Author & Neuroendocrinologist Robert Sapolsky | JCCSF

[Music] [Applause] [Music] [Applause] [Music] well thank you it's a real pleasure being hometown and at the JCC this place has a special place in the hearts my wife and I and that he was in this very building that both of our children learned that they were not going to be professional basketball players so the JCC is quite meaningful to us let me start off by telling you about a fantasy I've had with some regularity it starts off with a team of us overpowering his security guards okay well it's a fantasy so when I go whole hog I single-handedly overpower his security guards I burst into a secret bunker he grabs for his Luger I slap it out of his hand he grabs for a cyanide pill I knock that out of his hand he comes at me with otherworldly strength snarling we grapple I managed to get him down on the ground get handcuffs on him and then get to say Adolf Hitler I arrest you for crimes against humanity so at this point the the Medal of Honor version of the fantasy ends and the viscera start what would I do if I had Hitler and if I really allow myself to go there it's not hard to imagine sever his spine at the neck leaving him paralyzed take out his eyes puncture his eardrums cut out his tongue leave him unable to speak to move to express only to feel inject him with some cancerous thing let's go to fester in every corner of his body and he spends eternity with this is what I would want to have done to Hitler I've had this fantasy since I was a kid I still have it now and then and when I do my heart beats faster my breathing speeds up all these plans for the most evil soul and history most deserving a punishment I got a problem with that though and that I don't believe in Souls or evil or punishment and I think the word wicked only belongs in a musical but at the same time there's all sorts of people I'd like to see killed but I'm against the death penalty very firmly but there's all sorts of violent schlocky movies I like going to but I'm for very strict gun control except for there's one time at a kid's birthday party we went to this laser quest place I had so much fun hiding in a corner shooting at people over and over in other words your basic confused human when it comes to figuring out the place for aggression in our lives now I don't need to get up on a soapbox here about the problems we have as a species with aggression we have had poison gas come out of shower heads anthrax and letters passenger planes as missiles mass rape as a military strategy we are a miserably violent species but there's some complications with that the first one being we don't hate violence because when it's the right kind we leap forward to watch it we hand out metals we disproportionately vote for mate with the people who are best at that kind of violence we don't hate violence because when it's the right kind we love it the other complication is we are the weirdest species on earth when it comes to being violent okay we could be like any other chimp out there and like cudgel somebody over the head and be violent that way but we can also do something no more physically taxing than pulling a trigger or signing an order or looking the other way or damning with faint praise or being passive-aggressive let me give you an example of one of the weirdest things I've ever heard about human violence and this had to do with something that occurred in Indonesia in the early 1960s there was a right-wing coup that brought in a military dictatorship for the next 30 years and in the aftermath of this there was a vendetta against every leftist every atheist every communist all the usual 500000 Indonesians were killed over the six months after this coup right-wing death squads would come and kill every person in the village in the usual and some decades later the writer VS Naipaul was travelling from Indonesia and he heard this crazy rumor which was sometimes when those death squads would come to a village to kill everyone they would bring along with them a traditional gamelan orchestra one day Naipaul meets one of these old grizzled veterans of these death squads and he's some national hero and talking to him and saying oh yes yes we got rid of our nation's enemies we did such a greater and Naipaul eventually worked up the nerve to say to him you know I heard this story that sometimes you guys would bring a gamelan orchestra when you would come to kill you and he said oh yes yes whenever we could we would bring one along and I Paul said why would you do that and in one phrase the man summarized everything that is bizarre about us as a species he looked puzzled and he said to make it more beautiful of course if we're species that brings along orchestras to make our genocides more beautiful we are a very complex ly violent species now the biggest complication in making sense of us in terms of violence and aggression is that in addition to us being this miserably violent species we're this unprecedented ly altruistic and compassionate species and most of all we're getting better at it look every single thing on this chart was invented in the last century you look at barber Tuckman's Europe you look at your Europe and 1800 you look at all the things that are taken for granted things are getting better we have this wild puzzle here of we have the ability to be spectacular ly damaging and spectacularly altruistic and this leaves us with a puzzle how do we make sense of ourselves as a species where do we fit ourselves in in making sense of our best behaviors and our worst ones how do we understand the biology of it now one thing that's clear is it's incredibly simple and boring if all you want to explain is the motoric aspects of behavior brain tells your spine to tell your muscles to do something or other and hooray you've behaved what's complicated is understanding the meaning of the behavior because in one setting you pull a trigger and it's an appallingly violent act in another setting you pull a trigger and you've suicidally drawn fire on yourself to save somebody else in one setting you put your hand on somebody else's and it's an act of profound compassion and another it's a first step of a deep betrayal of a loved one the challenge is understanding the context of our behaviors and that is one tough and biological challenge where the exact same motoric behavior could mean such radically different things so how do we begin to understand the biology of that one thing that is clear is you're gonna get nowhere if you get in your head that you are going to be able to explain everything with this brain chemical or this gene or this hormone or this childhood experience or this evolutionary mechanism if you think you're gonna explain it all with one of these buckets you are gonna get nowhere at all instead when we see somebody commit one of these behaviors and we ask why did that behavior occur we're actually asking a whole hierarchy of questions what went on in that person's brain one second before that commanded those muscles what went on in the seconds two minutes before in the environment that triggered those neurons to do that what went on in the hours two days before hormone levels in the bloodstream that made the brain more or less sensitive to certain stimuli and then we're often running months worth of neural plasticity back to adolescence childhood fetal life back to your genetic makeup and from there it's perfectly pertinent to start asking questions like so centuries ago what were your ancestors doing for a living what sort of cultures did they invent in sort of ecosystems and finally why does that behavior occur millions of years worth of questions about why we evolve to be the behaving species that we are to make sense of it we have to incorporate all of these ok so giving a quick tour of this approach somebody does one of these behaviors an appalling one a wonderfully compassionate one somewhere ambiguously in between and we asked our biological question why did that behavior occur and we start off with one second before what went on in that person's brain now if we're starting off with appalling behaviors the first place in the brain you arrived at is the amygdala the amygdala is about aggression it's about violence it's about all of those dark side stimulate the amygdala and a human a monkey a rat you elicit unprovoked aggression surgically destroy the amygdala you create an organism who's incapable of aggression the amygdala and aggression go hand and hat but the really important thing is if you sit down some amygdala gist and ask them what the amygdala is about the first word they come up with is not going to be aggression the first word is going to be fear the amygdala is about fear anxiety the amygdala is what learns for you that don't go there bad things happen the amygdala is