When you're trying to choose which ice cream flavor to get, what's actually happening in your brain? How do you decide? It seems pretty easy, but that's only if you don't see the storms of activity lighting up the brain. And how do you make long term decisions like that You're not going to eat the ice cream at all, but instead you're going to eat some broccoli. And what does any of this have to do with the ancient Greeks, or what alien hand syndrome is, or what the rules should be around how the president can launch the nuclear bomb. Welcome to Inner Cosmos with me David Eagleman. I'm a neuroscientist and author at Stanford and in these episodes we dive deeply into our three pound universe to uncover some of the most surprising aspects of our lives. Today's episode and next week's is about decision making. Although you generally feel like you're just moving through a day, decision making lies at the heart of everything we do. The complexity of the world presents itself to us, and we are constantly weighing alternatives. If you couldn't do that, you couldn't navigate the now, and you couldn't plan out your future. So by having a richer understanding of how choices battle it out in the brain, we can learn how to make better decisions for ourselves. And, as we're going to see next week, because this is a two partern, we'll even see how we can use this to build a better criminal justice system. So let's start at the very beginning. Should you choose the taco or the brito? Should you go for that T shirt or a more formal shirt. Should you take care of this email first or that bill payment first? Do you feel like the mint, chocolate chip or cookies and cream? On any day, you're making one thousand little decisions, which phone calls to make, which shooes to wear, whether to take the shorter path or the faster path, how exactly you should answer a question, what you should agree to on your schedule tomorrow. This, it turns out, is one of the most central things the brain does, make decisions. Your brain is a decision making machine. It takes the complexity of the world and it squeezes things down to single decisions. So how do brains do this? Now? When economists and psychologists first started looking at this question, they assumed that we humans act rationally. The idea is we look at our options, we add up the pros and cons, and we make the optimal decision. That's not necessarily how it goes with our brains. And in this episode and the next one, we're going to get a really good understanding why. So let's get going with these drawing where there are two ways to interpret the same image. You've probably seen these things. If you look at the picture one way, it looks like a rabbit, and if you keep staring at it you can see that suddenly it looks like a duck. So you probably saw this when you were a kid, But just in case you didn't, I'm putting it on the show notes at eagleman dot com slash podcast. The point is the image is what we call perceptually by stable, which is just a way of saying that when you stare at the picture, your brain can make one interpretation of what you're seeing or the other interpretation, and it switches back and forth. You see the rabbit and then the duck, and then the rabbit and then the duck. The critical thing to appreciate is that nothing on the page changes, so the only thing that's changing is something inside your brain. So some years ago I collaborated with my neurosurgery colleagues to study this sort of thing. Now, neuroscience, what I do is pretty different from brain surgery what a neurosurgeon does, but happily we tend to be friends and we can often help each other. So I accompanied surgeries while my colleagues were operating on people's brains. And you may know, one of the incredible things about neurosurgery is that you can do this while a patient is awake and talking to you. And this is because you can put little electrodes these are small metal wires into the brain and the brain has no pain receptors, so it doesn't hurt. The patient can't feel that. Now, why does the brain have no pain receptors. It's generally because nothing ever touches your brain. Your brain, which is about the consistency of jello, is well protected in the thick plates of the skull, so evolutionarily, there was no point in developing pain receptors in the brain anyway. As a consequence, a neurosurgeon only needs to use local anesthesia when making a cut on the scalp, and then they drill a burhole into the skull, and once the brain is exposed, you can poke things into the tissue while you and the patient are having a conversation about what it's like and what you find there is that this empire of eighty six billion neurons is constantly storming with activity. Every neuron in your head is having these little spikes of electrical voltage known as action potentials, and every neuron is firing off some tens or hundreds of these spikes every second of your life. Every idea you've ever had, every memory you can ever recollect, every choice that you've ever contemplated, is written in the language of these tiny, mysterious spikes. And using a very very tiny electrode think of a super small wire that you just push into the brain, you can eavesdrop on these spikes. Now, let's call the patient on the table, Marcia. So Marcia is wide awake and talking to me, and I can show her this bistable picture of the rabbit duck and ask her to tell me what she sees. Now, the moment that Marcia switches to rabbit or duck, her brain has made a decision. A decision doesn't have to be conscious in this case, it's a perceptual decision by her visual system, and the mechanics of this switchover are totally hidden under the hood. Now, what's interesting is that in theory, a brain should be able to see both the rabbit and the duck at the same time, but in reality, brains don't do that. What brains do is they take ambiguous data and they make a choice. In this case, it eventually remakes the choice, and it might switch back and forth over and over. But the point is that our brains are always crushing ambiguity down to a choice. So when Marsha's brain lands on the interpretation that the drawing is of a duck or a rabbit, we can listen through the electrode to the responses from a small number of neurons these cells in her brain. Some neurons shift to a higher rate of activity while other neurons slow down their activity. And that happens right when Marcia says, oh, now I see it as a duck, and then when she says, oh, now it's a rabbit again, the neurons are changing their activity. Now, the neurons we happen to be eavesdropping on are not by themselves responsible for the perceptual change. Instead, they're operating in concert with billions of other neurons. So the changes we're listening to are just pieces of this massive changing pattern taking hold across large swaths of brain territory. But the idea is that when one pattern wins out over the other in Marcia's brain, a decision has been landed upon. Now it's a rabbit. Now it's a duck. Now. Just as a side note, it's not always about the neurons speeding up or slowing down their spikes. Sometimes neurons change