Your Brain is a Time Machine with Dean Buonomano

23:20And you think about something like language, right? So language is very temporal. And here's one of my favorite examples. I want to say two sentences. The order of the words is the same, but the meaning is different. So they gave her cat food or they gave her... You guys anticipate. You guys are way ahead of the game. You guys are way ahead of the game. That's because we're smart. We figured out what you did there. They gave her cat food or they gave her cat food. So you're naturally paying attention to the timing and the intervals. And that's altering your communication. And it's totally unconscious, right?

23:59You're not thinking, oh, the pause was different. So that timing is always going on. Now, Gary's original question was perception of time. That often means the conscious perception of the flow of time, which is a very deep philosophical question that implies consciousness. So one of the most salient percepts that we have is that time is always flowing. And this reaches at the core of something that has tension with physics and neuroscience that I've written about and I'm sure you have talked about.

24:32Neil deGrasse Tyson:So the flow of time implies some self-awareness of an arrow of time, correct? Yes, generally the case because it's generally flying forwards. Yeah, I would say that's correct. From the past to the future. But in there, if I see someone in my family and I see them get old and die, does my self-awareness that maybe I'll get old and die too, is that part of my sense of the flow of time? Yeah, so that's a great question. I want to come back to that specific point about death. But first, in terms of the perception of time. So many physicists would argue that the perception of time, the flow of time, that the past is no longer real, the present is real and the future is not yet real, is an illusion or a mental construct or something imposed by the brain.

25:20And this is the debate between what we call eternalism or the block universe and presentism. So under eternalism, the past, present, future are equally real. And under presentism, only the present is real. And that's how we perceive. And this is this fundamental debate about what's the nature of time. And there's this ongoing debate where the physicists say, hey, you neuroscientists figure this out because obviously time is not flowing. Why does it feel like it's flowing? And then the neuroscientists say, well, you physicists figure this out because, you know, time is flowing. But there's two points in physics.

25:56And the physics, and it will be interesting to hear all of your opinions, but the physics is really most of an interpretation in which because of relativity, because the physics doesn't have a specific point, you are here, doesn't say there's anything special here. The equations of physics are time symmetric or time reversible. So that leads to one interpretation that the past, present and future are equally real, much like space. You can be anywhere in space. You can be any moment in time. But I've argued, and that I think the brain is telling us something true about the physical universe, that it is because we evolved to survive in a universe governed by the laws of physics, in a mesoscopic part of that universe.

26:41Not at the micro, not at the cosmo, but at the mesoscopic level to survive in this world governed by the laws of physics. So I think and have argued that it is really flowing and our brain creates this conscious perception of the flow because it's a real part of what we experience and of the universe.

27:01Neil deGrasse Tyson:That's a cool new word for me, mesoscopic. Mesoscopic. We would say macroscopic, microscope. You don't need a microscope to see it. But mesoscopic feels a little more authentic, like meso being middle. Right. So, Dean, we've created memories, right? So that's us understanding some timing. And I can travel backwards in my mind and revisit memories. I am present in the now, but I can throw myself forward with an imagination of what might be in X time going forward. So as the physics of that, as opposed to the neuroscience of that, how do we interpret? And are we actually time traveling? Because we experience time dilation when we dream.

27:50I mean, your dream will last 30 seconds and it will feel like you've been in there for half an hour.

27:55Neil deGrasse Tyson:That's the whole plot line of the movie Inception. Oh, I never saw that. Was it good? Yeah. I think that was the movie where everyone, you can go inside of someone else's dream. and but the timing of it the dream is way longer than the actual time frame if you do this a few times in then you know it's a fraction of a second equals days or something and you have to like budget for that as they go in and out of each other's dreams so what i only saw i only saw the spoof one rick and morty oh okay fair enough so are we now if we're in the physics looking at this Is this a quantum state? And then how does the neuroscience figure this out from their angle of approach?

28:37So I think it would be best to start that by looking at the neuroscience before we get to the physics. Because one of the unique things about human cognition, one thing that distinguishes us from most other animals, is our ability to do exactly what you're saying, Gary, which is engage in what we'll call mental time travel. mental time travel, which is, you know, you think of something as fundamental as the invention of agriculture, right? For some, it's not that complicated, right? Plant a seed, reap the benefits later. But it evades most other animals and it evades the ability of humans to figure that out for many years.

29:15And it involves mental time travel. It says, I have to do something now that will only give me benefits months or years into the future. And that was a very hard step for us to connect the temporal dots between things that are cause and effect over weeks, months, and years.

