Speaker 1: From the brain's point of view, What is humor when
Speaker 1: something is funny? Why do we breathe in and out rapidly?
Speaker 1: Do other animals laugh? Why do most jokes come in threes?
Speaker 1: What do mystery novelists, magicians and comedians have in common?
Speaker 1: And could AI be truly funny? Welcome to Inner Cosmos
Speaker 1: with me and David Eagleman. I'm a neuroscientist and author
Speaker 1: at Stanford and in these episodes we sail deeply into
Speaker 1: our three pound universe to understand why and how our
Speaker 1: lives look the way they do. Today's episode is about humor.
Speaker 1: Although humor is one of the most valued aspects of
Speaker 1: our lives, you've probably heard very little about it from
Speaker 1: the scientific point of view, and that changes today. So
Speaker 1: why do we laugh? After all? It's very strange behavior.
Speaker 1: Imagine that you are a space alien and you are
Speaker 1: studying humans. So through years of study, you note that
Speaker 1: humans seem to have a relatively high bandwidth channel of
Speaker 1: communication by an extraordinarily rapid and precise use of their
Speaker 1: larynx and their vocal cords. They move their tongue and
Speaker 1: their lips very rapidly. They blow air at just the
Speaker 1: right moments, and in this way they have language. They
Speaker 1: communicate to each other at about thirty nine bits per second,
Speaker 1: which is a pretty good transmission rate and way higher
Speaker 1: than any other animal species as far as you the
Speaker 1: alien can tell. But there's something else. These human creatures
Speaker 1: do something that's very strange. Every once in a while,
Speaker 1: they do a much lower frequency, lower bandwidth thing where
Speaker 1: they make a series of rhythmic, involuntary contractions of their diaphragm,
Speaker 1: which causes a sequence of vocalized exhalations, usually a series
Speaker 1: of short repeated vowel sounds like ha or he or ho. Now,
Speaker 1: you notice that this typically begins with some language or
Speaker 1: event that triggers the brain's reward centers and lights up
Speaker 1: something about the emotional networks, and that triggers the activation
Speaker 1: of facial muscles, particularly around the mouth and eyes, And
Speaker 1: often the human's mouth will open up wide and the
Speaker 1: corners of the lips will get drawn back and upward,
Speaker 1: and the respiratory starts doing these rapid cycles of inhalation
Speaker 1: and exhalation, which throws a wrench in the normal breathing patterns,
Speaker 1: and the heart rate increases and the blood pressure rises,
Speaker 1: and the eyes might start to produce tears, and the
Speaker 1: skin around the face might start turning red because of
Speaker 1: the increased blood flow. Sometimes the whole body shakes or quivers,
Speaker 1: especially in the shoulders and torso, and this physical manifestation
Speaker 1: that can spread to the limbs, leading to movements like
Speaker 1: clapping or slapping or bending over. Now, the question you
Speaker 1: ask as the alien is why do they do this
Speaker 1: strange laughing thing? Is there an evolutionary reason behind it?
Speaker 1: Do any other animals on the planet do it? So
Speaker 1: you go back to your alien university to present your findings,
Speaker 1: and the faculty there drills you with questions that you're
Speaker 1: supposed to know the answer to, like why do humans
Speaker 1: go to clubs and movies with the hopes that they
Speaker 1: will trigger a lot of these diaphragm contractions And if
Speaker 1: they get fewer contractions than expected, do they seem disappointed?
Speaker 1: Why do they get together with other humans that they
Speaker 1: trust to stick food in their mouths and hope to
Speaker 1: do these strange diaphragm contractions while eating, even though it's
Speaker 1: dangerous and could cause them to choke on their food.
Speaker 1: So we're going to take this in a few acts. First,
Speaker 1: we're going to address what is humor, And in the
Speaker 1: second act we'll ask why do we laugh? In other words,
Speaker 1: why do we do it out loud instead of silently.
Speaker 1: So let's start with the general notion of comedy about
Speaker 1: something being funny. As it turns out, people have been
Speaker 1: wondering about this for a long time, and the first
Speaker 1: known theories about humor go back to Plato. Now, Plato
Speaker 1: had a very dim view of laughter. He generally saw
Speaker 1: it as something malicious that people do. In his view,
Speaker 1: audiences laugh at people who have ignorance about themselves, who
Speaker 1: imagine themselves to be richer than they are, or better
Speaker 1: looking than they are, or more virtuous than they are,
Speaker 1: and we laugh at them, which he found to be
Speaker 1: a morally objectionable thing to do. Now, his student Aristotle
Speaker 1: appreciated wit in conversation, but he agreed with Plato that
Speaker 1: people laugh at the misfortunes or mistakes of others, which
Speaker 1: reinforces their own sense of self worth and status. Think
Speaker 1: of an audience laughing at a character in a comedy
Speaker 1: who's consistently making foolish mistakes. So this is what's known
Speaker 1: nowadays as superiority theory, and the idea is that comedy
Speaker 1: stems from feelings of being better than other people, and
Speaker 1: no one really challenged this idea that that's what comedy
Speaker 1: was about. Until the mid eighteenth century people started to think,
Speaker 1: wait a minute, you don't really need feelings of superiority
Speaker 1: to laugh at something. Just think of a funny poem
Speaker 1: or pun. And on the flip side, we often feel superior,
Speaker 1: like the way you might feel superior to a horse
Speaker 1: or a squirrel, but that doesn't mean we laugh at them.
