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Robert Sapolsky: The Biology of Humans at Our Best and Worst — Transcript

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0:13thing.
0:14I I welcome everybody and I want to
0:17share a text about Robert Sapolsky that
0:20I have pirated from web.
0:23Uh
0:24somebody has written elegantly about
0:26him. I wouldn't be able to.
0:28As a boy in New York City, Robert
0:31Sapolsky dreamed
0:34of living inside the African dioramas in
0:37the Museum of Natural History.
0:40By the age of 21, he made it to Africa
0:43and joined the troop of baboons.
0:46Although the life of a naturalist
0:48appealed to him because it was a chance
0:50to get the hell out of Brooklyn,
0:52he never really left people behind. His
0:56gift for storytelling led the New York
0:59Times to suggest, "If you cross Jane
1:01Goodall
1:03with a brocked belt comedian,
1:06she might have written a book like A
1:09Primate's Memoir, Sapolsky's account of
1:12his early years as a field biologist."
1:16The uniqueness of Sapolsky's perspective
1:18on the human condition
1:20comes from the ease with which
1:23he combines his insights from the field
1:25with his findings as a neuroscientist.
1:28What makes Sapolsky great is that he
1:31connects science with society and human
1:34life and with human nature. He tackles
1:37the question of human mind with similar
1:39questions that kept Aristotle,
1:42Copernicus, and Shakespeare awake in the
1:45middle of the night.
1:46For more than 30 years, Sapolsky has
1:48divided his time between fieldwork and
1:51primates and highly technical
1:53neurological research in his laboratory
1:55at Stanford.
1:57As result, he can effortlessly move from
2:00a discussion of pecking orders in
2:02primates
2:03to an explanation of how
2:05neurotransmitters work during stress and
2:08gets laughed during it.
2:12Sapolsky regards his this sobering news
2:14with characteristic good humor, finding
2:17hope in our own capacity to prevent some
2:20of these problems
2:21in the small steps with which we live
2:24our everyday life. The humor and
2:26humanity he brings to sometimes sobering
2:29subject matter makes Sapolsky a
2:31fascinating speaker, as you will
2:33witness.
2:35He He lectures widely on topics as
2:37diverse as stress and stress-related
2:39diseases, baboons, the biology of our
2:42individuality,
2:44and so on. You name it.
2:46Sapolsky is a MacArthur Genius Fellow, a
2:49professor of biology at neurology and um
2:53Department of Biology
2:56at Stanford University, and a research
2:58associate with the Institute of Primate
3:00Research at the National Museum of
3:02Kenya. In 2008, National Geographic and
3:06PBS aired an hour-long special on stress
3:10featuring Robert Sapolsky and his
3:12research on the subject matter. Sapolsky
3:15was awarded Rockefeller University's
3:17Lewis Thomas pre uh prize for writing
3:20about science. His articles have
3:22appeared in publications such as
3:24Discover and The New Yorker, and he
3:26writes a biweekly column for The Wall
3:28Street Journal entitled Mind and Matter.
3:32In addition to A Primate's Memoir,
3:35Sapolsky has written four other books
3:37including The Trouble with Testosterone,
3:39Why Zebras Don't Get Ulcers,
3:44and Monkey Love and Other Essays on Our
3:47Lives as Animals, and his most recent
3:50book, Behave: The Biology of Humans at
3:53Our Best and Worst.
3:55To quote my colleague David Eagleman, a
3:58neuroscientist at Stanford University,
4:01his latest book
4:02as wide as it is deep, it is colorful,
4:06electrifying, and moving. Sapolsky
4:09leverages his deep expertise to ask the
4:12most fundamental questions about being
4:15human, from acts of hate to acts of
4:18love, from our compulsion to dehumanize
4:21and to rehumanize.
4:24We are delighted that Robert has
4:26accepted our invitation to talk about
4:28the biology of humans at our best and
4:31worst. This lecture is kindly and
4:33generously sponsored by a gift from
4:36Christina and Hamid Moghadam to Iranian
4:39Studies program at Stanford and by the
4:41Laboratory of Cognitive and Behavioral
4:43Neuroscience and Cognitive Neuroscience
4:46Interest Group. I welcome everybody in
4:48joining me to welcome Robert Sapolsky.
4:51Thank
5:01Well, singularly strange to have so many
5:04people in an audience not wondering if
5:05this is going to be on the final. So,
5:08uh
5:09thank you all for being here. Now,
5:12let me start off a little bit
5:13unorthodoxly here. Let me start off with
5:16a fantasy I first had as a kid. And it
5:19was a fantasy of the day I captured
5:22Hitler.
5:24I overpowered his elite guard. I burst
5:27into his secret bunker. I wrestled his
5:30Luger out of his hand. We grappled with
5:33each other. I pinned him down, got
5:34handcuffs on him, and was able to say,
5:37"Adolf Hitler, I arrest you for crimes
5:39against humanity."
5:41And at that point, the the Medal of
5:43Honor version of this fantasy would get
5:45a little bit harder to maintain, and
5:47viscera would start to creep in.
5:49What would I do if I had had Hitler?
5:52And if I let myself go there, it wasn't
5:54actually hard to think about it. Sever
5:57his spine at the neck.
5:58Take out his eyes, puncture his eardrum,
6:01cut out his tongue, inject him with some
6:03sort of cancer that would just pustulate
6:05in every cell in his body. I had this
6:08fantasy at various points when I was a
6:09kid, and sometimes I still do. And when
6:13I do, my heart beats faster, and my
6:16breathing gets faster.
6:18All this planning for the most evil
6:21human in all of history, the soul most
6:23deserving of damage, of punishment.
6:26Except I have a problem with that, which
6:27is I don't believe in souls, and I don't
6:30believe in evil, and I don't believe in
6:31punishment. I think wicked only belongs
6:33in the title of the musical, but at the
6:36same time, at the same time, there's all
6:37sorts of people I would like to see
6:39dead.
6:40But I'm against the death penalty.
6:42But there's lots of violent schlocky
6:44movies I like going to. But I'm for very
6:46strict gun control. But then there was a
6:48time I went to that Laser Quest place,
6:51and I had such a good time hiding in a
6:53corner shooting at people.
6:55In other words, I'm your basic confused
6:58human when it comes to feelings about
7:00violence.
7:01Now, I don't need to get up on a soapbox
7:03here about the problems we've got with
7:05violence as a species. We've used shower
7:08heads to deliver poison gas, letters
7:10with anthrax, passenger planes as
7:13weapons, rape as a military strategy. We
7:16are a miserably violent species.
7:19But there's two problems with that, at
7:21least. The first one is we don't hate
7:23violence. We hate the wrong kind of
7:25violence. When it's the right kind, we
7:28get all excited. We leap into see it. We
7:31hand out medals. We disproportionately
7:33vote for mate with the people who are
7:35best at that. When it's the right kind
7:37of violence, we love it.
7:40The other complication is, when it comes
7:42to being a violent species, we're just
7:44extraordinarily
7:46weird. I mean, some of the time we're
7:48just like any old chimp, we could take
7:50some big old heavy rock and cudgel
7:52somebody's brain in, but some of the
7:54time we can be wildly violent doing
7:56nothing more metabolically taxing than
7:59pulling a trigger or signing an order or
8:02looking the other way or damning with
8:04faint praise or being
8:06passive-aggressive. We do very odd
8:08things when it comes to violence. Let me
8:10give you the one of the single strangest
8:12examples of violence I've ever heard of.
8:15And this is one having to do with
8:16Indonesia in the 1960s.
8:19Mid-60s, there was a coup that overthrew
8:22the government there, instituted a
8:23right-wing military dictatorship for the
8:25next 30 years, and in the year afterward
8:27approximately half a million Indonesians
8:30were killed by right-wing death squads.
8:33If you were an intellectual, if you were
8:35a leftist, if you were of any of the
8:37ethnic minorities that were out-groups
8:39there, savagery, death squads would come
8:42to a village, systematically kill every
8:44single person in that village.
8:47So, decades later the writer V.S.
8:48Naipaul was traveling through Indonesia
8:50and he would hear stories about what
8:52happened at the time, and he kept
8:53hearing this crazy story, which was
8:55sometimes these death squads would show
8:58up at a village to kill everyone, and
9:00they would bring along a traditional
9:02Indonesian gamelan orchestra.
9:05Nuts. One day, he runs across one of
9:08these old grizzled veterans of one of
9:10these death squads, and he's talking to
9:11the guy, and he's proud to sort of brag
9:14about all the villagers and civilians he
9:16killed saving the nation. And Naipaul
9:18finally said, "You know, I heard this
9:19crazy thing about how sometimes you
9:21people would bring like gamelan
9:23orchestras to these massacres. Is that"
9:26And the guy said, "Oh, yes, yes,
9:27whenever we could we would bring an
9:28orchestra along." And Naipaul said, "Why
9:30would you do that?" And in one sentence
9:33the guy looked puzzled and just
9:35encapsulated everything that's weird
9:38about our violence. He said, "To make it
9:40more beautiful, of course."
