"A world without memory is a world of the present," Alan Lightman wrote in Einstein’s Dreams. "The past exists only in books, in documents. In order to know himself, each person carries his own Book of Life, which is filled with the history of his life…Without his Book of Life, a person is a snapshot, a two-dimensional image, a ghost."

Most people would probably agree with Lightman. Most people think that our self -knowledge exists only through the memories we have amassed of our selves. Am I a kind person? Am I gloomy? To answer these sorts of questions, most people would think you have to open up some internal Book of Life. And most people, according to new research, are wrong.

Neuroscientists would call Lightman’s Book of Life episodic memory. The human brain has a widespread system of neurons that store away explicit memories of events, which we can recall and describe to others. Some forms of amnesia destroy episodic memories, and sometimes even destroy the capacity to form new ones. In 2002, Stan B. Klein of the University of California at Santa Barbara and his colleagues reported a study they made of an amnesiac known as D.B. D.B. was 75 years old when he had a heart attack and lost his pulse. His heart began to beat after a few minutes, and he left the hospital after a few weeks. But he had suffered brain damage that left him unable to bring to mind anything had done or experienced before the heart attack. Klein then tested D.B.’s self-knowledge. He gave D.B. a list of 60 traits and asked him whether they applied to him not at all, somewhat, quite a bit, or definitely. Then he gave the same questionnaire to D.B.’s daughter, and asked her to use it to describe her fater. D.B.’s choices significantly correlated with his daughter’s. D.B.’s Book of Life was locked shut, and yet he still knew himself.

A few other amnesiacs have shown a similar level of self-knowledge, but it’s hard to draw too many lessons from them about how normal brains work. So recently Matthew Lieberman of UCLA and his colleagues carried out a brain-scanning study. They wanted to see if they could find different networks in the brain that make self-knowledge possible. They also wanted to see if these networks functioned under different circumstances–for example, when thinking about ourselves in very familiar contexts and unfamiliar ones.

They picked two groups of people to test: soccer players and improv actors. They then came up with a list of words that would apply to each group. (Soccer players: athletic, strong, swift; actors: performer, dramatic, etc.) They also came up with a longer list of words that applied specifically to neither (messy, reliable, etc.). Then they had all the subjects get into an fMRI scanner, look at each word, and decide whether it applied to themselves or not.

The volunteers’ brains worked differently in response to different words. Soccer-related words tended to activate a distinctive network in the brains of soccer players, the same one that actor-related words switched on in actors. When they were shown words related to the other group, a different network became active. And, as Lieberman and his colleagues report in an upcoming issue of the Journal of Personality and Social Psychology, it just so happens that they had predicted precisely which two networks would show up in their scans. (Here’s the full pdf on Lieberman’s web site.)

When people were presented with unfamiliar words, they activated a network Lieberman calls the Reflective system (or C system for short). The Reflective system taps into parts of the brain already known to retrieve episodic memories. It also includes regions that can consciously hold pieces of information in mind. When we are in new circumstances, our sense of our self depends on thinking explicitly about our experiences.

But Lieberman argues that over time, another system takes over. He calls this one the Reflexive system (or X system). This circuit does not include regions involved in episodic memories, such as the hippocampus. Instead, it is an intuition network, tapping into regions that produce quick emotional responses based not on explicit reasoning but on statistical associations. (The picture I show here is a figure from the paper, with the X and C systems mapped out.)

The Reflexive system is slow to form its self-knowledge, because it needs a lot of experiences to form these associations. But it becomes very powerful once it takes shape. A soccer player knows whether he is athletic, strong, or swift without having to open up the Book of Life. He just feels it in his bones. He doesn’t feel in his bones whether he is a performer, or dramatic, and so on. Instead, he has to think explicity about his experiences. Now D.B.’s accurate self-knowledge makes sense. His brain damage wiped out his Reflective system, but not his Reflexive system.

This research is fascinating on its own, and even more so when you think about the evolution of the self. Judging from the behavior of humans and apes, I’d guess that the Reflective system seems to be far more developed in us, while apes may share a pretty well developed Reflexive system. Does that mean that a Reflexive self existed before a Reflected one? Is the self we see in the Book of Life a recent innovation sitting an ancient self that we can’t put into words? And does that mean that chimpanzees have a Reflexive self? Is that enough of a self to warrant the sort of rights we give to humans because they are aware of themselves?