Speaker 1: So other theories began to blossom, and now there are
Speaker 1: many theories of humor. One of them, for example, is
Speaker 1: relae theory. This was originally proposed by A Lord Shaftsbury
Speaker 1: in the seventeen fifties, and he suggested the slightly strange
Speaker 1: idea that we laugh to release animal spirits that have
Speaker 1: built up inside us. Now, this doesn't make much sense
Speaker 1: in our modern vocabulary, but later proponents of this idea,
Speaker 1: like Sigmund Freud and Herbert Spencer, they cast this same
Speaker 1: idea in a different light. They said, look, humor is
Speaker 1: a way to release psychological tension or suppressed emotions, like
Speaker 1: think of laughing at a joke that touches on a
Speaker 1: taboo subject. So laughter serves as a release valve for
Speaker 1: pent up energy in your nervous system, and in this view,
Speaker 1: it's a purely physiological issue. And you see this happen
Speaker 1: sometimes when someone laughs at a totally inappropriate moment, like
Speaker 1: someone has died, and the excess energy comes out in
Speaker 1: a way that looks different from what they're feeling internally. Relatedly,
Speaker 1: by the way, Freud also suggested that humor and laughter
Speaker 1: might act as a defense mechanism, and in this way
Speaker 1: it allows people to deal with uncomfortable emotions or social tensions,
Speaker 1: and it can reduce stress and anxiety. But there are
Speaker 1: other ways that people look at humor. One very common
Speaker 1: school of thought looks at humor as a way of
Speaker 1: indicating play. It says, look, play is absolutely essential for
Speaker 1: learning how to do real things in the world. And
Speaker 1: so the idea is that humor engages all this cognitive
Speaker 1: practice and social practice in a playful context. For example,
Speaker 1: look at the way that children engage in silly wordplay
Speaker 1: or crazy imaginative scenarios. That stuff cracks them up. They're playing.
Speaker 1: And there's a closely related way of looking at this too.
Speaker 1: When that evolutionary psychologists like the idea that humor and
Speaker 1: laughter is all about social bonding. Humor is a tool
Speaker 1: for strengthening the bonds within a group. You build cohesion
Speaker 1: this way, you build a sense of community. So just
Speaker 1: think about inside jokes that you do with your friends
Speaker 1: that reinforce your group identity and your camaraderie. And I
Speaker 1: think that the slang that each generation introduces is a
Speaker 1: form of the same thing, making sure that the adults
Speaker 1: are on the outside and you and your pals are
Speaker 1: on the inside. It's a way of bonding. Now, the
Speaker 1: ideas about humor don't end there. Other thinkers like Marvin
Speaker 1: Minsky and Jerry Saul's focus on a different aspect of humor,
Speaker 1: the cognitive aspect. They care about the mental processes involved
Speaker 1: in understanding and appreciating comedy. So they're looking at the
Speaker 1: cognitive effort required to understand some cognitive play on words.
Speaker 1: So take a joke like this today. I found a
Speaker 1: book with the title how to Solve fifty of Life's Problems,
Speaker 1: So I bought two of them. So the last sentence
Speaker 1: comes as a surprise, and the brain goes back and
Speaker 1: tries to reinterpret what it heard. There's a puzzle in there.
Speaker 1: Which forces you to reshape your interpretation, or specifically, your
Speaker 1: interpretation of the speaker's interpretation. And then it falls into
Speaker 1: place that there's another way to see this, and it
Speaker 1: strikes us as funny because it's both nonsensical and a
Speaker 1: little bit sensical. And some other theories zoom in even
Speaker 1: more on the types of humor that have to do
Speaker 1: with linguistics, in other words, about the structure and use
Speaker 1: of language, like wordplay or jokes that rely on double
Speaker 1: meanings like I'm addicted to break fluid, but it's okay
Speaker 1: because I can stop at any time, or jokes that
Speaker 1: rely on homophones, like a photon checks into a hotel,
Speaker 1: the front desk asks if it has any luggage and
Speaker 1: it says, no, Oh, I'm traveling light. So the punchline
Speaker 1: is a phrase that can be reinterpreted and has two
Speaker 1: meanings that surprisingly fit. Now, fundamentally, your brain is always
Speaker 1: trying to squeeze the complexity of the world down to
Speaker 1: a single interpretation. And something about the back and forth
Speaker 1: here between two interpretations that can both work makes something funny.
Speaker 1: Or take a kid's joke like why aren't lobsters generous
Speaker 1: because they're shellfish? This relies on two sounds that are
Speaker 1: almost the same, so your brain entertains them both and
Speaker 1: finds humor in the surprise that they both work. So
Speaker 1: I've told you about two thousand years of people making
Speaker 1: theories about humor. It's about superiority, it's about releasing tension,
Speaker 1: it's about play, it's about social bonding or linguistics or
Speaker 1: so on. And the thing to appreciate here is that
Speaker 1: these aren't mutually exclusive. Each of these theories has something
Speaker 1: to say about some element of humor, provide a different lens.
