The Hidden Rules Holding Society Together: Steven Pinker on Common Knowledge

Why do we speak in euphemisms instead of saying exactly what we mean? Dr. Heather Berlin and Dr. Christoph Koch sat down with cognitive scientist and bestselling author Steven Pinker to explore common knowledge — not what everyone knows, but what everyone knows that everyone knows. Get it? Common knowledge is an awareness of something that is public or “out there” and it has an enormous impact on our social, political, and economic lives. From unspoken rules of flirtation to the fall of the Berlin Wall, Pinker reveals how the social force of common knowledge shapes everything from our most intimate relationships to global financial markets. His work illuminates central ideas of the Perception Box, a framework developed by Elizabeth R. Koch for understanding the forces within us that shape how we see ourselves, relate to others, and move through the world. Steven Pinker is the Johnstone Family Professor in the Department of Psychology at Harvard University where he conducts research on language, cognition, and social relations. Pinker is the author of thirteen books, including his latest book When Everyone Knows That Everyone Knows… and seminal texts like The Language Instinct, The Blank Slate, and How the Mind Works. His writing has appeared in The New York Times, Time and The Atlantic. Dr. Heather Berlin is a neuroscientist, clinical psychologist, and Professor of Psychiatry and Neuroscience at the Icahn School of Medicine at Mount Sinai in New York City. Dr. Christof Koch is Chief Scientist for the Tiny Blue Dot Foundation and the current Meritorious Investigator and former President of the Allen Institute for Brain Science. Join us for new episodes of Science of Perception Box every Thursday. Follow the show on YouTube, Spotify, Apple Podcasts, Amazon Music, or wherever you get your podcasts. Love Science of Perception Box? Write us a review on your podcast app, or tell a friend! Visit unlikelycollaborators.com for more information. Episode Chapters: 00:00 Why Honesty Fails 02:56 Defining Common Knowledge 06:38 Awkwardness and Innuendo 15:24 Markets and Shared Beliefs 28:44 Bubbles and Bank Runs 31:05 Freedom of Speech 31:49 Berlin Wall Tipping 32:46 Science Versus Assumptions

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Heather Berlin?

  So why can't people be completely honest?

• 0:02Speaker 01

  Complete honesty, which is common knowledge, you know what the other person knows, what you're saying, and they know that, and you know that, can threaten the nature of a relationship.

• 0:13Speaker 02

  Hi, I'm Elizabeth Koch. What's a perception box? It's this invisible mental box that each one of us lives inside, built from the material of our beliefs, life experiences, and the meaning we've made out of those experiences. You could think of it as a kind of reality filter that's constantly shaping how we see ourselves, other people, and the world around us. This podcast explores how, although the walls of this box are always present, they can expand in moments of curiosity, awe, and wonder, or contract in response to fear, anxiety, and anger. In each episode, we invite experts to share how to create lasting shifts in our perception.

• 0:57Speaker 02

  I'd like to introduce our esteemed hosts, Heather Berlin, professor of psychiatry and neuroscience at the Icahn School of Medicine at Mount Sinai, and Kristof Koch, chief scientist for the Tiny Blue Dot Foundation and former president of the Allen Institute for Brain Science. Welcome to the Science of Perception Box. This week, our guest is Dr. Steven Pinker. We tend to think that communication is about saying what we mean, but much of it is guessing what others know, assume, expect, or intend. Steven's work shows how much of our social world depends on this and how easily things break down when those interpretations don't align. This episode reminds us that even in ordinary moments,

• 1:41Speaker 02

  we're not just communicating, we're navigating each other's perception boxes.

• 1:47Heather Berlin?

  So first, we want to open up with our own stories. So Kristof, has there ever been an interaction that you've had where you've realized after the fact that you were in the dark about some common knowledge? Like, everybody else knew, but you didn't know?

• 2:03Speaker 03

  So as you probably know, I don't own a car and a bike everywhere. And of course, as biker, you have to be incredibly tuned to the mores and the customs of interaction between cars and bikes. You know, you have to look and nod. Is the car giving me a nod so I can pass in front of her? I can enter the lane. So far, this has all worked out. But recently, a couple of months ago, I had this incident where there was another biker who came into my lane. And I thought he had given me the signal to proceed by nodding, and I accepted that by nodding back, but he didn't get that. So I knew that he knew that I knew, but he didn't close that loop. And so we ran into each other as a consequence

• 2:48Speaker 03

  of not fully completing the acknowledgement of the acknowledgement.

• 2:52Heather Berlin?

  That's a great example. So, well, welcome to the podcast, Steven. Can you define common knowledge?

• 2:59Speaker 01

  Common knowledge in the technical sense from philosophy and game theory refers to the case where I know something, you know something. I know that you know it, you know that I know it, I know that you know that I know that you know it, ad infinitum. So common knowledge in the technical sense is interesting because it's necessary for coordination, for people to be on the same page, to do things that may be arbitrary but are advantageous if everyone does it the same way. So driving on the right versus the left, stopping at a red light, these are all paradigm cases, excellent examples. It actually doesn't matter whether you drive on the right or the left. It does matter that everyone drives on the same side and that everyone knows that everyone else is driving on the same side.