their pattern of activity in more subtle ways. They become synchronized or desynchronized with other neurons even while they're maintaining their original pace. Now here's the thing. Although we can look at this in Marsha's brain and correlate the changes with seeing the rabbit or the duck, the thing to appreciate is that your brain makes thousands of decisions every day of your life, and that dictates your experience of the world. What are you gonna wear today, who are you going to text today, How are you going to interpret what was meant by that email? Are you going to exercise today? Or are you gonna eat that bag of chips or pass it up. We don't typically chew on it, but these small decisions underlie every action we take. Who you are emerges from the brain wide battles for dominance that rage in your skull every moment of your life. So listening to that neural activity in Marsha's head, it's impossible not to be in awe because this is what every decision in the history of our species sounded like. Every marriage proposal, every declaration of war, every leap of imagination, every mission launched into the unknown, every act of kindness, every lie, every breakthrough, every decisive moment. It all happened right here in the darkness of the skull, emerging from patterns of activity in networks of biological cells. So let's take a closer look at what's happening behind the scenes during a decision. So imagine you're making a simple choice. You're standing in the drinksisle at the store, and you're trying to decide between two flavors of sports strength that you like equally. So you're looking at lemon and blueberry. Now from on the outside, someone's looking at you standing in the aisle. It doesn't look like you're doing much. You're simply stuck there in the aisle, looking back and forth between these two options. But inside your brain, a simple choice like this has unleashed a hurricane of activity. Now keep in mind that by itself, no single neuron has much influence. But each neuron is connected to thousands of others, and they in turn connect to thousands of others and so on. In this massive, loopy, intertwining network, they're all releasing chemicals that excite or depress each other. Within this web, a particular constellation of neurons represents the Lemon drink, and this pattern is formed from neurons that mutually excite each other. Now they're not necessarily next to each other. They might span distant brain regions involved in smell and taste, and vision and your unique history of memories involving lemons sports strengths. Each of these neurons by itself has very little to do with lemon. In fact, each neuron plays many different roles at different times in ever shifting coalitions. But when these neurons all become active collectively at the same time in this particular arrangement, that's the Lemons sports drink. To your brain. So as you're standing in front of the drinks, this federation of neurons eagerly communicates with one another, like the way that dispersed individuals link online. Now, these neurons aren't acting alone in their electioneering. At the same time, the competing possibility the blueberry flavored drink is represented by its own neural coalition, and thousands or millions of neurons there are talking with each other and trying to get the vote out. Now, each coalition lemon and blueberry, tries to gain the upper hand by intensifying its own activity and suppressing the others. Neural populations compete against one another, just like police parties struggle for dominance. They fight it out until one of them triumphs in this winner take all competition, and whichever network wins defines what you do next. Now, this is what is so cool about brains as compared to let's say, are digital computers. The brain is a machine that runs on conflict between different possibilities, and all these possibilities are always trying to outcompete the others, and there are always multiple options. Even after you've selected the lemon or the blueberry drink, you find yourself in a new conflict. Should I drink the whole thing right now? Part of you feels like it's a good idea to make sure you have plenty of hydration, And at the same time, part of you he recognizes that it's very sugary and you don't want to do too much of that. And part of you also knows you're going to have to go to the bathroom soon if you drink the whole thing. So whether you polish off the whole drink now or save some for later is simply a matter of the way that the infighting goes as a result of the ongoing conflict in the brain. You can argue with yourself, you can curse it yourself, you can cajole yourself. But who exactly is talking with whom? It's all you, but it's different parts of you now. As I said, we're not usually aware of these internal conflicts, but sometimes we can use simple tasks to bring this to the surface. For example, there was a simple psychological task introduced in the nineteen thirties, which we call the Stroop task, and it's very easy. All you do is you look at a word printed on a page, and the word might be in red ink or blue, or green or yellow, and all you need to do is say the color of the ink. So if I show you the word garage and the ink is yellow, all you do is you say yellow. Now that sounds very easy to do, But the trick is that the words I show you might themselves be color words. Like I show you the letters R, E, D, but the ink is in green. So when you see this, you're supposed to shout out green, but it proves very difficult. Or I show you the word purple written in yellow ink, or the word blue written in red ink. Check out some examples on the show notes. Now, the instructions are very easy. All you're supposed to do is say the color of the ink. So why is the stroop task so hard? It's because one network in your brain has the task of identifying the color of the ink and putting a name to it. But at the same time, you have competing networks in your brain that are responsible for reading words. And these are so proficient that word reading has become a deeply ingrained automatic process. And so you can feel the strugg as these systems contend with each other and to get the right answer. You have to actively suppress the strong impulse to read the word in favor of really concentrating on the ink color. So with a simple task like this, you can directly experience the conflict. But most of the time things are running so smoothly under the hood that you don't even realize that you have all these competing networks. And it's only under very special circumstances that it can become easy for us to witness in another person the internal conflict between the different parts of the brain. So this can happen when a person has a particular kind of epilepsy, where the epileptic seizures spread from one hemisphere to the other. In these cases, some patients have undergone what is called a split brain surgery, which the brain's two hemispheres get surgically disconnected from each other. So normally your two hemispheres are connected by a super highway of nerves called the corpus colosum, and this allows the right and left