two states of consciousness, and the one I call primary consciousness is what animals have. It’s the experience of a unitary scene in a period of seconds, at most. Yet there’s no consciousness of consciousness, nor any narrative history of the past or projected future plans.
"Humans are conscious of being conscious, and our memories, strung together into past and future narratives, use semantics and syntax, a true language. We are the only species with true language, and we have this higher-order consciousness in its greatest form. If you kick a dog, the next time he sees you he may bite you or run away, but he doesn’t sit around in the interim plotting to remove your appendage. He can have long-term memory, and he can remember you and run away, but in the interim he’s not figuring out, 'How do I get her?' because he does not have the tokens of language that would allow him narrative possibility. He does not have consciousness of consciousness like you.
"If you touch a hot stove, you pull your finger away, and then you become conscious of pain. The problem is this: No one is saying that consciousness is what causes you to instantly pull your finger away. That’s a set of reflexes. But consciousness sure gives you a lesson, doesn’t it? You’re not going to go near a stove again."
—From an interview with DISCOVER, 2009
Michael S. Gazzaniga
Cognitive neuroscientist at the University of California, Santa Barbara
"The brain is a vastly parallel distributed system. The consciousness trick is that any particular mental state you might be in is enabled by neural circuits specific to that state. All of these circuits that are distributed throughout the brain allow for what we call conscious experience.
“I like to think of it as being like a pipe organ. When one note is playing, that’s what you’re conscious about. Then the next note starts playing, and that’s what you’re conscious about. These things come on and off constantly, and there’s this appearance of unity to it all, but in fact it’s each of these separate circuit systems being enabled and being expressed in a particular moment in time.
“Consciousness is not a thing in the brain that information gets poured into and you’re aware of it. It’s the constant struggle of all these circuits to come up to the top and hold the stage for that second.”
—From a DISCOVER roundtable, 2008
Professor of neuroscience at New York University Medical Center
"I seriously believe that consciousness does not belong only to humans; it belongs to probably all forms of life that have a nervous system. The issue is the level of consciousness. Maybe in the very primitive animals . . . there may not have been consciousness, just primitive sensation, or irritability, and primitive movement. But as soon as cells talked to one another, there would be a consensus.
"This is basically what consciousness is about—putting all this relevant stuff there is outside one’s head inside, making an image with it, and deciding what to do.”
—From an interview for NOVA, 2001
Sir Charles Sherrington
British physiologist, 1932 Nobel Prize in Physiology
"The great topmost sheet of the mass, that where hardly a light had twinkled or moved, becomes now a sparkling field of rhythmic flashing points with trains of traveling sparks hurrying hither and thither. The brain is waking and with it the mind is returning.
"It is as if the Milky Way entered upon some cosmic dance. Swiftly the head mass becomes an enchanted loom where millions of flashing shuttles weave a dissolving pattern.”
—From his book Man on His Nature, 1940
Director of the Brain and Creativity Institute at the University of Southern California
‘‘The drama of the human condition comes solely from consciousness. Of course, consciousness and its revelations allow us to create a better life for self and others, but the price we pay for that better life is high. It is not just the price of risk and danger and pain. It is the price of knowing risk, danger, and pain. Worse even: It is the price of knowing what pleasure is and knowing when it is missing or unattainable.
“The drama of the human condition thus comes from consciousness because it concerns knowledge obtained in a bargain that none of us struck: The cost of a better existence is the loss of innocence about that very existence. The feeling of what happens is the answer to a question we never asked, and it is also the coin in a Faustian bargain that we could never have negotiated. Nature did it for us.”
—From his book The Feeling of What Happens, 1999
Neuroscientist at the University of Wisconsin at Madison
"Everybody knows what consciousness is: It is what vanishes every night when we fall into dreamless sleep and reappears when we wake up or when we dream. It is also all we are and all we have: Lose consciousness and, as far as you are concerned, your own self and the entire world dissolve into nothingness...
"Neurobiological facts constitute both challenging paradoxes and precious clues to the enigma of consciousness. This state of affairs is not unlike the one faced by biologists when, knowing a great deal about similarities and differences between species, fossil remains, and breeding practices, they still lacked a theory of how evolution might occur.
"What was needed, then as now, were not just more facts but a theoretical framework that could make sense of them.”
—From Biological Bulletin, 2008
Neurologist and writer
"Waking consciousness is dreaming—but dreaming constrained by external reality.”
—From his book An Anthropologist on Mars, 1995
Professor of psychology at Harvard
"Maybe philosophical problems are hard not because they are divine or irreducible or meaningless or workaday science, but because the mind of Homo sapiens lacks the cognitive equipment to solve them. We are organisms, not angels, and our minds are organs, not pipelines to the truth.
"Our minds evolved by natural selection to solve problems that were life-and-death matters to our ancestors, not to commune with correctness or to answer any question we are capable of asking.
"We cannot hold 10,000 words in short-term memory. We cannot see in ultraviolet light. We cannot mentally rotate an object in the fourth dimension. And perhaps we cannot solve conundrums like free will and sentience.”
—From his book How the Mind Works, 1997