• 3:43Speaker 01

  And so, in general, traffic works. In England, everyone does it on the left, and here we do it. Everyone does it on the right, works out fine. It's often in cases where there isn't common knowledge where you get failures to coordinate, as in Kristof's example of failure to establish common knowledge between a cyclist and a motorist. That often happens when there isn't some public signal that each one sees, knowing that the other one sees it, such as a traffic light, such as a zebra crossing, such as a stop sign. The reason that they are there is to establish these conventions that work by common knowledge. If I see the stop sign, I know that everyone else sees the stop sign, and we all know that that's the place to stop.

• 4:26Speaker 03

  But looking at people can replace that.

• 4:28Speaker 01

  Indeed.

• 4:29Speaker 03

  Partially.

• 4:30Speaker 01

  Partially, yes. The relevance to social relations is that I suggest that our relationships are situations of coordination, coordination games in the sense of game theory, that just as driving on the right works because everyone knows that everyone knows that you drive on the right, you and I are friends because, not because we signed a contract that stipulates our responsibilities, because I know that we're friends, and you know that we're friends, and I know that you know, and you know that I know, and so on. Or alternatively, relations of deference. The person who is kind of higher on the status hierarchy stands his ground because he knows that the beta will give way. The beta gives way because he knows the alpha will stand his ground, et cetera, et cetera, et cetera.

• 5:14Speaker 01

  Or transactional relationships, or romantic relationships. I suggest that each one of those is a coordination game and that they are ratified or upended by certain common knowledge generators, signals that each one perceives, knowing that the other one is perceiving it too, language being the most efficient way of generating common knowledge. So in the case of, Kristof mentioned that eye contact can often generate common knowledge. That is, eye contact, we know, even from the ethological literature in animal communication, is a very potent signal because you're looking at the part of the person that's looking at the part of you that's looking at the part of them that's looking at the part of you. And so eye contact can generate common knowledge.

• 5:58Speaker 01

  It often resolves these ambiguities in, say,

• 6:04Speaker 01

  a car stopping and a pedestrian crossing. Establishing eye contact would be a way of generating that common knowledge.

• 6:11Speaker 03

  Or two people or two cars merging on a freeway. The other guy just sort of briefly nods to let you go ahead.

• 6:17Speaker 01

  And in fact, I was tickled to see a sign in the San Francisco airport parking lot, which I actually photographed and included in the book. And it has a cartoon of a pedestrian and a driver in a dashed line joining their eyes, and it says, "Make eye contact before crossing." There it is, yes.

• 6:37Heather Berlin?

  That's great. But in a way, I mean, this common knowledge is a way to have, you know, what you're saying, you know, why it's important, it's for social, it's for coordination among groups of people. But what happens when, you know, people get it wrong? You know, I'm thinking about, you know, when you all pull up to a four-way stop and nobody knows where to go, and you're both waving to go. But I mean, that's a smaller example. But like, are there disagreements? I think, you know, you know something that you might think I know something different, or we don't agree on what is common knowledge?

• 7:09Speaker 01

  Oh, you bet. And in the traffic case, it could lead to a collision. That's the ultimate miscoordination. In social interactions, it can lead to the situation that we call awkwardness, or if it is deliberate and protracted outrage. For example, if two people have a platonic relationship, and one says, would say to the other, "Hey, do you want to have sex?" That could be really awkward, which is why we have the phenomena of euphemism, innuendo.

• 7:42Speaker 03

  Do you want to come up and watch my Netflix?

• 7:45Speaker 01

  Or Netflix, yes. And I suggest that all of the rituals of genteel hypocrisy, politeness, consist in avoiding the common knowledge that might threaten a relationship while still slipping the information in. The idea is that there's private knowledge, there could even be reciprocal knowledge, but not necessarily the common knowledge that would threaten the relationship. So just to be more concrete, if he says, "Do you want to come up for Netflix and show?" And she says, "No." I mean, she's a grown up. She knows what "come up for Netflix and show" means. So she knows what he intended. And, you know, he's a grown up, he knows that she knows. But does he know that she knows that he knows? And does she know that he knows that she knows?

• 8:30Speaker 03

  Deniability, right?

• 8:32Speaker 01

  Well, it's not even so much the deniability of the proposition because, you know, again, she's no fool.

• 8:38Speaker 03

  But he could always say, "Oh, I just meant watching a movie. I didn't intend anything else."

• 8:43Speaker 01

  I think it's the deniability of the common knowledge. That is, she could plausibly think, "Well, maybe he thinks I'm naive. Maybe he thinks that it went over my head." And he could think, "Well, maybe she thinks I'm dense, and I don't realize that she knows that I know." And that higher-order deniability allows them to preserve the relationship of platonic friends, or colleagues, or to come up with an even more fraught situation, supervisor and supervisee. Whereas blurting out, "Do you want to have sex?"

• 9:15Speaker 03

  Violates.

• 9:16Speaker 01

  Direct speech generates common knowledge. That common knowledge would contradict the tacit understanding of the platonic friendship or the collegial relationship.

• 9:26Speaker 03

  I couldn't go back to the.

• 9:28Speaker 01

  So you can't go back.

• 9:29Speaker 03

  To the relationship I had before.

• 9:30Speaker 01

  Exactly. And again, because common knowledge is what cements particular kinds of relationships, and direct speech generates common knowledge, innuendo, euphemism.