9:42There is no other primate on Earth that
9:44could make sense of our violence when
9:46we're bringing along orchestras to make
9:48it more beautiful.
9:50Now, the single most complicated about
9:52thing about us being this miserably
9:54violent species is at the same time,
9:57we're the most altruistic, most
9:59cooperative, most empathetic species on
10:01Earth. And we're getting better at it.
10:04Consider every single thing up here was
10:06invented in the last century. All these
10:09ways in which we are extending sort of
10:11an umbrella of empathy and protection
10:14and all sorts of unlikely directions.
10:16We're this phenomenally violent species.
10:19We're this phenomenally cooperative,
10:21empathetic one. How do we begin to
10:23possibly make sense of the biology of us
10:26at our best and worst? Now, one of the
10:28things is clear about it. It is utterly
10:30boring if all you want to figure out,
10:33try to make sense of us as a primate
10:35amid all the others. Where do these
10:37extremes of our behavior come from? It's
10:39totally boring if all you want to do is
10:42understand the motoric aspects of the
10:44behavior. Your brain tells your spine,
10:47tells your muscles to do something, and
10:49hooray, you've behaved. What's much more
10:52interesting is to understand the meaning
10:54of the behavior. Because in one setting,
10:57you pull a trigger and it's an appalling
10:59act. In another setting, you heroically,
11:02suicidally pull fire onto yourself, and
11:05it's an awe-inspiring act. In one
11:07setting, you put your hand on someone
11:10else's, and it's a moment of deep
11:11compassion. In another, the exact same
11:14motoric behavior, and it's a first step
11:16of a deep betrayal. The challenge with
11:19us in understanding our behavior is
11:21understanding the context of it. And
11:24that's real challenging. Now, one of the
11:26things that is absolutely clear with
11:28that is you are going to get nowhere in
11:30understanding these features of our
11:31behavior. If you decide, here is the
11:34part of the brain that explains
11:36everything that's going on, or here is
11:38the hormone, or the gene, or the
11:41childhood experience, or the anything,
11:44here's the whatever that explains
11:45everything. Instead, if we're going to
11:47make any sense of these complex
11:50context-dependent behaviors of ours, we
11:53have to look at many layers. So, one of
11:55these behaviors happens, it's wonderful,
11:58it's appalling, it's ambiguous, usually
12:00somewhere in between, and we ask the
12:02biological question, why did that
12:04behavior just happen? And when we do
12:06that, we're actually asking a whole
12:08array of questions. What went on 1
12:11second before in that person's nervous
12:13system that instructed those muscles to
12:16do that good, bad, in-between behavior.
12:19But we're also asking, what was going on
12:22seconds to minutes before in the sensory
12:24world that triggered those neurons? And
12:26we're also asking, what was going on
12:28with hormone levels hours to days before
12:31that made that organism more or less
12:33sensitive to certain sensory stimuli
12:35that caused and then back to adolescence
12:38and childhood and fetal life and back to
12:40when you were just a fertilized egg, and
12:41then back to what sort of culture your
12:44ancestors came up with, and what sort of
12:46ecosystems, and what evolutionary forces
12:49sculpted all of that. If you want to get
12:51a sense, you're going to have to ask
12:53that question on all these levels. Okay,
12:55so beginning with that, one of our
12:57behaviors has happened, and we do our
12:59first version of saying, why did that
13:00occur? What went on in the brain 1
13:03second before that context-dependent
13:06trigger was pulled, that
13:07context-dependent hand was touched? Why
13:10did that occur?
13:11So, if we're going to start off with the
13:13worst of our human behaviors, right off
13:15the bat, we start off with a part of the
13:17brain, the amygdala. The amygdala is
13:20about aggression. It's about violence.
13:22Stimulate the amygdala in a rat, a
13:25monkey, a human, you get unprovoked
13:27aggression, destroy the amygdala, you're
13:29unable to elicit aggression anymore. The
13:31amygdala is about aggression.
13:33If you take an amygdalologist though,
13:36and you sit him down, and you say,
13:37"What's the amygdala about?" Aggression
13:39is not the first word they're going to
13:40mention. The first one is fear. The
13:43amygdala is about fear. It's about
13:46phobias, innate fears. Even more
13:48importantly, it's about where you learn
13:51to be afraid of things. Fear
13:53conditioning and such. In other words,
13:56you cannot understand the neurobiology
13:58of violence without understanding the
14:00neurobiology of fear. And in a world in
14:03which no amygdaloid neuron need be
14:05afraid, there'd be a lot more of a
14:07sleeping between lions and lambs.
14:10Now, the whole thing about the amygdala
14:11and processing fear is it does something
14:14very interesting with sensory
14:15information. Okay, so you see something
14:18officially scary. Oh, no, there's a
14:20rattlesnake. How does this get processed
14:22in your brain? The most straightforward
14:24thing is visual information goes to the
14:27sensory way station, the thalamus, and
14:29then it sends it on to the visual
14:31cortex.
14:32And then begins a whole science fair
14:35project. The first layer of your visual
14:37cortex breaks this down into pixels. And
14:41then it hands it to the second layer,
14:42which turns it into lines, and then the
14:44next layer, moving lines, and layer
14:47after that, and layer, and going through
14:49your memory, and like your golden book
14:51of snakes, and and finally somewhere up
14:53in your cortex, it says, "Oh my, that's
14:55a rattlesnake. Perhaps we should let
14:57those fellows down in the amygdala know
14:58about it." This is glacial from the
15:00standpoint of the nervous system. Turns
15:03out, in addition to that pathway,
15:05there's a shortcut. That very first
15:07volley of visual information getting to
15:09that thalamus has a shortcut that gets
15:12to the amygdala. In other words, the
15:14amygdala knows that you're looking at a
15:17rattlesnake while your visual cortex is
15:19still fussing around with the
15:21instruction manuals and later too. In
15:23other words, you your amygdala can know
15:26what that is before you're even
15:28consciously aware of it. And this is all
15:31in the course of hundreds of
15:33milliseconds, tenths of a second. Okay,
15:35that's great. That's very good if your
15:37amygdala already knows you're looking at
15:38a rattlesnake. That's terrific. But
15:40there's a downside, which is there's a
15:43reason why you've got your visual cortex
15:45doing all that complexity. It's to make
15:48sure you're accurate about what you
15:50decide you're looking at. And that
15:52amygdala getting that lightning fast
15:54reflexive information is all set up to
15:57make a mistake. And before you know it,
16:00you think of the guy who just happens to
16:02look in a certain way, the guy is
16:04holding the cell phone is actually
16:06holding a handgun instead, and you pull
16:08that trigger. In other words, the
16:11amygdala gets all this privileged
16:13information at the intersection of
16:15aggression and fear, this privileged
16:17information, but catastrophically at
16:20times, the information's not terribly
16:22accurate.
16:24Next part of the brain, area called the
16:26insula, insular cortex. Take any mammal
16:29out there and give it some rotten,
16:31disgusting, spoiled food to bite into.
16:34And as soon as it does, the insula
16:35activates and that triggers all these
16:37reflexes. Animal gags, it spits it out,
16:40its stomach heaves, it throws up
16:41whatever. The insula keeps you from
16:43poisoning yourself with toxic food.
16:46That's great. So you get some like
16:47college freshman who volunteers for this
16:49and goes into a brain scanner and bites
16:51into some rancid, fetid food. And same
16:54deal, insula activates.
16:56But now instead, don't have the person
16:59eat something disgusting. Have them just
17:01think about it. Think about those little
17:04legs pushing against your lips as you
17:06try to And you're going to activate your
17:08insular cortex. Ah, in most mammals, it
17:11does gustatory disgust. In us, it also
17:14does thoughts about gustatory disgust.
17:17But then something even more
17:18interesting. The Don't give the person
17:21something disgusting to eat. Don't make
17:23them think about something disgusting
17:24eat. Make them think about something
17:26else that's disgusting. Make them think
17:28about something that is morally
17:30disgusting. And the insula activates. In
17:33humans, this part of the brain also
17:36mediates moral disgust. And presumably
17:3940, 50,000 years ago when we came up
17:41with the notion of norm violations that
17:44could be so extreme that it winds up
17:46being appalling,
17:48they had a meeting. They said, "We can't
17:50invent a new part of the brain. What's
17:52that insula does disgusting foods,
17:54disgusting behavior. I don't know,
17:55sounds similar. Expand it in there. Give
17:58me some duct tape." And now suddenly
18:00your insula also does moral disgust.
18:03That's why if something is sufficiently
18:05morally disgusting, we feel sick to our
18:07stomachs. It leaves a bad taste in our
18:10mouth. We feel queasy. Now this is great
18:13because this certainly gives a lot of
18:14visceral force to things that we find to
18:16be morally appalling. But there's a
18:18problem with this, which of course is
18:21that one person's morally disgusting
18:23behavior is somebody else's perfectly
18:25normal loving lifestyle. In other words,
18:28moral disgust is a moving target. And
18:31the trouble with the visceral force of
18:33moral disgust is it just begs you to use
18:36it as a litmus test to decide, how do I
18:39figure out what's right and wrong in the
18:40world? Well, if it seems so different
18:43from what I normally do that I'm feeling
18:45a little queasy, it's wrong, wrong,
18:47wrong. And this wisdom of repugnance is
18:50a way of making some very bad moral
18:52choices. Okay, so what we see with the
18:54insula, most mammals it's about sensory
18:57disgust. In us instead, it's about moral
18:59disgust which is intensely
19:01context-dependent.
