The Current - Steven Pinker: When everyone knows that everyone knows

Episode Date: October 16, 2025

The Harvard professor Steven Pinker is the author of "When Everyone Knows That Everyone Knows," a new book on common knowledge. He believes that awareness of what others know, or lack of it, is key to figuring out how humans coordinate to form everything from personal relationships to our shared belief in money or power or national borders.

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Hello, I'm Matt Galloway, and this is the current podcast. We're going to spend the next bit of time talking about the concept of common knowledge. I know who is with me here in the studio to talk about that, but I don't know if you know. I did mention it earlier in the program, but I don't know if you're listening then. So I don't know if you know who this is. So for the moment, to me, this is private knowledge. But once I tell you that this is the Canadian academic and Harvard professor Stephen Pinker, now I know that you know and you know that I know that you know. So it's common knowledge.

Common knowledge in this sense is not just shared knowledge. It is the awareness that other people know what we know and that influences how we coordinate with each other. All of this is the subject as Stephen Pinker's new book when everyone knows that everyone knows common knowledge and the mysteries of money, power in everyday life, Stephen Pinker. Good morning. Good morning. This is complicated. Maybe too complicated in that introduction there. We'll talk about what this is, but you explain it in a number of different ways. One is through the story of the emperor's new clothes. How does that explain what common knowledge is? When the little boy said the emperor was naked, he wasn't telling them anything they didn't already know. They could see the emperor was naked, but he was changing

the state of their knowledge. At the moment that he blurted it out with an earshot of everyone else, they now knew that everyone else knew that they knew and that everyone else knew that everyone else knew. And that changed their relationship with the emperor from obsequious deference to ridicule and scorn. So the story illustrates several things about common knowledge. First, that it's not the same as private knowledge. Everyone knowing something,

which is what happened before the little boy blurted it out, is different than everyone knowing that everyone knows something, which is the state after. The second is it sounds impossible when you describe it in the literal sense of I know that she knows and she knows that I know, I know that she knows that I know that she knows. Your head starts to spin with a couple of levels, let alone an infinite number, which is what the concept requires. But common knowledge can be generated at a stroke when an event is public, when it's out there,

when I see something or hear something, and I see you seeing it. see me seeing it, that triangle is enough to just grant us common knowledge. We don't have to think through all the layers. We could, but we get an instant sense that something is public, out there, self-evident, conspicuous. And the third moral of the story is that it changed their relationship with the editor, with the emperor, sorry, and social relationships, like all forms of human coordination, depend on common knowledge, whether we're friends, whether I defer to you, whether we're lovers, whether we're transactional partners, it's not as if we sign a contract for most of those things. What it means to be friends is I know that you know that we're

friends and you know that I know we're friends and that's kind of what friendship is. Or if I defer to you because I know you'll stand your ground and you stand your ground because you know I'll defer to you, which I do because I know you'll stand your ground and so on at infinitum. So social relationships are ratified and suspended by common knowledge, and they can change when the common knowledge changes. You mentioned friends, and one of the things that you talk about in the book to kind of illustrate this is a TV show, Friends. Indeed. This is a clip from the episode where Chandler and Monica have become a couple. They're trying to keep it a secret, but as these things go, it leaks out. Have a listen. They thought that they could mess with us. They're trying to mess with

us? They don't know that we know they know we know. Joey, you can't say anything. Couldn't if I wanted to. You say that this is about coordination, that these sorts of layers of knowledge are prerequisite in some ways of social life. What do you mean by that? Yes.

By the way, one thing that that clip illustrates is a psychological process called recursive mentalizing. That's a fancy phrase for reading the mind of a mind reader. So mentalizing is jargon for trying to get in someone's head. Recursive mentalizing is trying to get into the head of someone who's trying to get into the head of someone else and who may be trying to get into the head of someone else. And the humor in that clip is that the slow-witted Joey confesses to not being able to follow.