29:35Neil deGrasse Tyson:As an immediate cause and effect would be obvious. Absolutely. You punch somebody in the face and they're hurt and they punch you back. That's an immediate response. They know who to blame. They know who to blame. But a seed in the ground, oh my gosh. This ability to jump, make these cognitive leaps across time is an incredibly sophisticated thing we do, but we're still not very good at it. And that's a problem, right? Because, you know, climate change, you know, we're not acting or saving for retirement. But I go back and I think about the first ancestors that had that ability to look into the future.

30:09And this goes back to what Neil said. Can you imagine what it was like for the first human to make this cognitive leap and say, oh, shit, I'm going to die, right? Because it's this ability to engage in mental time travel that we became aware of death. And many people have argued that there was a co-evolution between our ability to engage in mental time travel and religion, because religion was the antidote to this vision that we saw that we were going to die. So, it said, well, don't worry, there's another life after this. And there's a great quote by Jorge Luis borges that says except for man all animals are immortal for they are ignorant of death i don't

30:52Neil deGrasse Tyson:know if that's true wow but that's a great quote if it's not fully true yeah yeah so with respect to looking into the future though i look in my backyard and i see squirrels going freaking nuts no pun intended in the fall hiding food because they know that food won't be there Is that not also a form of looking into the future? Or is it blind instinct? Yes. So that's probably the answer, Neil, is that they're programmed to do that. So a squirrel that never experienced a winter will still do the same thing. But not only that, Chuck. Interesting. Consider this, Chuck. Humans have been known to engage in future-oriented activities without necessarily thinking what will happen nine months into the future.

31:42Yeah, that's called screwing.

31:45Neil deGrasse Tyson:that's why do they do that you left that for our imagination chuck oh i'm sorry he was setting up so you didn't no one had to say that well i mean i said it for the kids thank you but the point is is that the squirrels are probably engaging in that activity because it brings them pleasure at that moment in time so we've been talking about memory like it's just a thing, like, you know, like memory on your computer. But our brains are, of course, organic tissue with chemicals and electrical synapses. And so how is a memory actually stored? Can we can we just like lay some foundation there? Yeah.

32:28So, you know, one of the most fundamental tenets in neuroscience and one that has been borrowed by artificial intelligence, by the way, is that information and memory is stored by changes in the coefficient or the weight or the strength of the connection between neurons or artificial units. So, you know, we use these large language models and how they store information is by just tuning billions and billions and billions of weights. And all those weights are is how much each neuron influences the other. So, if I'm one neuron and Chuck is another neuron, we can change the strength of the connection between those, and then it will behave differently and learn.

33:07And this is very fundamentally different from what Neil referred to in terms of a computer memory. So in a computer memory, there's a very clear dichotomy between the memory and the computations being performed. So there's the CPU, and there's the RAM. And this is the standard von Neumann, so-called von Neumann architecture. In the brain, that distinction doesn't make as much sense, because it's the activity flowing through these networks that is both the computation and the memory. So it's extraordinarily hard to separate those two things in the case of human memory. Oh, wow. That's really, that's very cool.

33:44Neil deGrasse Tyson:So I've read some connections between this discussion and Morse code, but how do they relate at all? Well, so there's two aspects to Morse code, right? One is understanding code and one is the timing. So they're both valid questions, But the memory part is sort of not that different whether you're doing Morse code or you're doing normal language or you're reading. You have to store information. But the timing is unique in Morse code, right? Because there in Morse code, everything's the duration of the dot or the dash and the interval between them. So how does the brain do that? So this gets to Gary's original question is how the brain tells time on this scale.

34:21And that's been a mystery. It used to be thought it was due to oscillations. But our work and other people's work has shown that that's probably not the case. has more to do with neural dynamics. So imagine, you know, we're a bunch of neurons and I'm neuron that activates Chuck and Chuck activates Gary and Gary activates Neil. So that forms a dynamical system. It forms a trajectory in neural space and that you could use that to tell time. So depending on who's active, so Neil might be the last one to be active. So if we know if he's active, is he firing, that means that one second has passed. and if Chuck, maybe that's 500 milliseconds.

34:59So the brain is this dynamical system and these patterns of activity can become a clock, if you will. Holy moly. Interesting. That is fascinating. So these, now, there's a saying, neurons that fire together, wire together.