• 9:44Speaker 01

  Politeness leads to private knowledge, but not common knowledge. You can maintain the fiction of a photonic friendship.

• 9:52Heather Berlin?

  As a therapist, I'm advising people on relationships and I'm often telling them, you know, be open, be honest, tell a person how you really feel, you know, but that's not always.

• 10:02Speaker 03

  Probably not everyone.

• 10:03Heather Berlin?

  No.

• 10:03Speaker 01

  Sometimes, yeah. I mean, no, and clearly, so therapy, especially couples therapy, marital counseling, family counseling, consist of encouraging people to make something common knowledge that was previously private knowledge, in the case that there was something dysfunctional about that equilibrium, about the relationship that they'd been locked into. But in other circumstances, the, if equilibrium is working out, you're best off not saying everything that's on your mind. This is what we call, we have names for this, knowing when to keep things out of common knowledge. We call it tact, savoir faire, social skill.

• 10:43Speaker 01

  That's what social skill often consists of. It's the ordinary civility that we try to implement in human relationships. I mean, a simple example is just ordinary politeness. If you could pass the salt, that would be great. Now, literally, that doesn't make a whole lot of sense. It's, you know, counterfactual, hypothetical, why are you musing about possible worlds at the dinner table? But what you're doing is, you're avoiding treating the other person like a servant by saying, you know, give me the salt.

• 11:11Heather Berlin?

  Right.

• 11:12Speaker 01

  And that respect for the relationships that are in force. Are we, how intimate are we? How formal are we? Is it hierarchical? Is it communal? Those are things that are cemented by common knowledge. And when we don't want to upset them, we avoid the common knowledge of threats to that basis of those relationships.

• 11:34Speaker 03

  To what extent are those consciously represented and done, initiated consciously? So for instance, the example of pass me the salt, that's just something that's a habit. You've cultivated your entire life, you just blurt it out, right? That's not consciously intended to, so to what extent is common knowledge consciously?

• 11:55Speaker 01

  Yeah. So in cases like that, where it's pro forma, where it's become a, itself, the indirect request is itself become a convention, very little of it is in consciousness. It's just what you do. In novel situations, where you don't know where you stand with a person, you're thrust into a unique, unprecedented situation, then I think it can be conscious, like, oh, how do I put it? How do I state this? I have to criticize them, but I don't want to, you know, seem to be superior. In those cases, I think it can be conscious. How will they react to this? But in many cases, it's simply the conscious correlate of common knowledge is not, I think that she thinks that I think that she thinks. I

• 12:38Speaker 01

  think we can do that up to a certain levels of, a certain number of levels of embedding. More commonly, it's a sense that some things are out there, they're public, they're self-evident, they're conspicuous, they're salient, you can't take it back because it's out there. And we refer to that feeling using idioms for a visible event or object, like the elephant in the room, or it was in your face, or it's out there. So I think that's more commonly the subjective feeling.

• 13:10Speaker 03

  So you point out a remarkable consequence of this that I was unaware of. So there's this, maybe you can tell us a little bit about Robert Auman's agreement theorem and the remarkable conclusion.

• 13:22Speaker 01

  I just heard from him this morning in an email, a new, a new version of his proof. So this is a famous theorem, published 50 years ago, exactly, known as the agree to disagree theorem. A short version is rational people cannot agree to disagree. More technically, rational agents with the same priors, that is, understanding of the world, who make their posteriors common knowledge, that is, each one knows the other's assessment of the strength of the evidence for some proposition. There, those posteriors must be the same. So just to back up a bit, priors from, from a base theorem refers to background, understanding

• 14:05Speaker 01

  of the world. Posteriors means your degree of belief in some proposition, having looked at the evidence. Was there a second shooter, JFK assassination? Did the SARS-CoV-2 virus escape from a lab in Wuhan? So if you assign a probability to that, you know, I'm 40, I think 40% sure that it was a lab leak that led to COVID. So if you have two rational agents, and they both start off with the same understanding of the world, they, each one examines the evidence, they don't share the evidence, they just share their

• 14:42Speaker 01

  conclusions. If the conclusions are common knowledge, that is, not only do they share them, but each one knows that the other one knows.

• 14:48Speaker 03

  Because they may also have private knowledge, asymmetric, there may be asymmetric knowledge, right? Like some agent knows something.

• 14:54Speaker 01

  The evidence is private, that each one looks at is private. Then they come to a conclusion, which they state with a degree of probability, they each tells the other publicly, then they must converge. They cannot be different. That's the theorem.

• 15:10Speaker 03

  And so two, so, so incidentally, I only discovered recently, Auman, the professor at Hebrew University, is actually cousin of Oliver Sacks.

• 15:18Speaker 01

  Yes, that is right.

• 15:21Speaker 03

  Two remarkable facts about Auman's theorem. One, maybe you can talk a little bit how it applies to a game, the game that most of us play, which is financial markets, stock market, right? We all have invested our money for our retirement, and that depends on this little theorem.

• 15:37Speaker 01

  It's a way in which, I mean, at first it seems preposterous. That is, well, for one thing, just agreeing to disagree seems like a virtue. It seems like the ultimate in civility. And

• 15:50Speaker 03

  Which is what we encourage students to do.

