This chapter from PHI: A Voyage from the Brain to the Soul, by Giulio Tononi (Pantheon, 2012) describes Tononi’s theory of consciousness as a measure of information. The brain, Tononi postulates, consists of billions of neurons: think of them as if they were transistorlike bits that, when tallied, sum to equal more than their parts. That increment above and beyond—Tononi calls it phi—represents the degree to which any being, whether human or mule, remains conscious.
From the forthcoming book PHI: A Voyage from the Brain to the Soul, by Giulio Tononi
Copyright © 2012 by Giulio Tononi
Published by arrangement with Pantheon Books, an imprint of The Knopf Doubleday Publishing Group, a division of Random House, Inc.
Integrated Information: The Many and the One
In which is shown that consciousness lives where information is integrated by a single entity above and beyond its parts
When is an entity one entity? How can multiple elements be a single thing? A question simple enough— but one, thought Galileo, that had not yet been answered. Or perhaps, it had not been asked.
The sensor of the digital camera certainly had a large repertoire of states— it could take any possible picture. But was it a single entity? You use the camera as a single entity, you grasp it with your hands as one. You watch the photograph as a single entity. But that is within your own consciousness. If it were not for you, the observer, would it still be a single entity? And what exactly would that mean?
While musing such matters, Galileo was startled by a voice. J., a man with the forehead of an ancient god, addressed him in a polished tone: “Take a sentence of a dozen words, and take twelve men, and tell to each one word. Then stand the men in a row or jam them in a bunch, and let each think of his word as intently as he will; nowhere will there be a consciousness of the whole sentence. Or take a word of a dozen letters, and let each man think of his letter as intently as he will; nowhere will there be a consciousness of the whole word,” J. said.
Or take a picture of one million dots, and take one million photodiodes, and show each photodiode its own dot. Then stand the photodiodes well ordered on a square array, and let each tell light from dark for its own dot, as precisely as it will; nowhere will there be a consciousness of the whole picture, said Galileo. “So you see that, Galileo,” J. continued. “There is no such thing as the spirit of the age, the sentiment of the people, or public opinion. The private minds do not agglomerate into a higher compound mind. They say the whole is more than the sum of its parts; they say, but how can it be so?”
An image came to Galileo. An astronomer was watching the sky in Padua, during an eclipse, and precisely at the same moment, another astronomer was watching the night sky at the antipodes. Would there be a single consciousness contemplating, in one great image, the entire dome of the sky, the austral and boreal skies joined seamlessly at the horizon? A single image of the entire sky, experienced within one consciousness? That was absurd, thought Galileo, and its absurdity had nothing to do with the distance between the scientists. Whether the two were separated by the diameter of the earth, or by a fraction of an inch, like two photodiodes on the camera sensor, made no difference. Because in both cases, the two parties could not interact. And if they could not interact, they could not form a single entity, and they could not have a single, unified conscious experience.