As an example, I’ll mention what I’ll call the “radio theory” of brains. Imagine that you are a Kalahari Bushman and that you stumble upon a transistor radio in the sand. You might pick it up, twiddle the knobs, and suddenly, to your surprise, hear voices streaming out of this strange little box. If you’re curious and scientifically minded, you might try to understand what is going on. You might pry off the back cover to discover a little nest of wires. Now let’s say you begin a careful, scientific study of what causes the voices. You notice that each time you pull out the green wire, the voices stop. When you put the wire back on its contact, the voices begin again. The same goes for the red wire. Yanking out the black wire causes the voices to get garbled, and removing the yellow wire reduces the volume to a whisper. You step carefully through all the combinations, and you come to a clear conclusion: the voices depend entirely on the integrity of the circuitry. Change the circuitry and you damage the voices.
Proud of your new discoveries, you devote your life to developing a science of the way in which certain configurations of wires create the existence of magical voices. At some point, a young person asks you how some simple loops of electrical signals can engender music and conversations, and you admit that you don’t know—but you insist that your science is about to crack that problem at any moment.
Your conclusions are limited by the fact that you know absolutely nothing about radio waves and, more generally, electromagnetic radiation. The fact that there are structures in distant cities called radio towers—which send signals by perturbing invisible waves that travel at the speed of light—is so foreign to you that you could not even dream it up. You can’t taste radio waves, you can’t see them, you can’t smell them, and you don’t yet have any pressing reason to be creative enough to fantasize about them. And if you did dream of invisible radio waves that carry voices, who could you convince of your hypothesis? You have no technology to demonstrate the existence of the waves, and everyone justifiably points out that the onus is on you to convince them.
So you would become a radio materialist. You would conclude that somehow the right configuration of wires engenders classical music and intelligent conversation. You would not realize that you’re missing an enormous piece of the puzzle.
I’m not asserting that the brain is like a radio—that is, that we’re receptacles picking up signals from elsewhere, and that our neural circuitry needs to be in place to do so—but I am pointing out that it could be true. There is nothing in our current science that rules this out. Knowing as little as we do at this point in history, we must retain concepts like this in the large filing cabinet of ideas that we cannot yet rule in favor of or against. So even though few working scientists will design experiments around eccentric hypotheses, ideas always need to be proposed and nurtured as possibilities until evidence weighs in one way or another.
Scientists often talk of parsimony (as in “the simplest explanation is probably correct,” also known as Occam’s razor), but we should not get seduced by the apparent elegance of argument from parsimony; this line of reasoning has failed in the past at least as many times as it has succeeded. For example, it is more parsimonious to assume that the sun goes around the Earth, that atoms at the smallest scale operate in accordance with the same rules that objects at larger scales follow, and that we perceive what is really out there. All of these positions were long defended by argument from parsimony, and they were all wrong. In my view, the argument from parsimony is really no argument at all—it typically functions only to shut down more interesting discussion. If history is any guide, it’s never a good idea to assume that a scientific problem is cornered.
At this moment in history, the majority of the neuroscience community subscribes to materialism and reductionism, enlisting the model that we are understandable as a collection of cells, blood vessels, hormones, proteins, and fluids—all following the basic laws of chemistry and physics. Each day neuroscientists go into the laboratory and work under the assumption that understanding enough of the pieces and parts will give an understanding of the whole. This break-it-down-to-the-smallest-bits approach is the same successful method that science has employed in physics, chemistry, and the reverse-engineering of electronic devices.
But we don’t have any real guarantee that this approach will work in neuroscience. The brain, with its private, subjective experience, is unlike any of the problems we have tackled so far. Any neuroscientist who tells you we have the problem cornered with a reductionist approach doesn’t understand the complexity of the problem. Keep in mind that every single generation before us has worked under the assumption that they possessed all the major tools for understanding the universe, and they were all wrong, without exception. Just imagine trying to construct a theory of rainbows before understanding optics, or trying to understand lightning before knowledge of electricity, or addressing Parkinson’s disease before the discovery of neurotransmitters. Does it seem reasonable that we are the first ones lucky enough to be born in the perfect generation, the one in which the assumption of a comprehensive science is finally true? Or does it seem more likely that in one hundred years people will look back on us and wonder what it was like to to be ignorant of what they know? Like the blind people in Chapter 4, we do not experience a gaping hole of blackness where we are lacking information—instead, we do not appreciate that anything is missing.30
I’m not saying that materialism is incorrect, or even that I’m hoping it’s incorrect. After all, even a materialist universe would be mind-blowingly amazing. Imagine for a moment that we are nothing but the product of billions of years of molecules coming together and ratcheting up through natural selection, that we are composed only of highways of fluids and chemicals sliding along roadways within billions of dancing cells, that trillions of synaptic conversations hum in parallel, that this vast egglike fabric of micron-thin circuitry runs algorithms undreamt of in modern science, and that these neural programs give rise to our decision making, loves, desires, fears, and aspirations. To me, that understanding would be a numinous experience, better than anything ever proposed in anyone’s holy text. Whatever else exists beyond the limits of science is an open question for future generations; but even if strict materialism turned out to be it, it would be enough.