• 15:52Speaker 01

  You gotta know how to agree to disagree. Yes. And he's saying this is irrational. Under the, of course, like all mathematical theorems, it's true to the extent that the idealizations of the theorem are true.

• 16:03Speaker 03

  But on the financial market, it's, it is true to a certain extent.

• 16:06Speaker 01

  Financial market is true, and it corresponds to the advice from just about every honest financial expert. Don't try to time the market, don't try to outsmart the market, don't speculate. Buy a boring basket of securities, an index fund like the S and P 500, and be content to partake of the increase in productivity of the economy as a whole. Don't think that you've got, don't act on a stock tip. The relevance of the theorem is that, you know, unless you are engaged in insider trading, that is, you have private knowledge, if you're, you know, reading the papers, if you're following the stock market, all of that is common knowledge.

• 16:46Speaker 01

  The prices are common knowledge. And so priced into the value of a security is all of the common knowledge among the people who have researched it, who do know about it. If it is likely to go up, if there's reason to believe that, well.

• 17:05Speaker 03

  It's already factored into the price.

• 17:06Speaker 01

  If you know it, probably everyone else knows it, knows that everyone else does it. The price has risen to already incorporate that anticipation. So you can't count on making a profit by buying at the current price if the price is common knowledge. And that is, and if the prices, according to Auman's theorem, for rational agents, the posteriors have to be the same, which means that your evaluation of the present value of the stock should be the same as everyone else's. That is, what the share is currently selling for. So it's irrational to buy it on the expectation that it will rise. If it's, if there's reason to believe it will rise, the price will already reflect that and you can't make a profit.

• 17:49Speaker 03

  Okay. So let's switch now from financial market and you'll see how this is relevant to perception box, to our conscious experience of reality, right? So I have a perception of reality. I think we're sitting inside a studio. You have something very similar. But of course, as, you know, 200 years of research and everyday knowledge has revealed, common sense has revealed, people radical disagree. So the nicest, the simplest one that I know you also mentioned is hashtag the dress, right? So roughly half of humanity sees this dress white and yellow, and the other half sees it as blue and black. And it's not something we infer, you know, they just look at it and it's, it's a spontaneous perception occurring within 150 milliseconds, and they can't change it. So it's unlike,

• 18:34Speaker 03

  you know, the bi-stable old woman, young, young woman, right? It's, it's, it's stable. So that tells us at least, and in this case, we think we know it has to do with your prior assumption about background, about background.

• 18:46Heather Berlin?

  The light, whether it's blue light or indoor, outdoor light, and your brain makes a assumption.

• 18:52Speaker 03

  Since Auman theorem says we should all come to the same posterior, and obviously we don't, does it mean we are all profoundly irrational in this sense, in our perception of reality, social or more physical?

• 19:06Speaker 01

  We're obsessed with the cases where there, there's a divergent belief, but there's a massive amount of convergent belief that we never comment on because it works so well that it's below the level of consciousness. So the dress was a highly exotic stimulus display. And even though we've worked in perception for decades, I was taken aback by the dress because it's very rare that you get something where there's such a sharp divergence.

• 19:30Speaker 03

  Bi-stable.

• 19:30Speaker 01

  It's not bi-stable. I can't get, I've studied it, I've, I've written an article about it. I can't get it to flip. That's very unusual.

• 19:39Heather Berlin?

  You can if you play with the background. We can, I can make you flip it if I put a certain background that changes your.

• 19:44Speaker 01

  Yeah, it changes the image. The vast majority of the time, if, you know, I ask Heather, what color is that, is that?

• 19:51Heather Berlin?

  That horrific yellow?

• 19:52Speaker 01

  That horrific yellow, even, even the horrific, but putting aside the horrific, just the yellow, you know, we agree. And that's how come you can order something on the internet and specify the color and you get the color that you want.

• 20:03Speaker 03

  So clearly people have, where it matters a lot to people, they have a lot of differences in, in experiencing the world.

• 20:11Speaker 01

  Yeah, I mean, they, they do, and they're fascinating. But there's also amazing commonalities. I mean, captured in the story of the Tower of Babel, where people Able to coordinate by the common knowledge of a single language, built a tower that threatened God in the heavens himself. And if you look around, everything, aspect of our life is the result of massive coordination. So the TV cameras, the lights, you know, 100,000 years ago, none of that existed. It wasn't that some single genius invented them all. Clearly, there was massive coordination, both of knowledge of physics and electronics and materials, and people delivering things so that the components get together at the same place,

• 20:55Speaker 01

  systems of laws and commerce and money, you know, massive amounts of coordination, all of which depend on common knowledge, language being an important way of generating common knowledge, that gives us the world that we're living in. Now, there are some differences, especially when it comes to normative questions of right and wrong and ought. But that's, that level of disagreement is overlaid on a massive amount of common knowledge that has allowed us to transform the world by working together.

• 21:27Speaker 03

  But that difference can have profound, can lead to profound consequences in the way people experience the world.

• 21:34Heather Berlin?

  So you're saying some people are colorblind. Some people see the world through, say, depression colored glasses, and they have that kind of schema that they see everything through that. So there's a valence to the way we perceive the world, but there is also these commonalities. The idea is what happens when we perceive, is our personal schemas or a way that we perceive the world differently. Can we separate that out from common knowledge? Or is there a schism within common knowledge?