And the humor in the clip is the audience can barely follow. They actually do in that clip, which shows that we are capable of recursive mentalizing. but that more often we just react to something that is out there. But what it does in general is it gets people on the same page. It isn't enough to know what the other guy's choice is because he might try to guess what your choice is. You've got to know that the other person knows that you know that they know. So an example is a rendezvous.

Imagine you've got an incommunicado couple and they get separated and they try to find each other without being able to communicate directly. So he might think, well, she likes to hang out in the bookstore, so I'll go find her there. But she might think, well, he likes to hang out in the camera store, so I'll find him there. Then she might think, oh, well, he knows that I like to go to the bookstore, so he won't go to the camera store. He'll try to meet me at the bookstore. Then he'll remember that I know that he likes to go to the camera store, so he won't meet me

the bookstore after all. And this can go on indefinitely. Only, nothing short of common knowledge. In their case, you know, if they managed to have a cell phone call, that would settle it, because blurting something out when you know the other person is listening generates the common. knowledge necessary for that kind of coordination. But it really is something that runs through daily life. I mean, there are examples that you give, just in terms of eye contact that I think are faster. You go for a jog every so often and you talk about how, in some ways, common knowledge keeps you alive when there's a car that's coming towards you. Indeed, yes. If I wanted to cross the street in the middle of the block and a courteous driver will stop and if I can't see him through

the window, I'm still squeamish about actually kind of taking up on his implicit offer because he may not know that I'm planning to cross might get impatient and then might step on the gas. But if you can see him, if you are able to make eye contact. Indeed. Now, here's the thing about eye contact. And I have a whole chapter on nonverbal signals. In particular, eye contact, laughing, blushing, and weeping. Eye contact is the ultimate common knowledge generator 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. So when you make eye contact, you've got common knowledge. It's instant. It's instinctive. It's therefore a potent signal,

not just in humans, but in our primate ancestors, where it's a threat signal. The alpha looks at the beta, who then looks away, which, by the way, also happens in humans. Bosses and supervisors look at employees who then look away. If two primates' stares meet and they look at each other, there's going to be a fight. That means that neither one of them is deferring to the other. My late colleague at Harvard, Irv DeVore, an anthropologist, said on the basis of his research of cultures across the world, if two people anywhere on Earth look into each other's eyes for more than six seconds, then either they're going to have sex or one of them's going to kill the other. Now, that's a bit of an exaggeration, but eye

contact is a potent signal. The reason I say it's an exaggeration is that humans, unlike chimpanzees, flexible in how we use signals, we can kind of mix and match. And for us, eye contact can mean any situation in which we want to make private knowledge common. That is, when you look someone in the eye, what's been implicit, what you've known but hasn't been out there, the game is over. What about blushing? So for blushing, I think that's another common knowledge generator, because the thing about blushing is you feel it for the heat in your cheeks from the inside, at the same time as you know that other people are seeing the reddening from the outside, and what makes a blush so painful is you know that they know that you're

blushing, and they know that you know that you're blushing. And there's nothing you can do about it either. And it's involuntary, and it can be all the worse when someone points it out of this when they say, you're blushing. In fact, if you just say to someone, you're blushing, and they're not blushing, that can make them blush. And blushing is basically an acknowledgement that you have committed some faux pa, you violated some social norm. Or at least you know that other people think you have, whether or not you have. And I think the ultimate point is to acknowledge you and I know what the norms are. I may have screwed up, but I know you think I've screwed up.

That means that you and I are operating under the same rules. I'm not some weirdo. I'm not a psychopath. I'm not a loose cannon. We're operating in the same social system. There aren't a lot of events that bring people together to watch the same thing anymore. The Super Bowl is one of them. It's one of those things where millions and millions of people, not just in the United States, but elsewhere, come together and they'll watch the game, but they'll watch the ads as well.