halves to coordinate and to work in concert. So, for example, if you are feeling chilly, both of your hands cooperate. One holds your jacket hem while the other tugs up the zipper. But When the corpus closum gets cut, the two hemispheres aren't talking anymore, and you can get a very wild and haunting clinical condition that's called alien hand syndrome. So the two hands can act with totally different intentions. So a person with a severed corpus colosum begins to zip up a jacket with one hand and the other hand the alien hand suddenly grabs the zipper and pulls it back down. Or the person might reach for a piece of pizza with one hand and their other hand leaps into action to slap the first hand. The normal conflict running in the brain now comes to the surface because the two hemispheres are now acting independently of one another. They're not working things out under the hood anymore. Alien hand syndrome typically fades in the weeks after surgery, as the two halves of the brain take advantage of any remaining connections to start coordinating again. But what it reminds us is that even when we think we're being single minded, our actions result from these immense battles that continually rise and fall in the darkness of the cranium. Now to appreciate some of the major competing systems in your brain. Consider a philosophy experiment known as the trolley dilemma. I spoke about this once about sixty episodes ago, but if you haven't heard this one, it paints an important point. So here's how it goes. A trolley is barreling down a train track and you are a bystander, and you notice that there are four workers who are doing repairs down the track, and you realize that they are going to get it and killed by this trolley. Then you notice that there's a lever right near you, and if you pull this lever, that'll divert the trolley onto a parallel track. But wait a minute. You realize that there's one worker on that track, and if you pull the lever, that one worker will get killed. So here's the question. Do you let four people get killed or do you pull the lever so that only one person is killed. When people are asked what they would do in this scenario, almost everyone pulls the lever. After all, it's better than only one person gets killed rather than four, right, But now consider a slightly different scenario. In the second scenario begins with the same premise that trolley is barreling down the track and four workers are going to get killed. But this time you're standing on a bridge that goes over the tracks, and you notice that there's a large man standing on the bridge watching the birds. And you realize that if you push him off, he'll land right on the track and his body will be sufficient to stop the trolley and save the four workers. So do you push him off? In this second scenario? Almost no one I talk with is willing to push the man. Why not? Well, when I ask them, they give answers like that would be murder and that would just be wrong. But wait, isn't it the same equation? In both cases? The question is would you trade one life for four? So why do the results come out so differently in the second scenario. Ethicists have addressed this problem from many angles, but brain imaging has been able to provide a fairly straightforward answer to the brain. The first scenario about pulling the lever, that's just a math problem. The dilemma activates regions that are involved in solving logical problems. But in the second scenario, where you have to physically interact with the man and push him to his death, that recruits additional networks. Into the decision. Now you have the involvement of brain regions involved in emotion. In this second scenario, you're caught in a conflict between two systems that have very different opinions. Your rational networks tell you that one death is better than four, but your emotional networks trigger this gut feeling that murdering a bystander is wrong. You're now dealing with these competing drives, with the end result that your decision is likely to change entirely from the first scenario. Now, the trolley dilemma sheds light on real world situations. Just think of modern warfare, which has become more like pulling the lever rather than pushing the man off the bridge. When a person pushed which is the button to launch a long range missile, it involves only the networks involved in logical problems. Operating a drone can become like a video game. Cyber attacks reconsequences at a distance, So the rational networks are at work here, but not necessarily the emotional networks. The detached nature of distance warfare reduces internal conflict, and it makes this easier to wage. So in the nineteen sixties there was a military thinker who suggested that the button to launch nuclear missiles should be implanted in the chest of the president's best friend. That way, if the president chooses to launch nukes, he'd have to inflict physical violence on his friend first, he'd have to tear him open, and that consideration would recruit emotional networks into the decision. After all, the world would not be better if we all behaved like row robots when making life and death decisions. Unchecked reason can be dangerous. Our emotions are actually a powerful and often insightful constituency, and we'd be remiss to exclude them from the parliamentary voting. Although the neuroscience is new, this intuition about having different drives has a long history. The ancient Greeks suggested that we should think of our lives like we are charioteers trying to hold on to two horses. We've got the horse of reason and the horse of passion, and each horse pulls slightly off center in opposite directions, and your job is to keep control of both horses, keeping yourself moving down the middle of the road. So I've asserted that emotions are really important and we shouldn't try to be like mister Spock. But I want to double click on that claim, and the way we can do that is by seeing what happens when a person loses the capacity to include emotions in decision making. So let's take someone like Hammy Myers, who I filmed in my television show called The Brain. Cammy is a former engineer and some years ago she got into a motorcycle accident and the consequence was damaged to her orbitofrontal cortex, which is the region just above the orbits of the eyes. Now, this is a critical region to integrate signals streaming in from the body, Signals that tell the rest of the brain what state her body is in. Is she hungry, is she nervous? Is she excited? Is she embarrassed? Is she thirsty? Is she joyful? Now? The interesting thing is that Cammy doesn't look like someone who has suffered a traumatic brain injury. But if you were to spend even five minutes with her, you would detect there's a problem with her ability to deal with decision making. So let's say you say, hey, do you want the lemon drinker the blueberry? And she can describe all the pros and the cons while the lemon drinks a little more sour, but the blueberry has more sugar, and so on. But she can't actually decide. She can't finalize a choice. Even the simplest situations leave her mired and