Our brains are huge, particularly if you take into consideration the relative size of our bodies. Generally, the proportion of brain to body is pretty tight among mammals. But the human brain is seven times bigger than what you’d predict from the size of our body. Six million years ago, hominid brains were about a third the size they are today, comparable to a chimp’s. So what accounts for the big boom? It would be flattering ourselves to say that the cause was something we are proud of–our ability to talk, or our gifts with tools. Certainly, our brains show signs of being adapted for these sorts of things (consider the language gene FOXP2). But those adaptations probably were little more than tinkerings with a brain that was already expanding thanks to other factors. And one of those factors may have been tricking our fellow hominid.

In the 1980s, some primatologists noticed that monkeys and apes–unlike other mammals–sometimes deceived members of their own species, in order to trick them out of food or sneak off for some furtive courtships. The primatologists got to thinking that deception involved some pretty sophisticated brain power. A primate needed to understand something about the mental state of other primates and have the ability to predict how a change in that mental state might change the way other primates behaved.

The primatologists then considered the fact that humans aren’t the only primates with oversized brains. In fact, monkeys and apes, on average, have brains twice the size you’d predict for mammals of their body size. Chimpanzees and other great apes have particularly big brains, and they seemed to be particularly adept at tricking each other. What’s more, primates don’t simply have magnified brains. Instead, certain regions of the brain have expanded, such as the neocortex, the outer husk of the brain which handles abstract associations. Activity in the neocortex is exactly the sort of thinking necessary for tricking your fellow ape.

Taking all this into consideration, the primatologists made a pretty gutsy hypothesis: that the challenges of social life–including deception–actually drive the expansion of the primate brain. Sometimes called the Machiavellian Intelligence hypothesis, it has now been put to its most rigorous test so far, and passed quite well. Richard Byrne and Nadia Corp of the University of St. Andrews in Scotland published a study today in the Proceedings of the Royal Society of London. (The link’s not up yet, but here’s a New Scientist piece.) They found that in 18 species from all the major branches of primates, the size of the neocortex predicts how much deception the species practices. Bigger brains mean more trickery. They were able to statistically rule out a number of other factors that might have created a link where none existed. And they were able to show that deception is not just a side-effect of having a big brain or something that opportunistically emerges more often in big groups. Deception is probably just a good indicator of something bigger going on here–something psychologists sometimes call "social intelligence." Primates don’t just deceive one another; they also cooperate and form alliances and bonds, which they can keep track of for years.

While deception isn’t just an opportunistic result of being in big groups, big groups may well be the ultimate source of deception (and by extension big brains). That’s the hypothesis of Robin Dunbar of Liverpool, as he detailed last fall in the Annual Review of Anthropology. Deception and other sorts of social intelligence can give a primate a reproductive edge in many different ways. It can trick its way to getting more food, for example; a female chimp can ward off an infanticidal male from her kids with the help of alliances. Certain factors make this social intelligence more demanding. If primates live under threat of a lot of predators, for example, they may get huddled up into big groups. Bigger groups mean more individuals to keep track of, which means more demands on the brain. Which, in turn, may lead to a bigger brain.

If that’s true, then the human brain may have begun to emerge as our ancestors huddled in bigger groups. It’s possible, for example, that early hominids living as bipeds in patchy forests became easier targets for leopards and other predators. Brain size increased modestly until about two million years ago. It may not have been able to grow any faster because of the diet of early hominids. They probably dined on nuts, fruits, and the occasional bit of meat, like chimpanzees do today. That may not have been enough fuel to support a really big brain; brain tissue is incredibly hungry, demanding 16 times more energy than muscle, pound for pound. It was only after hominids began making butchering tools out of stones and got a steady supply of meat from carcasses that the brain began to expand. And it was probably around this time (between 2 and 1.5 million years ago) that hominids began evolving the extraordinary powers of deception (and other sorts of social intelligence) that humans have. We don’t just learn how other people act–we develop a powerful instinct about what’s going on in their minds. (I wrote about the neuroscience behind this "mentalizing" last year in an article for Science.)

So next time you get played, temper your anger with a little evolutionary perspective. You’ve just come face to face with a force at work in our evolution for over 50 million years.

UPDATE 7/3/04: A skeptical reader doubted some of my statements about the brain and the energy it requires. Those who crave more information should check out Northwestern University anthropologist William Leonard’s article “Food for Thought” in Scientific American.