all about that what have we just seen you can't begin to understand the neurobiology without understanding the neurobiology of fear the neurobiology of aggression outside of the context of fear now the way the amygdala processes scary threatening stimuli is really important it has a wonderful advantage and a disastrous disadvantage okay so suppose you see something scary and your eyes detect it and what's the obvious thing the information goes into your brain there's this sensory Waystation called the thalamus and it gets sent to your visual cortex and then your visual cortex starts this science fair project the first layer of neurons figures out what the dots are and then the next layer turns those into lines and then the next layer turns them into shapes and dimensionality and eventually four months later you figure out oh myit's a rattlesnake perhaps we should let the amygdala know about this you are long dead under those circumstances it turns out at that weigh station that switch point that thalamus there's a short cut and the visual information also Revere's off and head straight into the amygdala in other words your amygdala gets information about a rattlesnake while your visual cortex is still looking for the instruction manuals in other words your amygdala can decide it is seeing something scary before you're even conscious of what it is that could be wonderful that would be great if we are processing scary stuff on the scale of a tenth of a second a hundred milliseconds the amygdala is already getting you to a defensive stance that's very good evolutionarily oh but there's a downside which is there's a reason why you've got that fancy complicated cortex grinding away it's tough because it's accurate the downside is the amygdala gets a visual information scary information real fast faster than your cortex does but it's not necessarily very accurate and before you know it in the right setting with the right sort of person that you're looking at you decide that the cellphone they're holding is actually a handgun and you pull a trigger so what do we see here you can't make sense of the neurobiology of aggression outside of the neurobiology of fear in a world in which no amygdaloid neuron need be afraid we'd all be sleeping between lions and lambs but what's the most important is the amygdala gets privileged information all sorts of ways but the downside is accuracy isn't great and the outcome can be disastrous okay next part of the brain that winds up being relevant area called the insular cortex take any mammal on earth and give them some rotten disgusting rancid piece of food which they bite into and the insular cortex activates tenth of a second reflux pathways are activated you gag you spit the thing out you throw up you're nauseous your eyes flinch it's a great adaptive mechanism and every mammal out there it detects poisonous toxic foods and it keeps you from swallowing the stuff the insula detects disgusting gustatory stimuli okay so take a human and somehow get them to volunteer to do the same thing and you stick them in a brain scanner and you give them some rancid horrible thing to bite into and yes they're insular cortex activates as well now don't give them something rancid and disgusting to taste just make them think about it think about that struggling little insect and its legs pushing against your lips as you push it down and you are gonna activate your insular cortex Oh in humans not only does it mediate gustatory disgust it mediates us imaginary imagining disgusting things that are gustatory but now take the person don't give them something disgusting to eat don't make them think about eating something disgusting make them think about something else and what you'll see is the insular cortex activates the insula in us also mediates moral disgust in other words the same part of the brain that tells you this is toxic rancid food is the part that also tells you this is a moral transgression that is so severe I feel sick to my stomach I feel queasy it leaves a bad taste in my mouth so this is great this is actually very adaptive because if a moral transgression was just some cerebral abstraction it would take a lot of motivation to get up and actually try to right that wrong if your stomach is lurching that's the fuel that we get the viscera to try to go and do something about it so that's great but there's a downside which is obviously one person's morally disgusting way of behaving is somebody else's perfectly normal loving lifestyle moral disgust is a moving target and the danger is for somebody to decide that a sense of disgust is a good litmus test for whether something is right or not because what that's good to do every single time is bias you towards deciding them and there are really different ways in which they behave that's so different it's got to be wrong wrong wrong I can't tell you why but it's just wrong when they do stuff so what we see here is in every animal out there the insula is about sensory disgust gustatory and us it can also do moral disgust and what's most important there is it's that moving target and the insula is the pathway by which we decide just because they're different it's got to be something that's deeply wrong and no surprise the first part of the brain the insula talks to is the amygdala ok balancing it a bit we bring in an expiration call the frontal cortex it is spectacular it's the most recently evolved part of our brain we've got more of it than any species out there the frontal cortex here's what it does in a nutshell the frontal cortex makes you do the harder thing when it's the right thing to do long-term planning gratification postponement impulse control emotional regulation every time you have a mammal in a situation like this where it's not grabbing the cookie that frontal cortex is working like mad doing the thing that's harder but better now the whole thing about the frontal cortex is very easy to view its job is mostly it sends projections down to the amygdala and its job is to muffle the amygdala before it goes and does something stupid and disastrous like basically it's this picture of top-down regulation the only thing that the frontal cortex cares about with the amygdala is to show up there now and then and preach like Christian Temperance or something and otherwise is up there in the lofty heights it turns out though that it's not just the frontal cortex talking to the amygdala it's at least as powerfully the case of the amygdala talk to the frontal cortex and what's that about that's the world in which in a highly aroused highly stressed state you decide to do something which seems brilliant at the time and you regret for the rest of your life judgment goes down the tubes when the amygdala is running the frontal cortex rather than the other way around now the fact that the frontal cortex has been marinated in all these emotional inputs from down below begins to explain just how very just how heterogeneous the tasks for the frontal cortex are all of these require you to have a frontal cortex that works well think about this you were tempted to lie about something for some sort of gain and your frontal cortex is the thing that's going to be working like crazy if you were going to resist that temptation however once you decide you are going to lie you need a frontal cortex to lie effectively you need a frontal cortex to make sure you make the right amount of eye contact and control your facial expressions and don't let your throat your voice crack if this is a part of the brain that is central to both avoiding temptation and then once used to come to it doing a good job at it this is a very complex brain region so what we see here about the frontal cortex is it makes you do the harder thing when it's the right thing to do the right thing critically is a value free judgment and what you see is this is not a picture of this is this like Olympian cerebral area up there it's sitting there just soaking in your emotions and hormones and all of that we do not not make decisions in a purely cognitive way okay next brain region region having to do with a neurotransmitter called dopamine dopamine is about pleasure cocaine works on the dopamine system particular part called the mezzo limbic mesocortical dopamine system cocaine is about pleasure because it works on dopamine pathways okay and as you see here take a human take a monkey take a rat and unexpectedly they get a reward from out of no and the system activates the dopamine neurons get all excited now do something a little bit different now instead of just giving a reward from out of nowhere what you do is whoa what just happened I just pushed a button here okay what you do now is you train that individual a light comes on a signal comes on in the room and that means if you now go and work