19:03And what we see there is the insula is
19:05central to us deciding that just because
19:08something is so different that it's
19:10hitting all sorts of visceral alarms,
19:12that there's something that's got to be
19:14right. I can't tell you why, but when
19:17they do that, it's just simply wrong.
19:19And the first place in the brain, the
19:20insula, screams that news to next is the
19:23amygdala.
19:25Meanwhile, another part of the brain in
19:28reference to all of this, frontal
19:29cortex. Frontal cortex, the most
19:31interesting part of the brain, it's most
19:33recently evolved. We've got more of it
19:34proportionally than any other species.
19:36What does the frontal cortex do? It
19:38makes you do the harder thing when it's
19:40the right thing to do.
19:42Gratification postponement, long-term
19:45planning, impulse control, emotional
19:48regulation. The frontal cortex is the
19:50part of the brain that says, "Hold on,
19:52hold on, hold on. You're going to be
19:54happy you did it." It does all of those
19:57harder things when it's the right thing.
20:00Now, of course, the picture is frontal
20:02cortex and the amygdala have a lot to do
20:03with each other, which is the frontal
20:05cortex spends a whole lot of time
20:07sending inhibitory projections down into
20:09the amygdala saying, "I wouldn't do that
20:11if I were you. I know it seems really
20:13tempting right now. You're going to
20:14regret it. I wouldn't do that. I
20:15wouldn't" racing to the amygdala before
20:17that shortcut gets the amygdala to do
20:19something stupid and impulsive there.
20:22And the picture you get is basically all
20:24of the frontal cortical amygdaloid
20:26interactions are top-down. The only
20:29thing the frontal cortex has to do with
20:30the amygdala is like showing up and
20:32preaching Christian temperance and
20:34things like that. And other than that,
20:36it's this very one-directional
20:37relationship. In actuality, it's
20:40two-directional because we see versions
20:43of this all the time. This is every
20:45single time in some moment of arousal,
20:48of fear, of stress, of who knows what,
20:51you make some decision that seems
20:53brilliant at the time, and you spend the
20:55rest of your life regretting it. Ah,
20:58it's not just one direction. Bottom-up
21:00explains an awful lot of when we decide
21:03something is the right thing to do in
21:05one given moment, and may not think that
21:07way 1 and 1/2 seconds from now.
21:10And what this speaks to is the whole
21:11notion of doing the harder thing when
21:13it's the right thing to do. The right
21:15thing is once again very context
21:17dependent. I mean, think about this. All
21:19of these are circumstances where you
21:21need self-control to pull things off. I
21:23mean, look at this. You're in a
21:25circumstance where you're being tempted
21:27to lie about something for personal
21:29gain, and you're trying to avoid the
21:31temptation to do that. Your frontal
21:34cortex is playing a central role if
21:36you're going to resist that temptation.
21:39But, the second you decide you are going
21:42to lie, your frontal cortex is essential
21:44for you doing a good job at it.
21:46Remember, make eye contact now and then,
21:48and don't let my voice crack and
21:50control. If you've got a part of the
21:51brain that's both central to resisting
21:54the temptation to lie, but once you
21:55decide to lie, doing a good job at it,
21:58this is a very, very complex brain
22:00region here. Okay.
22:02So, the frontal cortex makes you do the
22:04harder thing when it's the right thing
22:05to do. That's very much a
22:06context-dependent behavior. And the main
22:08thing is the frontal cortex is not this
22:10gleaming cerebral bit of like cognition.
22:14It's just marinating all the visceral
22:17yuck coming up from underneath. It's a
22:19very bidirectional relationship.
22:22Few more brain regions. One more, the
22:25dopamine system. Dopamine, a
22:27neurotransmitter. One use of it in the
22:29brain in the mesolimbic dopamine system.
22:32Dopamine has to do with pleasure, with
22:34reward. Cocaine works on the dopamine
22:37system. Give a rat, a monkey, a human a
22:40reward from out of nowhere, the do- the
22:42dopamine system activates. Dopamine is
22:45about reward.
22:46But, then people figured out it's
22:48actually about something much more
22:50interesting than that. Now, set up this
22:52paradigm. A little light comes on in the
22:55room as a signal,
22:57and that means if you go to this lever
22:59and you press it 10 times, you get a
23:01reward. Signal saying it's the start of
23:03one of those sessions, go do the work,
23:05you get a reward. Once that rat, monkey,
23:08human learns this relationship, what
23:10happens now? When does dopamine rise?
23:13Does it rise when you get the reward?
23:16Absolutely not. It rises when the signal
23:19comes on. That's the yeah, I know how
23:22this works. This is going to be great.
23:24I'm all over this lever pressing stuff.
23:27This is terrific. Dopamine is about
23:29reward, but even more so, it's about the
23:31anticipation of reward. And remarkably,
23:34if you block the rise in dopamine there,
23:37the organism doesn't press the lever.
23:40It's about the goal-directed behavior.
23:42It's about the pursuit of reward rather
23:45than about reward itself.
23:47Now, what I just showed you in these
23:49circumstances was you press the lever,
23:51you get the reward. Press the lever,
23:53reward 100% of the time. What if now you
23:55switch things switch things to you press
23:58the lever and only 50% of the time you
24:01get a reward. What happens to dopamine
24:03now? It goes through the roof like
24:06crazy. Because what have you done?
24:09You've just inserted a critical word
24:11into this neurochemistry, the word
24:13maybe. And nothing fuels dopamine like
24:16maybe. Being right on that fulcrum of
24:20today's my lucky day, but I'm such a
24:22screw-up, but no, today is my lucky
24:24socks, but I'm a total dork, and just
24:26going back and forth on that, and that
24:28maybe nothing cranks out reward-related
24:32behavior, motivated behavior like
24:35intermittent reinforcement, a maybe put
24:37in there. And this is what the
24:38neuroscientists who built Las Vegas know
24:41inside out, the power of this. Okay. So,
24:44what's dopamine doing here? It's about
24:45reward, even more so anticipation
24:47reward, even more so goal-directed
24:49behavior in order to get that reward.
24:53And what we see is maybe putting
24:56uncertainty into the system is crazily
24:58crazily stimulating and if you want to
25:00take an organism and get it pumping out
25:03dopamine like crazy, all you need to do
25:06is put it in a circumstance when they
25:08are punishing an individual that has
25:09done a norm violation.
25:12We will come back to that. Okay, couple
25:14more brain regions. Fusiform cortex,
25:16it's a primate specialty, it recognizes
25:18faces. Anterior cingulate, it has to do
25:21with empathy, feeling somebody else's
25:23pain, but they both come with fine
25:26print.
25:27Flash up faces, fusiform cortex is
25:30activating. Flash up the face of someone
25:32from a different race and on the
25:35average, the fusiform doesn't activate
25:37as much. The face doesn't register as
25:40much. You don't remember it as
25:41accurately. Show somebody a film clip of
25:44a hand being poked with a needle and the
25:47anterior cingulate activates in empathy
25:50if the hand skin color is different from
25:52your own, it doesn't activate as much.
25:55Whose face? Whose pain? All of these is
25:58qualifiers. Okay, so this begins to give
26:00us just a sense, tip of the iceberg, of
26:03what's going on in that one second
26:05before that behavior occurs. But no
26:08brain is an island and when we look at
26:10one of these behaviors, good, bad, and
26:12between, we're asking why did this
26:14behavior occur, we're now also asking
26:17something about seconds to minutes
26:19before. What sensory information had an
26:22effect on the amygdala, the frontal
26:24cortex, etc. Where do these wind up
26:27being relevant?
26:29And what I put in this slide here is
26:31summarizing a gazillion different
26:33studies showing sensory information is
26:36altering our behavior in ways where we
26:38haven't a clue this is happening. For
26:41example, put up a pair of eyes on a bus
26:44stop and people litter less.
26:47Have a pair of eyes like that flash up
26:49subliminally for less than a second
26:51while somebody is playing an online game
26:54and they cheat less. They become more
26:56generous. You're being watched.
26:59Give somebody some horrible cod liver
27:02oil to drink and it tastes horrible and
27:04for minutes afterward people will be
27:06more punitive about norm violations.
27:09They're confusing a bad taste with a bad
27:12act. Or how about this one? Put somebody
27:15in a room and give them a questionnaire
27:16to fill out about their political views
27:19and if there's smelly garbage in the
27:21room, people become more socially
27:23conservative.
27:25Doesn't do a thing to your economic
27:27views, your geopolitical views. You feel
27:29the same way about our trade deficit
27:31with Swaziland that you did this
27:33morning, but them and their different
27:36lifestyles suddenly begin to seem them
27:39and disgusting and wrong wrong wrong
27:41just because visceral disgust alarms are
27:44going off cuz there's smelly garbage in
27:46the room.