In the New York Times this morning, the poet Diane Ackerman has written an essay about the brain, in which she waxes eloquent about its ability to discern patterns in the world. The essay is distilled from her new book, An Alchemy of the Mind, which I’ve just reviewed for the Washington Post. I didn’t much like the book, although it took me a while to figure out what was bothering me about it. If you read the essay, you can get the flavor of the book, not to mention Ackerman’s general style in her previous books (which have taken on subjects such as endangered species and the senses). Ackerman has a fondness for sipping tea, tie-dye dresses, and hummingbird feeders, and an even greater fondness for writing about them. I know people who have been put off by her aesthetics, and I find them cloying as well. But that wasn’t really at the heart of my dislike of the book. (And besides, my own aesthetics leans towards shark tapeworms and dissected sheep brains, so I’m hardly one to complain about other people.) It took me a few days to realize that the problem with the book was embedded in a deeper problem: how we talk about nature (which includes our own minds).

By we, I don’t mean cognitive neuropsychologists or planetologists or molecular ecologists. I mean the rest of us, or the collective us, the ones who consciously or unconsciously create the language, metaphors, and stories that serve as our shared understanding of the world. The words we use, even in passing, to describe genes or brains or evolution can lock us into a view of nature that may be meaningful or misleading. When people say, "Being dull is just written into his DNA," they may only intend a light joke, but the metaphor conjures a false image of how personality emerges from genetics and environment and experience. This figure of speech may seem like nothing more than a figure of speech until people step into the office of a genetics counselor to find out about their unborn child.

The brain suffers from plenty of bad language. In some cases, the language is bad because it’s unimaginative. In Alchemy of the Mind, Ackerman points out that calling neurotransmitters and receptors keys and locks does a disservice to their soft, floppy nature. In other cases, though, the language is bad because it’s based on gross simplifications of outmoded ideas. Yet it survives, taking on a life of its own separate from the science. My favorite example, which I wrote about last year, is the bogus story you always hear about how we only use ten percent of your brain.

Ackerman indulges in this sort of bad language a lot. One example: she loves referring to our "reptile brain," as if there was a nub of unaltered neurons sitting at the core of our heads driving our basic instincts. The reality of the brain–and of evolution–is far more complex. The brain of reptilian forerunners of mammals was the scaffolding for a new mammal brain; the old components have been integrated so intimately with our "higher" brain regions that there’s no way to distinguish between the two in any fundamental way. Dopamine is an ancient neurotransmitter that provides a sense of anticipation and reward to other animals, including reptiles. But our most sophisticated abilities for learning abstract rules, carried out in our elaborate prefrontal cortex, depend on rewards of dopamine to lay down the proper connections between neurons. There isn’t a new brain and an old brain working here–just one system. Yet, despite all this, it remains seductive to use a phrase like "reptile brain." It conjures up lots of meanings. Ackerman floods her book with such language, which I grouse about other bad language in my review.

Which makes me wonder, as a science writer myself: is all poetry is ultimately dangerous? Does scientific understanding inevitably get abandoned as we turn to the juicy figure of speech?

Update: 6/14/04 11 AM: NY Times linked fixed

I always like book reviews that combine books that might not at first seem to have that much in common. In the new issue of Natural History, the neuroscientist Williams Calvin reviews Soul Made Flesh along with The Birth of the Mind, a fascinating book by Gary Marcus of NYU. If you haven’t heard of Marcus’s new book–which explores how genes produce minds–definitely check it out.

It’s strange enough hearing yourself talking on the radio. It’s stranger still to see a transcript someone makes of you talking on the radio. Recently I was interviewed about Soul Made Flesh on Australian Broadcasting Corporation’s show "All in the Mind." Instead of an audio archive, ABC has posted a transcript of the show. While I can’t claim I spoke in perfect paragraphs, we had an interesting talk about how the brain became the center of our existence.

I was asked a couple weeks ago to contribute a piece to a special series of articles in Newsweek about the future of Wi-Fi. I must admit that a fair amount of the stuff that’s on the Wi-Fi horizon seems a little banal to me. It’s nice to know that I will be able to swallow a camera-pill that will wirelessly send pictures of my bowels to my doctor, but it hardly cries out paradigm shift. On the other hand, I’ve been deeply intrigued and a little disturbed by the possibility that the next digital device to go Wi-Fi is the human brain. Here’s my short essay on the subject.

My book Soul Made Flesh looks at the roots of neuroscience in the 1600s. The first neurologists saw their work as a religious mission; they recognized that it was with the brain that we made moral judgments. In order to finish the book, I looked for living neuroscientists who carry on those early traditions today. I was soon fascinated by the work of Joshua Greene, a philosopher turned neuroscientist at Princeton. Greene is dissecting the ways in which people decide what is right and wrong. To do so, he poses moral dilemmas to them while he scans their brains. I mentioned Greene briefly in Soul Made Flesh and then went into more detail in a profile I wrote recently. Greene and I will join forces tomorrow on the show “New York and Company” on WNYC tomorrow around 12:30 pm. You can listen to us on the radio or on the web.