press a lever ten times you're going to get a reward signal do the work get the reward under those conditions when does dopamine rise not when you get the reward right there when the signal comes on what's that that this is gonna be great I am all over this I know how that lever stuff works I know the rules here there's gonna be fabulous what we see here is dopamine is not so much about reward as it's about the anticipation of reward and most remarkably if you block that Raw's from dopamine they don't press the lever dopamine is also about the motivation the goal directed behavior to do what's needed to get that reward now one more wrinkle about dopamine what I've shown you here is a circumstance where you do the work you get the reward a hundred percent predictability shift things now so that only about fifty percent of the time you do the work and you get the reward what happens to dopamine then it goes through the roof like nothing you've ever seen what have we just done here we've introduced something very important into our neuro chemistry we've introduced the word maybe and nothing feels us like the word maybe maybe is that fulcrum of this is gonna be great but I'm such a loser but I've got my lucky socks on today but I'm gonna screw up again and maybe yes maybe no and we Teeter on that fulcrum and that uncertainty of maybe pumps motivated behavior out of us like nothing on earth and this is something that the neurobiologist who invented Las Vegas understood from day one permiten C is an enormous force in the system so we see dopamine's about reward even more so it's about the anticipation of reward even more so it's about the goal directed behaviors you are motivated to do to get that reward and we see that nothing motivates the system more than inserting maybe uncertainty intermittency into the system there and what is fascinating and we will get to is there are a few things out there that more reliably activate this dopamine system than somebody getting to righteously punish somebody else okay couple more brain regions one area called the fusiform cortex it's a primate specialty it recognizes faces another region called the anterior cingulate it's got something to do with empathy poke your finger with a pin and the anterior cingulate is one of the parts of the brain that activate poke the finger of your loved one with a pin and your anterior cingulate activates it's the part of the brain that feels somebody else's pain okay so fusiform cortex does facial recognition anterior cingulate does empathy but then it turns out there's fine print look at somebody's face and if it's the face of somebody of a different race on the average the fusiform doesn't activate as much it doesn't register it as much as a face and you remember it less accurately show somebody a film clip of somebody's hand being poked with a needle and the anterior cingulate activates but if the person's skin is a different color from yours there isn't as much activation so it depends whose face whose pain it all depends on those cases okay so we've gotten a sense now of what's going on with a brain one second before but no brain is an island so we return to our scenario one of our behaviors occurred it's appalling it's wonderful it's in-between and now we ask the why to that behavior occur question stepping further back what went on in the seconds two minutes before sensory stimuli that caused that amygdala to do whatever that caused that frontal cortex that inhibited that insulin what in our sensory worlds are stimulating some of these neural responses and what's most striking there is amid the obvious stuff yes if you see somebody coming at you with a knife the visual information there could sure get your amygdala going what is most interesting is sensory information is streaming into us all the time and we haven't a clue what it's doing to our behavior some examples here Center put up a pair of eyes like that on a poster on a bus stop and people literally have those eyes flash up on a computer screen and people cheat less when they're playing an online game flash it up for a tenth of a second on the screen below subliminal detection you're not even sure what you saw and people become more honest in their play okay how about this one far left give somebody something like cod liver oil a spoonful something that tastes totally disgusting and in the minutes afterward they are more condemning of a moral transgression and advocate a more severe punishment because you got a bad taste in your mouth next example on the bottom there person sits either in the hard wooden chair or the nice cushy sofa and they read what are supposedly resumes of job applicants and they evaluate them afterward sit in a hard wooden chair and you are more likely to assess somebody as having a rigid inflexible personality this is for real this is you sit in a chair like that and you're more likely to perceive somebody as being a hard-ass this is totally wild one of my favorite examples on the right here put somebody in a room and let them fill out a questionnaire about their political views social views economic geopolitical puts somebody in a room with smelly garbage and they become more socially conservative doesn't do a thing to your economic rich you political views you're sitting there and subliminally something's feeling disgusting something's feeling disgusting and you're more likely to decide oh when those people do that is not okay I am not good with that you shift people that way more examples top right this is a study that should give anyone major pause this came out in a very prestigious Journal a few years ago and it looked at the parole board system in Israel happened to be Israeli scientists and they looked at over the course of the year the five thousand parole decisions that were made by judges there whether to grant somebody freedom or send them back to jail and what they showed was over the course of those thousands of judgments the single best predictor of whether a judge would grant parole or not was how many hours it had been since the judge had eaten a meal if you came before a judge right after a meal 60% chance of being paroled right before a meal you're down there 2-0 or so and what's remarkable about this is two things the first one is we understand the biology of this blood sugar levels have something to do with how well your frontal cortex works what's the frontal cortex have to do with it making you do the harder thing of thinking about somebody else's mitigating circumstances and what the world has been like for them low blood sugar and it's much easier to say screw it send them back to jail the second remarkable thing about that is if you took any of those judges 1/2 second after they made that decision and said oh so why'd you send that guy back to jail but this guy got parole and they would quote freshman philosophers to you they would never in a million years say because of my blood sugar levels in the metabolic rate in my frontal cortex finally top left one of the most disturbing finding depressing as hell in this entire field take people stick them in a brain scanner and flash up pictures of faces flash them up for a tenth of a second you're barely even sure what you're seeing and flash up a picture of a face of another race from yours and in the average person the amygdala activates the amygdala activates in 80 milliseconds 80 thousands of a second oh my god we are hardwired to be racist and all thinks this is incredibly depressing well replicated finding but now do the study a little bit differently I recently found out that San Francisco has a baseball team and apparently there's a team in Los Angeles that it doesn't get along with well so now what you do is the same study with San Franciscans who are baseball fans you're flashing up faces and they're wearing baseball caps either through the Giants were the Dodgers and flash up a face and it doesn't matter what the skin color is if it's a Dodgers hat for a tenth of a second the amygdala activates whoa we are innately wired for racism this thing invented in the 19th century baseball and baseball fandom and all of that in milliseconds completely overrides it because we have a completely different category then of who is an us and who is of them just from a brief visual cue okay so in those seconds two minutes before we are seeing we are just being pummeled non-stop by all sorts of sensory inputs we're not even aware of we would never guess or being relevant and often ones that we don't even know are there subliminal ok so now we push further back we've seen our appalling act our wonderful act in between and we asked why did this behavior occur what occurred in the hours two days before that made that organism more or less sensitive to that bad smell that particular site whatever and