27:47How about this one? Sit somebody in a
27:49chair, either a hardwood one or a nice
27:51plush sofa like that, and give them job
27:54applications from like resumes of
27:56supposed applicants and they evaluate
27:58them afterward. If you sit in a hardwood
28:00and chair, on the average you were more
28:03likely to assess applicants as having a
28:06rigid inflexible personality. You're
28:09more likely to think they're hardasses
28:12because of the chair you're sitting in.
28:15Or how about this one up on the right
28:17there? This was a study in PNAS, very
28:19prestigious journal, a few years ago,
28:21looking in a country all of the parole
28:24board hearings in that country over the
28:26course of a year, 5,000 hearings,
28:28looking at who was sent back to jail
28:30versus who was given parole, looking at
28:32all sorts of variables and out of it
28:34popped an extraordinary finding. The
28:37single biggest predictor of whether or
28:40not a prisoner got parole or not was how
28:43many hours it had been since the judge
28:45had had a meal.
28:47If you went before a judge right after a
28:49meal, 60% chance of being paroled. 4
28:53hours later, down to zero. Just this
28:55line, along comes lunch, down again.
28:58Little snack afterwards, down again it
29:00goes. And what is extraordinary about
29:02this is two things. First, we understand
29:04the biology of this. Blood glucose
29:06levels have something to do with whether
29:08your neurons can work really hard. And
29:11what counts as working really hard in
29:13your frontal cortex
29:15viewing the world from someone else's
29:17perspective, trying to think about their
29:19mitigating circumstances. The frontal
29:21cortex takes a lot of energy to do the
29:24harder thing. And what's even more
29:26striking is if you took any of those
29:27judges 2 seconds after they made that
29:30decision, and you said, "Okay, so why do
29:31you send this guy back to jail, but this
29:33guy walked?" They're not going to say,
29:34"Oh, because of my blood glucose." No,
29:36they're going to cite like freshman
29:37philosophy class or something. And all
29:39the while, this is the interoceptive,
29:42the internal sensory information that
29:45was shaping that decision. Finally, top
29:48left, the most depressing finding in
29:51this whole field is you take people, put
29:53them in a brain scanner, and you're
29:55flashing up faces, like 10th of a
29:58second, barely noticeable, high-speed.
30:00And for your average person, you flash
30:03up the face of someone of a different
30:04race, and the amygdala activates.
30:07Oh, crap. Hardwired on a 10th of a
30:11second to have a racist response like
30:14that. Is this inevitable? Are we like is
30:17this hopeless for us to ever get Now, do
30:19the experiment a little bit differently.
30:21I recently found out that apparently San
30:23Francisco has a baseball team. So, and
30:26that supposedly they have this rival
30:28that they get very worked up about. And
30:30now you're flashing up the faces, and
30:32each face is wearing a baseball cap. And
30:35if you get the right San Francisco
30:37baseball fanatic, if it's the home team,
30:40you get one response. If it's the rival,
30:43the amygdala activates and you're not
30:45processing skin color. Oh my god, the
30:48innate nature of human racism my ass.
30:50All it takes is this cultural thing we
30:53invented one or two centuries ago and
30:56which one counts as an us or them in
30:58baseball loyalties overrides that and
31:01you've recategorized people within
31:03milliseconds there.
31:05Okay, so in terms of the sensory stuff,
31:07we are constantly being buffeted,
31:10constantly being influenced by sensory
31:12information like this and half the time
31:14we haven't a clue it's there or can't
31:16imagine it's relevant to our judicial
31:19decisions. Okay, so now pushing further
31:22back, our behaviors occurred, what's
31:25relevant in the hours to days before?
31:27What do hormones have to do with what
31:30goes on here?
31:31Now, if we're talking about humans at
31:33their worst, right off the bat we know
31:35which hormones to round up,
31:36testosterone. So what's the deal with
31:39testosterone? Why are males of every
31:41species and every cultures such a pain
31:44in the rear on this planet here? It's
31:46because testosterone makes you
31:47aggressive.
31:48Testosterone doesn't make you
31:50aggressive. Here's what it actually
31:52does.
31:53Take five male rhesus monkeys, put them
31:55in a group, let them form a dominance
31:57hierarchy. A defeats B three times, B
32:01never defeats A. This is the hierarchy.
32:04Now take C and inject C with
32:06testosterone. Give C like so much
32:08testosterone, like every amygdaloid
32:10neuron is growing antlers and that guy
32:12just enormous. So now does C get
32:15involved in more fights? Absolutely.
32:18Is this the pattern that occurs now? Is
32:20C suddenly challenging A and B and
32:23rising in the hot? Absolutely not. C
32:26never does a thing with A and B. What
32:28happens instead is C becomes a total
32:32nightmare to D and E. Testosterone does
32:35not invent aggression. Testosterone
32:38exaggerates pre-existing social patterns
32:41of aggression.
32:42And it turns out it does something even
32:44more subtle than that.
32:46And this is people beginning to realize
32:48what testosterone really does is when
32:50your status is being challenged,
32:53testosterone makes you do whatever you
32:55need to do to maintain status. Now, if
32:57you're a baboon and somebody's
32:58challenging your status, the way you
33:00maintain it is you have a fight with
33:01them. It's synonymous. But if you're
33:03human, things get more complicated. And
33:06for example, you can have an economic
33:08game where people get status by making
33:11generous offers.
33:13And give people testosterone and they
33:15become more generous in the game.
33:17In other words, if you shot up a whole
33:19bunch of Buddhist monks with
33:21testosterone, they would run amok doing
33:24random acts of kindness all over the
33:26place. The trouble isn't that
33:28testosterone makes us aggressive, the
33:30trouble is that we reward aggression
33:32with status so readily.
33:34Meanwhile, if we're talking about sort
33:37of the good side of our behavior, the
33:39hormone that immediately comes to mind
33:40is oxytocin. Oxytocin is officially the
33:44grooviest hormone of the world. Oxytocin
33:47promotes mother-infant bonding, pair
33:50bonding, trust, expressivity,
33:52cooperation, generosity. Give fruit
33:55flies oxytocin, they become better
33:57listeners, all sorts of stuff like that.
33:59Oxytocin promotes prosocial behavior.
34:03Oxytocin does no such thing. Once you
34:06look more closely. One example of this,
34:09this was worked on a few years ago in
34:10the Netherlands and volunteers there
34:12were given this classic problem in
34:14philosophy, the runaway trolley problem.
34:17A trolley has broken loose from its
34:18brakes, is hurtling down the tracks,
34:20it's going to kill five people. Is it
34:22okay to push one person onto the track
34:25who will be killed but will slow down
34:27the trolley? Can you sacrifice one to
34:29save five? Basic utilitarian stuff.
34:31Philosophers have been dealing with the
34:33runaway trolley problem since I don't
34:35know Aristotle took his first trolley.
34:36It turns out how you frame it matters.
34:39Is it okay to push a person versus is it
34:42okay to pull a lever that dumps the
34:43person? You get totally different
34:45answers from people. Okay, so they give
34:47these volunteers the runaway trolley
34:49problem. And the key thing in this study
34:51was they gave a name to the person you
34:55were pushing on the track. Either it was
34:58somebody with a classic good old boy
35:01Dutch name like Dirk or Peter or
35:03something, or it was one of two groups
35:05that consistently evoke negative
35:08connotations in Holland, people from
35:10Germany. Oh, that's right, World War II,
35:13or people with Muslim names. So, now you
35:16got a choice. So, are you going to push
35:18Dirk onto the tracks? What about
35:19Wolfgang? What about Mahmoud? And it
35:22turns out you give people oxytocin and
35:25they're far more likely to spare Dirk,
35:27and they fall over themselves to throw
35:30Auto and Wolfgang and Mahmoud under the
35:32tracks there. Oxytocin doesn't make us
35:35more prosocial. It makes us more
35:37prosocial to people who feel like an us.
35:40If it's a them, it makes us crappier and
35:43more xenophobic to them.
35:45So, in both cases, we've got hormones
35:48affecting our brains, our sensory
35:49systems, but far more subtly than you
35:52might think. And the problem with
35:53testosterone is that we reward status to
35:56aggression so readily, not that
35:58testosterone causes it. And the thing
36:01about oxytocin is it doesn't make us
36:02more prosocial, it exaggerates this
36:05divide between us's and them's. Okay, so
36:08now pushing further back with our
36:10behavior. What about weeks to months
36:12before? And the critical thing in this
36:15realm is it turns out over that time
36:17span, the brain changes. The brain
36:20changes dramatically. Neurons form new
36:24connections, they shrivel up old ones.
36:26Brain regions get bigger, they get
36:28smaller. It's the biggest revolution top
36:31left. It turns out the adult brain in
36:33one region makes new neurons, completely
36:36new neurons under certain certain The
36:38brain shows neuroplasticity.
36:41Incredibly exciting stuff.
36:43With all sorts of fine print there.