indecision why. It's because she can no longer read her body's emotional summaries, and as a result, decisions become incredibly difficult for her. In other words, because of her brain injury, no particular choice is now tangibly different from any other choice, and without decision making, very little gets done. Tammy reports she often spends all day on the sofa, So her brain injury tells us something crucial about decision making. It's easy to think about the brain commanding the body from on high, but in fact, the brain is in constant feedback with the body. The physical signals from the body give a quick summary of what's going on and what to do about it. To land on a choice, the body and the brain have to be in close communication, and for that you need the orbit or frontal cortex. Now you can, of course understand this in your own life. Consider a situation like this. You get a package misdelivered to your door, but it belongs to your next door neighbors. So you go over to deliver it to them, But as you approach their gate, their dog growls and bares its teeth. So do you open the gate and press on to their front door? Your knowledge of the statistics of dog attacks, that's not the deciding factor here. Instead, the dog's threatening posture triggers a set of physiologic responses in your body. You get an increased heart rate, you get a tightening of the gut, a tensing of the muscles, you get pupil dilation, changes in blood hormones, opening of sweat glands, and so on. And all these responses are automatic and unconscious. So in this moment, standing there with your hand on their fence latch, there are a lot of external details you could assess, like what's the color difference between the dog's ears and nose, But your brain doesn't care about that. Way your brain really needs to know right now is whether you should face the dog or deliver the package. Another way, the state of your body helps you in this task. It serves as a summary of the situation. Your physiological signature can be thought of as a low resolution headline like this is bad or this is no problem, and that helps your brain decide what to do next. Most situations involve too many details to compute a purely logical decision. To guide the process, we need these abridged summaries. I am safe here, I am in danger here. The physiological state of the body maintains this instant two way dialogue with the brain, and every day we read the states of our bodies like this. But in most situations, our physiologic signals are more subtle and so we aren't aware of them. But these signals are crucial to steering the decisions we have to make. So consider being in a restaurant. This is the kind of place which leaves TAMMI paralyzed within decision. Do I want an appetizer, which one? What kind of salad dressing? Which dessert should I order? Thousands of choices bear down on the restaurant goer, with the end result that we spend hours of our lives staring at menus, making our neural networks commit to one decision over another. And although we don't commonly realize it, our body helps us to navigate this boggling complexity. Take the choice of which Italian dish are going to order? There's too much data for you to grapple with. You can think about calories or price, or salt content, taste or whatever. There's lots of data to draw from here. But if you were a robot, you'd be stuck here all day trying to make your decision with no obvious way to trade off. Which details matter more. To land on a choice, you need a summary of some sort, and that's what the feedback from your body gives you. For example, thinking about your budget might make your palm sweat, or you might salivate thinking about the last time you consumed the angel hair pasta, or thinking about the excessive creaminess of the alfredo might put a cramp in your intestines. You simulate your experience with one pasta, and then you simulate the next and the next, and your bodily experience helps your brain to quickly place a value on the first pasta offering, and another on the second pasta, and on the third and so on, and this is what allows you to tip the balance in one direction or another. You don't just extract the data from the pasta descriptions, you so feel the data. These emotional signatures are more subtle than the ones related to facing down a barking dog. But the idea is the same. Every choice that you face is marked by a bodily signature, and that helps you decide. Earlier, when I was deciding between the lemon and the blueberry, exercise drink, I told you that there was a battle between networks. The physiological states from my body are the key things that help tip that battle, that allow one network to win over another. But for Tammy, because of her brain damage, she can't integrate her bodily signals into her decision making, so she has no way to rapidly compare the overall value between options. She has no way to prioritize the dozens of details that she can articulate. That's why Tammy stays on the soface so much of the time. None of the choices in front of her carry any particular emotional value. There's no way to tip one network's campaign over any other, so the debates in her neural parliament continue along in deadlock. Because the conscious mind has low bandwidth, you don't typically have full access to the bodily signals that tip your decisions. Most of the action lives far below awareness. Nonetheless, these signals can have far reaching consequences on the type of person you are and who you'll become. So what we've been introduced to today is this incredible thing that brains do called decision making, where neurons consider options and things are set up so that one coalition can smash everything else down so you get to one outcome. And even though we typically don't give it much consideration, decision making lies at the heart of everything we do during a day. Without the ability to consider alternatives and weigh them and select one over others, the complexity of the world would just paralyze us. And one of the lessons that surfaced is that although you feel like you have a single identity, you're not of a single mind. Instead, you're a collection of many competing neural networks. You are, in a sense, a machine built of conflict. So what we covered is that every decision you make involves your past experiences stored in the states of your body, as well as an analysis of your presence situation. Do I have enough money to buy X instead of Y? Is options Z available? But there's one more part to the story of decisions, perhaps the most important part of all, and that is predictions about the future. And that is where we're going to pick up next week. Until then, keep making good decisions and I'll see you next time. Go to eagleman dot com slash podcast for more information and to find further reading, and send me an email at podcast at eagleman dot com with questions or discussions, and check out and subscribe to Inner Cosmos on YouTube for videos of each episode and to leave comments. Until next time, I'm David Eagleman, and you made the very nice decision to join me here in the Inner Cosmos