Arthur C. Clarke was fond of pointing out that any sufficiently advanced technology is indistinguishable from magic. I don’t view the dethronement from the center of ourselves as depressing; I view it as magic. We’ve seen in this book that everything contained in the biological bags of fluid we call us is already so far beyond our intuition, beyond our capacity to think about such vast scales of interaction, beyond our introspection that this fairly qualifies as “something beyond us.” The complexity of the system we are is so vast as to be indistinguishable from Clarke’s magical technology. As the quip goes: If our brains were simple enough to be understood, we wouldn’t be smart enough to understand them.
In the same way that the cosmos is larger than we ever imagined, we ourselves are something greater than we had intuited by introspection. We’re now getting the first glimpses of the vastness of inner space. This internal, hidden, intimate cosmos commands its own goals, imperatives, and logic. The brain is an organ that feels alien and outlandish to us, and yet its detailed wiring patterns sculpt the landscape of our inner lives. What a perplexing masterpiece the brain is, and how lucky we are to be in a generation that has the technology and the will to turn our attention to it. It is the most wondrous thing we have discovered in the universe, and it is us.
*The basic architecture of this reward circuit is highly conserved throughout evolution. The brain of a honeybee uses the same reward programs that your brain does, running the same software program on a much more compact piece of hardware. (See Montague, et al., “Bee foraging.”).
**In Lifelines, biologist Steven Rose points out that “reductionist ideology not only hinders biologists from thinking adequately about the phenomena we wish to understand: it has t
wo important social consequences: it serves to relocate social problems to the individual … rather than exploring the societal roots and determinants of a phenomenon; and second, it diverts attention and funding from the social to the molecular.”
Appendix
Acknowledgments
Many people have inspired me in the writing of this book. Some had atoms that went their separate ways before my atoms came together—I may have inherited some of their atoms, but, more importantly, I was fortunate enough to inherit the ideas they left behind as messages in a bottle. I have also been fortunate to share existence contemporaneously with a network of tremendously smart people, which began with my parents, Arthur and Cirel, and continued with my graduate thesis adviser, Read Montague, and was sustained by mentors such as Terry Sejnowski and Francis Crick at the Salk Institute. I enjoy daily inspiration with colleagues, students, and friends such as Jonathan Downar, Brett Mensh, Chess Stetson, Don Vaughn, Abdul Kudrath, and Brian Rosenthal, to name a few. I thank Dan Frank and Nick Davies for their expert editorial feedback, and Tina Borja and all the students in my lab for line-by-line readings; these students include Tommy Sprague, Steffie Tomson, Ben Bumann, Brent Parsons, Mingbo Cai, and Daisy Thomson-Lake. I thank Jonathan D. Cohen for a seminar he gave which shaped some of my thinking in Chapter 5. Thank you to Shaunagh Darling Robertson for proposing the title Incognito. I am grateful to launch my books from the solid bedrock of the Wylie Agency, which includes the gifted Andrew Wylie, the exceptional Sarah Chalfant, and all their skilled coworkers. I am deeply grateful to my first agent, Jane Gelfman, for believing in me and in this book from the beginning. I thank Jamie Byng for his boundless enthusiasm and deep support. Finally, my gratitude goes to my wife Sarah for her love, humor and encouragement. The other day I saw a sign that simply read HAPPINESS—and I realized that the thought of Sarah was my instant mental headline. Deep in the canopies of my brain forest, happiness and Sarah have become synaptically synonymous, and for her presence in my life I am grateful.
* * *
Throughout the book you will often find the narrator’s term we instead of I. This is for three reasons. First, as with any book that synthesizes large bodies of knowledge, I collaborate with thousands of scientists and historians over the course of centuries. Second, the reading of a book should be an active collaboration between reader and writer. Third, our brains are composed of vast, complex, and shifting collections of subparts, most of which we have no access to; this book was written over the course of a few years by several different people, all of whom were named David Eagleman, but who were somewhat different with each passing hour.
About the Author
David Eagleman is a neuroscientist at Baylor College of Medicine, where he directs the Laboratory for Perception and Action as well as the Initiative on Neuroscience and Law. His scientific research has been published in journals from Science to Nature, and his neuroscience books include Wednesday Is Indigo Blue: Discovering the Brain of Synesthesia (with Richard Cytowic) and the forthcoming Live-Wired. He is also the author of the internationally best-selling book of fiction Sum: Forty Tales from the Afterlives.
SUM is also available as an eBook: 978-0-307-37802-6
Visit David Eagleman’s website: www.eagleman.com
Or follow him on: twitter.com/@davideagleman
Notes
Works listed in full in the Bibliography are referred to only by short title here.