36:46First off, amid having the brain, having
36:48this enormous potential for
36:49neuroplasticity, there's limits. No
36:52amount of neuroplasticity is going to
36:54make any of us into a Yo-Yo Ma, or no
36:57amount of neuroplasticity currently is
36:59going to do much for you if your spinal
37:01cord has been severed.
37:03Moreover, more importantly,
37:04neuroplasticity is a value-free
37:07phenomenon because sometimes
37:09neuroplasticity can make you much better
37:12at being a saint, and sometimes it can
37:14make you better at ethnically cleansing
37:15villages. It's not an intrinsic good or
37:18bad.
37:19Now, pushing further back. How about
37:22back to your adolescence? And it turns
37:24out everything about adolescent behavior
37:26is explained by two facts. First off,
37:29your dopamine system is going full blast
37:32by the time you're about 11 or 12.
37:34Second, your frontal cortex is
37:37half-baked when you're a teenager.
37:39Frontal cortex is not fully online,
37:42amazingly enough, until you're about 25
37:45years old. In other words, this is why
37:47juveniles behave in juvenile ways.
37:50Impulse issues and sensation-seeking and
37:53novelty-seeking and peer effects and
37:55conformity and all of that. And what's
37:57this for our purposes? What is this
38:00relevant to in terms of that second
38:01where you either are or aren't going to
38:03pull that trigger? What this tells you
38:05is late adolescence, early adulthood is
38:08when environment is having its biggest
38:10effects on what kind of frontal cortex
38:13you're going to have in as an adult.
38:15And that has a critical implication.
38:17Okay, so adolescence is all about
38:19dopaminergic maturity, frontal cortical
38:21immaturity. But the critical thing there
38:23is if the frontal cortex is the last
38:26part of the brain to come online, by
38:29definition, it's the part of the brain
38:32least shaped by your genes and most
38:34shaped by your experience and
38:36environment. And it's got to be that way
38:39because what's the difficult subtle
38:41doing the right thing when it's the
38:42harder thing to do kind of stuff that
38:44takes forever to master,
38:47cultural relativity, context-dependent
38:50rules. Thou shalt not kill, but it's
38:52really good to kill them, and you don't
38:54lie, but this is a good time to lie, and
38:56hypocrisy and self-serving stuff. And
38:58that no genes are going to code for
39:00that. Your frontal cortex needs 25 years
39:03to master stuff like that.
39:06Hurdling further back, how about now
39:08back to childhood? What does that have
39:10to do with the adult brain and adult
39:13decision you will make in that one
39:14second there as to what to do? All of it
39:17is built around something that is
39:18totally obvious, which is childhood
39:21matters, and different types of
39:23childhoods produce different types of
39:25adults.
39:27And the central question of that field
39:28is how do different types of childhoods
39:31produce different frontal cortexes and
39:34different amygdalas and different What
39:36are the mechanisms by which early
39:38experience has a lifelong organizational
39:41effect on brain and behavior? Now, what
39:43this brings us into is this insanely
39:45trendy field called epigenetics.
39:48Genetics, your genes, your DNA
39:51sequences, experience doesn't change
39:54those. What epigenetic experience
39:56changes though is the regulation of
39:59those genes, when they are activated.
40:02Okay, what would this look like?
40:04Amazingly enough, it turns out in the
40:06world of rat mothers, some rat mothers
40:08are better at mothering than other rat
40:10mothers. Okay, what counts as a good rat
40:12mother? She picks up her pup a lot, she
40:15licks it a lot, she grooms it a lot.
40:17This is a wonderful rat mother.
40:19And it turns out if you are subject as a
40:22rat pup to such attentive rat mothering,
40:26that causes an epigenetic change in a
40:28part of your brain.
40:30And as a result, as an adult, you
40:33secrete lower levels of stress hormones
40:35into your bloodstream.
40:38Great.
40:39But with an interesting implication. So
40:41because you were groomed and licked a
40:43lot as an infant, your brain
40:45epigenetically shifted and now as an
40:47adult, you have nice low levels of
40:49stress hormones. When you are a mother,
40:52because of those low levels, you're
40:54going to lick and groom your kids more.
40:56And thus, this trait is going to be
40:58passed on to the next generation. Not
41:01through genes, but through environmental
41:03experience-dependent
41:05changes in regulation of genes. And the
41:08same thing works prenatally. You're a
41:10rat fetus and you're being exposed to
41:12tons of stress hormones. Why? Because
41:15your mom is stressed and secreting a lot
41:18into her circulation, which gets into
41:20your circulation, which gets into your
41:21brain and causes epigenetic changes such
41:24that as an adult, your amygdala is going
41:27to be bigger and it's going to be more
41:29reactive to threat and you're going to
41:31have higher stress hormone levels.
41:34And as a result, when you're pregnant,
41:37your fetus is going to be exposed to
41:38more of these stress hormones. In other
41:41words, we have early environment shaping
41:44all sorts of aspects of how the brain
41:46and the endocrine systems are put
41:47together and most importantly, thanks to
41:49these epigenetic changes starting during
41:52fetal life, environment does not begin
41:54at birth, these changes can be
41:56long-lasting, lifelong, even
41:59multigenerational.
42:01Okay, but now, one step further back.
42:03Forget when you were a kid or a fetus,
42:05how about back when you were nothing
42:07more than just a fertilized egg? What do
42:09genes have to do with it? And there's no
42:12subject in this whole lecture
42:14that's more contentious than the role of
42:16genes and behavior. And this is because
42:18we live in an hysterically giddy period
42:22about genetics these days. We've
42:24sequenced the human genome. They can do
42:26it in an evening now if you go into the
42:28right like, you know, McDonald's or
42:30whatever. The genome, the code of codes,
42:33the holy grail, the notion that your
42:35genes shape everything that happens in
42:38you. And the thing is, your genes have
42:40no idea what they're doing. Saying that
42:43a gene knows, for example, when it is
42:45going to regulate cell biology, saying
42:48that a gene knows what it's doing is
42:49like saying that a cake recipe knows
42:51when you're going to make the cake or
42:53decides when you were going to make the
42:55cake. Genes don't regulate themselves.
42:58What regulates genes? Environment does.
43:01Environment can be very local. The local
43:04environment in a cell that's running out
43:06of energy, and that turns on a gene
43:08which makes more of a glucose
43:10transporter protein and the cell takes
43:12up more energy. Change in environment
43:15alters gene activity and you fix the
43:17problem.
43:18Or environment could be on the level of
43:20the whole body. High levels of
43:21testosterone, and as a result in this
43:24muscle cell certain genes are turned on
43:26and the muscle cell grows bigger. You
43:28put on muscle mass. Or environment could
43:31be environment in the conventional
43:33sense. You've just given birth, you
43:35smell your baby, and as a result genes
43:39are turned on and you start making
43:40oxytocin. Oh my god, genes run all of
43:43life. They're the same
43:45That's You smell your baby's tush and as
43:47a result you change gene transcription.
43:50Genes don't really know what they're
43:51doing. Genes are being regulated by
43:53environment. And the critical thing is,
43:56different environments regulate the same
43:59genes in different ways. Do not dream of
44:02writing down any of this, but what we
44:04have here are a whole bunch of genes
44:06that have effects on behavior only in
44:09certain environments. For our purpose,
44:11the most interesting one in red there, a
44:14gene called MAO alpha, monoamine oxidase
44:16alpha, it's got something to do with
44:17this neurotransmitter serotonin. All
44:20that matters is it comes in two
44:22different flavors, and by all logic, one
44:24of those flavors should set you up for
44:27higher levels of aggression.
44:29And a huge huge study was done some
44:32years ago following 17,000 kids for
44:35decades, and the answer comes back, if
44:37you've got the wrong version of this
44:39gene, you are indeed, as a young adult,
44:42more likely to already have a history of
44:44antisocial violent behavior.
44:47If and only if you were abused as a
44:50child. If you weren't raised with abuse,
44:53zero effect whatsoever. In other words,
44:56it's not what the gene is, it's not what
44:58the environment is, but the interaction
45:00between the two. In other words, genes
45:02decide nothing, instead they're being
45:04regulated by environment sufficiently so
45:07that it never makes sense to ask what a
45:08gene does or an environment does, only
45:11in a particular context of interaction.
45:14Okay, that's great. So, that tells us
45:16something about why genes in a penguin
45:18may work differently in the middle of
45:20the Sahara or something.
45:22But yeah, you're not going to see
45:24penguins there, but you're going to see
45:25humans there, and in Antarctica, and in
45:29tundra, and in rainforest, and
45:31polygamous societies, and monogamous,
45:33and capitalist, and socialist. There's
45:35no species on Earth that lives in more
45:37different environments, thus by
45:39definition, there's no species on Earth
45:42that is freer of genetic determination
45:45than we are.
45:46Okay, so now we're back to fertilized
45:48egg, that's the end of us, but
45:50amazingly, we got to push further back
45:52because to make sense of all of this, we
45:54now have to ask, what were your
45:56ancestors doing? What sort of cultures
45:59were they inventing because that's going
46:01to influence how you are going to turn
46:04into that adult that you are. What sort
46:06of cultures did they invent turns out to
46:08be very sensitive to what sort of
46:10ecosystems they lived in. For example,
46:13across the world, desert dwellers are
46:16statistically more likely than chance to
46:18invent monotheistic religions.