Speaker 1: And what this proliferation of theories really highlights is the
Speaker 1: multifaceted nature of humor and all the processes cognitive and
Speaker 1: emotional and social involved in finding something funny. So if
Speaker 1: you are that space alien, you'd find there's not just
Speaker 1: one single answer for your colleagues who are peppering you
Speaker 1: with questions and trying to understand earth humor. Instead, you'd
Speaker 1: have to come to the conclusion that there are many
Speaker 1: angles to this strange behavior. But we haven't even gotten
Speaker 1: to the best angle yet. I want to zoom in
Speaker 1: on one theory in particular that I think sits right
Speaker 1: at the center of much of comedy, and that has
Speaker 1: to do with the violation of expectation. The engine of
Speaker 1: most jokes involves setting up an expectation and then breaking it. Now,
Speaker 1: why does that work. It's because the brain is constantly
Speaker 1: predicting what it thinks is likely to happen, and in
Speaker 1: certain circumstances, when the next steps seem clear, but then
Speaker 1: they're suddenly violated, that's often funny. So this theory of
Speaker 1: humor is called incongruity theory, and the school of thought
Speaker 1: is favored by philosophers like Emmanuel Kant and Arthur Schopenhauer,
Speaker 1: and it suggests that humor arises when there's a discrepancy
Speaker 1: between what you think is about to happen and what
Speaker 1: actually happens. So let's take an example. I saw a
Speaker 1: post on social media yesterday that read, my husband and
Speaker 1: I have reached the difficult decision that we do not
Speaker 1: want children. If anybody does, send me your contact details
Speaker 1: and we can drop them off tomorrow. So your brain
Speaker 1: starts off with a particular understanding and then that's tripped up.
Speaker 1: Or here's another example. My dog used to chase people
Speaker 1: on bikes a lot. It got so bad that I
Speaker 1: finally had to take his bike away. Now, jokes like
Speaker 1: this work in part because language is so low bandwidth.
Speaker 1: When you hear the sentence, you're making lots of assumptions
Speaker 1: unconsciously under the hood without ever realizing it. Another example
Speaker 1: is the way that we predict words ahead of hearing
Speaker 1: them again without even realizing it. So any comedy can
Speaker 1: take advantage of that. So I can tell you last
Speaker 1: month I got diagnosed as being colorblind. That really came
Speaker 1: out of the orange. Now there's only a surprise there
Speaker 1: because your brain was predicting what it thought was going
Speaker 1: to come next. And this is the reason so many
Speaker 1: jokes are structured in patterns of threes. The first guy
Speaker 1: does something, and then the second guy establishes the pattern.
Speaker 1: Then your brain has a clear prediction for what the
Speaker 1: third guy is going to do, and the comedy comes
Speaker 1: when he breaks that pattern. So a structure of three
Speaker 1: is the fastest possible path to setting an expectation and
Speaker 1: then swerving off that road. And by the way, this
Speaker 1: issue about the brain setting expectations, this is something that
Speaker 1: you can start seeing in the first few months of life,
Speaker 1: even well before infants have language. You can study this,
Speaker 1: and that's because when an infant is surprised by something,
Speaker 1: they'll pay more attention to it. So, for example, you
Speaker 1: put a teddy bear behind a screen, and then you
Speaker 1: remove the screen and now there's a rabbit there. Even
Speaker 1: a very young infant will stare and stare at that,
Speaker 1: indicating that even though they can't speak to you yet,
Speaker 1: their brain had set up in expectation and the rabbit
Speaker 1: doesn't match it. One way that we know that comedy
Speaker 1: is about breaking expectations is because comedy has to surprise.
Speaker 1: Imagine that you're at a dinner party and the guy
Speaker 1: across from you tells a good joke and everybody laughs,
Speaker 1: and then he tells exactly the same joke a second time.
Speaker 1: It would be zero funny. The second time everyone would
Speaker 1: look at one another. So what does that tell us?
Speaker 1: That something funny has to surprise. So what we've seen
Speaker 1: so far is that humor has to betray your expectations.
Speaker 1: But I've left something out so far. There's another element
Speaker 1: to something being funny, because we quite often find that
Speaker 1: our expectations don't get fulfilled, and almost all of these
Speaker 1: situations aren't actually funny. Imagine you open your suitcase and
Speaker 1: you realize that you grabbed the wrong one at the airport.
Speaker 1: That would be surprising, Or an airplane engine suddenly falls
Speaker 1: onto the roof of your car. That would certainly violate
Speaker 1: your expectations, but it wouldn't be funny at all. So
Speaker 1: comedy requires a second element. It requires a sense of harmlessness.
Speaker 1: If some event or some punchline triggers fear or anxiety
Speaker 1: or disgust or whatever instead of amusement, it's not funny.
Speaker 1: Humor requires a very delicate balance of unexpected and harmless.
