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Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science based tools for mental health, physical health and performance.
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I'm Andrew Huberman and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. And now for my discussion with Dr. Eric Jarvis.
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Eric, so great to have you here.
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Thank you.
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Yeah.
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Very interested in learning from you about speech and language. In terms of the study of speech and language and thinking about how the brain organizes speech and language. What are the similarities? What are the differences? How should we think about speech and language?
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There really isn't such a sharp distinction. Let me tell you how some people think of it now that there's a separate language module in the brain that has all the algorithms and computations that influence the speech pathway on how to produce sound and the auditory pathway on how to perceive and interpret it for speech or for sound that we call speech. I don't think there is any good evidence for a separate language module. Instead, there is a speech production pathway that's controlling our larynx, controlling our jaw muscles, that has built within it all the complex algorithms for spoken language. There's the auditory pathway that has built within it all the complex algorithms for understanding speech. Not separate from a language module. This speech production pathway is specialized to humans and parrots and songbirds, whereas this auditory perception pathway is more ubiquitous amongst the animal kingdom. This is why dogs can understand. Sit, Siente, say, come here, boy, get the ball, and so forth. Dogs can understand several hundred human speech words, grade eights, you can teach them for several thousand, but they can't say a word.
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What do we understand about modes of communication that are like language but might not be what would classically be called language?
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Right. So next to the brain regions that are controlling spoken language are the brain regions for gesturing with the hands. And that hand parallel pathway has also complex algorithms that we can utilize. And some species are more advanced in these circuits, whether it's sound or gesturing with hands, and some are less advanced. Humans are the most advanced at spoken language, but not necessarily as big a difference at gestural language compared to some other species as you and I are talking here today. And people who are listening but can't see us, we're actually gesturing with our hands as we talk, without knowing it or doing it unconsciously. If we were talking on a telephone, I would have one hand here and I'd be gesturing with the other hand without even you seeing me. Why is that? Some have argued and I would agree, based upon what we've seen, is that there is an evolutionary relationship between the brain pathways that control speech production and gesturing. The brain regions I mentioned are directly adjacent to each other. Why is that? I think that the brain pathways that control speech evolved out of the brain pathways that control body movement. When you talk about Italian, French, English and so forth, each one of those languages come with a learned set of gestures that you can communicate with. Now how is that related to other animals? Well, Koko, a gorilla who was raised with humans for 39 years or more, learned how to do gesture communication, learned how to sign language, so to speak. Right. But Koko couldn't produce those sounds. Koko could understand them as well by seeing somebody sign or hearing somebody produce speech. But Koko couldn't produce it with her voice. And so what's going on there is that a number of species, not all of them, a number of species, have motor pathways in the brain where you can do learned gesturing, rudimentary language if you wanted, say with your limbs, even if it's not as advanced as humans. But they don't have this extra brain pathway for the sound. So they can't gesture with their voice in the way that they gesture with their hands.
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One thing that I've wondered about for a very long time is Whether or not primitive emotions and primitive sounds are the early substrate of language. When I smell something delicious, I typically inhale more, and I might say, or something like that. Whereas if I smell something putrid, I typically turn away, I wince, and I will exhale, trying to not ingest those molecules or inhale those molecules. I could imagine that these are the basic dark and light contrasts of the language system, this kind of primitive to more sophisticated pyramid of sound to language. Is this a crazy idea?
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Do we have any.
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Do we have any evidence this is the way it works?
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No, it's not a crazy idea. And in fact, you hit upon one of the key distinctions in the field of research that I started out in, which is vocal learning research. Most vertebrate species vocalize, but most of them are producing innate sounds that they're born with, that is babies crying, for example, or dogs barking. And only a few species have learned vocal communication, the ability to imitate sounds. And, and that is what makes spoken language special. When people think of what's special about language, it's the learned vocalizations that is what's rare. So all the things you talked about, the breathing, the grunting and so forth, a lot of that is handled by the brainstem circuits right around the level of your neck and below, like a reflex kind of thing, or even some emotional aspects of your behavior in the hypothalamus and so forth. But for a learned behavior, learning how to speak, learning how to play the piano, teaching a dog to learn how to do tricks is using the forebrain circuits. What has happened is that there's a lot of forebrain circuits that are controlling learning how to move body parts in these species, but not for the vocalizations. But in humans and in parrots and some other species, somehow we acquired circuits where the forebrain has taken over the brainstem. And now using that brainstem not only to produce the innate behaviors or vocal behaviors, but the learned ones as well.