35:18Neil deGrasse Tyson:That's a saying? Where'd you get this saying? In the hood? This is not in the hood, man. This is not in the hood, man. Where have you been hanging out, Chuck? That's hilarious. So what I'm wondering is when you think about this dynamic grouping, could you then change? Could your brain either falter and fail with these groupings because of misfiring? Or could you change it in some way purposely because you get these neural pathways to kind of line up and fire together? Yeah. So that's a really great question, Chuck. And it relates to what you just described, neurons that fire to wire together, is called a form of Hebbian plasticity.

36:00It's a host of associated plasticity named after a famous Canadian psychologist, Donald Hebb. And that was sort of the original algorithm that how do neurons figure out who to wire together. And it's a very powerful algorithm. And it says that if I see your face, my visual neurons are firing. At the same time, my auditory neurons might be hearing your name. So maybe it's It's a good idea that those auditory neurons and visual neurons hook up with each other because then I can now see your face and then recall your name. So it's a very, very powerful, simple algorithm called the sociosynaptopasticity.

36:38But back to the timing, you also have this ability to generate sequences. So if I say A, B, C, D, you predict what's going to happen. Or in music, if I go ta-ta-da-ta-ta, you can also fill that in. So there, you need to not only just feel what's happening together, but what's about to happen. So that requires another rule on top of this idea that associative, that neurons that wire together, fire together. It might be that neurons that fire first wire to the neurons that fire second. So there's all these levels of different algorithms on top of each other. But you're exactly right.

37:14Neil deGrasse Tyson:So this brings a question because so much of when any of us learned about the brain, it was, well, this section of the brain is language and this is facial recognition. So this is very spatially mapped. And most of this conversation just now is a temporal mapping of the brain, which is a whole other dimension here. The space time of the brain, this time thing all feels very fresh and new to me. Is it new in your field? It absolutely is, Neil. And, you know, I'll make the point that I think time is at the center of a perfect storm of scientific problems from free will, consciousness, determinism, how the brain works, even AI, and the more fundamental question of the nature of time.

38:01So I think time is complicated, more complicated than space. What do I mean by that? That's a bit hand-wavy, right? But what was probably the first field of modern science? I would argue that the first field of modern science was probably geometry, right? There's not many things discovered 3 ,000 years ago that we still teach in school, like Pythagoras theorem. So why was geometry the first field of modern science? It has no time. Geometry, as originally developed, was timeless. It's static. It's not changing. It really took 2 ,000 years and the likes of Galileo, Newton, and Leibniz to really bring in time and dynamics and add time to space.

38:49And I think neuroscience is in many ways at that same stage where we've ignored time and we're just maturing enough to start addressing these complex questions pertaining to time.

39:04Neil deGrasse Tyson:I can add to that that the syllabus sequence in physics matches closely how this actually got discovered. Like you said, geometry, there's no time dimension in any geometric calculation at all, right? And so you move forward. There's not in trigonometry either or in algebra that physics has to come in. And early physics, time was kind of simple. You know, you go you move this this far for three seconds and then you turn left and you go another 10 seconds later on. And this I remember this like it's yesterday when we finally had these functions that changed over time. so it wasn't just a force pushing it was a force that changed over time we had to track that and this involved differential equations a whole other layer of math had to go on top of the math we were previously using and that's really what separated you know if you were going to drop out of physics that's when it was going to happen typically and and without calculus we wouldn't really be able to deal with time to the degree that we need to.

40:12And that's the foundation of modern science, of the economy and technology and so forth.

40:17Neil deGrasse Tyson:And there you go with Leibniz and Newton, the two sort of, I was going to call them fathers of time, but they're parents of time.

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41:56So, D, we have something called a temporal window of integration. Now, correct me if I'm wrong here. So if I'm talking to you personally face to face, I will see your lips move before I hear the sound that you make. Right. And the brain fixes it. Yeah.

42:16Neil deGrasse Tyson:So is this now the illusion of time? Wait. And is that because the light signals to your brain are processed faster than the auditory signals? So there's two things there. So let me just to make sure we don't confuse them. So obviously, because light travels faster, a lot faster than sound, I see your lips moving reach my retina more rapidly than the sound reaches my ear. But, and this is the tricky part, the sound processing is actually much quicker. So if you see me clap and I ask you to react to the sound or to the sight, your reaction time is actually quicker to the sound. So they say ping pong players, I'm not sure this is true.

43:02They say ping pong players sometimes react to the sound of the ball before they see the ball. Because the brain processes auditory information. And that's because the retina is incredibly slow. The retina relies on biochemical reactions. But we do have a window of integration. So whether you're sitting in the cheap seats in a soccer stadium or the expensive seats, we can adjust this window of integration. So it's adaptive. We can tune it so that if you're watching a movie up close or far, it seems everything's integrated. As long as it's in a window of two or three or 400 milliseconds, your brain can fix it.