Speaker 1: And by the way, I should specify that this means
Speaker 1: a sense of harmlessness for the listener. There can be
Speaker 1: cruel jokes against other groups of people, out groups, and
Speaker 1: the jokes can involve bad things happening to them, But
Speaker 1: the idea is that the listener doesn't feel threatened. So
Speaker 1: if you are the space alien and you are being
Speaker 1: quizzed about what is required for human comedy, that's the
Speaker 1: main thing. It has to surprise and it has to
Speaker 1: not threaten the listener. And we'll come back to this
Speaker 1: in a few minutes, but first I want to mention
Speaker 1: that I was thinking about this harmlessness issue the other
Speaker 1: day and I realized this is consistent with something that
Speaker 1: I read from Woody Allen many years ago. He said,
Speaker 1: comedy equals tragedy plus time. In other words, events that
Speaker 1: are pain full or upsetting can over time become sources
Speaker 1: of humor. The time gives some emotional distance, so when
Speaker 1: something tragic first occurs, the emotions around it, like the
Speaker 1: grief and the anger and the shock, they're too raw
Speaker 1: for people to find anything funny about the situation. But
Speaker 1: as time passes, emotions tend to soften, the pain goes down,
Speaker 1: and people can look back on an event with a
Speaker 1: different mindset, and sometimes they see absurdities or ironies that
Speaker 1: weren't apparent before. So you and your partner lose your
Speaker 1: tempers about something because you said X and your partner
Speaker 1: thought you meant why, and you're both furious. But six
Speaker 1: months later you both love telling the story and you
Speaker 1: get comic value from it each time. And, by the way,
Speaker 1: comedians use this all the time to craft new material.
Speaker 1: The idea is that with just the right amount of time,
Speaker 1: this sting of some tragic event can fade enough that
Speaker 1: people can laugh at it without guilty or uncomfortable. But
Speaker 1: the time component is crucial because the comedian has to
Speaker 1: be sure that the audience is ready to find humor
Speaker 1: in the tragedy. In any case, time works because sometimes
Speaker 1: we have a perspective shift, we've changed how we collectively
Speaker 1: interpret the event, and sometimes it's just a coping mechanism.
Speaker 1: But in any case, this comes back to the point
Speaker 1: that humor can't be something that is directly threatening to
Speaker 1: us right now, So let's return to incongruity theory, which
Speaker 1: is that something funny has to violate your expectations. Now
Speaker 1: that's how this is thought about by philosophers. But now
Speaker 1: that neuroscience is on the scene, I think there's an
Speaker 1: even richer way to think about this. And this is
Speaker 1: something you hear me talk about on almost every episode.
Speaker 1: This is the issue of the internal model. So in
Speaker 1: the darkness of your skull, you have a model of
Speaker 1: what the world is and how it's working, and this
Speaker 1: is what gives you an understanding of what's going on
Speaker 1: out there, and it gives you your pre So imagine
Speaker 1: you hear a comedian tell his story. The comedian says,
Speaker 1: so I walked into the doctor's office and the doctor
Speaker 1: says to me, take off your clothes and put them
Speaker 1: there in the corner. Next to mine. Now, what the
Speaker 1: comedian's doing here is taking advantage of the assumptions of
Speaker 1: your internal model, the thoughts that went unthunk, even though
Speaker 1: they certainly could have been true that the doctor was naked,
Speaker 1: but they were never even considered until you were told
Speaker 1: that information, and then you have to retrospectively revise your
Speaker 1: whole model of that situation. Or take the joke I
Speaker 1: mentioned earlier about how my dog used to chase people
Speaker 1: on bikes a lot. Linguistically, this could have been interpreted
Speaker 1: by your brain as the dog riding the bike, and
Speaker 1: possibly some neurons in your brain entertain that relationship for
Speaker 1: a fraction of a second, but then they dismiss it,
Speaker 1: and so that unconscious possibility never even gets close to
Speaker 1: your consciousness until you suddenly have to do a wholesale
Speaker 1: go back to the beginning and re understand the whole situation.
Speaker 1: And by the way, while we're talking about subverting expectations,
Speaker 1: this is not just used by comedians, but also by
Speaker 1: mystery novelists and magicians. They all have something in common.
Speaker 1: They rely on surprising your internal model to entertain. So
Speaker 1: for the mystery novelists, it's the plot twist They set
Speaker 1: everything up for you, and if they're doing their job right,
Speaker 1: they know that all these clues can be scattered around you.
Speaker 1: But right now you think a particular model of the
Speaker 1: world is true, and then they surprise you by showing aha,
Speaker 1: all these things you saw are consistent with a different
Speaker 1: structure than the one you assumed, and with the magician,
Speaker 1: it's the same thing. They move their hands, they show
Speaker 1: you this, they draw your attention to that, and all
Speaker 1: along they are making sure that you believe a particular
Speaker 1: model of the world. They need you to believe that
Speaker 1: everything is operating one way, and then they violate your expectation.
Speaker 1: They flout your brain's predictions and leave you reveling in
Speaker 1: the mystery that one thing seemed true, but you're now
Speaker 1: looking at a different situation. And if you were that
Speaker 1: space alien trying to figure out humans, you'd probably notice
Speaker 1: that we spend a lot of our time flocking to
Speaker 1: mystery novelists and magicians and comedians. You would fly back
Speaker 1: to your planet and try to explain to your alien
Speaker 1: colleagues that humans continuously pay money to have these professionals
Speaker 1: give us some sort of story and then subvert our expectations.