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Do we have any sense of when modern or sophisticated language evolved amongst the
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primates which we humans belong to? We are the only ones that have this advanced vocal learning ability. Now, when you. It was assumed that it was only Homo sapiens, then you can go back in time now, based upon genomic data, not only of us living humans, but of the fossils that have been found for Homo sapiens of Neanderthals, of Denisovan individuals, and discover that our ancestor, our human ancestors, supposedly hybridized with these other hominid species. It was assumed that these other hominid species don't Learn how to imitate sounds. I don't know of any species today that's a vocal learner that can have children with a non vocal learning species. I don't see it. Doesn't mean it didn't exist. When we look at the genetic data from these ancestral hominids, where we can look at genes that are involved in learned vocal communication, they have the same sequence as we humans do for genes that function in speech circuits. I think Neanderthals had spoken language. I'm not going to say it's as advanced as what it is in humans, I don't know. But I think it's been there for at least between 500,000 to a million years.
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Maybe we could talk a little bit more about the overlap between brain circuits that control language and speech in humans and other animals. I was weaned in the neuroscience era where bird song and the ability of birds to learn their tutor song was and still is a prominent field subfield of neuroscience. And this notion of a critical period, a time in which language is learned more easily than it is later in life. And the names of the different brain areas were quite different. One opens the textbooks. We hear Wernicke's and Broca is for the humans. And you look at the birds of it. I remember, you know, hpc, robust arch, striatum area X.
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That's right, yes.
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How similar or different are the brains, brain areas controlling speech and language in say, a songbird and a young human child?
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Yeah. So going back to the 1950s or even a little earlier, and Peter Mahler and others who got involved in neuroethology, the study of neurobiology of behavior in a natural way. Right. They start to find that behaviorally there are these species of birds like songbirds and parrots. And now we also know hummingbirds, just three of them out of the 40 something bird groups out there on the planet. Orders that they can imitate. Sounds like we do. That was a similarity. In other words, they had this behavior that's more similar to us than chimpanzees have with us or than chickens have with them. They're closer relatives. Then they discovered even more similarities. These critical periods that if you remove a child, this unfortunately happens where a child is feral and is not raised with human and goes through their puberty phase of growth. It becomes hard for them to learn a language as an adult. There's this critical period where you learn best even later on when you're in regular society. It's hard to learn. Well, the birds undergo the same Thing. Then it was discovered that if they become deaf, we humans become deaf, our speech starts to deteriorate without any therapy. If a non human primate, or let's say a chicken becomes deaf, their vocalizations don't deteriorate very little. At least, well, this happens in the vocal learning birds. There are all these behavioral parallels that came along with a package. Then people looked into the brain. Fernando naravan, my former PhD advisor and began to discover the area X you talked about about the robust nucleus of the arcopallium. These brain pathways were not found in the species who couldn't imitate. There was a parallel here. Then jumping many years later, I started to dig down into these brain circuits to discover that these brain circuits had parallel functions with the brain circuits for humans, even though they're by a different name like Broca's and laryngeal motor cortex. Most recently we discovered not only the actual circuitry and the connectivity are similar, but the underlying genes that are expressed in these brain regions in a specialized way different from the rest of the brain, are also similar between humans and songbirds and parrots, all the way down to the genes. And now we're finding the specific mutations are also similar. Not always identical, but similar. Which indicates remarkable convergence for so called complex behavior in species separated by 300 million years from a common ancestor. Not only that, we are discovering that mutations in these genes that cause speech deficits in humans, like in FOXP2, if you put those same mutations or similar type of deficits in these vocal learning birds, you get similar deficits. Convergence of the behavior is associated with similar genetic disorders of the behavior.
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Do hummingbirds sing or do they hum?
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Hummingbirds hum with their wings and sing
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with their syrinx in a coordinated way.
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In a coordinated way. There's some species of hummingbirds that actually will. Doug Ashweller showed this, that will flap their wings and create a slapping sound with their wings that's in unison with their song. And you would not know it, but it sounds like a particular syllable in their songs. Even though it's their wings and their voice at the same time.