I want to play an ad that ran in the Super Bowl in 2022. This is an ad for a crypto company features comedian Larry David being very wrong about new inventions throughout history. I call it the wheel I don't think so it's coffee it's new we're putting a man on the moon are you out of your mind

I can't even get tuna without celery nobody's gone to the moon ever he says he's never wrong about these sorts of things I mean whether he was wrong or not is another matter perhaps why that ad during the Super Bowl Why do you think that had worked during the Super Bowl? Yes, as you noted, the Super Bowl is a nationwide, maybe even a global common knowledge generator. Because when you're watching the Super Bowl, you know that other people are watching it.

And you know that they know that other people are watching it. So much hoopla is made over it. That makes it very tempting to advertisers who need to sell products that depend not on the features of the product, but on the fact that everyone is adopting it at the same time. The original example was the introduction of the Macintosh computer by Apple in 1984, where they had the problem that no matter how insanely great the Macintosh was, and it was revolutionary in its time, because those were the days in which people were using PCs that had 24 rows of 80 characters,

and you had to memorize these arbitrary commands. So the idea of a computer with a Windows and icons and menus and a pointing device was truly revolutionary. But the ad that they ran to introduce it, the most expensive ad in the history of television, run only once, directed by Ridley Scott of Blade Runner fame, did not mention the Macintosh computer because that wasn't the point of the ad. The point of the ad was to address people's fears that they might be oddballs if they bought an esoteric new computer and they were the only ones. Where would you get consumables? Would the price ever come down? And so they had to convey the knowledge that everyone is going to be buying this, not just you. And so they advertised it on the Super Bowl, riffing off the fact that it was 1984, the title of Orwell's dystopian novel, where there was a woman who invades a corporate meeting, throws a mallet at a screen, which then explodes, and the crawl introduces the Macintosh.

Again, saying nothing about the Macintosh. Now, when it came to crypto, there's another kind of network effect. if you want another case in which the product depended on common knowledge. Most people who bought crypto don't buy it because they want to buy drugs or weapons or whatever people buy crypto for. They bought it as a speculative investment. That is, they thought that if they bought it today, they could sell it at a profit tomorrow to people who are willing to pay more.

Why would those people pay more tomorrow? Because, well, they're hoping to sell it to someone else at an even bigger profit the day after tomorrow. A greater fool, as they say, in the investment world. world. And so the crypto exchanges had to gin up the common expectation that everyone is buying crypto. Well, if the whole country is going to be buying it, I better buy mine now so I can sell it to them when there's a greater demand. What happens with the crypto exchange when, I mean, this is, this was for FTX. Sam back in free, ends up in prison. And it turns out that maybe the common knowledge was wrong, or at the very least what we believed in, a lot of people

but it wasn't getting hold water. Larry David was right. I don't think so. Although, I mean, at least that's the way it panned out in the first few months after the ad. Ironically enough, because FDX was the crypto exchange founded by Sam Bankman-Fried, who then went to jail for fraud. Crypto in general has recovered since then. So maybe Larry David was wrong. Although, as with any bubble, it expands for as long as it expands.

and then when the market starts running out of greater fools, or when there's common knowledge that the asset itself might be overpriced, then investors run for the exits and you can have a bust and a crash and people can lose their shirts. Chambers Plan employee benefits is not-for-profit, and that's great for your business. Chambers Plan supports businesses with one to 50-plus employees across Canada and reinvest surpluses to help.

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with thoughtful service, destination-focused dining, and cultural enrichment, on board, and on shore. With a variety of voyages and sailing dates to choose from, now is the time to explore Europe's waterways. Learn more at viking.com. Let me play one more thing for you, and this is, in some ways maybe it goes back to the emperor with no clothes on.

