Why do people speak in innuendo when they're on a date?

Why do dictators try to squelch protests?

Why do we join up with bullies to gang up on an outcast?

Why do humans stand out from the rest of the animal kingdom by blushing and

laughing and crying? And what does any of this have to do with George Costanza or when Harry

met Sally or anonymity on social media or cancel culture or why we generally don't say everything we mean.

Welcome to Intercosmos with me, David Eagleman. I'm a neuroscientist and author at Stanford. And in these

episodes, we sailed deeply into our three-pound universe to understand why and how our lives look the way they do.

This is an I-Heart podcast.

Thank you. This is an I-Heart podcast. Today's episode is about a phenomenon known as common knowledge, which is something that I know and you know and we both know that we know it. Now, this could seem like a very

particular sort of thing to pay attention to, but many psychologists and economists over the past

decades have started to think that a deeper understanding of common knowledge could explain

all kinds of things about human nature and behavior and societies.

And for a very long time, this has grabbed the attention of my friend and colleague,

Stephen Pinker, who just this week has a new book coming out on common knowledge, called

When Everyone Knows That Everyone Knows.

And so I called him up to discuss this topic.

I'll take just a moment to frame this before I begin the interview.

At the heart of the issue is that we are a massively social species.

We form lifelong relationships and we join clubs and we're parts of tribes and we're citizens

of countries and we're parts of tribes and we're citizens of countries.

And we're also a highly intelligent species.

...