thus made the amygdala the frontal cortex etc more or less likely to do whatever what two hormones have to do with it so if we're talking about violent human behavior you know right off the bat we're gonna have to start off with testosterone what's the deal with testosterone why is it that testosterone is at the centerpiece of the fact that in every culture on earth and in virtually every species out there males are such a pain in the rear when it comes to violence testosterone causes aggression turns out that's not remotely what testosterone does let me show you an example of this okay so here we have five male rhesus monkeys you put them together and they form a domino hierarchy ADA feeds be three times B never defeats a a is highest-ranking B next you get a dominance hierarchy like that now take C in the middle there shoot C up with testosterone give C so much testosterone that like every neuron is amygdalas growing antlers tons of testosterone is C now good to get involved in more fights absolutely is this what occurs is suddenly C challenging a and challenging B and rising in the hierarchy not in the slightest what happens instead is C becomes a total nightmare to D and E testosterone doesn't invent new patterns of aggression testosterone amplifies the pre-existing social learning you have about aggression testosterone lowers the threshold for external stimuli to trigger it so that's a very different picture of testosterones actions but it turns out it does something even more subtle than that and this is some wonderful work done by John Wingfield UC Davis and what's called the challenge hypothesis it turns out testosterone doesn't so much affect aggression what testosterone does is when you're being challenged it makes you do whatever behavior you need to hold on to your status now if you're a baboon when you're being challenged you hold under status by being violent aggression and challenged status is synonymous but humans humans are different because you can put humans in a situation where you get status by being generous for example in a certain economic game where you get brownie points by giving larger offers in economic exchanges and remarkably give people testosterone and they become more generous when they're playing that game in other words if you took a thousand Buddhist monks and shot them up with testosterone they would run amok doing random acts of kindness the whole point there is it's not that testosterone makes us aggressive it's that we hand out status for aggression so readily now if we're thinking about our best behaviors and we're thinking hormones immediately we have to hurdle into the greatest hormone on earth when it comes to this enter cringe Oregon what's officially the grooviest hormone on earth oxytocin oxytocin promotes mother-infant bonding oxytocin in monogamous species promotes the formation of pair bonds oxytocin makes us more trusting it makes us more expressive amazingly showing what evolution is done in the last 20,000 years when you and your beloved dogs stare in each other's eyes you both secrete oxytocin and if they inject the dog with oxytocin the dogs gonna stare at you longer boosting your oxytocin levels up for oxytocin's about trust it's about exper civet 'i give fruitflies oxytocin and they sing like Joan Baez it's the most wonderful hormone on earth so oxytocin is pro-social it promotes pro-social behavior turns out oxytocin doesn't no such thing one example of this this was work that came out of the Netherlands a few years ago and what they did in that study was they gave subjects classic problem and philosophy the runaway trolley problem trolleys running down tracks out of control it's about to hit and kill five people is it okay to push one person on to the track they'll get killed but they'll stop the trolleys okay to kill one to save five classic problem in utilitarian philosophy and you get totally different answers depending on how you phrase it people make whole living studying the trolley ology problem with moral philosophy so here's what they did they got a bunch of volunteers and they gave them the runaway trolley problem and would you push this person onto the track and they gave a name to the person being pushed on the track third of the time it was somebody with apparently just a standard good-old-boy dutch name like Dirk or Peter or something and the rest it was from the two groups that have consistent negative aversive connotations for people in Holland Germans oh yeah world war ii forgot about that and people who were Muslim and now you give somebody a choice do you push Dirk in front of the trolley do you push Otto do you push Mahmud and what you see is give somebody oxytocin a Dutch person and they're less likely to want to push Dirk onto the track and they're much more likely to do an Achmed or Otto what do we see here oxytocin doesn't make us more pro-social it makes us more pro-social to people who count as us it makes us crappier and more preemptively xenophobic to them it takes that fault line in our heads between us and them and exaggerate sit ok so we look at these hormones and what we see is our endocrine systems are affecting our brains or sensory systems all the time we're being marinated it and when it comes to testosterone the critical thing there isn't that it causes or even potentiates aggression the cause of our Earth's miseries is that we reward aggression so readily when it comes to oxytocin the punchline there is it's wonderfully pro-social for people like us and for them's it does just the opposite ok pushing further back our wonderful are terrible are in between behavior why does that behavior occur what did events in your brain of the weeks two months before have to do with it and this is this whole new trendy world of neuroplasticity your brain changes in response to experience you will see depending on the experience you grow new connections between neurons you shrivel up other ones neurons form new processes other ones that you make new neurons you kill neurons the making one up on the top left is the biggest revolution in neuroscience in the last quarter century the adult brain makes new neurons ones in green there and a part of the brain called the hippocampus your brain changes in response to experience that's so exciting there's hundreds of thousands of neuroscientists out there spending their careers studying neural plasticity and their naming their kids neural plasticity but we see a downside here we see this wonderful potential for the brain to change itself what you see though is no matter how many rounds of thousand hours of practice you do evoking neuroplasticity none of us are going to be yo-yo ma or LeBron James none of us with a severed spine are going to be able neuroplasticity our way into a reconnected one there's definite limits as to how far it could go even more importantly neural plasticity is a value-free concept and sometimes your brain could be neroli plastic and as a result you get much better at being a saint and some of the time you get much better at being an ethnic cleanser it's independent of moral value okay so now we push further back good behavior bad behavior in between what went on in your adolescence having something to do with now whether you are going to pull that trigger in that moment what about adolescence and it turns out all of adolescent behavior is explained by two key facts the one is by the time you're about 12 years old your dopamine system is going full blast the other fact is your frontal cortex isn't fully online when you're a teenager it doesn't fully mature until get this until you're about 25 years old and other words teenagers are running around with frontal cortexes that are running on like two cylinders or so and dopamine systems that are completely out of control and what's this this is why teenagers are sensation seekers and novelty seeking and are so appalling ly violent and so incredibly self sacrificial and join cults and found religions and give away their life savings and change or and this is this is why teenagers or teenagers because this dopamine system is a gyroscope without a frontal cortex building its hand on now and then to keep things balanced so that explains a lot about teenage behavior but it also explains is a lot about us in our adult state because what that means is late adolescence early adulthood is when experience is generating the frontal cortex you're going to have as an adult and that has a critical implication if the frontal cortex is the last part of your brain to mature by definition it's the part of your brain least influenced by genes and most shaped by environment and experience and almost certainly it had to evolve that way okay you put your visual cortex together in about three years 25 years for your frontal cortex is it fancier