This was from the debate in last year's U.S. presidential election, Joe Biden up against Donald Trump. There were questions about Joe Biden, age, whether he was fit to run or not. And then this happened in the debate. Strengthen our health care system, making sure that we're able to make every single solitary person eligible for what I've been able to do with the COVID, excuse me, with dealing with everything we have to do with, look, if we finally beat Medicare. How does that speak to the idea common knowledge and what happened after.

It was painful to listen to again. Yes. So opinion polls showed that prior to that famous televised debate, a majority of Americans, including a majority of Democrats, thought he was too old to run for re-election. Then he turned in that stumbling debate performance. We heard one of the highlights. And the percentage who thought that he was unfit, it crept up by a few percentage points. But the difference was that everyone knew that everyone was watching that.

that debate. Like the Super Bowl, it was a national event. So there was now common knowledge where previously there had just been private knowledge of Biden's infirmity. And again, that changed his stature, his status, his preeminence, and it doomed his candidacy. Do you think he would have been pushed out without that common knowledge coming to the surface? I mean, again, people knew, but nobody said anything in a way that, a bit like the emperor, it took the little boy. Do you know what I mean? It took the little boy, yes. And it took that public forum where everyone knew that everyone else was watching. It's an interesting question of what would have happened in the world in which he chose not to be in that debate.

Probably would have been even more of a disaster. I guess it's the same disaster. You can't really compare them, given the outcome of the election. But every presidential campaignist had debates in the fall. So if he had postponed the first debate to September and presumably turned in the same stumbling performance, there wouldn't have been time even for Kamala Harris to replace. Now, of course, the outcome would have been the same, but I think it would have been even more humiliating debacle. How healthy is the idea of common knowledge right now?

One of the things that you read about in the book is how dictators will try to crush common knowledge. There are forces around the world who want to strip away that idea that everybody knows, everybody knows, everybody knows. Is it under threat, do you think? Well, it always has been. Dictatorships have never allowed people to generate common knowledge through. the media, through speech, through assembly. That's why, almost a criterion for differentiating an autocracy from a democracy is whether you have freedom of speech and freedom of assembly. You might think, why should dictators care about freedom of speech? I mean, they got the guns,

let the people bitch and moan all they want. If they're not happy with the government, there's nothing they can do about it. The thing is, there is something they can do about it if they act together. But the thing is, it's not so easy for the citizens of a country to coordinate if they act separately. If each one of them stands up in protest, the government can pick them off. So the challenge in standing up to government is getting everyone to protest at the same time.

They can do that. There are editorials in the press that say turn up for this demonstration a week from Sunday, but that's exactly what dictatorships don't allow. The Arab Spring succeeded for as long as it succeeded because of this newfangled thing

called social media, which allowed them to evade government censorship. Governments unfortunately catch on, sometimes called the dictator's learning curve, and so they throttle social media. I guess one of the reasons why people might wonder now whether it's under a particular form of threat is that some of the things that we all share our knowledge of seem to be being questioned by those in power. Words like truth and freedom, we think, I know that you know, that I know what truth is, and yet there are forces that are trying to destabilize, that. Does that not put common knowledge under threat? So common knowledge is always relative to some

group of people connected by a network of information sharing. So it can be as small as two people, that's what I contact does, or as large as a nation. In the 20th century, we had an unusual situation where affordable newspapers and then broadcast media could allow there to be common knowledge throughout a country. With the advent first of cable news, news of AM Talk Radio, then at the internet and social media, there's been a kind of fractionation where the pools of common knowledge have been smaller. So you only read the posts from people who think like you and they're the ones who repost what you post. So there may be a fractioning of the common understanding of things like in the United States was the 2020 election stolen.

Some people are just with common knowledge that it was. More technically common belief, because it can't be knowledge if it's false. There's a difference between the two. There is. And most of the time when I speak of common knowledge, technically I'm referring to common belief. Knowledge has to be true for it to count as knowledge. Belief can be anything that people believe, and believe that other people believe that other people believe. Do you believe all knowledge should be common knowledge? Absolutely not. And that's what the final chapter of the book, which is called radical honesty, rational hypocrisy, is about that very question. And in our social lives, there's an awful lot of things that we work hard to keep out of common knowledge. That's why we use euphemism.