Speaker 1: So why do we find this appealing. One possibility is that,
Speaker 1: as we're always trying to build a model of the world,
Speaker 1: we derive pleasure from the discovery of a flaw in
Speaker 1: our model. In other words, we are machines built to
Speaker 1: self correct, and it is rewarding to find an error
Speaker 1: and fix it. So part of the joy of humor
Speaker 1: is the feeling that you had a model and now
Speaker 1: you have a better one, a model that has more
Speaker 1: explanatory power. So in the three guys walk into a
Speaker 1: bar joke, the first guy sets an example, the second
Speaker 1: guy gets your internal model to believe that it understands
Speaker 1: a pattern, and then the third guy reveals there's a
Speaker 1: different way, a broader way that you could have understood
Speaker 1: the whole premise, I suggest we find it rewarding to
Speaker 1: change the internal model, and this is what solving riddles
Speaker 1: is about, or why people listen to science podcasts. There
Speaker 1: is some pleasure derived from the realization that your model
Speaker 1: was incomplete and now you see things with a broader
Speaker 1: view than you were able to just a moment ago.
Speaker 1: At its heart, I suggest that comedy is all about
Speaker 1: thinking that you have the world understood and then finding
Speaker 1: you didn't and you now have of a bigger model,
Speaker 1: and again when the change is harmless, not threatening, then
Speaker 1: we find it funny. Now, I want to take a
Speaker 1: one minute tangent here to tackle a question that I've
Speaker 1: been wondering about for a while. Can artificial intelligence be funny?
Speaker 1: And the answer to this, I think is very illuminating.
Speaker 1: On the one hand, AI can sometimes be hilarious and
Speaker 1: tell you great jokes, but this is because it is
Speaker 1: repeating or modifying a joke that has been said somewhere
Speaker 1: in the vast corpus of human writing, even if you've
Speaker 1: never heard it. A couple of episodes ago, I named
Speaker 1: this the intelligence echo illusion, by which I simply mean
Speaker 1: that we often mistake the echo of things that other
Speaker 1: people have said before for intelligence in AI, or in
Speaker 1: this case, for true comedy in AI. But it's nothing
Speaker 1: but repeat in any case. Although AI can repeat a
Speaker 1: good joke, what AI stinks at is making up an
Speaker 1: entirely new joke. I did some experiment to drill down
Speaker 1: on this. It's not because AI can't figure out what
Speaker 1: people expect next and then shift away from that. Instead,
Speaker 1: it's because a good joke has to replace the expectation
Speaker 1: with an alternative that also makes sense with a new frame.
Speaker 1: The punchline can't just be unexpected. Instead, it has to
Speaker 1: be cleverly engineered to have some second meaning, a second interpretation.
Speaker 1: So I'll give you an example that I just ran
Speaker 1: this morning. I didn't want chat gpt to tell me
Speaker 1: a joke i'd heard before, so I forced it to
Speaker 1: make up something new by prompting it to tell me
Speaker 1: a joke about lobsters and peanut butter. So here's what
Speaker 1: it came up with.
Speaker 2: Three lobsters walk into a grocery store. The first lobster
Speaker 2: goes to the seafood section and asks for butter. The
Speaker 2: grocer gives him a tub of butter, and he happily
Speaker 2: scuttles away. The second lobster goes to the same section
Speaker 2: and asks for butter. The grocer gives him a tub
Speaker 2: of butter, and he too happily scuttles away. The third
Speaker 2: goes to the grocery stores pantry section and asks for
Speaker 2: peanut butter. The grocer looks surprised and asks why peanut butter.
Speaker 2: Aren't you going to cook with butter like the other lobsters.
Speaker 2: The third lobster replies, Nah, I'm allergic to butter, I
Speaker 2: always shell out for peanut butter instead.
Speaker 1: What now, I would call that the dumbest joke I've
Speaker 1: ever heard, But it doesn't even qualify as a joke.
Speaker 1: Why because the punchline, while it is a violation of expectation,
Speaker 1: doesn't offer a second interpretation that makes sense. So crafting
Speaker 1: a joke, at least for the moment, seems to be
Speaker 1: beyond the scope of large language models. They have no
Speaker 1: problem understanding that the structure of joke requires violating expectation,
Speaker 1: but they have no idea how to violate it. They
Speaker 1: don't know how to construct something that makes sense on
Speaker 1: two levels at the same time, which appears to be
Speaker 1: a requirement of humor. Now, let's return to the question
Speaker 1: that the space al asked at the beginning. Maybe it
Speaker 1: now understands why violations of expectation amuse humans as long
Speaker 1: as those violations are harmless. But why do humans engage
Speaker 1: in this very loud monkey call that they label laughter?
Speaker 1: And this is a good question because the alien notices
Speaker 1: that when you're having other emotions, you typically just experience
Speaker 1: them internally. When you're feeling shy, you don't do a
Speaker 1: high pitched yell when you're feeling morose. You don't sing
Speaker 1: and clap when you eat something and you find it delicious.
Speaker 1: You don't stand up in the restaurant and scream so
Speaker 1: that all the other diners know it. You simply experience
Speaker 1: emotions on the inside. So when we find something funny,
Speaker 1: why does that physically trigger these high amplitude, low frequency vocalizations.
Speaker 1: Why does your diaphragm contract over and over causing these
Speaker 1: rapid exhalations which cause your vocal cords to rapidly open
Speaker 1: and close create a loud sounds. Now, this is strange.