• 21:58Speaker 01

  There can be lots of schisms, but what makes humans, humans, what makes it possible for there to be technology and science and society, and even the coordination that you have in ancient agricultural civilizations, unusual among species, among mammals, but made possible by our, the capability of our species to coordinate on a range of scales from couples to corporations, all of which is enabled by common knowledge.

• 22:29Heather Berlin?

  I just want to say about decision making, like in terms of common knowledge and the bystander effect. And how does common knowledge affect decision making and things like the bystander effect?

• 22:39Speaker 01

  Yeah, so I did publish a paper on experiments on bystander effect. This is a classic in social psychology phenomenon, inspired by a famous event of the 1960s, which turned out to be bogus, Kitty Genovese.

• 22:53Heather Berlin?

  Kitty Genovese, yes.

• 22:54Speaker 01

  So the headline was 30, 32 people witnessed murder, no one calls the police. A woman named Kitty Genovese returned home from work one night and was brutally attacked.

• 23:07Speaker 03

  This was here in New York, I believe.

• 23:09Speaker 01

  In Queens, that's right. And that was a symbol of alienation and enemy and apathy. Turns out, the report was bogus. Actually, some people did call the police. Some people didn't because they just thought it was a fight between two drunks. A woman did come out and comfort the poor victim. Anyway, there is a phenomenon, though, that the more people who witness an event where something needs to be done, the less likely that anyone will do it. That's the bystander effect, and it has been shown in social psychology experiments.

• 23:43Speaker 03

  You mean coming to aid of?

• 23:44Speaker 01

  Coming to aid. So if there's a bunch of people filling out a questionnaire in a lab, and there's a crash and a scream and a plaintive cry, "Help, the cabinet fell on my foot, I can't get out." If there are 10 people filling out the questionnaire, it's likely that no one will help than if there's one person or even two people. So what's going, that's the bystander effect.

• 24:06Heather Berlin?

  You assume other people are gonna

• 24:08Speaker 01

  Yes.

• 24:08Heather Berlin?

  take the responsibility.

• 24:09Speaker 01

  Crucially, you do that only if you know that everyone knows, that is, if there's common knowledge. Well, we showed, we didn't actually stage a real emergency, but we had people imagine themselves in a situation where someone had to do something. If you didn't know that other people knew, even if other people witnessed it, then you're more likely to spring into action. So it's an example of what in game theory is called the volunteer's dilemma, where the optimal outcome is if someone else steps in. The worst outcome is if no one steps in. In between is if you have to step in. And there's a medieval story that captures it called Who Will Bell the Cat?

• 24:52Speaker 01

  Where the mice are, of course, in danger of getting eaten by the cat in the house. And one of them figures out, well, if only we hung a bell around the neck of the cat while it was asleep, then when the cat approached, it would warn us and we'd be safe. And the question is, who will bell the cat? Where the mouse who volunteers to bell the cat is incurring some risk of waking the cat and being eaten, even though it's in the interests of all the mice if at least one mouse does it. So it's equivalent to a situation of an outguessing standoff. That, say, in soccer, in a penalty kick, the kicker has to shoot left or right, the goalie has to defend left or right.

• 25:34Speaker 01

  Each one wants to do the opposite of what the first one does. The optimal solution is to act randomly, because any tell or predictability will be exploited by the other. And indeed, in a volunteer's dilemma, in, you know, who's going to refill the communal coffee pot? Who's going to go out and investigate where the screams were coming from? The, in game theory, the optimal response is to mentally roll the dice and act with a certain probability, which depends on how many other bystanders there are. The more bystanders, the lower the odds at which you should act. But it crucially depends on the degree of knowledge.

• 26:16Speaker 03

  Do people actually do that? Do they follow that law that the probability with which they come to help?

• 26:22Speaker 01

  They act pretty close to optimal rational agents. And the reason it depends on knowledge is if everyone knows, but let's say you don't know that they know, then you're less likely to shirk, because if each person thinks he's the only one he knows, he'll have to step into it. If he knows that other people know, then he can afford to shirk.

• 26:45Heather Berlin?

  But then, at that point, the more people there are, the lower the probability that you as an individual,

• 26:50Speaker 01

  If there's common knowledge.

• 26:51Heather Berlin?

  If there's common knowledge, then how does anybody ever decide who's going to respond? I mean, then you could get an actual, real life

• 26:57Speaker 01

  Yeah, you could.

• 26:58Heather Berlin?

  kind of Kitty Genovese situation.

• 26:59Speaker 01

  And we do, people, you know, walk by a homeless person who then the next morning, you know, has frozen to death.

• 27:05Heather Berlin?

  Right.

• 27:05Speaker 01

  Each one hoping that others will act first. So there are real, even though the original report ironically was bogus, I mean, it does refer to an actual social situation.

• 27:15Heather Berlin?

  Right.

• 27:16Speaker 03

  So to get back to your earlier point that we live in a world built on large scale consensus and shared, shared perception of reality, including social reality, it is true, when we go back to the well-explored financial market, that people rampantly, consistently, everyone speculates. Is everyone acting irrationally?