neuron series that's a tougher construction project no it's exactly the same why the 25 year delay we've been selected for that because that's how our frontal cortex learns all the really subtle social rules don't kill but it's good to kill them you don't lie but here's a circumstance where you lie hypocrisy rationalization why I'm an exception those don't come by the time you're three years old that takes a quarter century to even begin to wire that up properly that's why frontal maturation is so delayed okay pushing further back now good bad in between what about what happened in your childhood what happened in your fetal life that produced the adult brain endocrine system etc that's now deciding whether or not to pull that trigger now what is clear is something that used to not be clear which is childhood matters and the type of childhood you have is utterly shaping of the sort of adult you have coming out the other end obviously what has been revolutionary though in recent years is beginning to understand the nuts and bolts biology of how early experience in life sets your brain for being different forever after your hormonal system etc a trendy wildly trendy new field called epigenetics epigenetics the notion that you have your genes your DNA sequence from birth but what experienced us especially early in life is make it easier or harder to certain turn certain genes on or off what epigenetics is about is the way in which experience leaves an imprint on your DNA so what does this look like here's one example of this it turns out bizarrely enough the world is filled with mother rats some of whom were wonderful and who were not great mothers okay what counts is a good mother rat she licks her pups a lot she grooms him she picks him up carries around a lot this is great rat mothering and something that was first shown in the early 60s was if you lucked out and as an infant rat you had one of those highly attentive good mothers as an adult you would have lower levels of stress hormones in your bloodstream as a result you had an epigenetic change in one part of your brain and as a result less stress hormone levels so now you have this epigenetically shaped by early life experience brain on your hands you're an adult rat now and you've just had your baby and if you have lower stress hormone levels you're more likely to be a mother who grooms and licks her pups a lot and thus you pass on that trait to the next generation not passing on of the genes what's now called non genetic non-genomic transmission of traits multi-generational early life experience changes adults in a way that replicates the mothering pattern and passed on remarkably the same thing can occur when you're a fetus if your fetus and you have the bad luck that your mother is stressed like mad during the pregnancy and thus you were exposed to high levels of stress hormones as a fetus as an adult you're gonna have a bigger amygdala which is going to be more reactive to threat and generate higher stress hormone levels and thus when you are pregnant your fetus is going to be exposed to higher stress hormone levels and passed on multi-generationally okay so what do we see here obviously early environment beginning in fetal life sculpts for brain sculpts your endocrine systems and these epigenetic changes in some cases can be lifelong most remarkably in some cases they can even be multi-generational and where epigenetics is most dynamic is during fetal life environment does not begin at birth okay so now we push further back about back to our good/bad in between behavior how bout back when you were nothing more than a fertilized egg when you were just your genes what do genes have to do with it and there's no field I'm in talking about this evening that is more contentious more ripe for misinterpretation ideology all of that than what genes have to do with behavior and this isn't surprising that there's a lot of people out there who are fervently taken with the deterministic power of genes because we've sequenced the human genome when we spent more money on that than any life science project out there and DNA it's the Holy Grail it's the code of codes it determines everything your DNA tells every cell in your body what to do your genes have no idea what they're doing your genes no more decide what your cells what your organs what your body does no more decides than the recipe on a cake box decides when you make the cake it's just the instructions what actually is regulating genes the environment the environment is what determines when your genes are turned on and off now some of the time on the top their environment could be very boring your cellular environment some cell is running out of energy and as a result a gene is turned on which makes more of a thing called a glucose transporter and thus the cell takes a more glucose more energy so a cellular environment that's energy poor turns on an appropriate gene and you fix the problem sometimes environment can be your whole body suppose for example you're being exposed to higher levels of testosterone and as a result in some muscle cell genes are turned on and the cell grows bigger you put on muscle mass from testosterone and some of the time environment can be environment in the conventional sense the world out there you give birth and you smell your child for the first time and you were gonna turn on genes and your hypothalamus having to do with oxytocin oh my god genes determine everything that happens in your body that's ridiculous you smell baby's tushy Eugene changed gene transcription genes are determining noting genes are controlled by environment and the critical thing is the same gene functions in different ways in different environments do not dare write down anything on this table here but what we have here is a list of some of everybody's favorite genes that have something to do with behavior where in each case they have an effect on behavior only in a certain environment and the example is probably most pertinent to us is the one in red it's got to do with the gene called Mao alpha monoamine oxidase alpha turns out it comes in a couple of different flavors and if you have one flavor in rats in lab monkeys all of that you are more prone towards impulsive aggression so what about in humans what if you've got that version of the Mao alpha gene is that associated with more aggression and anti-social behavior absolutely if and only if you were abused as a child no child abuse doesn't matter what version you have what we see here is the gene does something but it's dependent on the environment it's useless to ask what one does outside the context of the other so genes decide nothing instead the environment is regulating what your genes do and what we see above all else is interactions between gene environment so that after a while it winds up being meaningless to ask what does this gene do it only works to ask what is this gene do in a particular environment now in theory that could be very exciting but nonetheless there's not a whole lot of penguins living in the Gobi Desert so like they all live in the same environment but but us we live in rainforests and desert and tundra and cities and Hamlet's and socialist societies and capitalist ones and monogamous employment there's no species on earth that lives in more varied environments in other words there's no species on earth that is more freed from the deterministic powers of genes okay so if that takes us all the way back to being a fertilized egg but remarkably we gotta push further back in making sense of those behaviors what were your ancestors up to what sort of cultures did they evolve in what sort of ecosystems because that's going to have something to do with how you grew up what you see is there's certain patterns that go along with certain types of ecosystems certain types of cultures that get invented for example a statistically consistent finding throughout this planet desert dwellers are more likely to invent monotheistic religions rain forest dwellers are more likely to invent polytheistic ones and what we see is a whole bunch of other traits that go along with it having something to do with why warfare is far more common amongst desert pastoralists than among rainforest hunter-gatherers you see other things as well different community sizes produce different types of religions study hunter-gatherers and small bands like that and hunter-gatherers the gods they invent could care less what humans are doing the gods they are all off - like elk hunt or whatever it is hunter-gatherers do not invent gods that have any interest in humans it's not until you start seeing people living in permanent settlements at higher density it's not until people are living in high enough of densities that they interact with strangers and they interact