Weasel words. Weasel words. That's the name of the chapter, exactly. Because sometimes we might have a relationship that is held up by common knowledge, and we don't want to pollute or challenge the relationship, even if the common knowledge that underlies the relationship is based on a kind of fiction. And that's when we use politeness and, benevolent hypocrisy and white lies, even if it doesn't fool anyone, there's still the possibility

that the other person doesn't know you know and the relationship can survive. So I give the example of a bribe. Let's say you're trying to bribe your way into a restaurant. You don't have a reservation. It's a 45-minute wait. You want to jump the queue by slipping a $20 bill to the matri-D. You probably wouldn't say, if I gave you $20, would you seat me immediately? Say what they say is things like, gee, I was wondering if you might have a cancellation. or is there any way to short my weight? All the while holding out the bill, crucially in peripheral vision,

not actually looking at it. Or a sexual come-on, the classic come-on, which I'd come up and see my etchings. Nobody wants to go up and see your etchings. Well, maybe they're wonderful, but everybody knows what you're talking about. Well, and now it's been,

which I'd like to come up for Netflix and Chill. Or, you know, I've been to a bunch of fundraising dinners for my university, and the dean never says, look, we know why we're all here. We want you to give $50 million and in exchange, you'll get your name on a building. Now, at some point, that conversation has to take place.

But there's always a lead-up where they use weasel words like, we're counting on you to show leadership in our campaign for the future. You've been such a good friend to the university. What happens if somebody just blurts it out, if we don't use the weasel words? I mean, you say that gentle circumlocation makes social life possible, Yes. If you blurt it out, then you get the emotion called awkwardness. If it is seen as an accidental faux pa, if it's seen as tuberase, then you get outrage. And that's because our social relationships, they're held by different kinds of common knowledge, depending on what the relationship is. And they're kind of regulated by the desire to avoid this emotion that we call awkwardness, which consists of applying the rules of one relationship to another. So in the case of the major D, you're applying the mindset of a transactional relationship, quid pro quo, which is, of course, perfectly fine if you're in a store and you're buying a candy bar,

but that's not what a matre d is all about. He is in a position of authority. It's his domain, and he decides who gets seated, and that's why it's insulting to treat him as a mere sales clerk. It's just fascinating how much of this just operates under the hood. This is what you do, is study how we interact, but as social beings, we just follow these cues. It just happens naturally.

That's right. This is what being a social creature consists of, is navigating and negotiating and negotiating what kind of relationship we have. Because your relationship to your spouse is different than your relationship to your boss, which is in turn different from your relationship to your Uber driver and so on. We have different kinds of relationships. I suggest they're basically three fundamental types. There's communality. You share everything. You're in it for each other.

like in families, in friendships. There's authority relationships, dominance hierarchy. There's the alpha, and then there's the rest of the pecking order. And then there are more transactional relationships, quid pro quo, even Stephen. We're really, really sensitive to which one holds. We don't want to behave in a way appropriate

to one relationship type of four and another. And to avoid that, we have all of the rituals of politeness, hypocrisy, euphemism. There are certain comedies that play out what it would be like if one person through a magic spell or a potion can't lie, can't be hypocritical. I think the most famous recent one is a comedy called Liar Liar, starring Jim Carrey. It's fascinating to just think about the things, as I say, that we take for granted in the ways that we interact. Stephen Pinker, thank you very much. Thank you.

Stephen Pinker is a Canadian cognitive psychologist. his new book is when everyone knows that everyone knows common knowledge and the mysteries of money, power, and everyday life. You've been listening to the current podcast. My name is Matt Galloway. Thanks for listening. I'll talk to you soon. For more CBC podcasts, go to cbc.ca slash podcasts.