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Hummingbirds are clapping to their song.
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Clapping. They're snapping their wings together in unison with a song to make it like if I'm going ba da da da da ba da, you know, I banged on the table. Except they make it almost sound like their voice with their wings. What's amazing about hummingbirds, and we're going to say vocal learning species in general, is that for whatever reason, they seem to evolve multiple complex traits. You know, this idea that evolving language, spoken language in particular, comes along with a set of specializations.
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When I was coming up in neuroscience, I learned that, I think it was the work of Peter Marler that young birds learn songbirds, learn their tutor song and learn it quite well, but that they could learn the song of another tutor. In other words, they could learn a different. And for the listeners, I'm doing air quotes here, a different language, a different bird song, different than their own species song, but never as well as they could learn their own natural. Genetically linked song.
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Yes.
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Genetically linked, meaning that it would be like me being raised in a different culture and that I would learn the other language, but not as well as I would have learned English. This is the idea, yes. Is that true?
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That is true, yes. And that's what I learned growing up as well, and talked to Peter Mahler himself about before he passed. He used to call it the innate predisposition to learn, which would be kind of the equivalent in the linguistic community of universal grammar. There is something genetically influencing our vocal communication on top of what we learn culturally. There is this balance between the genetic control of speech or a song in these birds and the learned cultural control. Yes. If you were to take. In this case, we actually tried this at Rockefeller later on, take a zebra finch and raise it with a canary. It would sing a song that was like a hybrid in between. We call it a kninch, and vice versa for the canary. Because there's something different about their vocal musculature or the circuitry in the brain with a zebra finch, even with a closely related species. If you would take a zebra finch, young animal, and in one cage next to it place its own species, adult male. Right. And in the other cage place a Bengalese finch next to it, it would preferably learn the song from its own species neighbor. But if you remove its neighbor, it would learn that Bengalese finch very well.
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Fantastic.
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So there's. It has something to do with also the social bonding with your own species.
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That raises a question that I, based on something I also heard but don't have any scientific peer reviewed publication to point to, which is this idea of pidgin, not the bird, but this idea of when multiple cultures and languages converge in a given geographic area, that the children of all the different native languages will come up with their own language. I think this was in island culture, maybe in Hawaii, called pidgin, which is sort of a hybrid of the various languages that their parents speak at home and that they themselves speak and that somehow pidgin Again, not the bird, but a language called pidgin, for reasons I don't know, harbors certain basic elements of all language. Is that true? Is that not true?
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What is going on here is cultural evolution remarkably tracks genetic evolution. If you bring people from two separate populations together that happen in their separate populations, evolutionarily, at least for hundreds of generations. So someone speaking Chinese, someone speaking English, and that child then's learning from both of them? Yes, that child's going to be able to pick up and merge phonemes and words together in a way that an adult wouldn't, because why? They're experiencing both languages at the same time during their critical period years in a way that adults would not be able to experience. And so you get a hybrid, and the lowest common denominator is going to be what they share. And so the phonemes that they've retained in each of their languages is what's going to be, I imagine, used the most.
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So we've got brain circuits in Songbirds and in humans that in many ways are similar, perhaps not in their exact wiring, but in their basic contour of wiring. And genes that are expressed in both sets of neural circuits in very distinct species that are responsible for these phenomenon we're calling speech and language. I mean, what are these genes doing?