46:21Rainforest dwellers invent polytheistic
46:23ones and all sorts of baggage that goes
46:26along with that.
46:27Another pattern, when you look at humans
46:30living in small hunter-gatherer bands,
46:32the religions they invent
46:34involve almost all the time involve gods
46:37who could care less what humans are
46:39doing. It's not until humans are living
46:42in sufficiently high density that you're
46:45interacting with strangers, that you
46:48interact anonymously, then humans start
46:51inventing what are called moralizing
46:53gods. Gods who are watching us and gods
46:56who are judging us and gods who are the
46:58pair of eyes up there on the bus stop
47:01there when we're getting complex enough
47:03that we can't do it ourselves.
47:05Or another critical distinction has to
47:07do with traditional ways of making a
47:09livelihood. In the traditional world,
47:11people are either top left
47:12hunter-gatherers, top right
47:14agriculturalists or horticulturalists,
47:16or in the center pastoralists.
47:19Pastoralists, people wandering the
47:21grasslands or the deserts with their
47:24herds of camels and cows and goats and
47:27all of that and there's a particular
47:29vulnerability if you're a pastoralist.
47:31If you're a rainforest hunter-gatherer,
47:33bad people cannot come at night and
47:35steal your rainforest. If you're an
47:38agriculturalist, they can't come at
47:39night and steal 20 acres of your maze.
47:42But if you're a pastoralist, people
47:44could come at night and steal your
47:46herds, rustle your herds there and
47:50everywhere around the world,
47:52pastoralists come up with cultures of
47:54honor built around violent retribution,
47:58warrior classes, honor killings,
48:00vendettas that stretch for centuries.
48:03And what is most remarkable is within
48:05minutes of birth, if you were a child in
48:08a culture of honor, your mother is
48:10speaking to you at a higher volume and
48:13holding you for a shorter length of time
48:15than if you were a child in one of these
48:17other cultures.
48:18If you were born into a collectivist
48:20culture, on the average, your mother is
48:23nursing you for longer lengths of time
48:25in your first week of life than if you
48:27were born in an individualist culture.
48:29In other words, within minutes of birth,
48:33everything we've already seen is now
48:35being shaped by what your ancestors were
48:37doing for a living centuries before.
48:40In other words, ecosystems shape
48:43cultures, shape brains, shape behaviors.
48:46And some of these differences are
48:47manifest within minutes of birth. In
48:50other words, brains and bodies and
48:52behaviors and cultures and genes all
48:55coevolve.
48:57Finally, if we're gotten this far back
48:59and we're talking about things like
49:01genes, by definition, we're talking
49:03about evolution. What does the evolution
49:05of behavior have to do with any of this?
49:08And modern thinking about the evolution
49:09of behavior has long ago trashed the
49:12notion that we behave for the good of
49:14the species or behave in order to
49:16survive. We behave in order to pass on
49:18copies of genes. Contemporary thinking
49:21about the evolution of behavior is built
49:23around three building blocks. First one,
49:26individual selection. What organisms do
49:29is try to leave as many copies of their
49:31genes in the next generation as
49:33possible, maximizing reproductive
49:35success, the selfish gene concept. And
49:38this explains a ton of human behavior.
49:42For example, remarkably, 16%
49:46of Earth's humans are direct descendants
49:48of Genghis Khan, the most reproductively
49:51successful human of all time. All sorts
49:54of powerful humans act to maximize their
49:57reproductive success. Next building
49:59block. Yes, some of the time you pass on
50:01as many copies of genes as you can, but
50:03some of the time an even better way of
50:05doing it is helping your relatives pass
50:08on copies of genes, kin selection. And
50:11humans have invented a version of kin
50:13selection that makes other primates
50:15shrivel up with envy. We can bequeath
50:18our material wealth to our relatives.
50:20There's inheritance. We have a way of
50:23magnifying differences through
50:25generations that way. We do kin
50:27selection like nobody else out there.
50:30Final building block, individual
50:32selection or helping relatives or
50:34sometimes there's selection for
50:35cooperating with utter strangers, being
50:38cooperative and altruistic with them as
50:41long as they do it back. Reciprocal
50:43relationships of cooperation. And we
50:46obviously do that on a level like no
50:48other species out there. Forget
50:50scratching your back and you scratch
50:52mine. We've invented barter and economic
50:54system and all of that. In other words,
50:56the building blocks of modern
50:58evolutionary thinking explain a ton
51:00about human behavior.
51:03Until you look more closely.
51:05Individual selection. And then we have
51:08religious sects that are celibate, that
51:10choose to go extinct like the Shakers,
51:13who don't pass on copies of your genes,
51:16behaving only for the good of close
51:17relatives. And then we have blended
51:20families with children adopted from all
51:22over the planet. Or reciprocal altruism.
51:26We will cooperate with strangers if they
51:28cooperate back. Think of this. This is a
51:30behavior we do which chimps could not
51:33possibly make any sense of. You're in a
51:36foreign country, you're going to the
51:37airport, you're about to leave there,
51:39you are never going to set foot in that
51:40country again. No person you see there
51:43you will ever set flies on again. And as
51:46you walk into the terminal, you pause
51:48for a second and hold the door open for
51:51someone. Everything about the evolution
51:53of reciprocity and cooperation says
51:56there's no way that could ever become
51:57commonplace, and that defines us. In
52:00other words, evolution of behavior built
52:03around these three principles, they
52:04explain a ton about social behavior in
52:07lots of other species, and they explain
52:09a ton about us until you look more
52:11closely.
52:13Okay, so what have we gotten to now?
52:15We've now officially seen one of our
52:17behaviors occur, and if you want to
52:19understand if that behavior is good,
52:20you've got to incorporate everything
52:22from 1 ms before to millions of years of
52:25selection and evolutionary pressure. In
52:27other words, one can officially conclude
52:29at this point it's complicated.
52:32Oh, great. I had to sit through 50
52:34minutes of this to get to that point?
52:36It's complicated. Let's try to make that
52:37conclusion a little bit more useful.
52:39It's complicated, so be real careful and
52:43real cautious and real sure you really
52:46understand what's going on if you decide
52:48you understand why some behaviors
52:50happened, especially if it's a behavior
52:52that you're judging harshly.
52:55Now, for my purposes, the single most
52:57important thing about all of this is all
52:59of these realms of factoids I've been
53:02downloading here, all of them have one
53:04thing in common. They change. They can
53:08change over time. They change in
53:10response to experience. They change in
53:13the most fundamental ways, over long
53:16periods, over short periods. Ecosystems
53:18change. This is a rock carving of a
53:21hippo, which was carved 3,000 years ago
53:24in the middle of the Sahara when the
53:26Sahara was lush grassland.
53:29Ecosystems change.
53:31Cultures change. In the 18th century,
53:34the most terrifying people in Europe
53:36were the Swedes. They spent the whole
53:38century rampaging through Europe, and
53:40then something happened, something
53:42changed, and this is what the Swedish
53:44military does now instead. They haven't
53:47had a war in more than a century.
53:49Cultures change. Cultures change
53:52dramatically. Most importantly, brains
53:55change. New connections, lose old ones,
53:59expansions,
54:00brains change, behaviors change, people
54:03change. Sometimes astounding magnitudes
54:07of change occur. They could take
54:09decades. This man, John Newton, was a
54:12British theologian who in his old age
54:15played a central role in the abolition
54:17of slavery in the British Empire in the
54:19beginning of the 1800s. And amazingly
54:22enough, as a young man, John Newton made
54:25a living as the captain of a slave ship.
54:28And after he retired from the sea, he
54:31spent decades investing in the slave
54:33trade and growing wealthy from it until
54:36one day something changed. Something
54:39changed, celebrated in a hymn that he
54:42wrote that has made him famous, the hymn
54:44Amazing Grace.
54:47Another version of change that can
54:49happen over decades. On the left is a
54:51man named Zenji Abe on the morning of
54:54December 6th, 1941 about to lead one of
54:57the squadrons of bombers, Japanese
54:59bombers that attacked Pearl Harbor. He
55:02was one of the lead pilots in it. And on
55:04the right is Zenji Abe to the day 50
55:08years later where as an old man, he came
55:11to Pearl Harbor where there is a
55:13ceremony happening for the elderly
55:15survivors of the attack and in broken
55:17English, he went to up to those men and
55:20he apologized to them for what he had
55:22done.
55:23So change can occur on that level.
55:25Sometimes change can occur over the
55:28course of hours to days.
55:30One of the most remarkable events in
55:32World War I was the Christmas truce of
55:351914.
55:36The first Christmas, the first December,
55:38various powers that be decreed that
55:41there would be a 3-hour truce along the
55:43trenches in France, 3 hours in the
55:45afternoon before Christmas Eve, so that
55:48soldiers from both sides could come out,
55:49retrieve their dead from no man's land.
55:52So, the fighting stopped and people came
55:54out and retrieved their dead.