Speaker 1: Right to appreciate this, ask yourself a different kind of question.
Speaker 1: Why don't humans have the equivalent of a comedy club
Speaker 1: in the domain of beautiful art. Imagine you sit down
Speaker 1: at a museum with a lot of other people, and
Speaker 1: the mc brings out a wonderful painting for everyone to
Speaker 1: stare at, and then wheels out a beautiful statue, let's say,
Speaker 1: carved by Michaelangelo, and so on. You can't really imagine
Speaker 1: that you'd get a bunch of people physically making weird
Speaker 1: rhythmic sounds and filling the hall with noise. Instead, people
Speaker 1: go to museums and they quietly walk around and they're
Speaker 1: filled with a sense of beauty. But it's a private,
Speaker 1: quiet experience. So the question is why is laughter different?
Speaker 1: So in trying to understand this, one can ask the
Speaker 1: question of who else laughs? As in what other species?
Speaker 1: When we think about humans in relation to other species,
Speaker 1: we see that other species are collaborative and seem to
Speaker 1: have emotions like pain and hunger. But are they laughing?
Speaker 1: And the surprising answer is it appears some other animals
Speaker 1: do laugh, or at least they do things that are
Speaker 1: very similar to human laughter. For example, our primate friends,
Speaker 1: the chimpanzees and bonobo's and gorillas and orangutans make these
Speaker 1: vocalizations during play, and it seems to resemble the way
Speaker 1: that humans laugh. These sounds tend to be softer and
Speaker 1: more rhythmic compared to human laughter, but it appears to
Speaker 1: serve a similar function in social interactions. So here is
Speaker 1: an adolescent gorilla making these sounds when the zookeeper tickles
Speaker 1: his foot through the bars. A link the video on
Speaker 1: the show notes, and you can see the gorilla pulls
Speaker 1: his foot away when it tickles, but then he presents
Speaker 1: it again to be tickled. Another time, so you can
Speaker 1: hear these sounds during physical play like tickling or chasing,
Speaker 1: and the hypothesis is that it signals that the interaction
Speaker 1: is playful rather than aggressive. Almost all animals play because
Speaker 1: it helps them figure out how to get along with
Speaker 1: others and how to build skills that they're gonna need later,
Speaker 1: and so laughter is a broadcast signal to the others
Speaker 1: to say, this is not actually serious. This is play.
Speaker 1: In other words, I'm not actually trying to hurt you,
Speaker 1: and even though we're being physical and wrestling or whatever,
Speaker 1: I'm just trying to figure out what I will need
Speaker 1: later in life. And it's not just primates. You can
Speaker 1: also hear laughter in rats. They do this ultrasonic chirping
Speaker 1: at fifty killer hurts. This is really high frequency, so
Speaker 1: you can't hear this with your ears, but this can
Speaker 1: be measured with a microphone and then transferred to our
Speaker 1: range so we can hear it. And rat laughter sounds
Speaker 1: like this, And it turns out that rats do this
Speaker 1: when they play with each other and also when they
Speaker 1: are being tickled by humans. This seems to be a
Speaker 1: form of laughter, and it's associated with positive emotions and
Speaker 1: social bonding and By the way, rats that chirp more
Speaker 1: frequently tend to be more playful and sociable. And it's
Speaker 1: not just rats, but dogs also. They do something called
Speaker 1: play panting when they're doing social play, and some researchers
Speaker 1: think that this is like laughter. The dogs pant with
Speaker 1: this rhythmic, breathy sound, and they do this during playful interactions.
Speaker 1: But it's not because they're out of breath. It's that
Speaker 1: the signals to other dogs that their behavior is friendly
Speaker 1: and non threatening. And you know where else you find
Speaker 1: these physiologic signals that are like laughter dolphins. Dolphins do
Speaker 1: all kinds of vocalizations like whistles and clicks, and these
Speaker 1: seem to serve a similar function to laughter in terms
Speaker 1: of reinforcing social bonds and communication about what is the
Speaker 1: threat and what is not. So the latest estimate is
Speaker 1: that there are at least sixty five animal species who
Speaker 1: seem to laugh. And if you are the alien scientist,
Speaker 1: this is a really important clue. Essentially, in all these
Speaker 1: cases you detect the same general story that these laughter
Speaker 1: like sounds are employed to indicate that the behaviors are playful,
Speaker 1: they're not aggressive. In other words, I'm biting you, but
Speaker 1: I'm not really trying to hurt you. And across species
Speaker 1: you find that these laughter signals are used to strengthen
Speaker 1: social bonds and bring the group closer together. Okay, but
Speaker 1: the exact nature of laughter and animals may still be
Speaker 1: a little bit different from humans because we have our
Speaker 1: own evolutionary pathway. So why do we laugh while like
Speaker 1: our animal brethren, we laugh to indicate play, to tell
Speaker 1: the other this is not serious, and in humans this
Speaker 1: grows more subtle. We have more nuanced situations. So in
Speaker 1: human societies, if someone makes a social mistake, or someone
Speaker 1: finds themselves uncomfortable or risks someone else's standing, laughter is
Speaker 1: a broadcast signal to say, this is play, don't worry
Speaker 1: about it. And there's another suggestion too, made by my
Speaker 1: colleague Vs. Rahma Chandren in ninety eight, and he suggested
Speaker 1: that laughter is a way of alerting those around you
Speaker 1: that there's something dangerous, but it's no longer a threat. Essentially,
Speaker 1: laughter is like a monkey call that tells everyone else
Speaker 1: things are fine. It carries information that there has been
Speaker 1: a false alarm. So you see the man's ladder fall
Speaker 1: backwards and he lands on a haystack, and everyone needs
Speaker 1: to be alerted that he's okay, So you send out
Speaker 1: this call. If he hit rocks, nobody would laugh. On
Speaker 1: this note, I'll just mention I have a sort of
Speaker 1: painful memory from when I was ten years old and
Speaker 1: I was in a martial arts class and the instructor
Speaker 1: picked up a dumbbell with several plates on it, and
Speaker 1: he didn't realize that there wasn't a cuff on the end,
Speaker 1: and all the plates slipped off and almost landed on
Speaker 1: his foot but missed, and I laughed, and I got
Speaker 1: in trouble for it, and everyone thought it was deeply inappropriate.