anonymously that people start inventing moralizing gods gods who are keeping track of what you're doing and those whether you've been naughty or nice and reward or punish based on that you don't start inventing gods who police human behavior until you're big enough that you interact anonymously with strangers another classic distinction here which is how are your ancestors making a living and traditionally there were three different ways of doing it you could be a hunter-gatherer top left you could be an agricultural list or a horticulturalist or you could be this relatively rare state of being a pastor lists people wandering the grasslands the deserts with their cows their camels their goats and it turns out if you're a pastor list there's a very certain type of vulnerability there nobody no matter how bad and mean they are can show up in your rainforest and steal your rainforest overnight it's hard for people to show up and steal all twenty acres of your planted crops there that haven't popped up yet but people can come at night and rustle your cattle can steal your camels pastoralists are vulnerable to losing their livestock and every pasture list culture and Earth comes up with what is termed a culture of honor built around great hospitality to the stranger who is a traveler enormous ly violent retribution for any norm violations this is the world of warrior classes and clan vendetta's and feuds that go on for centuries and cultures of Honor produce very distinctive types of horrific violence okay so culture different ecosystems produce different cultures produce different types of behaviors what is remarkable is for example suppose one of the biggest distinctions out there culturally between what are called individualistic cultures the u.s. is the poster child of it or collectivist cultures typically East Asian and what you see is if you are born into one of those cultures within a minute of life on the average mothers and individualistic cultures are talking to their babies more loudly than those in collectivist cultures they're holding them for less time they're waiting less time to pick up a baby when they're crying this baby will be sleeping alone on the average earlier and from the first minutes of your life culture is leaving an imprint on who you are and thus what we see is brains and genes and cultures co-evolve so what this brings us to now is our final category going all the way back because if we're talking about genes we've got to talk about the evolution of genes what went into the millions of years of evolution that produced us into the sort of species we are making this decision whether or not to pull that trigger now modern evolutionary biology and thinking about behavior the evolution of behavior has three building blocks three foundational notions the first one is called individual selection animals behave in order to leave as many copies of their genes in the next generation as possible what is called The Selfish Gene concept individual selection animals including humans try to maximize reproductive success and what we see here is a great example of this in humans currently 16 million people on this planet are direct descendants of djenka scon the most reproductively successful human on earth and we all know the worlds of powerful men with multiple wives and polygamous societies and many kids lots of individual selection second building block sometimes a way to pass on more copies of your genes is to reproduce a lot sometimes a better way is to help your relatives reproduce a lot something called kin selection which winds up being a function of how related you are producing this famous quip I'd gladly lay down my life for two brothers or eight cousins because if you help a full sibling reproduce twice that has the same evolutionary impact as you've reproducing one time okay so animals are driven by kin selection cooperation among relatives things of that sort and humans show the exact same thing we've developed kin selection in a way that makes any other primate green with envy we've invented material culture and then we've invented this phenomenon of passing it on to our descendants inheriting wealth that is kin selection out the wazoo finally third building block reciprocal altruism in some settings it makes sense to cooperate with individuals even if they aren't related to you as long as these are stable symmetrical reciprocal relationships and what's that about that's the whole economic world so what we see here is human behavior is completely explained by these building blocks of evolutionary biology individual selection in selection and reciprocal altruism until you look more closely the individual selection you maximize passing on copies of your own genes but then you have human religions where people don't reproduce where they're celibate like the Shakers kin selection you maximise the passing on of copies of genes of those who share lots of genes with you and then you have blended families adopting children from the other side of the planet reciprocal altruism we are altruistic to somebody with the expectation that is done in return and then we do something that is unprecedented you were in a city on the other side of the planet you're going to the airport you're about to fly from there you are never good to see a person there again there's no chance for reciprocity but nevertheless as you enter the terminal you pause for a second to hold the door open for someone there is no evolutionarily biologically informed chimp who could make any sense of the fact that we do then so what we see here is evolution of behavior is built around individual selection kin selection reciprocal altruism which explains a ton about human behavior until you more look more closely ok so what have we gotten to here we see we ask why - that behavior occur and we're asking questions about neurobiology of one second before - genetics culture prenatal all the way to millions of years of evolution what we've managed to arrive at here this long into this lecture is the in conclusion that it's complicated oh great I had to sit for 15 minutes through that - here it's complicated let's try to make this a little bit more useful it's complicated so be damn sure you understand how things really work before you decide that you do and go and judge somebody especially if you're judging them harshly now for me the single most important thing about all of these biology factoids I just downloaded on you is every single one of them can change every single one of them can change over time change with experience and potentially with enormous consequence ecosystems change this is a rock carving of a hippo in the middle of the Sahara where 2,000 years ago this was lush grassland ecosystems change cultures changed in the 18th century the scariest people in all of Europe were the Swedes they spent the entire century rampaging through Europe and then something changed and these days this is what the Swedish military spends its time doing they haven't had a war in more than a century cultures change most importantly people change neurons grow new connections others parts of the brain could bigger parts get smaller and we show ourselves capable of extraordinary change let me spend the last couple of minutes here showing some incredibly powerful examples of it first one John Newton this was a British theologian who played a central role in the abolitionist movement the abolishment of slavery from the British Empire in the early 1800s remarkably this he accomplished in his old age remarkably as a young man he worked as the captain of a slave ship for years and years and most remarkably after he got a little bit tired of the sea and retired he invested in the slave trade and 34 years after he retired from investing in slavery he wrote his first pamphlet opposing slavery and became the moral Titan of abolition in the British Empire something changed something changed in this theologian which he celebrated in a hymn that he wrote that he is most famous for the hymn Amazing Grace next example this man on the Left Zen gob this is the morning of December 6th 1941 where he was the lead pilot on a bomber squadron that has hacked Pearl Harbor and this is the same man 50 years to the day where as an old man he came to a survivor ceremony in Hana at Pearl Harbor came up to these elderly men who had survived his attack and he apologized to them and he and some of these men as pictured there spent the rest of their lives in close touch that could change also changed the scan occur over the course of decades sometimes change can occur over the course of hours or days one of the most moving events in World War one was the famed Christmas truce of 1914 December 1914 the first Christmas of the war various powers-that-be including the Pope decided