55:57And then they started helping soldiers
55:59from the other side carry their dead
56:01back.
56:02And then they started helping each other
56:04dig graves in the frozen ground.
56:06And then they started having ceremonies
56:08and funerals together and praying over
56:11each other's dead. And before it was
56:13over with, they were sharing Christmas
56:15dinner and praying together and
56:16exchanging presents and singing. And by
56:19the next day, up and down the trench
56:21lines of France, German and British
56:23soldiers were playing soccer together
56:26and weren't keeping score. And they
56:28exchanged weapons and they exchanged
56:30addresses so that they could visit each
56:32other after the war was over with. And
56:34they made vows with each other to shoot
56:36over each other's heads that it would so
56:38they wouldn't hurt each other. And it
56:40took the officers arriving two to three
56:42days into this and threatening to shoot
56:45these men to get them to go back to try
56:47and kill each other.
56:48And the main point there is all of that
56:50acculturation and all of that military
56:53and military training and all of that
56:54propaganda evaporated in the course of
56:57hours as to who counted as an us and who
56:59was a them. Us is us in the trenches,
57:02all of us in the damn trenches, and them
57:05as any officer in the back lines who
57:07would have us die for their power.
57:09And that just happened over the course
57:11of hours.
57:12And sometimes change can occur in
57:14minutes.
57:16One of the things that galvanized the
57:18anti-war movement during the Vietnam War
57:20in the United States more than anything
57:22was the My Lai Massacre.
57:24A brigade of American soldiers went into
57:27the village of My Lai, undefended, no
57:30weapons, made up of elderly people and
57:33children, went in there and killed 350
57:36to 500 civilians. Mutilated bodies,
57:39gang-raped before killing, killed every
57:42animal in there, burned the fields, an
57:44appalling atrocity. Appalling in part
57:47because the US government covered it up
57:49for a year. Appalling because when it
57:51finally had to admit it, it handed out
57:53just a slap on the wrist to the
57:55commanding officer. And appalling
57:57because almost certainly this was not
57:58the only instance of that.
58:01On the right is a man named Hugh
58:03Thompson. This is the man who stopped
58:05the My Lai Massacre.
58:07Thompson was a helicopter pilot. He was
58:09piloting a gunship that was flying over
58:11the village, and he had gotten reports
58:13of shooting there, assumed that American
58:15troops were under attack from Viet Cong,
58:17flew over, landed there to see what help
58:20he could give, got out of the
58:21helicopter, and saw American troops
58:24shooting old women in the head. Saw
58:26American troops pulling babies
58:28underneath from out of their dead
58:29mothers to kill them. And this man saw
58:33what was happening. And at that point
58:35there was a small surviving number of
58:37villagers huddling at one end of the
58:39village, and a group of American
58:41soldiers coming towards them. And this
58:44man got in his helicopter and landed it
58:46in between the two. And he trained his
58:49machine guns on the American soldiers
58:51and said, "If you make one more move, I
58:53will mow you down."
58:55In other words, over the course of
58:57minutes, he had completely changed who
59:00was an us and who was a them.
59:02And the main point of all of these
59:04people is none of them have any brain
59:06regions that us that we don't have. None
59:09of them invented any new types of
59:10neurotransmitters. They do epigenetics
59:13the same way we do, the same hormones,
59:15the same everything. They put their
59:16pants on one leg at a time the same way
59:19we do. Almost none of them had any
59:21indications beforehand that this was
59:23going to be someone capable of this sort
59:25of extraordinary change.
59:27So, what I think we're left with here at
59:29the end is sort of an inversion of that
59:32like inevitable Santayana cliche of
59:35those who don't hunt and study history
59:36are destined to repeat it. What we have
59:38here, I think, is in fact quite the
59:40opposite. Those who don't study the
59:43history of astonishing human change and
59:46don't understand the science that begins
59:48to explain why to make that more likely,
59:51those of us who don't study that are
59:52destined not to be able to repeat
59:55moments like these.
59:57So, on that note, thank you for your
59:58attention and good luck with your own
1:00:00best and worst moments.
1:00:23Let's see. Questions
1:00:25format? Sure.
1:00:32Yeah.
1:00:33Well, I have a question. Is there free
1:00:34will, right? I mean, we are in
1:00:36particular maker of
1:00:38And there is the particular stimulus
1:00:39that we happened to me.
1:00:42Do I have a free will or are we
1:00:43completely predictable how how we how we
1:00:46react given who I am?
1:00:48Well, well, that's pretty rude.
1:00:51Um
1:00:52Well, actually, that's not rude at all
1:00:53because you know, if I'm trying to be a
1:00:56a good house guest, what I would say is,
1:00:58"Well, if there is some free will, you
1:01:01know, it's in increasingly boring
1:01:03places." And you know, if you want to
1:01:05claim it was free will such that you've
1:01:07lost your lower teeth today instead of
1:01:09your top ones instead of the other
1:01:11go for it. Be happy. You know, you got
1:01:13free will there. In actuality, I don't
1:01:15think it's possible to look at this
1:01:17whole range of ways in which our
1:01:19behavior
1:01:21is being shaped by biology. I don't see
1:01:23there to be a shred of possibility of
1:01:26free will sitting in there. As far as
1:01:28I'm concerned, free will is what we call
1:01:30the biology that hasn't been discovered
1:01:32yet. Um, I've absolutely no problem at
1:01:36all with the notion that there's no free
1:01:37will.
1:01:38I have vast problems with trying to
1:01:40imagine how are we supposed to live with
1:01:43that conclusion, and I've no idea what
1:01:45that should look like, but all I know is
1:01:47if we're drunk going to do the hard work
1:01:49to try to get a sense of where that
1:01:51should be accepted is we should probably
1:01:53start with the criminal justice system
1:01:55and worry about flossing somewhere down
1:01:57the line there. It's an enormous
1:02:00challenge, but there's some domains
1:02:02where it is absolutely essential that we
1:02:04do it because basically the science that
1:02:06informed the current criminal justice
1:02:08system is based on neuroscience from the
1:02:11mid-19th century, and that's appalling.
1:02:15Yeah.
1:02:17Uh,
1:02:17first of all, I must just say that your
1:02:19online course that human behavior
1:02:21biology on YouTube is like the main
1:02:23reason I applied to Stanford.
1:02:27Oh, wow.
1:02:30Um,
1:02:31if if you happen to know the president
1:02:33of Stanford, can you kind of mention
1:02:34that to him? I would love to hang out
1:02:36with him.
1:02:38Well, actually, I don't know. Have you
1:02:39paid your bills?
1:02:43Uh, so I have a couple of questions.
1:02:47First, in the
1:02:49that like when you introduced the maybe
1:02:51to these rats when you were
1:02:53levers,
1:02:55why was like the evolutionary How do we
1:02:58explain that that increases the
1:03:00dopamine?
1:03:01Okay, because very few things out there
1:03:05have 100% certainty of you do the work,
1:03:08you get the reward.
1:03:09And what we hopefully get very good at
1:03:12is sensing where the optimum point is on
1:03:15that curve between effort and likelihood
1:03:17of reward.
1:03:18Now, what people are even better at is
1:03:21manipulating us into distorting what
1:03:23that curve looks like, and that's what
1:03:25Las Vegas is. Where in actuality you
1:03:28have what? A hundredth of 1% of a chance
1:03:30of get But, because today you're the
1:03:33lucky one who got the free drink and
1:03:35you're on the penthouse that they put
1:03:37you in that's actually on the second
1:03:38floor and all of that and all of that is
1:03:40to set you up to mistake one chance in a
1:03:43hundred thousand for Yeah, I'm at about
1:03:45the 50% mark. Up goes dopamine. There go
1:03:48the life savings. Um, we're very good at
1:03:52realizing viscerally, dopaminergically,
1:03:55that intermittent reward demands a whole
1:03:58lot of behavior because it's very
1:04:00rewarding. We're lousy at accurately
1:04:02assessing exactly what the curve looks
1:04:04like.
1:04:09Have you read the book by Judith Rich
1:04:12Harris, The Nurture Assumption? I would
1:04:14which she did not mention
1:04:16parents that much here, but I'm just
1:04:17curious if you agree with her
1:04:21assessment that parents are not that
1:04:22important in explaining
1:04:27in explaining your personality
1:04:29differences.
1:04:30Well, it depends. When my kids are doing
1:04:32great, I don't believe that for a
1:04:33second. Um,
1:04:35like
1:04:36context dependency, that's the whole
1:04:38point there. Um,
1:04:39Harris is a psychologist who produced
1:04:41sort of the wildly controversial book in
1:04:43the mid-90s. Um, that in the most
1:04:46inflammatory form said parents don't
1:04:48matter.
1:04:50Give me a break, but she did a very good
1:04:51critique of a lot of the developmental
1:04:53literature in terms of parental effects.
1:04:55What she very legitimately emphasized
1:04:57was how at a surprisingly young age, how
1:05:00strong peer effects are on kids.
1:05:03Enormously powerful. And where that is
1:05:06never more apparent is in teenagers.