• 27:39Speaker 01

  Well, so John Maynard Keynes wrote about this in the 1920s, in which he analogized speculative investing to a beauty contest, but not a beauty contest where everyone tries to pick the prettiest face. A contest where the winner is the one who picks the face that the most other people pick, knowing that the other people are picking a face with the same goal. And so you buy a stock not in speculation, not because the company is going to churn out widgets and you'll share in the profit.

• 28:12Speaker 03

  But because other people, you think other people will buy this?

• 28:15Speaker 01

  Exactly.

• 28:16Speaker 03

  No, wait, but the price should have factored that in, right? If it's really opt, if it's an optimal market.

• 28:22Speaker 01

  Yes, but with speculation, there is the, you know, the expectation that other people have an expectation, that other people have an expectation that it will rise, which makes it rise up to a point at which the market runs out of, as they call it, greater fools, who are going to pay even more for it than you pay for it. That can't happen indefinitely, and that's when you get a crash. You can also get a converse loop of common expectation. It's not common knowledge because there's nothing objective to know, but it's a common belief in other people's belief. The opposite is a bank run, where people withdraw money from the bank as they, either they think the bank is insolvent, they don't even have to think that. They can just think that other people think the bank is insolvent,

• 29:07Speaker 01

  or think that other people think that other people think.

• 29:09Speaker 03

  That's why we ran out of toilet paper early on in COVID 19.

• 29:13Speaker 01

  Exactly.

• 29:13Speaker 03

  And when there's suddenly no more toilet paper in ladies and gentlemen.

• 29:18Speaker 01

  Thing is that with the, as with bank runs, as with sometimes stock bubbles, such as meme stocks, where one influencer has a post saying, "This is an interesting stock for us all to buy," even if the fundamentals are crummy, like the GameStop video chain stores, brick and mortar video game stores that were kind of doomed in terms of the fundamentals. But one influencer said, "Hey, let's start buying it." And people bought it because they knew other people were buying it because they knew other people were buying it. Conversely, if there's, if a rumor gets out that a bank is unsound,

• 30:00Speaker 01

  that can, that common knowledge, that, I should say, that public conspicuous signal can generate common expectation. So that's why we care so much about what's public, what's private, why certain nationally televised events, like a presidential debate, like the Super Bowl, can move the whole country.

• 30:21Speaker 03

  So as a nerd, I can't help but asking, is there a particular threshold? When you say everyone knew, of course, not everyone knew, because not 330 million Americans knew, right? So is there a threshold when 0.25%, I mean, 25.5% has to know, and then it's very unstable, and then suddenly it flips? Because there do seem to be these tipping points, right? Where this is stable, this is stable, and you can flip between the two.

• 30:46Speaker 01

  I don't think enough people have researched it with enough data to be able to establish the tipping point. There is not an answer, but it would be, and what we have to, the parameters would be the reach of the median percentage of people viewing, you know, other things. It's a difficult problem, but I think a fascinating one.

• 31:05Heather Berlin?

  I think that's why it's so important to have freedom of speech also is because you want to, I mean, people are thinking things, but you want to know what people are thinking.

• 31:12Speaker 01

  You put your finger on it. That is exactly why freedom of speech is so crucial, namely can mark a transition from private knowledge to public knowledge, allowing people to act collectively in their own interests. I quote the, a line from the movie Gandhi, in which the eponymous character tells a British colonial officer, "In the end, you will leave because 100,000 Englishmen simply cannot control 350 million Indians if the Indians refuse to cooperate." And what common knowledge does is it allows the 350 million Indians to refuse to cooperate, that is to coordinate their resistance.

• 31:49Speaker 03

  I lived through one such experience when the wall came down in, in East Berlin and abruptly, abruptly, literally, everyone abandoned the regime. They just walked over that night over from East Berlin to West Berlin. It was clear to everyone, this means curtains for the communist government.

• 32:06Speaker 01

  No, it's interesting. And, and I think historians have traced, like, what was the first domino? And I think there was a public pronouncement by a local official that he was not going to shoot the people who scaled the wall, right?

• 32:20Speaker 03

  Yes, and then he's, and then he said, "We've now granted exit visas." This is his press speaker, exit visa. And then the press asked him, uh, when, for how long? And then he looked down and says, "Well, I'm not sure, but it's tonight." And that was the night, October 8th, when everyone walked over and it was all over.

• 32:40Speaker 01

  That's a great example. Likewise, the overthrow of Ceausescu in Romania.

• 32:45Speaker 03

  Oh, yeah, Romania.

• 32:46Heather Berlin?

  How has science revealed common knowledge that wasn't truly shared by everybody? So has there been scientific breakthroughs that have, you know, changed our people's common knowledge about, yeah?

• 32:58Speaker 01

  And tellingly, the common knowledge that it challenges can often be common knowledge of, of norms, including moral norms. And I think it's precisely because a scientific discovery that threatens common knowledge is often repressed, punished, why you get cancellations, deplatformings, social media shaming mobs, and outright repression, like killing or imprisoning the heretical scientist. My favorite example, I guess, is Darwin's theory of evolution, which was by challenging the commonly held belief in divine creation with a moral purpose, by saying, "We just

• 33:42Speaker 01

  evolved from lowly apes by natural physical processes," was thought to threaten that moral order. There's a famous, turns out apocryphal quotation from a, one version, it's the wife of a vicar in Victorian England, who, when told about Darwin's theory, exclaimed, "Descended from apes, my dear, let us hope it is not true, but if it is, let us hope it not become widely known."