Christmas Eve afternoon there was going to be a three-hour ceasefire up and down the trenches of France and Belgium so that men could come out and retrieve their dead from no-man's land so at the appointed time the gun stopped firing and people came out and retrieved their dead and then after a while they started helping the guys on the other side carry their dead and then they started helping each other dig graves in the frozen ground and then they prayed together at the ceremonies at the burial ceremonies and before it was over with German and British soldiers shared Christmas dinner they exchanged gifts they sang songs they pray together the next day has documented up and down the trench lines of Europe they played football together and they didn't keep score and they didn't care who was on which side and they exchanged gifts and they exchanged addresses so they could visit each other after the damn war was over with and they made agreements with each other to shoot over each other's heads and it lasted four days at some of these places and it took the officers showing up and threatening to shoot these men to get them to go back to trying to kill each other in other words a whole lifetime of propaganda a whole lifetime of nationalism whatever military training of us and them and all it took was a couple of hours to completely redefine who was in US and who was of them us being us all of us stuck in this hell of trench warfare and them being any bloated officer in the back line who would have us killed for their advantage and some of the time extraordinary change can happen over the course of minutes probably the single most traumatic event in terms of turning America against the Vietnam War was the me Lai massacre 1968 an American Brigade went into a village filled with unarmed civilians predominantly elderly people women and children and before it was over with had killed 350 to 500 civilians mutilating bodies gang rapes before killing people killing the livestock burning the fields this was appalling because it happened because the US government hid it for a year because when it finally had to confront it it handed out a slap on the wrist only to the commanding officer and because it almost certainly wasn't the only time this occurred this man on the right man named Hugh Thompson this is the man who stopped the meal I massacre he was flying a helicopter gunship he had heard word that they were shooting in this me live village he flew over there seemed he would see American troops defending the village against Viet Cong landed got out and saw American soldiers shooting old women in the head pulling babies out from underneath the bodies of their mothers to decapitate them looked at this realized what was happening and what he did was in an instant all of his training evaporated as to who was an US and who was of them there was the last group is surviving civilians over there and a group of American soldiers coming at them and he landed his helicopter between the two and pointed his machine guns and his fellow American soldiers and said I will mow you down if you do not stop and what's most remarkable about each one of these men each one of these transformations is they've got the same neurotransmitters we do and the same toast sort of neural wiring and the same endocrine glands and that same gene regulation there's nothing different about them from us they put their pants on one leg at a time and what we're left with here at the end is bringing out that inevitable George Santayana cliche those who go study history are destined to repeat it what we have here is an inversion of this those who don't study the history of extraordinary human change and who don't study the science of what circumstances make those more likely to occur are destined not to be able to repeat moments of incandescent change of that sort so on that note good luck with your own best and worst behaviors and thank you [Music] [Music] [Applause] so we have time for a few questions you can stay if you need to take off I'm over here so my question is when babies are born drug and alcohol exposed and had exposure through the whole 40 weeks of pregnancy what part of the brains the brain is that affected and do through growing up the children's brain develop that they can overcome you know the problems that they faced in utero and at birth great the answer is which part of the brain every single part of the brain the two that are probably most affected is the frontal cortex where remarkably prenatal substance abuse exposure you were born there with neurons whose chromosomes are already prematurely aged and what that sets you up for is a prefrontal cortex that isn't going to be quite as good an adult in Maine you do the harder thing when the right thing to do the other area that is most affected is that dopamine system and you down regulate the dopamine expression in that system forever after what's that a profile of you are prone towards addiction you need a bigger oomph of addictive stuff to get the same release of dopamine you were now set up for repeating the same pattern in terms of interventions what you see is one of the truisms of all of this stuff with epigenetics yes epigenetic effects can be lifelong they could be multi-generational nonetheless every single one of them is potentially reversible things change nervous systems change but the rule of thumb is the longer you wait the more of an uphill battle it's going to be next question is way up in the back here okay hi you had that great slide with three different types of like economy so the the rainforest the kind of the hunter-gatherer and that I have the culturalist agriculturalists yeah so I wonder what behaviors the today's society give rise to so working in a corporation okay I think I'm wisely not gonna go near that one with a 10-foot Pole but there is one realm of contemporary American life where this is very pertinent which is historically the original colonies were settled by people from different parts of the British Isles and the New England tend to have Puritans the middle States had mercantile sort of London type folks Quakers and all of that the American South was predominantly settled by herders herders shepherds from northern England Scotland Ireland people who brought a culture of honor to the American South and there is a whole universe of southern studies now built around what southern culture of Honor is about and it is the direct descendant of that you see highest murder rates in the country in the American South not in the cities not by non-whites not over material games this is not somebody sticking up a 7-eleven what this is is people killing somebody they know often a relative at some get-together where they take affront at some honorific slight and that's what demographically accounts for the higher murder rate throughout the south not only that if you go when you kill somebody who say came on to your significant other so you taught them a good lesson you were most likely to be acquitted by a jury in the south you were least likely to be prosecuted by a DA in the south if convicted you are likely to get the shortest jail sentence and what you see there is 400 years after like Scottish Shepherds settled like the hill country in the south there's still an imprint of that centuries later had people actually do studies showing different endocrine responses to slice personal affronts between southerners and northerners in this country classic studies like that that's a realm in which all of this what were your ancestors doing for a living is remarkably still going on in the present one additional realm of that where cultures of Honor impede on Western European and American life is the importation of one type of culture of honor that has honor killings killings of daughters killings of younger sisters who refuse to marry the person chosen for them when they're 13 who have the affront to want to go to college who want to have a job who talked to a boy and the relatives get together and kill that girl and this has occurred in every Western European country in the United States in Canada of immigrants from Pakistan and related countries that drink cultures of Honor that have honor killings that is very much a part of our present landscape so what they were doing back when is still very relevant now thank you next question on your left hi hi I understand it's complicated I just like to know if your work has made you more or less optimistic or pessimistic about the trajectory of humankind thank you okay well the answer is yes I I am by nature immensely pessimistic and nonetheless like reading this stuff like I had to have read about like I spent like six months just reading everything I could find about the Christmas truce in the trenches and amazing things Nelson Mandela