Graziano - Consciousness and the Social Brain

SPECULATIVE EVOLUTIONARY TIMELINE OF CONSCIOUSNESS

The theory at a glance: from selective signal enhancement to consciousness. About half a billion years ago, nervous systems evolved an ability to enhance the most pressing of incoming signals. Gradually, this attentional focus came under top-down control. To effectively predict and deploy its own attentional focus, the brain needed a constantly updated simulation of attention. This model of attention was schematic and lacking in detail. Instead of attributing a complex neuronal machinery to the self, the model attributed to the self an experience of Xthe property of being conscious of something. Just as the brain could direct attention to external signals or to internal signals, that model of attention could attribute to the self a consciousness of external events or of internal event. As that model increased in sophistication, it came to be used not only to guide ones own attention, but for a variety of other purposes including understanding other beings. Now, in humans, consciousness is a key part of what makes us socially capable. In this theory, consciousness emerged first with a specific function related to the control of attention and continues to evolve and expand its cognitive role. The theory explains why a brain attributes the property of consciousness to itself, and why we humans are so prone to attribute consciousness to the people and objects around us. Timeline: Hydras evolve approximately 550 million years ago (MYA) with no selective signal enhancement; animals that do show selective signal enhancement diverge from each other approximately 530 MYA; animals that show sophisticated top-down control of attention diverge from each other approximately 350 MYA; primates first appear approximately 65 MYA; hominids appear approximately 6 MYA; Homo sapiens appear approximately 0.2 MYA

CONSCIOUSNESS AND THE SOCIAL BRAIN

Michael S. A. Graziano

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Library of Congress Cataloging-in-Publication Data

Graziano, Michael S. A., 1967

Consciousness and the social brain / Michael S.A. Graziano.

pages cm

Includes bibliographical references and index.

ISBN 9780199928644

1. Consciousness. 2. Brain. I. Title.

BF311.G692 2013

153dc23

2012048895

9 8 7 6 5 4 3 2 1

Printed in the United States of America

on acid-free paper

For Sabine

Many thanks to the people who patiently read through drafts and provided feedback. Thanks in particular to Sabine Kastner, Joan Bossert, and Bruce Bridgeman. At least some of the inspiration for the book came from Mark Ring, whose unpublished paper outlines the thesis that consciousness must be information or else we would be unable to report it. Some of the material in this book is adapted from a previous article by Graziano and Kastner in 2011.

CONSCIOUSNESS AND THE SOCIAL BRAIN

I was in the audience watching a magic show. Per protocol a lady was standing in a tall wooden box, her smiling head sticking out of the top, while the magician stabbed swords through the middle.

A man sitting next to me whispered to his son, Jimmy, how do you think they do that?

The boy must have been about six or seven. Refusing to be impressed, he hissed back, Its obvious, Dad.

Really? his father said. You figured it out? Whats the trick?

The magician makes it happen that way, the boy said.

The magician makes it happen. That explanation, as charmingly vacuous as it sounds, could stand as a fair summary of almost every theory, religious or scientific, that has been put forward to explain human consciousness.

What is consciousness? What is the essence of awareness, the spark that makes us us? Something lovely apparently buried inside us is aware of ourselves and of our world. Without that awareness, zombie-like, we would presumably have no basis for curiosity, no realization that there is a world about which to be curious, no impetus to seek insight, whether emotional, artistic, religious, or scientific. Consciousness is the window through which we understand.

The human brain contains about one hundred billion interacting neurons. Neuroscientists know, at least in general, how that network of neurons can compute information. But how does a brain become aware of information? What is sentience itself? In this book I propose a novel scientific theory of what consciousness might be and how a brain might construct it. In this first chapter I briefly sketch the history of ideas on the brain basis of consciousness and how the new proposal might fit into the larger context.

The first known scientific account relating consciousness to the brain dates back to Hippocrates in the fifth century B.C. At that time, there was no formal science as it is recognized today. Hippocrates was nonetheless an acute medical observer and noticed that people with brain damage tended to lose their mental abilities. He realized that mind is something created by the brain and that it dies piece by piece as the brain dies. A passage attributed to him summarizes his view elegantly:

Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant.

The importance of Hippocratess insight that the brain is the source of the mind cannot be overstated. It launched two and a half thousand years of neuroscience. As a specific explanation of consciousness, however, one has to admit that the Hippocratic account is not very helpful. Rather than explain consciousness, the account merely points to a magician. The brain makes it happen. How the brain does it, and what exactly consciousness may be, Hippocrates left unaddressed. Such questions went beyond the scope of his medical observations.