• 34:12Heather Berlin?

  Right.

• 34:12Speaker 01

  So you could have said commonly known. And the, the, the connection to, to, to common knowledge is that moral norms are matters of common knowledge. You don't do something, why? Because it just isn't done. You know, everyone knows that, everyone knows, you just don't do it. And that can be threatened if someone does it and gets away with it. Or if a commonly held belief, such as we are moral because God created us and we have immortal souls and, you know, all of that, if it's threatened, if people stop believing it, then the fear is that they will no longer hold on to the commonly held moral norms to go along with it.

• 34:52Speaker 01

  Hence the recurring phenomenon of repression of scientific discoveries.

• 35:03Heather Berlin?

  We end every show with a perception box question that sort of, so you can, it opens up your own perception box. And either Christopher or I asked the question this week, I'm going to be asking the question to both of you. Are you ever concerned about how your work might be perceived or translated or used in the future by others?

• 35:25Speaker 01

  I, I am concerned, not to the point of saying things that are false or not saying things that, you know, I think properly explained would do more good than, than, than harm, especially since almost always it's better to know the truth than to be deluded by falsehood. You know, I, I don't think men and women are indistinguishable in every respect. I'm also very clear to say that that doesn't mean that discrimination or harassment are okay, they're not okay for some pretty obvious reasons that we ought to reinforce. You know, likewise, I think there are different innate differences in intelligence and personality. So therefore, in a perfectly fair and equal society, there'll be unequal outcomes. Some people accomplish more, earn more than others.

• 36:10Speaker 01

  Some people will get in trouble with the law and others don't. That doesn't mean that we should screw over the poor or be unconcerned with the people who, who earn less. Again, a matter of fairness and compassion, that we might want to have social protections. But we shouldn't confuse where those differences come from. Some of them might come from discrimination, racism, prejudice. Some of them might come from differences in ability. Nonetheless, even if they come from differences in ability, we ought not to be callous about the fate of anyone in society.

• 36:46Heather Berlin?

  Like, both can exist at the same time. I kind of see it as a top-down, bottom-up sort of problem. It's like, sometimes you have the truth, the fundamental truth, the data, what it's showing, and it scales up and people might not like what they think that might mean at the moral level or a societal level, but it doesn't have to translate to that. You can have a fundamental truth and still create certain societal norms. But sometimes people take what they want to be morally true and impose that on the data, like, therefore this data has to say this in order for my moral value to be.

• 37:19Speaker 03

  They deny that the data is objective. They say it's all about power play. There isn't any objective reality out there.

• 37:24Speaker 01

  And that's true. So that was called the moralistic fallacy. That is, that ought implies is. This is the way, it would be nice if the world were, therefore, the world is that way. I mean, it's a fallacy. But yes, we're, we're, we're, we're subject to it. I think in general, this is a topic I took up in, in a previous book, Rationality, of why, and this actually goes back to our earlier discussion, Kristof Rais, of why there is so much disagreement over what would seem to be fundamental facts and a lack of common knowledge. What I suggest is that it's a feature of, of human psychology, that when it comes to questions that are outside our immediate experience, you know, what color is that? Is that shirt? Is there coffee on the table?

• 38:09Speaker 01

  There, there's, you know, a lot of agreement unless someone is, you know, schizophrenic. But when it comes to questions like, where did our species originate? Why are there economic booms and busts? Who's responsible for a war? Why do bad things happen to good people? Why do people get sick? For most of our history, there was no way to answer them. Science is very recent, data are at large scales are, are recent, objective journalism is, is recent, objective history is recent, all basically products of the Enlightenment and the scientific revolution, and unevenly known across the species at that. When we evolved, the only thing you could really be sure of was your immediate experience.

• 38:54Speaker 01

  For these big cosmic questions, you know, no one knew, you couldn't find out, and so you may as well believe the most uplifting myth, the one that unites your tribe, the one that gives a good moral message to, to children. And the very notion that there is an objective truth about big questions like, what's the cause of misfortune, is, is quite alien to our, to our minds. I mean, I think it's a, we ought to overcome it, we ought to teach it, we should advance the ideal that one should pursue objective truth about big questions, but it's an uphill battle. Most people are content thinking that the belief that we ought to hold is the one that's most morally uplifting.

• 39:35Speaker 01

  I think the gut feeling of most people is, we should believe, I'm going to believe what

• 39:42Heather Berlin?

  Feels good.

• 39:42Speaker 01

  What feels best, what I think is most morally appropriate.

• 39:46Speaker 03

  And including what's scary, and I discovered this personally during COVID, among scientists themselves, among academic scientists that sort of have truth written on their banner, you're just asking that question, or you showed you were massively biased.

• 40:02Speaker 01

  Well, no, that's right. And the, what's somehow called the scientific method, not that there's any one thing called the scientific, but just the, the norms, the mores of science are designed to push back against that, to marginalize it. You know, as, as Richard Feynman said, the most important thing in science is not to fool yourself because you're the easiest to fool.

• 40:20Heather Berlin?

  Especially in this day and age, I'd just say of like, where there's a lot of anti-science and disbelief in science is that it's imperfect, but at least it's a, a method that we're trying to overcome our own subjective cognitive biases.