did with rugby teams all of that because it's so damn curative after reading about the rest of stuff a middle of that one has to admit this is a much better world to live in than 200 years ago and all sorts of things are in place that were unheard of then and we extend sort of an umbrella of protection and a recognition of kinship and empathy in directions nobody ever dreamed of in the past you know against my better nature I'm forced to be optimistic the next mission is right in the front hi so I love the note of change and the optimism around that I guess what I grapple with still is that our ability to change isn't necessarily under our control and I wonder how you personally reconcile that and how we can retain that optimism even knowing that so little of our life is under our control or our ability is changes under our control great okay I will take the liberty of reinterpreting you as just having asked about god help us all free will ok so free will that one and I thought the optimism pessimism one was hard so free will what I think is pretty much impossible is to learn about all this stuff all of these influences all of these stories where the punch line is whoa I had no idea biology had something to do with that I had no idea that could be influenced by over and over and I think coming out the other end I think at the end of it it is very difficult to hold on to a concept of free will if I'm being you know congenial and a good houseguest or whatever I will say if there's some free will it's in all sorts of really boring places and it's getting cramped and tighter and tighter if you want to say it's free will why you decided to floss your bottom teeth this morning first instead of your top first I couldn't be happy you know good luck with that free will personally I don't think there is a shred of free will out there I think it is completely incompatible with modern science to my mind free will is what we call the biology that has not yet been discovered so that's cool and that's interesting and so okay no free will and all of that and at the same time that I am so comfortably assured that there's no free will whatsoever I haven't the remotest idea how we're all supposed to live in a world in which people didn't think there was such a thing as free will I have no idea at all what I'm convinced of by now is it's going to be much much easier to get people to think there's no free will when thinking about say a mass murderer it's much harder to think about oh there's no free will involved if somebody comes up and says to you oh that was a good lecture afterward it was my genes and culture and evolution and fetal life and all of that we're gonna have so much harder a time of giving up the notion of free will built around our best behaviors I think much harder than them and their worst behaviors so within this framework of not believing in free will how does anything change the fact that the knowledge for example that change can occur leaves a biological trace in your brain the knowledge that this has happened before that somebody no more special than you in a moment like that has turned out to be magnificent has taken three-and-a-half neurons there in your frontal cortex and nudged him in a direction of thinking it's more conceivable that you would do something like that in the next occasion not because of free will but because the knowledge that that could happen the knowledge that the world is a better place than 300 years ago the knowledge that just because you're male and you're soaked in testosterone that's not inevitable just because you're genetics isn't knowledge leaves a biological trace just as every other bit of experience does and what the right type of knowledge does is bias us and directions of feeling a sense of efficacy and actually trying to do something in circumstances where we would have thought it inconceivable otherwise so the lack of freewill and the fact that change can occur is compatible but within this biological framework we've got time for two more questions just to reminder to everybody we're going to be going to the atrium afterwards and it's gonna be signing books so stick around for that the next questions over here okay what factors in human behavior do you see that lead to the regression of morality in society and very quick spurts for example in this trumpian era we see the open acceptance of racism I think what it is don't get me started on him but I think what it is is we have leadership him and his buddies we have leadership that is unafraid of being openly venal of being openly remorseless of being openly incapable of empathy that has a brilliant instinct for identifying the weakest underdog and scapegoating them that has a brilliant ability to tap into people's angers and fears and anxieties and inflate them in the most toxic sorts of ways we got somebody with a real gift at it and a bunch of willing droid Republicans who are willing to enable him to do that and what he has done is glorify the worst instincts of our most afraid most disenfranchised people in this country and it is not by surprise who voted him into office and these are people who have been peripheral eyes dand left behind and made culturally irrelevant and economically irrelevant and he turned out to find out a perfect solution for that which is to be pissed at hell at all of the easiest scapegoats you can find and he's writing that very effectively with an intuition that far outstrips his intelligence [Applause] [Music] wait last question I say don't get me started about him hi I'm a student at UCSF and I'm studying how stress impacts birth outcomes I'm looking at stress both from self-report just a general perception and cortisol is there something else you think that may be meaningful in that relationship around stress thing okay for those of you who are not stress aficionados what's what's been brought up is the most wonderful bestest hormone on earth which is central to the stress response which is what I've studied something called cortisol also known as hydrocortisone it's the class of stress what's called glucocorticoids and if you can only measure one thing and you can't measure it within fractions of seconds of the event occurring cortisol is the best one out there it's the most integrative measure epinephrine adrenaline is telling you about what the last two and a half seconds of stress have been like cortisol what resting cortisol levels are like what levels are like after the end of a stressful event how long it takes you to get back to baseline those are the best measures as to what your recent weeks to months have been like that's the most accurate measure out there and best of all these days you don't have to get somebody's urine or puncture there are blood vessels you get a salivary sample and it tells you a ton so that's a great integrative measures chronic stress I have to take this one last question I'm really sorry but I see a hand up here oh why is half of the body green and half of it red [Applause] well it's not free will what it is is a publishers contract because the answer is I don't know this is the cover they came up with and I figured I should be agreeable because they were deciding how many copies to print and somebody at a publishing house in New York likes green and red and maybe they like Christmas or maybe they like people who have measles and two different colors at once but that's what they came up with and I haven't figured out a good way of explaining why it makes sense but I kind of like it but wonderful question thank you thank you all Robert Sapolsky [Music] you

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What drives human behavior? Why do we do what we do? Is free will an illusion? Has civilization made us better? Can we escape our tribal past? These questions are the subject of Stanford biology professor Robert Sapolsky’s new book Behave: The Biology of Humans at Our Best and Worst. Watch him as he explores why we are the way we are and explains why we ultimately do the things we do…for good and for ill.

Robert Sapolsky is a Professor of Biological Sciences and Professor of Neurology and Neurological Sciences at Stanford University, and a research associate with the Institute of Primate Research at the National Museum of Kenya. As a neuroendocrinologist, he has focused his research on issues of stress and neuron degeneration, as well as gene therapy strategies to help protect susceptible neurons from disease. A MacArthur Fellow, Sapolsky has been called “one of the best scientist-writers of our time” by Oliver Sacks and “one of the finest natural history writers around” by the New York Times. His books include A Primate’s Memoir, The Trouble with Testosterone, Why Zebras Don’t Get Ulcers, and Monkeyluv: And Other Essays on Our Lives as Animals.