When you're trying to choose which ice cream flavor to get, what's actually happening in your brain? How do you decide? It seems pretty easy, but that's only if you don't see the storms of activity lighting up the brain. And how do you make long term decisions like that You're not going to eat the ice cream at all, but instead you're going to eat some broccoli. And what does any of this have to do with the ancient Greeks, or what alien hand syndrome is, or what the rules should be around how the president can launch the nuclear bomb. Welcome to Inner Cosmos with me David Eagleman. I'm a neuroscientist and author at Stanford and in these episodes we dive deeply into our three pound universe to uncover some of the most surprising aspects of our lives. Today's episode and next week's is about decision making. Although you generally feel like you're just moving through a day, decision making lies at the heart of everything we do. The complexity of the world presents itself to us, and we are constantly weighing alternatives. If you couldn't do that, you couldn't navigate the now, and you couldn't plan out your future. So by having a richer understanding of how choices battle it out in the brain, we can learn how to make better decisions for ourselves. And, as we're going to see next week, because this is a two partern, we'll even see how we can use this to build a better criminal justice system. So let's start at the very beginning. Should you choose the taco or the brito? Should you go for that T shirt or a more formal shirt. Should you take care of this email first or that bill payment first? Do you feel like the mint, chocolate chip or cookies and cream? On any day, you're making one thousand little decisions, which phone calls to make, which shooes to wear, whether to take the shorter path or the faster path, how exactly you should answer a question, what you should agree to on your schedule tomorrow. This, it turns out, is one of the most central things the brain does, make decisions. Your brain is a decision making machine. It takes the complexity of the world and it squeezes things down to single decisions. So how do brains do this? Now? When economists and psychologists first started looking at this question, they assumed that we humans act rationally. The idea is we look at our options, we add up the pros and cons, and we make the optimal decision. That's not necessarily how it goes with our brains. And in this episode and the next one, we're going to get a really good understanding why. So let's get going with these drawing where there are two ways to interpret the same image. You've probably seen these things. If you look at the picture one way, it looks like a rabbit, and if you keep staring at it you can see that suddenly it looks like a duck. So you probably saw this when you were a kid, But just in case you didn't, I'm putting it on the show notes at eagleman dot com slash podcast. The point is the image is what we call perceptually by stable, which is just a way of saying that when you stare at the picture, your brain can make one interpretation of what you're seeing or the other interpretation, and it switches back and forth. You see the rabbit and then the duck, and then the rabbit and then the duck. The critical thing to appreciate is that nothing on the page changes, so the only thing that's changing is something inside your brain. So some years ago I collaborated with my neurosurgery colleagues to study this sort of thing. Now, neuroscience, what I do is pretty different from brain surgery what a neurosurgeon does, but happily we tend to be friends and we can often help each other. So I accompanied surgeries while my colleagues were operating on people's brains. And you may know, one of the incredible things about neurosurgery is that you can do this while a patient is awake and talking to you. And this is because you can put little electrodes these are small metal wires into the brain and the brain has no pain receptors, so it doesn't hurt. The patient can't feel that. Now, why does the brain have no pain receptors. It's generally because nothing ever touches your brain. Your brain, which is about the consistency of jello, is well protected in the thick plates of the skull, so evolutionarily, there was no point in developing pain receptors in the brain anyway. As a consequence, a neurosurgeon only needs to use local anesthesia when making a cut on the scalp, and then they drill a burhole into the skull, and once the brain is exposed, you can poke things into the tissue while you and the patient are having a conversation about what it's like and what you find there is that this empire of eighty six billion neurons is constantly storming with activity. Every neuron in your head is having these little spikes of electrical voltage known as action potentials, and every neuron is firing off some tens or hundreds of these spikes every second of your life. Every idea you've ever had, every memory you can ever recollect, every choice that you've ever contemplated, is written in the language of these tiny, mysterious spikes. And using a very very tiny electrode think of a super small wire that you just push into the brain, you can eavesdrop on these spikes. Now, let's call the patient on the table, Marcia. So Marcia is wide awake and talking to me, and I can show her this bistable picture of the rabbit duck and ask her to tell me what she sees. Now, the moment that Marcia switches to rabbit or duck, her brain has made a decision. A decision doesn't have to be conscious in this case, it's a perceptual decision by her visual system, and the mechanics of this switchover are totally hidden under the hood. Now, what's interesting is that in theory, a brain should be able to see both the rabbit and the duck at the same time, but in reality, brains don't do that. What brains do is they take ambiguous data and they make a choice. In this case, it eventually remakes the choice, and it might switch back and forth over and over. But the point is that our brains are always crushing ambiguity down to a choice. So when Marsha's brain lands on the interpretation that the drawing is of a duck or a rabbit, we can listen through the electrode to the responses from a small number of neurons these cells in her brain. Some neurons shift to a higher rate of activity while other neurons slow down their activity. And that happens right when Marcia says, oh, now I see it as a duck, and then when she says, oh, now it's a rabbit again, the neurons are changing their activity. Now, the neurons we happen to be eavesdropping on are not by themselves responsible for the perceptual change. Instead, they're operating in concert with billions of other neurons. So the changes we're listening to are just pieces of this massive changing pattern taking hold across large swaths of brain territory. But the idea is that when one pattern wins out over the other in Marcia's brain, a decision has been landed upon. Now it's a rabbit. Now it's a duck. Now. Just as a side note, it's not always about the neurons speeding up or slowing down their spikes. Sometimes neurons change