1:05:08Peer conformity effects are astonishing
1:05:10there. For example, put an adult in a
1:05:13brain scanner, ask somebody, "Okay, how
1:05:16do you think of yourself?"
1:05:18And they think of it and there will be a
1:05:19certain pattern of neural activation.
1:05:21Now you say, "How do other people think
1:05:23of you?" And there is a partially
1:05:25overlapping pattern of cortical and
1:05:26subcortical activation. Take a teenager
1:05:29and say,
1:05:30"How what what do you think of yourself?
1:05:32What do people think of you?" You get
1:05:34the exact same pattern. What do I think
1:05:36of myself? Whatever anybody else thinks
1:05:39of me because it's I'm going to go along
1:05:40with whatever they
1:05:41That's just one measure of it and that's
1:05:43a measure of that frontal cortex whose
1:05:45job it is in us as adults to say, "You
1:05:47know, maybe they're actually jerks and
1:05:50you shouldn't
1:05:51like take their opinions to heart." And
1:05:53that's your all the rationalizing wait a
1:05:55second type stuff. Um she's absolutely
1:05:58right. Childhood and adolescence even
1:06:00more so enormous amount of peer effects.
1:06:04I
1:06:05Uh I have a question here.
1:06:07Okay.
1:06:07Over here, in the middle.
1:06:09Okay, good.
1:06:11Um I have two questions actually. Uh the
1:06:13first um
1:06:13Look what you started.
1:06:16Okay.
1:06:17You set precedent. Um
1:06:19the first question has to do with uh
1:06:21your discussion of the fear response to
1:06:22the rattlesnake and uh later you
1:06:24mentioned that that fear response is
1:06:26conditioned. So I was wondering if you
1:06:27can talk a little bit about some of the
1:06:29ways that uh uh fear responses are
1:06:31conditioned particularly uh with regard
1:06:33to uh other races.
1:06:35And then the second uh
1:06:37I I I guess it's not a question, it's
1:06:39really a point, but you mentioned there
1:06:40were studies where um
1:06:42you know, adults had a a higher amygdala
1:06:45reaction looking at uh faces that were
1:06:47uh um different races there than theirs.
1:06:50There's another uh similar study, uh but
1:06:52then they assessed um how much contact
1:06:54these individuals had with these races
1:06:57over the course of their life and they
1:06:58found that there was inversely
1:06:59correlated so that the more contact they
1:07:01had uh with uh other races, the lower
1:07:04the the response was and vice versa.
1:07:07Good, perfect. Okay, so in terms of the
1:07:09first one, rattlesnakes, what of these
1:07:12get your amygdala going things are
1:07:14innate? Um even the things that are
1:07:16traditionally viewed as innate phobias
1:07:18that we have about snakes and spiders,
1:07:21the more technical term is that we show
1:07:23prepared learning for them. We are not
1:07:25innately afraid of spiders. It takes
1:07:28less aversive
1:07:32Okay, it takes less um
1:07:35it takes less aversive experience with a
1:07:37spider to decide that you're afraid of
1:07:39it than with say like a Teletubby, for
1:07:41example. We are predisposed towards
1:07:43making some associations more readily
1:07:45than others. That's closer to what a
1:07:47phobia actually is. So, the question
1:07:49becomes, do we have prepared learning
1:07:52for considering people of other races to
1:07:54be thems?
1:07:56A priori, intuitively, that makes
1:07:58perfect sense. I mean, it's such a
1:07:59marker and it's discernable at a
1:08:01distance and all of that. But then you
1:08:03think anthropologically for a second,
1:08:05and race evolved, I don't know, 40, 50,
1:08:08100,000 years ago or so at most,
1:08:11somewhere during that period, and we've
1:08:13been humans for a lot longer than that,
1:08:14but most importantly, it only has been
1:08:17in
1:08:20Okay, most importantly, it's only been,
1:08:22I don't know, in the last couple of
1:08:24millennia that your average person wound
1:08:27up within a thousand miles of somebody
1:08:29from another race.
1:08:30Hominid history was not sculpted by
1:08:34encountering somebody from another race
1:08:36who represented as much of an other as
1:08:38you can imagine in your whole life. It
1:08:40was utterly irrelevant because
1:08:42somebody's entire life was spent
1:08:43interacting with the people from the
1:08:45hunter-gatherer bands at most two or
1:08:47three valleys away.
1:08:49In terms of that other issue, the
1:08:50amygdaloid response, what you get at
1:08:52there is exactly, if one was being
1:08:54boringly technical and careful, every
1:08:57single time I would have said something
1:08:58during the talk, I would have said on
1:09:00the average, this is what happens. On
1:09:03the average, people's amygdala activates
1:09:06when seeing the face of somebody from
1:09:07another race. So, who are the people who
1:09:09are the exceptions? People who grew up
1:09:11in racially diverse neighborhoods. In
1:09:14other words, skin color is not a
1:09:16criterion for their us to them divide.
1:09:19People who have had a close intimate
1:09:20relationship with somebody of another
1:09:22race. Same exact conclusion. Okay, so
1:09:25good. Let's put all of us back into
1:09:27kindergarten and we can undo some of the
1:09:29world's animosity along those lines. But
1:09:31then wonderful work by somebody at
1:09:32Princeton named Susan Fiske has shown
1:09:35something remarkable. Forget having to
1:09:37go back to preschool and the diversity
1:09:39in it. What Fiske does in these studies
1:09:41is putting somebody in a scanner and
1:09:43you're flashing up the faces there and
1:09:45the usual sort of deal and she instructs
1:09:47people beforehand, "Okay, with each face
1:09:50that you see, decide yes or no, this
1:09:53button or that one. Decide, is this the
1:09:56sort of person who would like broccoli?"
1:10:00Broccoli, like a lot of wars have been
1:10:02fought over broccoli. This is like
1:10:03totally innocuous. Broccoli. And what
1:10:07are you doing then? You're looking at
1:10:08each face and you're imagining them in a
1:10:11market. You're imagining them in a
1:10:13restaurant. You're imagining them coming
1:10:15home and sitting down to dinner. And
1:10:17does this taste good and does it And in
1:10:19other words, you're imagining them as an
1:10:21individual. And when you individuate
1:10:24people like that, the amygdala doesn't
1:10:27activate because you're too busy
1:10:29thinking about if they look happy or
1:10:30not, biting into whatever you're
1:10:32thinking about them as a person. And you
1:10:35completely unwire the us them at that
1:10:37point. So, on one hand we have the
1:10:39option to go back and put everyone back
1:10:41in kindergarten in the different sorts
1:10:42of neighborhoods, but in a study like
1:10:45this, this is over the course of
1:10:46seconds,
1:10:48you rewire it. In other words, I think
1:10:51by the fact that we do us them stuff in
1:10:53our amygdala in the course of a
1:10:55milliseconds, I think we are incredibly
1:10:58hardwired to divide the world into us
1:11:01and them and to not be all the all that
1:11:03fond of the thems, but it is incredibly
1:11:06easy to manipulate us as to who counts
1:11:08as an us and who counts as a them and
1:11:10put a baseball cap on somebody and the
1:11:12neurobiology is different 100
1:11:14milliseconds later and that's the
1:11:16greatest example of that you can
1:11:17imagine.
1:11:19There's an experiment here being
1:11:20conducted to with trans
1:11:23transcranial magnetic conduction to
1:11:26suppress the amygdala and stimulate the
1:11:28frontal lobes. Do you think this will
1:11:30work?
1:11:32Well, it depends what working counts as,
1:11:35but one of the most extraordinary
1:11:37things, I mean, neuroimaging put
1:11:39somebody in a brain scanner, you're
1:11:40getting functional MRIs, you're seeing
1:11:42what parts of the brain activate in
1:11:43different certain totally cool, but it's
1:11:46correlative. This part of the brain's
1:11:48active activity correlates with this
1:11:51behavior, this emotional state,
1:11:53whatever. Transcranial magnetic
1:11:54stimulation is a means by which you can
1:11:57actually activate or inhibit small sets
1:12:00subsets of cortical neurons. And that is
1:12:03amazing some of the stuff that has come
1:12:05out of that. You turn off a part of the
1:12:07frontal cortex temporarily in somebody
1:12:10and they make different sorts of moral
1:12:11decisions. You shift how utilitarian
1:12:14they are in runaway trolley type
1:12:16problems and you are controlling their
1:12:19behavior in that case. This is mostly
1:12:22just a phenomenal research tool because
1:12:24you're moving away from a correlative
1:12:26relationship to a causal one. Aha, make
1:12:29those neurons fire and suddenly this
1:12:32person is far more likely to say, "Yeah,
1:12:34I'll push him in front of the trolley."
1:12:36That's a strong causal relationship.
1:12:38What you can actually do with that down
1:12:40the line is the stuff of dreams and
1:12:42nightmares and everything in between.
1:12:45My guess is it's not going to be used in
1:12:46terribly exciting abusive ways anytime
1:12:49soon, but but a phenomenal research
1:12:51tool.
1:12:53I think we're going to end there. Thank
1:12:55you so much.
1:13:00Thank you.

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