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One of the things that differ in the speech pathways of us and these song pathways of birds is some of the connections are fundamentally different than the surrounding circuits, like a direct cortical connection from the areas that control vocalizations in the cortex to the motor neurons that control the larynx in humans or the syrinx in birds. We actually made a prediction that since some of these connections differ, we're going to find genes that control neuro connectivity and that specialize in that function that differ. That's exactly what we found. Genes that control what we call axon guidance and formation connections. What was interesting, it was in the opposite direction that we expected. That is some of these genes, actually a number of them that control neuro connectivity were turned off in the speech circuit. It didn't make sense to us at first until we started to realize the function of these genes are to repel connections from forming repulsive molecules. When you turn them off, they allow certain connections to form that normally would have not formed. By turning it off, you got a gain of function for speech. Other genes that surprised us were genes involved in calcium buffering neuroprotection, like a parvalamine or a heat shock protein. So when your brain gets hot, these proteins turn on. And we couldn't figure out for a long time why is that the case. And then the idea popped to me one day and said, ah, When I heard the larynx is the fastest firing muscles in the body. All right. In order to vibrate sound and modulate sound in the way we do, you have to move those muscles three, four to five times faster than just regular walking or running. When you stick electrodes in the brain areas that control learn vocalizations in these birds, and I think in humans as well, those neurons are firing at a higher rate to control these muscles. What is that going to do? You're going to have lots of toxicity in those neurons. And unless you upregulate molecules that take out the extra load that is needed to control the larynx, then finally a third set of genes that are specialized in these speech circuit are involved in neuroplasticity. Neuroplasticity, meaning allowing the brain circuits to be more flexible so you can learn better. Why is that? I think Learning how to produce speech is a more complex learning ability than say, learning how to walk or learning how to do tricks and jumps and so forth that dogs do.
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In terms of plasticity of speech and the ability to learn multiple languages. But even just one language, what's going on in the so called critical period? And then the second question is, if one can already speak more than one language as a consequence of childhood learning, is it easier to acquire new languages later on?
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Actually, the entire brain is undergoing a critical period development, not just the speech pathways. And so it's easier to learn how to play a piano, it's easier to learn how to ride a bike for the first time and so forth as a young child than it is later in life. The brain can only hold so much information. And if you are undergoing rapid learning to learn to acquire new knowledge, you also have to put memory or information in the trash, like in a computer. You only have so many gigabases of memory, plus also for survival, you don't want to keep forgetting things. And so the brain is designed, I believe, to undergo this critical period and solidify the circuits with what you learned as a child. And you use that for the rest of your life. And now the question you asked about if you look learn more languages as a child, is it easier to learn as an adult? That's a common finding out there in the literature. There are some that argue against it, but for those that support it, the idea there is you are born with a set of innate sounds you can produce of phonemes, and you narrow that down because not all languages use all of them. You narrow down the ones you use to string the phonemes together in words that you learn and you maintain those phonemes as an adult. Here comes along another language that's using those phonemes or in different combinations you're not used to. And therefore it's like starting from first principles. But if you already have them in multiple languages that you're using, then it makes it easier to use them in another third or fourth language. So it's not like your brain has maintained greater plasticity is your brain has maintained greater ability to produce different sounds that then allows you to learn another language faster.
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What about modes of speech and language that seem to have a depth of emotionality and meaning, but for which it departs from structured language? I think of musicians like there are some Bob Dylan songs that to me, I understand the individual words. I like to think there's an emotion associated with it. At least I experience some sort of emotion and I have A guess about what he was experiencing. But if I were to just read it linearly without the music and without him singing it or somebody singing it like him, it wouldn't hold any meaning. So in other words, words that seem to have meaning but not associated with language, but somehow tap into an emotionality.
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Absolutely. So we call this difference semantic communication. Communication with meaning and effective communication, communication that has more of an emotional feeling content to it. I believe based upon imaging work and work we see in birds. When birds are communicating semantic information in their sounds, which is not too often, but it happens, versus effective communication sing because I'm trying to attract the mate, my courtship song or defend my territory. It's the same brain circuits. It's the same speech like or song circuits are being used in different ways. There's several other points here. I think it's important for those listening out there to hear is that when I say also this effective and semantic communication being used by similar brain circuits, it also matters the side of the brain in birds and in humans, there's left right dominance for learned communication, learned sound communication. So the left in us humans is more dominant for speech, but the right has a more balance for singing or processing musical sounds as opposed to processing speech. Both get used for both reasons. When people say your right brain is your artistic brain and your left brain is your thinking brain, this is what they're referring to. And so that's another distinction. The second thing that's useful to know is that all vocal learning species use their learned sounds for this emotional effective kind of communication. But only a few of them, like humans and some parrots and dolphins, use it for the semantic kind of communication we calling speech. That has led a number of people to hypothesize that the evolution of spoken language of speech evolved first for singing for this more like emotional kind of mate attraction, like the Jennifer Lopez, the Ricky Martin kind of songs, and so forth. And then later on it became used for abstract communication like we're doing now.