their pattern of activity in more subtle ways. They become synchronized or desynchronized with other neurons even while they're maintaining their original pace. Now here's the thing. Although we can look at this in Marsha's brain and correlate the changes with seeing the rabbit or the duck, the thing to appreciate is that your brain makes thousands of decisions every day of your life, and that dictates your experience of the world. What are you gonna wear today, who are you going to text today, How are you going to interpret what was meant by that email? Are you going to exercise today? Or are you gonna eat that bag of chips or pass it up. We don't typically chew on it, but these small decisions underlie every action we take. Who you are emerges from the brain wide battles for dominance that rage in your skull every moment of your life. So listening to that neural activity in Marsha's head, it's impossible not to be in awe because this is what every decision in the history of our species sounded like. Every marriage proposal, every declaration of war, every leap of imagination, every mission launched into the unknown, every act of kindness, every lie, every breakthrough, every decisive moment. It all happened right here in the darkness of the skull, emerging from patterns of activity in networks of biological cells. So let's take a closer look at what's happening behind the scenes during a decision. So imagine you're making a simple choice. You're standing in the drinksisle at the store, and you're trying to decide between two flavors of sports strength that you like equally. So you're looking at lemon and blueberry. Now from on the outside, someone's looking at you standing in the aisle. It doesn't look like you're doing much. You're simply stuck there in the aisle, looking back and forth between these two options. But inside your brain, a simple choice like this has unleashed a hurricane of activity. Now keep in mind that by itself, no single neuron has much influence. But each neuron is connected to thousands of others, and they in turn connect to thousands of others and so on. In this massive, loopy, intertwining network, they're all releasing chemicals that excite or depress each other. Within this web, a particular constellation of neurons represents the Lemon drink, and this pattern is formed from neurons that mutually excite each other. Now they're not necessarily next to each other. They might span distant brain regions involved in smell and taste, and vision and your unique history of memories involving lemons sports strengths. Each of these neurons by itself has very little to do with lemon. In fact, each neuron plays many different roles at different times in ever shifting coalitions. But when these neurons all become active collectively at the same time in this particular arrangement, that's the Lemons sports drink. To your brain. So as you're standing in front of the drinks, this federation of neurons eagerly communicates with one another, like the way that dispersed individuals link online. Now, these neurons aren't acting alone in their electioneering. At the same time, the competing possibility the blueberry flavored drink is represented by its own neural coalition, and thousands or millions of neurons there are talking with each other and trying to get the vote out. Now, each coalition lemon and blueberry, tries to gain the upper hand by intensifying its own activity and suppressing the others. Neural populations compete against one another, just like police parties struggle for dominance. They fight it out until one of them triumphs in this winner take all competition, and whichever network wins defines what you do next. Now, this is what is so cool about brains as compared to let's say, are digital computers. The brain is a machine that runs on conflict between different possibilities, and all these possibilities are always trying to outcompete the others, and there are always multiple options. Even after you've selected the lemon or the blueberry drink, you find yourself in a new conflict. Should I drink the whole thing right now? Part of you feels like it's a good idea to make sure you have plenty of hydration, And at the same time, part of you he recognizes that it's very sugary and you don't want to do too much of that. And part of you also knows you're going to have to go to the bathroom soon if you drink the whole thing. So whether you polish off the whole drink now or save some for later is simply a matter of the way that the infighting goes as a result of the ongoing conflict in the brain. You can argue with yourself, you can curse it yourself, you can cajole yourself. But who exactly is talking with whom? It's all you, but it's different parts of you now. As I said, we're not usually aware of these internal conflicts, but sometimes we can use simple tasks to bring this to the surface. For example, there was a simple psychological task introduced in the nineteen thirties, which we call the Stroop task, and it's very easy. All you do is you look at a word printed on a page, and the word might be in red ink or blue, or green or yellow, and all you need to do is say the color of the ink. So if I show you the word garage and the ink is yellow, all you do is you say yellow. Now that sounds very easy to do, But the trick is that the words I show you might themselves be color words. Like I show you the letters R, E, D, but the ink is in green. So when you see this, you're supposed to shout out green, but it proves very difficult. Or I show you the word purple written in yellow ink, or the word blue written in red ink. Check out some examples on the show notes. Now, the instructions are very easy. All you're supposed to do is say the color of the ink. So why is the stroop task so hard? It's because one network in your brain has the task of identifying the color of the ink and putting a name to it. But at the same time, you have competing networks in your brain that are responsible for reading words. And these are so proficient that word reading has become a deeply ingrained automatic process. And so you can feel the strugg as these systems contend with each other and to get the right answer. You have to actively suppress the strong impulse to read the word in favor of really concentrating on the ink color. So with a simple task like this, you can directly experience the conflict. But most of the time things are running so smoothly under the hood that you don't even realize that you have all these competing networks. And it's only under very special circumstances that it can become easy for us to witness in another person the internal conflict between the different parts of the brain. So this can happen when a person has a particular kind of epilepsy, where the epileptic seizures spread from one hemisphere to the other. In these cases, some patients have undergone what is called a split brain surgery, which the brain's two hemispheres get surgically disconnected from each other. So normally your two hemispheres are connected by a super highway of nerves called the corpus colosum, and this allows the right and left