43:40So in that sense, it's just your brain being flexible and sort of trying to align time and space. And this is something, I don't know if you know what the McGurk illusion is. The McGurk illusion is if I say ba, ba, ba, ba, but you see a video of me saying ga, ga, ga, ga, your brain mixes those things and you might hear something like da, da, da, da, because you're mixing audio and visual in your brain all the time, whether that's time or space. So, yes, this window of integration is extremely important, but adaptive. The brain fixes it for you like magic. It's like the editing programs you guys will use for this podcast.

44:20So, actually, we're all in one big kung fu theater movie from old school Saturday afternoon. Just like, so you kill my master. So that's a great example, Chuck, because those are so bad it's unfixable. The brain can't deal with that degree of messing up in the Kung Fu movies. That's exactly right. I like the imitation, though. Neil, how about Einstein's general relativity, where time slows down depending on the proximity of objects?

44:56Neil deGrasse Tyson:Yeah, no, but in neuroscience, it never slows down for you. You just always have your time. It's all happening to everybody else. Yeah. And you only know it's happening to everybody else because you're measuring it. so that's not a neuroscience so i don't you guys might think about that dean but i don't care however slow you think i'm moving my pulse is still doing 70 beats a second and i'm listening to my music so you're the one with the problem so the time is different for us or different places different yeah for gravity for speed all manner of things can can famously shown in that scene in in the movie interstellar where the the astronauts go down to the gargantuan planet yeah you're a black hole yeah and the black hole slows down the time but you're there with them and they're just living they're 15 minutes of time they get back to the spaceship the guy's got gray hair yeah of course it's the black dude they left up there to get all old they get back he's just like oh my god Where are you, Ben?

45:57Neil deGrasse Tyson:It was the black guy. How do you sync that with the arrow of time if there's this distortion going on and it's a flow forward? Well, both would be flowing forward, but as Neil said, you would never know that time is slow for you. You're incapable of knowing if it's fast or slow. The problem is when you try to sync between two people on these different frames of references, that becomes a problem and and raises paradox but um this relativity brings this question that we started off to is is the past present and future equally real eternal eternalism or not and this has extremely important consequences for hollywood because you know we as as i think neil said you know we is this is that pure fiction that you could time travel in real physical space um or not And a presentist like myself would argue, no, it's absolutely impossible.

46:55And an eternalist would argue it's at least theoretically possible.

46:59Neil deGrasse Tyson:Well, OK, but then you have cause and effect issues with that. So, Dean, famously in the film Total Recall, and Chuck, who is in Total Recall? I think he's a little more literate than that. I'm having trouble recalling. In the film Total Recall, which is surely on every neuroscientist bucket list to watch, they just implant your vacation in your head. And it's a memory that you never experienced. And, of course, this also hints at everything that happened in The Matrix, where everything's just implanted. and so many episodes of the brilliant hit series on Netflix called Black Mirror involve people uploading their memories, downloading them, replaying them.

47:50Neil deGrasse Tyson:And so where do you think the future of this is? And how real are those portrayals of your field? Yeah, I think that's a great question. And I think a lot of that relies on sort of a simplistic understanding of the brain as a computer, that you can somehow hook it up to an external device. And this is a very topical issue, right? Because companies that use brain-machine interfaces, most famously Neuralink's, the Musk company, are attempting to do this. And I think some people have the idea that, yes, if we have all these wires into my brain and they're hooked up to a computer, that we will be able to, I'll all of a sudden be able to speak Mandarin or I'll be able to fly a plane.

48:36I don't think I'm very... Or you'll know Kung Fu. Or know Kung Fu. More importantly. And then I'm very skeptical of those notions because I think they don't really capture how the brain actually works. Because as I was saying before, the brain is not like a von Neumann computer, which has a memory module and it has a CPU module and as a bus module that you can upload things. There's no clear separation between the memory and the computation. So I think you'd have to really modify how our brains work to upload things. So somebody might say, well, all you're doing is just interfacing the brain directly with these external computers so then I can fly the plane or do Kung Fu.