This week I am in England to give some talks about Soul Made Flesh, which has just been published here. In addition to talking on the BBC, I’ll be talking at Blackwell’s in Bristol on Tuesday, and at the Museum of the History of Science at Oxford University on Wednesday. I’ve posted details and links to even more details on the talks page of my web site.

It’s a bit daunting coming here, the very place where much of my book is set. But the response has been kind so far. This morning the eminent historian Lisa Jardine wrote a generally good review in the Sunday Times. Meanwhile, stateside, another Brit (Adam Zeman) wrote a positive review in The New York Times Book Review.

While I’m here, I hope to have a little spare time to blog a bit on some interesting new research (and fisk the latest creationist shenanigans). If logistics get the better of me, I’ll definitely get back on track next week when I get home.

In February I wrote an article in Popular Science about a project to implant electrodes in a monkey’s brain allowing the monkey to control a robot arm with its mind. The goal of this work is to let paralyzed people operate prosthetic limbs by thought alone. Now the research team has announced another big step in that direction: their first work on humans.

They implanted their electrodes into the brains of people undergoing surgery for Parkinson’s disease and tremor disorders, and then had the patients play a video game with a joystick. (In brain surgery, patients don’t get general anasthesia.) After a little gaming, the researchers removed the electrodes and the surgery resumed. The signals the electrodes captured from the brains of patients as they produced action commands proved to be so clear that a computer was able to use them to predict which way the patients had moved the joystick. Now the researchers are applying to the government to do long-term research on electrodes implanted in quadriplegics.

As is the case with many neuroscientific breakthroughs (memory-boosting drugs for the elderly, sleep-suppressing drugs for narcoleptics), the thorny question arises: should healthy people be allowed (or required for their job) to get an implant? After all, wouldn’t you want to run your computer, your car, or your military killer-robot with your mind?

Attention Virginian readers of the Loom: I’ll be heading to warmer climes later this week to speak in Charlottesville at the Virginia Festival of the Book. On Thursday at 4 I’ll be speaking on a panel about science and society. On Friday at 4 I’ll be speaking again on scientific discoveries and how they change us. I’m looking forward to listening to my fellow panelists, who include Robin Marantz Henig and James Shreeve. See you there.

I’ve posted a new batch of reviews for Soul Made Flesh on my web site. The newest is from Ross King, the author of Brunelleschi’s Dome and Michelangelo and the Pope’s Ceiling. His review in yesterday’s Los Angeles Times is a rare sort–he likes the book (which he calls "thrilling") for what the book really is, rather than as a projection of some phantom in his own mind.

A review of a different sort comes from Simon Conway Morris of the University of Cambridge. Conway Morris is a first-rate paleontologist who has shed a lot of light on how the major groups of animals alive today emerged in the Cambrian Period. In recent years he’s also started to nudge some more spiritual notions into public view, suggesting for instance that the evolution of life has displayed a built-in direction towards us, or at least something like us. Conway Morris reviews Soul Made Flesh in the March issue of Bioscience, which is published by the American Institute of Biological Sciences. I can’t complain about a review that calls my book "a wonderful read," but on the other hand, I found it odd that Conway Morris criticizes me for concluding that we know something more about how the brain works now than people did in 1600. He seems to think I’m attacking his personal notion of the human soul, when in fact I’m actually talking about how the seventeenth century notion of the soul was transformed–in part–into an understanding of the brain. As peculiar as it may be, it’s well-written, though.

Three weeks ago, I gave a talk at Stanford University about my new book Soul Made Flesh. A wonderful crowd turned out and peppered me with excellent questions afterwards, each of which could have become new talks of their own. CSPAN was there to film it, and they’ll be broadcasting the talk this Saturday, March 20, at 9 am EST on BookTV.

You may want to check out this little RSS a commenter forwarded to me that converts the BookTV schedule to any time zone. Also, if you miss the talk, it will probably repeated on another weekend, so check back to their site.

Here’s an added incentive to watch: you don’t have to look at the nervous, quavering face of an author, interspersed only by slow pans across a silent, expressionless audience. I brought along a Powerpoint file loaded with gorgeous, bizarre seventeenth century artwork to go along with the story of the search for the soul and the dawn of neurology. Straight from my laptop to your eyes.