Chapter 1. There’s Someone In My Head, But It’s Not Me
1 Music: “Tremendous Magic,” Time December 4, 1950.
2 Something I’ve always found inspiring: the year Galileo died—1642—Isaac Newton was born into the world and completed Galileo’s job by describing the equations underlying the planetary orbits around the sun.
3 Aquinas, Summa theologiae.
4 Specifically, Leibniz envisioned a machine that would use marbles (representing binary numbers) that would be guided by what we now recognize as cousins to punch cards. Although Charles Babbage and Ada Lovelace are generally credited with working out the concepts of software separation, the modern computer is essentially no different than what Leibniz envisaged: “This [binary] calculus could be implemented by a machine (without wheels) in the following manner, easily to be sure and without effort. A container shall be provided with holes in such a way that they can be opened and closed. They are to be open at those places that correspond to a 1 and remain closed at those that correspond to a 0. Through the opened gates small cubes or marbles are to fall into tracks, through the others nothing. It [the gate array] is to be shifted from column to column as required.” See Leibniz, De Progressione Dyadica. Thanks to George Dyson for this discovery in the literature.
5 Leibniz, New Essays on Human Understanding, published 1765. By “insensible corpuscles,” Leibniz is referring to the belief shared by Newton, Boyle, Locke, and others that material objects are made of tiny insensible corpuscles, which give rise to the sense qualities of the objects.
6 Herbart, Psychology as a Science.
7 Michael Heidelberger, Nature from Within.
8 Johannes Müller, Handbuch der Physiologie des Menschen, dritte verbesserte Auflage, 2 vols (Coblenz: Hölscher, 1837–1840).
9 Cattell, “The time taken up,” 220–242.
10 Cattell, “The psychological laboratory,” 37–51.
11 See http://www.iep.utm.edu/f/freud.htm.
12 Freud and Breuer, Studien über Hysterie.
Chapter 2. The Testimony of the Senses
1 Eagleman, “Visual illusions.”
2 Sherrington, Man on His Nature. See also Sheets-Johnstone, “Consciousness: a natural history.”
3 MacLeod and Fine, “Vision after early blindness.”
4 Eagleman, “Visual illusions.”
5 See eagleman.com/incognito for interactive demonstrations of how little we perceive of the world. For excellent reviews on change blindness, see Rensink, O’Regan, and Clark, “To see or not to see”; Simons, “Current approaches to change blindness”; and Blackmore, Brelstaff, Nelson, and Troscianko, “Is the richness of our visual world an illusion?”
6 Levin and Simons, “Failure to detect changes to attended objects.”
7 Simons and Levin, “Failure to detect changes to people.”
8 Macknik, King, Randi, et. al., “Attention and awareness in stage magic.”
9 The concept of a 2.5-D sketch was introduced by the late neuroscientist David Marr. He originally proposed this as an intermediate stage on the visual system’s journey to developing a full 3-D model, but it has since become clear that the full 3-D model never comes to fruition in real brains, and is not needed to get by in the world. See Marr, Vision.
10 O’Regan, “Solving the real mysteries of visual perception,” and Edelman, Representation and Recognition in Vision. Note that one group recognized the problem early on, in 1978, but it took many years to become more widely recognized: “The primary function of perception is to keep our internal framework in good registration with that vast external memory, the external environment itself,” noted Reitman, Nado, and Wilcox in “Machine perception,” 72.
11 Yarbus, “Eye movements.”
12 This phenomenon is known as binocular rivalry. For reviews, see Blake and Logothetis, “Visual competition” and Tong, Meng, and Blake, “Neural bases.”
13 The hole of missing photoreceptors occurs because the optic nerve passes through this location in the retina, leaving no room for the light-sensing cells. Chance, “Ophthalmology,” and Eagleman, “Visual illusions.”
14 Helmholtz, Handbuch.
15 Ramachandran, “Perception of shape.”
16 Kersten, Knill, Mamassian, and Bülthoff, “Illusory motion.”
17 Mather, Verstraten, and Anstis, The Motion Aftereffect, and Eagleman, “Visual illusions.”
18 Dennett, Consciousness Explained.
19 Baker, Hess, and Zihl, “Residual motion”; Zihl, von Cramon, and Mai, “Selective disturbance”; and Zihl
, von Cramon, Mai, and Schmid, “Disturbance of movement vision.”
20 McBeath, Shaffer, and Kaiser, “How baseball outfielders.”
21 It turns out that fighter pilots use this same algorithm during pursuit tasks, as do fish and hoverflies. Pilots: O’Hare, “Introduction”; fish: Lanchester and Mark, “Pursuit and prediction”; and hoverflies: Collett and Land, “Visual control.”
22 Kurson, Crashing Through.
23 It should be noted that some blind people can convert their felt world to two- or three-dimensional drawings. However, it is presumably the case that drawing the converging lines of a hallway is a cognitive exercise for them, different from the way that sighted people have the immediate sensory experience.
24 Noë, Action in Perception.
25 P. Bach-y-Rita, “Tactile sensory substitution studies.”