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I'd love to chat a moment about facial expression, many of which are subconscious. We are all familiar with the fact that when what somebody says doesn't match some specific feature of their facial expression, that it can, that mismatch can cue our attention. So how does motor circuitry that controls facial expression map onto the brain circuits that control language, speech, and even bodily and hand movements?
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You ask a great question because we both know some colleagues like Winrich Freible at Rockefeller University who study facial expression and the neurobiology behind it. Non human primates have a lot of diversity in their facial expression expression like we humans do. What we know about the neurobiology of brain regions controlling those muscles of the face is that these non human primates and some other species that don't learn how to imitate vocalizations, they have strong connections from the cortical regions to the motor neurons that control facial expressions. And even though it's more diverse in these non human primates, there was already a pre existing diversity of communication, whether it's intentional or unconscious through facial expression in our ancestors. And on top of that, we humans now add the voice along with those facial expressions. So it's like an email too. You're emailing and someone says something by email. Someone can interpret that angrily or gently and it becomes ambiguous. The facial expressions get rid of that ambiguity.
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I'm so glad you brought that out because my next question was and is about written language. What is the process of going from a thought to language to written word? And what's going on there. What do we know about the neural circuitry?
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What I think is going on is to explain what you're asking is about. I'm going to take it from the perspective. Reading something. You read something on a paper. The signal from the paper goes through your eyes. It goes to the back of your brain, to your visual cortical regions. Eventually that visual signal then goes to your speech pathway in the motor cortex in front here in Broca's area. You silently speak what you read in your brain without moving your muscles. Sometimes actually if you put electrodes, EMG electrodes on your laryngeal muscles, even on birds, you can see do this, you'll see activity there while reading or trying to speak silently, even though no sound's coming out. And so your speech pathway is now speaking what you're reading. Now to finish it off, that signal is sent to your auditory pathway so you can hear what you're speaking in your own head.
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That's incredible.
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And this is why it's complicated. Then you got to write. Here comes the fourth one. Now the hand areas next to your speech pathway has got to take that auditory signal or even the adjacent motor signals for speaking and translate it into a visual signal on paper. You're using at least four brain circuits, which includes the speech production and the speech perception pathways to write.
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Stutter is a particularly interesting case. What is the current neurobiological understanding of stutter and are what's being developed in terms of treatments for stutter?
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Yeah, so we actually accidentally came across stuttering in songbirds and we've published several papers on this to try to figure out the neurobiological basis. The first study we had was a brain area called the basal ganglia. The striatum part of the basal gang ganglia involved in coordinating movements, learning how to make movements when it was damaged in a speech like pathway. In these birds, what we found is that they started to stutter as the brain region recovered. Unlike humans, they actually recovered after three or four months. Why is that the case? Because bird brains undergoes new neurogenesis in a way that human or mammal brains don't. It was the new neurons that were coming in into the circuit, but not quite with the right proper activity, was resulting in this stuttering in these birds after it was repaired. Not exactly. The old song came back after the repair, but still it recovered a lot better. It's now known they call this neurogenic stuttering in humans with damage to the basal ganglia or some type of disruption to the basal ganglia at A young age also causes stuttering in humans. And even those who are born with stuttering, it's often the basal ganglia that's disrupted than some other brain circuit. And we think the speech part of the basal ganglia.
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Can adults who maintain a stutter from childhood repair that stutter?
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There are ways to overcome the stuttering through behavioral therapy. And I think all of the tools out there have something to do with sensory motor integration. Controlling what you hear with what you output in a thoughtful, controlled way helps reduce the stuttering.
A
Texting is a very, very interesting evolution of language. I wonder sometimes whether or not we are getting less proficient at speech because we are not required to write and think in complete sentences. What do you think's happening to language? Are we getting better at speaking, worse at speaking? And what do you think the role of things like texting and tweeting and shorthand communication, hashtagging, what's that doing to the way that our brains work?
C
Texting actually has allowed for more rapid communication amongst people. It's more like a use it or lose it kind of thing with the brain. The more you use a particular brain region or circuit, the more enhanced. It's like a muscle. The more you exercise it, the more healthier it is, the bigger it becomes and the more space it takes and the more you lose something else. So I think texting is not decreasing the speech prowess or the intellectual prowess of speech. It's converting it and using it a lot in a different way, in a way that may not be as rich in regular writing because you can only communicate so much nuance in short term writing. But whatever is being done, you got people texting hours and hours and hours on the phone. So whatever, your thumb circuit is going to get pretty big actually.