halves to coordinate and to work in concert. So, for example, if you are feeling chilly, both of your hands cooperate. One holds your jacket hem while the other tugs up the zipper. But When the corpus closum gets cut, the two hemispheres aren't talking anymore, and you can get a very wild and haunting clinical condition that's called alien hand syndrome. So the two hands can act with totally different intentions. So a person with a severed corpus colosum begins to zip up a jacket with one hand and the other hand the alien hand suddenly grabs the zipper and pulls it back down. Or the person might reach for a piece of pizza with one hand and their other hand leaps into action to slap the first hand. The normal conflict running in the brain now comes to the surface because the two hemispheres are now acting independently of one another. They're not working things out under the hood anymore. Alien hand syndrome typically fades in the weeks after surgery, as the two halves of the brain take advantage of any remaining connections to start coordinating again. But what it reminds us is that even when we think we're being single minded, our actions result from these immense battles that continually rise and fall in the darkness of the cranium. Now to appreciate some of the major competing systems in your brain. Consider a philosophy experiment known as the trolley dilemma. I spoke about this once about sixty episodes ago, but if you haven't heard this one, it paints an important point. So here's how it goes. A trolley is barreling down a train track and you are a bystander, and you notice that there are four workers who are doing repairs down the track, and you realize that they are going to get it and killed by this trolley. Then you notice that there's a lever right near you, and if you pull this lever, that'll divert the trolley onto a parallel track. But wait a minute. You realize that there's one worker on that track, and if you pull the lever, that one worker will get killed. So here's the question. Do you let four people get killed or do you pull the lever so that only one person is killed. When people are asked what they would do in this scenario, almost everyone pulls the lever. After all, it's better than only one person gets killed rather than four, right, But now consider a slightly different scenario. In the second scenario begins with the same premise that trolley is barreling down the track and four workers are going to get killed. But this time you're standing on a bridge that goes over the tracks, and you notice that there's a large man standing on the bridge watching the birds. And you realize that if you push him off, he'll land right on the track and his body will be sufficient to stop the trolley and save the four workers. So do you push him off? In this second scenario? Almost no one I talk with is willing to push the man. Why not? Well, when I ask them, they give answers like that would be murder and that would just be wrong. But wait, isn't it the same equation? In both cases? The question is would you trade one life for four? So why do the results come out so differently in the second scenario. Ethicists have addressed this problem from many angles, but brain imaging has been able to provide a fairly straightforward answer to the brain. The first scenario about pulling the lever, that's just a math problem. The dilemma activates regions that are involved in solving logical problems. But in the second scenario, where you have to physically interact with the man and push him to his death, that recruits additional networks. Into the decision. Now you have the involvement of brain regions involved in emotion. In this second scenario, you're caught in a conflict between two systems that have very different opinions. Your rational networks tell you that one death is better than four, but your emotional networks trigger this gut feeling that murdering a bystander is wrong. You're now dealing with these competing drives, with the end result that your decision is likely to change entirely from the first scenario. Now, the trolley dilemma sheds light on real world situations. Just think of modern warfare, which has become more like pulling the lever rather than pushing the man off the bridge. When a person pushed which is the button to launch a long range missile, it involves only the networks involved in logical problems. Operating a drone can become like a video game. Cyber attacks reconsequences at a distance, So the rational networks are at work here, but not necessarily the emotional networks. The detached nature of distance warfare reduces internal conflict, and it makes this easier to wage. So in the nineteen sixties there was a military thinker who suggested that the button to launch nuclear missiles should be implanted in the chest of the president's best friend. That way, if the president chooses to launch nukes, he'd have to inflict physical violence on his friend first, he'd have to tear him open, and that consideration would recruit emotional networks into the decision. After all, the world would not be better if we all behaved like row robots when making life and death decisions. Unchecked reason can be dangerous. Our emotions are actually a powerful and often insightful constituency, and we'd be remiss to exclude them from the parliamentary voting. Although the neuroscience is new, this intuition about having different drives has a long history. The ancient Greeks suggested that we should think of our lives like we are charioteers trying to hold on to two horses. We've got the horse of reason and the horse of passion, and each horse pulls slightly off center in opposite directions, and your job is to keep control of both horses, keeping yourself moving down the middle of the road. So I've asserted that emotions are really important and we shouldn't try to be like mister Spock. But I want to double click on that claim, and the way we can do that is by seeing what happens when a person loses the capacity to include emotions in decision making. So let's take someone like Hammy Myers, who I filmed in my television show called The Brain. Cammy is a former engineer and some years ago she got into a motorcycle accident and the consequence was damaged to her orbitofrontal cortex, which is the region just above the orbits of the eyes. Now, this is a critical region to integrate signals streaming in from the body, Signals that tell the rest of the brain what state her body is in. Is she hungry, is she nervous? Is she excited? Is she embarrassed? Is she thirsty? Is she joyful? Now? The interesting thing is that Cammy doesn't look like someone who has suffered a traumatic brain injury. But if you were to spend even five minutes with her, you would detect there's a problem with her ability to deal with decision making. So let's say you say, hey, do you want the lemon drinker the blueberry? And she can describe all the pros and the cons while the lemon drinks a little more sour, but the blueberry has more sugar, and so on. But she can't actually decide. She can't finalize a choice. Even the simplest situations leave her mired and