• 40:32Speaker 03

  The best methods humanity has discovered to understand.

• 40:35Heather Berlin?

  Right. And that's why it's always changing. It wasn't like, oh, you said this one time and now you change your mind. No, it's like, the evidence showed that it was, you know, I had to change my theory, I had to change my perception, my perspective, because the data said otherwise.

• 40:47Speaker 01

  Right. There's a famous quotation attributed to John Maynard Keynes, when he was, according to the story, he was challenged for changing his position. He said, "When the facts change, I change my mind. What do you do, sir?"

• 40:58Heather Berlin?

  I love that.

• 40:59Speaker 01

  He didn't say it, but I think Paul, Paul Samuelson probably said it for, uh, first, but it's, it's, it's a very good idea.

• 41:06Heather Berlin?

  Yes, I like that. So, so given all this knowledge that we have, even our understanding of common knowledge, I thought we should test our own common knowledge with a little game. So I have a list of acronyms that are in both like work-related and, and pop culture. You have 30 seconds on the clock. I'm going to say what they are, you can both guess at what they are, we'll see how many you can get. Ready?

• 41:28Speaker 01

  Okay.

• 41:29Heather Berlin?

  I see, why am I?

• 41:31Speaker 03

  In case you missed my earlier.

• 41:34Heather Berlin?

  It's.

• 41:35Speaker 01

  It, okay, yes.

• 41:35Heather Berlin?

  In case you missed it.

• 41:36Speaker 01

  In case you missed it.

• 41:37Heather Berlin?

  Okay. KPI.

• 41:39Speaker 03

  Key knowledge, uh, key, key knowledge.

• 41:42Heather Berlin?

  KPI.

• 41:45Heather Berlin?

  Key performance indicator.

• 41:49Heather Berlin?

  Are you like a head of an organization? Okay.

• 41:51Speaker 03

  I used to be.

• 41:53Heather Berlin?

  T L, semi colon, D R.

• 41:55Speaker 03

  Too long, did not read.

• 41:57Heather Berlin?

  Oh, that's good.

• 41:58Speaker 01

  Yeah.

• 41:58Heather Berlin?

  That obviously happens to you a lot. Or, no, okay. RFP, I know this one. Yes. We live in the academic world. S M H.

• 42:10Speaker 03

  Single, it's in the dating market, right?

• 42:14Heather Berlin?

  Shaking my head.

• 42:16Speaker 03

  That's an abbreviation.

• 42:18Heather Berlin?

  I guess in the, you know, text lingo.

• 42:20Speaker 03

  Yes.

• 42:22Heather Berlin?

  S O W.

• 42:24Speaker 03

  Statement of work.

• 42:25Heather Berlin?

  Very good. You're not looking, right? You're cheating? Okay.

• 42:28Speaker 03

  It's grants.

• 42:29Heather Berlin?

  Okay.

• 42:29Speaker 03

  Okay. Statement of work, you need an S O W.

• 42:33Heather Berlin?

  Okay, this is, this one I knew. G O A T.

• 42:36Speaker 01

  Greatest of all time.

• 42:37Heather Berlin?

  Yes, very good.

• 42:39Speaker 03

  Goat.

• 42:39Heather Berlin?

  Yes. P N L.

• 42:42Speaker 03

  Physical review, P R L.

• 42:45Heather Berlin?

  P and L.

• 42:47Speaker 01

  Oh, P and L.

• 42:48Heather Berlin?

  Yes.

• 42:50Speaker 03

  Purchasing.

• 42:50Speaker 01

  Profit and loss.

• 42:51Heather Berlin?

  Yes, very good. N S F W.

• 42:54Speaker 01

  Not safe for work.

• 42:55Heather Berlin?

  Very good. I feel like I'm grading, like I want to have like a little, uh, who's going to win? E O D.

• 43:02Speaker 01

  End of day.

• 43:03Heather Berlin?

  C O B.

• 43:05Speaker 01

  Close of business.

• 43:05Speaker 03

  Close of business.

• 43:07Heather Berlin?

  L M K.

• 43:08Speaker 01

  Let me know.

• 43:09Heather Berlin?

  Q A.

• 43:11Speaker 01

  Question and answer.

• 43:12Speaker 03

  Q and A.

• 43:13Heather Berlin?

  Quality assurance. Finally, P O V.

• 43:17Speaker 03

  Point of view.

• 43:18Heather Berlin?

  Yes, and we all have our own point of view.

• 43:23Heather Berlin?

  Good job. Never thought I'd be doing that one day, asking Steve Pinker and Kristof Kow. What is, you know, shaking my head mean? So I'd like to thank Steve Pinker for being our guest today. Thank you very much.

• 43:36Speaker 03

  Thank you, Heather. Thank you, Kristoff. Thank you for coming on. It was very enjoyable.

• 43:41Heather Berlin?

  If you'd like to learn more about your own perception box, spend some time this week answering the same perception box questions that we asked our guests. And check out our other questions on the website, unlikely collaborators.com. You can also subscribe to our YouTube channel and watch the show or listen wherever you get your podcasts. This has been Science of Perception Box, created by Unlikely Collaborators in partnership with Pod People. I'm Dr. Heather Berlin.

• 44:06Speaker 03

  And I'm Dr. Kristof Kow. Thank you very much for watching.