13
And if we do subscribe to the idea that no one has any free will in the stronger sense, because we are all just machines, then one logical consequence of this is to forgive, or even simply and fully to accept all the actions that everyone makes, just as we might accept natural events from inanimate sources. This might not be a realistically attainable perspective, but it would certainly be one free from anger, intolerance, and hatred.
14
Even though the human brain is a mere 2 percent of total body weight, in newborns this single organ requires a staggering 87 percent of the body’s total energy. A five-year-old has a brain that greedily guzzles nearly half of all the energy the child consumes, and even in adults this figure is at least a quarter, though that proportion can rise dramatically if we’ve had a mentally taxing day—for instance, when studying for exams. In fact, some biologists have suggested that the energy demands and complexity of a human brain are nearing the endpoint of what is biologically possible and that if you started trying to cram even more neuronal wires into the brain, the additional miniaturization that this would entail would turn all brain signal into random noise—and the cleverest organ in the known universe would suddenly become one of the dumbest.
18
It’s possible that in most, if not all, other examples of emergentism one would care to mention—for example, the collective intelligence of ants or macroeconomics—the recipe is little more than positive and negative feedback loops at the lower levels interacting to generate a more accurate, fitting informational solution at the level above.
19
The cause of this surprising limitation is a matter of intense current debate. One explanation suggests that three or four items are plenty, in almost all circumstances, to be the focus of our attention. There are exceptions, however. A student who is struggling with a mathematics assignment at school, or someone trying to learn the ins and outs of the latest overly complex gadget, may well wish it were possible for the human mind to handle more. But in our evolutionary past, we were rarely simultaneously faced with more than a few predators about to eat us, and we rarely chased after more than one or two sources of food or potential sexual partners. We didn’t need more in order to face the dangers of the world and take advantage of its benefits. In other words, perhaps there was never an evolutionary need to attend to more than just a few items at a time.
Another explanation, supported by computational models of how neurons interact, suggests that somewhere between three and four items is actually the maximum that can be practically sustained within a brain. Once attention has increased the signal for a given item, any neurons throughout the cortex that relate to any features of the object not only fire more actively, but also link together in a signature rhythm. If more than one object is being attended to simultaneously, multiple brain rhythms are required in order to keep the signals separate. But the brain can only sustain about three or four of these harmonies—any more and they begin to blend into each other too much, and the result becomes a disjunctive neural noise, where objects become confused with each other or simply forgotten.
20
At the time of this study, a normal person using a strategy to vastly improve his working memory was a highly unusual result. But about a decade later, in the early 1990s, the world memory championships started, where many other normal people would use their own heavily practiced strategies to compete on similar tasks. Now, after about twenty years of vibrant competitions, this initial feat of remembering 80 digits seems unimpressive. Many new techniques have been explored and there has been an increasing number of serious mental athletes. The current world record holder on virtually the exact same task as just described can correctly recall 240 numbers just spoken to him in sequence. The results from other tasks are equally awe-inspiring. The current world record for numbers of cards memorized in sequence in an hour is 1,456, and the shortest time to memorize a single pack of 52 cards is 21.9 seconds!
21
In Douglas Hofstadter’s whimsical and influential book
Gödel, Escher, Bach: An Eternal Golden Braid
, these logical structures in music and art are carefully explored, especially in terms of how they relate to the human mind.
22
The main neuroscientific evidence for the language instinct comes from the discovery of a gene called FOXP2. A mutation in this gene, it has been claimed, causes a selective language impairment, especially in the ability to speak fluently. But the mutation also causes general cognitive deficits, such as a lowering of IQ, which might underlie an impairment in the kind of chunking processes I’m describing rather than anything specific to language.
23
Actually, the primary visual cortex is not quite as dumb as all that. It can also act as a flexible slave system to more advanced regions of the brain. For instance, attention can enhance our perception of one part of space, partly via later regions controlling the activity of the primary visual cortex, so that those subregions within it, say, that code for the upper right quadrant, are more active, and so more ready to pick up changes in this location.
24
This theory is similar to two other modern theories of the brain, proposed by Gerald Edelman and Anil Seth, which also try to mathematically equate consciousness with the complexity of information the brain processes. I chose to highlight information integration theory because it is the most prominent and detailed of the three.
25
Actually, in this model there definitely is such a thing as too many connections, and some ugly compromise of connectivity is the ideal. The critical factor here is just how many different states a network can be in. This can be physically imagined by appeal to symmetries. Say there is a 3 by 3 by 3 cube of nodes, thus 27 nodes total. If all the nodes are connected to all the others (or similarly, if none of the nodes are connected), one corner node lighting up is the same as all the others. But say there is a middle ground, with each node connected to somewhere between 5 and 20 of the other 26 nodes. This time when a corner node lights up, its connections mean it is unique; there are no other corner nodes with the same configuration of connections as this one, and so its information state is unique. Because there are no symmetries of wiring, this particular cube could represent the most information out of the three options.
27
The original scientist who ran this study, Patricia Greenfield, provided evidence for the thesis that this staged development of abilities to chunk movements mirrored a child’s ability to learn the complexities of language—for instance, combining subcomponents of words together to form more complex words, and using multiple words in a grammatical structure. This task therefore is another clue that our ability for language might just boil down to our ability to chunk, especially in a hierarchical way.
28
It turns out that there are many factors that need to be taken into account for an accurate, useful ratio of brain to body to be determined. For instance, recent evidence suggests that some species are far better at packing in more neurons per brain weight than others, so measuring brain weight alone isn’t very informative.
29
I suspect that synesthesia is more prevalent in autistics than in the general population, although I don’t know of any studies that have as yet looked into this.
30
There is a clear relationship between chronic poor sleep and obesity, although the mechanism for this is unclear. I suspect that one part of the effect is the daily playing out of the equivalent of this chocolate-cake study, where poor sleep shrinks working memory, and thus mental control—and a less healthy diet ensues.
31
There’s some provisional evidence, however, that cognitive training is useful in staving off dementia in those over the age of sixty-five.
Copyright © 2012 by Daniel Bor
Published by Basic Books,
A Member of the Perseus Books Group
All rights reserved. No part of this book may be reproduced in any manner whatsoever without written permission except in the case of brief quotations embodied in critical articles and reviews. For information, address Basic Books, 387 Park Avenue South, New York, NY 10016-8810.
Books published by Basic Books are available at special discounts for bulk purchases in the United States by corporations, institutions, and other organizations. For more information, please contact the Special Markets Department at the Perseus Books Group, 2300 Chestnut Street, Suite 200, Philadelphia, PA 19103, or call (800) 810-4145, ext. 5000, or e-mail [email protected]
Library of Congress Cataloging-in-Publication Data
Bor, Daniel.
The ravenous brain : how the new science of consciousness explains our insatiable search for meaning / Daniel Bor.
p. cm.
Includes bibliographical references and index.
eISBN : 978-0-465-03296-9
1. Consciousness—Physiological aspects. 2. Brain. 3. Mind and body. I. Title.
QP411.B59 2012
612.8’2—dc23
2012016971