indecision why. It's because she can no longer read her body's emotional summaries, and as a result, decisions become incredibly difficult for her. In other words, because of her brain injury, no particular choice is now tangibly different from any other choice, and without decision making, very little gets done. Tammy reports she often spends all day on the sofa, So her brain injury tells us something crucial about decision making. It's easy to think about the brain commanding the body from on high, but in fact, the brain is in constant feedback with the body. The physical signals from the body give a quick summary of what's going on and what to do about it. To land on a choice, the body and the brain have to be in close communication, and for that you need the orbit or frontal cortex. Now you can, of course understand this in your own life. Consider a situation like this. You get a package misdelivered to your door, but it belongs to your next door neighbors. So you go over to deliver it to them, But as you approach their gate, their dog growls and bares its teeth. So do you open the gate and press on to their front door? Your knowledge of the statistics of dog attacks, that's not the deciding factor here. Instead, the dog's threatening posture triggers a set of physiologic responses in your body. You get an increased heart rate, you get a tightening of the gut, a tensing of the muscles, you get pupil dilation, changes in blood hormones, opening of sweat glands, and so on. And all these responses are automatic and unconscious. So in this moment, standing there with your hand on their fence latch, there are a lot of external details you could assess, like what's the color difference between the dog's ears and nose, But your brain doesn't care about that. Way your brain really needs to know right now is whether you should face the dog or deliver the package. Another way, the state of your body helps you in this task. It serves as a summary of the situation. Your physiological signature can be thought of as a low resolution headline like this is bad or this is no problem, and that helps your brain decide what to do next. Most situations involve too many details to compute a purely logical decision. To guide the process, we need these abridged summaries. I am safe here, I am in danger here. The physiological state of the body maintains this instant two way dialogue with the brain, and every day we read the states of our bodies like this. But in most situations, our physiologic signals are more subtle and so we aren't aware of them. But these signals are crucial to steering the decisions we have to make. So consider being in a restaurant. This is the kind of place which leaves TAMMI paralyzed within decision. Do I want an appetizer, which one? What kind of salad dressing? Which dessert should I order? Thousands of choices bear down on the restaurant goer, with the end result that we spend hours of our lives staring at menus, making our neural networks commit to one decision over another. And although we don't commonly realize it, our body helps us to navigate this boggling complexity. Take the choice of which Italian dish are going to order? There's too much data for you to grapple with. You can think about calories or price, or salt content, taste or whatever. There's lots of data to draw from here. But if you were a robot, you'd be stuck here all day trying to make your decision with no obvious way to trade off. Which details matter more. To land on a choice, you need a summary of some sort, and that's what the feedback from your body gives you. For example, thinking about your budget might make your palm sweat, or you might salivate thinking about the last time you consumed the angel hair pasta, or thinking about the excessive creaminess of the alfredo might put a cramp in your intestines. You simulate your experience with one pasta, and then you simulate the next and the next, and your bodily experience helps your brain to quickly place a value on the first pasta offering, and another on the second pasta, and on the third and so on, and this is what allows you to tip the balance in one direction or another. You don't just extract the data from the pasta descriptions, you so feel the data. These emotional signatures are more subtle than the ones related to facing down a barking dog. But the idea is the same. Every choice that you face is marked by a bodily signature, and that helps you decide. Earlier, when I was deciding between the lemon and the blueberry, exercise drink, I told you that there was a battle between networks. The physiological states from my body are the key things that help tip that battle, that allow one network to win over another. But for Tammy, because of her brain damage, she can't integrate her bodily signals into her decision making, so she has no way to rapidly compare the overall value between options. She has no way to prioritize the dozens of details that she can articulate. That's why Tammy stays on the soface so much of the time. None of the choices in front of her carry any particular emotional value. There's no way to tip one network's campaign over any other, so the debates in her neural parliament continue along in deadlock. Because the conscious mind has low bandwidth, you don't typically have full access to the bodily signals that tip your decisions. Most of the action lives far below awareness. Nonetheless, these signals can have far reaching consequences on the type of person you are and who you'll become. So what we've been introduced to today is this incredible thing that brains do called decision making, where neurons consider options and things are set up so that one coalition can smash everything else down so you get to one outcome. And even though we typically don't give it much consideration, decision making lies at the heart of everything we do during a day. Without the ability to consider alternatives and weigh them and select one over others, the complexity of the world would just paralyze us. And one of the lessons that surfaced is that although you feel like you have a single identity, you're not of a single mind. Instead, you're a collection of many competing neural networks. You are, in a sense, a machine built of conflict. So what we covered is that every decision you make involves your past experiences stored in the states of your body, as well as an analysis of your presence situation. Do I have enough money to buy X instead of Y? Is options Z available? But there's one more part to the story of decisions, perhaps the most important part of all, and that is predictions about the future. And that is where we're going to pick up next week. Until then, keep making good decisions and I'll see you next time. Go to eagleman dot com slash podcast for more information and to find further reading, and send me an email at podcast at eagleman dot com with questions or discussions, and check out and subscribe to Inner Cosmos on YouTube for videos of each episode and to leave comments. Until next time, I'm David Eagleman, and you made the very nice decision to join me here in the Inner Cosmos