Speaker 1: And the important part is that I felt terrible because
Speaker 1: I didn't find it funny. So I had no idea
Speaker 1: why that had come out of my mouth. But later
Speaker 1: I came to understand that laughter is an alerting system,
Speaker 1: and that gave me some insight into what had happened.
Speaker 1: I saw the plates slipping off, and I felt terrified,
Speaker 1: and then I saw that they all missed his foot
Speaker 1: by a few inches, and I was alerting the rest
Speaker 1: of the tribe that things were okay. I didn't expect
Speaker 1: people to laugh with me. I was simply communicating that
Speaker 1: things were not scary like we all thought for just
Speaker 1: a moment that they were about to be. Now, there
Speaker 1: are physical benefits to laughter. This may be true in
Speaker 1: animals too, but we really get this as humans. Laughter
Speaker 1: triggers the release of endorphins, which are natural painkillers and
Speaker 1: mood enhancers. So laughter reduces the perception of pain, improves
Speaker 1: overall pain tolerance, and it can improve mood. And it
Speaker 1: also improves immune function by increasing the production of antibodies
Speaker 1: and activating immune cells. And generally people find that it
Speaker 1: reduces the level of stress hormones like cortisol and adrenaline.
Speaker 1: So there are all kinds of cool things that laughter
Speaker 1: can do. But what I want to return to is
Speaker 1: the social aspect of it. And one of the things
Speaker 1: that's hard to miss is how laughter can be contagious.
Speaker 1: For example, go to YouTube to find a video of
Speaker 1: parrots laughing. They're just impersonating their human owners, but it
Speaker 1: is impossible to watch those videos and not laugh yourself.
Speaker 1: As I mentioned before, there are other weird cases where
Speaker 1: people laugh when they shouldn't, like when they hear some
Speaker 1: terrible news, because they just have too much emotion. Weirdly,
Speaker 1: this often has the property of becoming contagious. So someone
Speaker 1: hears something terrible and can't stop laughing, not because they
Speaker 1: believe it's funny, but because they have so much emotion
Speaker 1: that needs release. And what often happens is that the
Speaker 1: other people are horrified at first, but then they start
Speaker 1: laughing too, because it's very hard to help it. In fact,
Speaker 1: something I find fascinating is an expression that comedians say
Speaker 1: in private, which is that a comedian's two best friends
Speaker 1: are alcohol and density. Now the alcohol is obvious, but
Speaker 1: the density is worth unpacking. Comedians have always noted that
Speaker 1: if they get up to perform in front of a
Speaker 1: crowd of people who are spread out around the club,
Speaker 1: the exact same jokes aren't gonna go so well. They're
Speaker 1: not going to trigger the same laughter as they would
Speaker 1: if everyone was bunched up closely together. Why Because laughter
Speaker 1: spreads contagiously as long as everyone is sitting tightly packed.
Speaker 1: It's essentially impossible for someone to sit in the middle
Speaker 1: of a laughing crowd and not laugh themselves. Now again,
Speaker 1: evolutionary theorists argue that contagious laughter is a mechanism to
Speaker 1: foster a sense of unity in a group and that
Speaker 1: could help group survival. I'm not sure about the strength
Speaker 1: of that argument, because there are lots of ways that
Speaker 1: groups bond. Just look at something like fighting together. Look
Speaker 1: at the Spartans. They were tightly knit because they fought
Speaker 1: side by side and defended each other's lives. But I
Speaker 1: was thinking about this last night and it struck me
Speaker 1: that we don't really know if the Spartans were funny
Speaker 1: or not because they were such famous fighters. Maybe they
Speaker 1: were hilarious when they were sitting around the camp and
Speaker 1: eating dinner, and that's what caused the bonding. We just
Speaker 1: don't know. But the general are argument is that contagious
Speaker 1: laughter strengthens group cohesion. And by the way, there are
Speaker 1: other social aspects to laughter beyond contagion. One thing I
Speaker 1: find fascinating is laughter within hierarchies, where the person at
Speaker 1: the top laughs the loudest. The king and the plebeians
Speaker 1: don't laugh in the same way. You can see this
Speaker 1: clearly in very hierarchically structured cultures where laughter is used
Speaker 1: as a way to show deference or respect to authority figures,
Speaker 1: for example, laughing softly when superior makes a joke, even
Speaker 1: if it's not particularly funny as a way to show agreement.