49:29But really, it's not me that's doing it. It's the computer that's doing it. So you're just changing the interface. And the brain already has some pretty nice interfaces, right? They're called eyes and ears and hands. And the brain is very slow bandwidth. So I don't think we can dramatically enhance the bandwidth by magically implanting a million electrodes in our brains. So I'm skeptical of this. And you're probably familiar with Ray Kurzweil's arguments, too, that we'll achieve the singularity by melding with NAI. I think that really isn't consistent with our understanding of neuroscience at this point, in my opinion, Neil.

50:09Neil deGrasse Tyson:That's insightful for you to mention that if you plug into all these wires and then you know Kung Fu, it's really the wires that knew Kung Fu. It's just feeding you that information. Is it really you at that point? No, it's the AI that's doing it. Yeah. But can it sink your lips to your speech? That's what's really important. You're still stuck on that. So, Dean, before we wrap this up, and I think we will be shortly, is it actually possible that the brain is the only time machine that physics will allow? So, the answer to that question, in my mind, the answer to that question is yes. Because as a presentist, I don't think time travel in physics is a possibility.

50:54So when people look at things like wormholes and from general relativity, what general relativity says is that wormholes are a theoretical possibility. They're not really a prediction of general relativity. It says, well, it could happen depending on the assumptions that go into the equations, the initial conditions, and so forth. But I would argue that, yes, the closest we'll ever get to a time machine is our mental time travel. And that, in my opinion, actual time travel is a theoretical impossibility. I understand maybe Neil disagrees, maybe doesn't. I don't know.

51:33Neil deGrasse Tyson:But you're in good company with Stephen Hawking, who as much as he would have welcomed time travel. In fact, he hosted a party for future time travelers where it was. And nobody showed up. He chose a date, a time and a date and said, anyone from the future who can time travel, show up now. And then nobody showed up. So he advanced something called the time travel prevention conjecture. It sounds like that if it's not exactly that sequence of words where he's suggesting that one day we will discover a formal law of physics that prevents the time travel, which then prevents the paradoxes that have been such fertile content for time travel movies.

52:16Neil deGrasse Tyson:And my last question to you, sir, professor, is, and I have my answer on this, but I want to hear it from like a real neuroscientist. Do you think the human brain is smart enough to figure out the universe? Or is the human brain smart enough to figure itself out? Okay. Bam. So first place, neuroscience is the most recursive field in science, right? Because it's the only field in which the thing being studied is doing the studying. So that's a problem. There's reasons to be. it gives me job security, put it, but put it this way. There may be reasons to believe that no system is capable of understanding itself.

53:02So I happen to think that we might be able to pull it off, but maybe with AI, um, to answer Neil's question, we might be able to understand ourselves, but his first point was understand the universe. And I think this is a bit of a trick question that what does it mean by understand? But the answer to your question very informally, I would probably say no in one way. And that, you know, quantum mechanics is a good example. Do we understand quantum mechanics? I don't. We just calculate. Yeah, that's exactly right. So shut up and calculate. So the math has, so the brain has serious constraints. It has serious bugs.

53:42It has cognitive limitations. The greatest debugging device we ever invented is called mathematics because mathematics allows us to simulate, to model, to capture things we don't understand. So as Neil said. Don't understand intuitively. Yes, exactly. Exactly. Exactly. So if you mean understanding intuitively, I don't think, you know, most of the interpretations in quantum mechanics are, I do think are basically revolve around limitations of the human brain.

54:11Neil deGrasse Tyson:Yeah. So I don't. I'm with you on that thing. I was a little on the fence, but you pulled me back onto your side. I was always on your side because I think we're stupid.

54:24Yeah. So Chuck, to go along those lines, you know, there's this debate in AI whether AI is as smart as human beings are, but it's human beings are pretty low bar. Exactly. I'm with you a hundred percent. Yeah. My agree.

54:42Neil deGrasse Tyson:So listen, Professor, I've enjoyed this conversation. You sound like you're totally in it, and we might want to reach back to you to see what your next scores are on the human brain and what we can accomplish with it. When did your book come out? This has been out a while. This came out in 2017. 2017. Okay, give me the full title again. Your Brain is a Time Machine, the Neuroscience and Physics of Time. Love it. Love it. It's been a great pleasure. So thank you, Neil, Chuck, and Gary. You're welcome. You've got it. Well, this has been yet another installment of StarTalk Special Edition, and we're loving these neuroscience interviews.

55:17Neil deGrasse Tyson:Gary, Chuck, always good to have you. Pleasure, Michael. Always a pleasure. And Professor Buonamano. You're on our Rolodex now, so don't be surprised if we call on you again. Neil deGrasse Tyson, your personal astrophysicist. As always, keep looking up.

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