A
For those listening who are interested in getting better at speaking and understanding languages, are there any tools that you recommend? Should kids learn how to read hard books and simple books?
B
What do you recommend?
A
Should adults learn how to do that? Everyone wants to know how to keep their brain working better, so to speak. But also I think people want to be able to speak well and people want to be able to understand well.
C
Yeah. What I've discovered personally, right, is that, so when I switch from pursuing a career in science from a career in dance, I thought one day I would stop dancing. But I haven't because I find it fulfilling for me. And there have been periods of time, like during the pandemic, where I slowed down on dancing and so forth. And when you do that, you realize, okay, there are parts of your body where your muscle tone decreases a little bit somewhat, or you could start to gain weight. I somehow don't gain weight that easily. And I think it's related to my dance, if that's meaningful to your audience. But what I found is in science, we like to think of a separation between movement and action and cognition, and there is a separation between perception and production, cognition being perception, production being movement. But if the speech pathways is next to the movement pathways, what I discover is by dancing, it is helping me think, it is helping keeping my brain fresh. It's not just moving my muscles, I'm moving or using the circuitry in my brain to control a whole big body. You need a lot of brain tissue to do that. And so I argue if you want to stay cognitively intact into your old age, you better be moving and you better be doing it consistently. Whether it's dancing, walking, running, and also practicing speech, oratory speech and so forth, or singing is controlling the brain circuits that are moving your facial musculature and it's going to keep your cognitive circuits also in tune. And I'm convinced of that from my own personal experience.
A
This has been an incredible conversation and opportunity for me to learn. I know I speak for a tremendous number of people and I just really want to say thank you for joining us today. You are incredibly busy. It's clear from your description of your science and your knowledge base that you are involved in a huge number of things, very busy. So thank you for taking the time to speak to all of us. Thank you for the work that you're doing.
C
Thank you for inviting me here to get the word out to the community of what's going on in the science world.
A
Well, we're honored and very grateful too, Eric. Thank you.
C
You're welcome.
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Guest: Dr. Erich Jarvis
Date: April 23, 2026
Host: Dr. Andrew Huberman
In this Essentials episode, Dr. Andrew Huberman welcomes Dr. Erich Jarvis, a leading neuroscientist specializing in the biology of speech, language, and learned vocalizations. The discussion explores the key brain circuits underpinning speech and language in humans and other animals, the evolutionary relationship between vocal and gestural communication, the genetics and neural wiring of language, the profound overlap between music and language processing, and practical tools for promoting cognitive and linguistic flexibility throughout life.
"I don't think there is any good evidence for a separate language module." (C, [00:38])
"I think that the brain pathways that control speech evolved out of the brain pathways that control body movement." (C, [02:06])
"In humans and in parrots and some other species, somehow we acquired circuits where the forebrain has taken over the brainstem." (C, [06:30])
"I think Neanderthals had spoken language... I think it's been there for at least between 500,000 to a million years." (C, [08:07])
"The underlying genes that are expressed in these brain regions... are also similar between humans and songbirds and parrots, all the way down to the genes." (C, [10:19])
"All vocal learning species use their learned sounds for this emotional, affective kind of communication. But only a few... use it for the semantic kind of communication we call speech." (C, [25:58])
"By turning it off, you got a gain of function for speech." (C, [20:21])
"Learning how to produce speech is a more complex learning ability than say, learning how to walk." (C, [20:21])
"If you already have them in multiple languages that you're using, then it makes it easier to use them in another third or fourth language." (C, [23:24])
"Your speech pathway is now speaking what you're reading... that signal is sent to your auditory pathway so you can hear what you're speaking in your own head." (C, [31:21])
"Controlling what you hear with what you output in a thoughtful, controlled way helps reduce the stuttering." (C, [34:38])
"If you want to stay cognitively intact into your old age, you better be moving and you better be doing it consistently." (C, [36:59])
Dr. Jarvis and Dr. Huberman highlight the intricate, intertwined nature of movement, speech, and cognition—emphasizing that lifelong cognitive health depends on engaging both body and mind across a variety of communicative and motor tasks.