Speaker 1: And this is actually a good segue because I've told
Speaker 1: you that when we look across the animal kingdom, we
Speaker 1: see there are several plausible evolutionary stories for thinking about laughter.
Speaker 1: But it's also worth noting that within the human species,
Speaker 1: there are several cultural variations the way that laughter is
Speaker 1: expressed and interpreted and used. It's not the same everywhere.
Speaker 1: For example, in Western cultures, laughter is generally associated with
Speaker 1: humor and used to express enjoyment or amusement or sarcasm.
Speaker 1: But in East Asian cultures, laughter is not only a
Speaker 1: response to humor but also a tool for managing social harmony.
Speaker 1: For example, in Japan, people might laugh softly or politely,
Speaker 1: even in awkward or uncomfortable situations, as a way to
Speaker 1: diffuse tension or to avoid conflict. And in Mediterranean cultures
Speaker 1: like in Italy and Greece, laughter tends to be more
Speaker 1: exuberant and loud, and it often accompanies animated conversations and
Speaker 1: it's seen as a sign of enthusiasm and engagement, Whereas
Speaker 1: in Scandinavian cultures like Sweden and Norway, laughter tends to
Speaker 1: be more subdued and controlled and loud laughter can be
Speaker 1: perceived as inappropriate, and there are gender differences. In some
Speaker 1: Middle Eastern cultures, men and women are expected to laugh differently.
Speaker 1: Women are typically expected to laugh more softly or modestly
Speaker 1: in public, whereas men are free to laugh loudly. In
Speaker 1: Western societies, while there are no strict rules, studies show
Speaker 1: that women tend to laugh more frequently than men at
Speaker 1: social settings, often as a way of facilitating social interaction,
Speaker 1: and by the way, the responses to laughter can also
Speaker 1: be different. Just as an example, in Eastern European cultures
Speaker 1: like Russia, laughter informal or serious contexts is viewed as
Speaker 1: inappropriate and with suspicion, and what's done instead of laughter
Speaker 1: is a quick or reserved smile, especially in professional settings.
Speaker 1: But contrast this with Latin American cultures, where laughter is
Speaker 1: generally more freely expressed and is a key part of
Speaker 1: social interactions. People laugh easily in everyday conversations and they
Speaker 1: use it as a way to express warmth and friendliness.
Speaker 1: So laughter is a common human experience, but it does
Speaker 1: get molded a bit by cultural norms and values. Let's
Speaker 1: wrap up today's podcast. If you are the space Alien
Speaker 1: and you have to go home to explain to your
Speaker 1: colleagues what human laughter is about. You're going to find
Speaker 1: there's not just one answer why, because there are many
Speaker 1: different flavors of humor, from laughing at someone to laughing
Speaker 1: with someone, to laughing at clever wordplay with two meanings.
Speaker 1: And there's the kind of laughter where you are appreciating
Speaker 1: masterful violation of expectation. And physically, there are different kinds
Speaker 1: of laughter. Some humans have a quick contraction of the
Speaker 1: diaphragm and they make a snort, or you might find
Speaker 1: the unrestrained burst of laughter that we call a guffaw
Speaker 1: fully engaging the respiratory muscles. Or you might hear the
Speaker 1: puckish glee of a cackle, which is sharp and high pitched,
Speaker 1: with rapid, irregular exhalations from the lungs. Or you might
Speaker 1: spot the contentment of a chuckle, which is low pitched
Speaker 1: and sustained, involving rhythmic contractions of the diaphragm and the
Speaker 1: soft vocalizations. Or you might catch the slyness of a snicker,
Speaker 1: or the innocence of a high pitched giggle, or the
Speaker 1: thunderous roll of a belly laugh that deep, full bodied
Speaker 1: contraction of the abdominal muscles. So if you're the space alien,
Speaker 1: you'd have to conclude that humans seem to laugh for
Speaker 1: a variety of reasons in a variety of ways, and
Speaker 1: it's not as low bandwidth as you thought. In different circumstances,
Speaker 1: it can signal play, it can strengthen social bonds, it
Speaker 1: can reduce tensions, it can give emotional release, and it
Speaker 1: can communicate. It can nonverbally broadcast amusement or agreement or
Speaker 1: discomfort or false alarms. So while the alien and its
Speaker 1: compatriots might be confused, we don't care because we love
Speaker 1: to laugh. We have millions of years and billions of
Speaker 1: neurons behind it, all pushing us towards mirth. Until next time,
Speaker 1: may your neural path ways continue to be tickled. Go
Speaker 1: to Eagleman dot com slash podcast for more information and
Speaker 1: to find lots of reading about the science of humor.
Speaker 1: Send me an email at podcast at eagleman dot com
Speaker 1: with questions or discussion and check out. Subscribe to Inner
Speaker 1: Cosmos on YouTube for videos of each episode and to
Speaker 1: leave comments. Until next time. I'm David Eagleman, and this
Speaker 1: is Inner Cosmos.