Shadowing Practice: Essentials: How Smells Influence Our Hormones, Health & Behavior | Dr. Noam Sobel - Learn English Speaking with Video
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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.
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And now for my discussion with Dr. Noam Sobel.
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Dr. Sobel, Noam, welcome.
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Thank you.
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I must say, I am extremely excited for this conversation.
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I've been a huge fan of your work.
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And today I'd love for you to share with us all about the amazing landscape of chemo sensation,
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in particular olfaction or sense of smell and some related perceptual abilities or subconscious abilities, including pheromones, et cetera.
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To get everybody on the same page, I'd like to just start off by asking, what are the major components of our ability to smell?
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Obviously, where I like to think it involves the nose at some level.
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It does.
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If you could just give us the top contour or even deep contour, if you like, of the parts list and the various roles they play.
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Primary olfaction is referred to as orthonasal olfaction.
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That is, through our nose, we sniff and sniffing is a big thing.
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Well, I have a sense we might talk about that a lot today in all sorts of contexts.
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So we sniff in through our nose.
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And to answer your general question of the organization of the system.
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So molecules, airborne molecules travel up our nose, a distance in the human of about six or seven centimeters to about here,
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where they interact with, I will use the word sheet of receptors, but sheet is a bit misleading here.
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It's not a sheet, it's very convoluted.
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We have about seven million such receptors lining a structure known as the the olfactory epithelium.
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This is the sensory surface of the olfactory system, the olfactory epithelium.
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Again, probably about six or seven million receptors in the human.
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In the human, probably of about 350 different kinds.
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So that's amazing.
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That means a meaningful percentage of your genome is devoted just to this, just to the kinds of olfactory receptor subtypes you have in your nose.
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So odorants interact with these receptors here in our epithelium, where they undergo what is referred to as transduction,
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that is the odorants are docked at a receptor and turn into a neural signal.
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And this neural signal, in fact, action potentials, not gradient potentials of any kind,
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propagates via the olfactory nerve through the thinnest part of our skull, which is perforated.
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It has a lot of holes.
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The nerve goes through those holes and synapses at the first target in the brain, which is the olfactory bulb.
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The pattern of that synapsing follows what's referred to as the most extreme case of convergence in the mammalian nervous system.
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More specifically, what happens is that all the receptors of one subtype converge to one location in the bulb.
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And this location is referred to as a glomerulus or an implore glomeruli.
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And that may be a slight oversimplification.
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It's In fact, two glomeruli.
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The next view of how things work is
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that every such receptor subtype is responsive to a small subset of different molecular shapes, what's sometimes referred to as ototopes,
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the molecular aspects of the odorant.
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And each ototope will activate a different subset of receptors.
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Then because of this convergence, you end up having on the bulb in a way a map reflecting receptor identity.
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So let's say this coffee activates receptors of type 1, 3, and 7.
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So the glomeruli of receptors 1, 3, and 7 will light up, quote unquote, when I smell the coffee.
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And if you can take a snapshot of that, theoretically, you would have the map of coffee.
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This is sort of the textbook view of how the system works.
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And then information goes from the bulb to several targets in the brain.
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I mean, what is referred to as primary olfactory cortex is piriform cortex and enthrinal cortex.
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This is on the ventral surface of the brain, the lower portion of our temporal lobe.
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And information goes there directly, but it also goes directly to the amygdala.
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It probably goes directly to the hypothalamus.
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It may go directly to the cerebellum.
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It goes all over the brain.
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So information projects widely from there.
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And as far as people understand, the map that may exist on the bulb doesn't exist in the rest of the brain
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and the understanding of how coding occurs in the rest of the brain is murky.
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Again, in our lab, we already said, you know, yeah, we know this.
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This is all news.
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But to people who come from different worlds, we have to reiterate this.
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Sometimes when I give public lectures to non -olfaction audiences, I reiterate this.
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Humans have an utterly remarkable sense of smell.
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We look at human behavior a lot
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we try to look at it through our nose in the way we look at what people are doing.
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You know, we try to think, you know, if I was a dog, what would I think of this?
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And, you know, if you look at dogs, right, they've.. you know, when they interact, they visibly sniff each other.
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It's very obvious.
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They walk up to each other and they sniff each other.
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And yet humans don't typically walk up to a stranger and carefully sniff them, right?
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I mean, we're sort of obliged to sniff our babies.
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That's considered almost something you're supposed to do.
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And it's not culturally taboo to sniff our loved ones.
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It sort of doesn't seem like an odd thing to do, but we don't sniff strangers, right well or do we so we're finding more
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and more mechanisms where we do this
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and the one I'm referring to now for one example is we started looking at handshaking
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there's really poor understanding of how this behavior evolved like where did where did this thing come from you know
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if you look for the wikipedia version right then they'll tell you
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that it's to show that you're not holding a weapon in your hand
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but there's really no good evidence for that and we started looking at people handshaking and we noticed,
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or it seemed to us that we're noticing that people will shake hands and then go like this.
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For those of you listening, not watching, Noam is taking his hand and wiping it on his face.
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Grabbing his nose or touching the side of his cheek.
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Yeah, these things that we do all the time.
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After a handshake.
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Well, so first of all, we do them all the time, just period, right?
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The baseline here is really high and we'll get to that in a second.
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But these behaviors that you could easily not notice, right?
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And so we asked whether that's a real thing.
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And this was a study led by Don Frumine in our lab at the time.
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So what we did is we brought in participants to our lab and we sat them in the room,
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experiment room, and told them the experiment would start soon and they should wait for us there.
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They didn't know what they were coming from.
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Unbeknownst to them, they were already being videoed and they would sit there for three minutes.
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And during those three minutes, we could later quantify how much indeed they just by baseline,
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how much they touch their nose or their forehead or their chin or how many times their hand reaches their face.
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And by the way, that baseline is not low.
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And then three minutes later, an experimenter would walk into the room and would share a consistent text.
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It would be, you know, we're still setting up our equipment in the other room.
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And so just wait here and we'll be right back with you.
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But in the meantime, just wait here.
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and in half of the cases, it included a handshake.
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This was a new experimenter, not the one who put them in the room.
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So that's the first time they met.
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So it'd be a low, I'm, you know, so -and -so, they would put out their hand and shake their hand or not.
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And so you had handshake and no handshake conditions.
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And then you can quantify that behavior of the hand going to the nose after handshake.
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And there was a remarkable increase in the hand going to the nose after handshake.
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It's unreal. So interesting.
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So the hand goes to the nose.
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Now we did a few controls here.
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to verify that this is an olfactory behavior.
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One is unbeknownst again to participants, we measured nasal airflow and people not only bring their hand to their nose, they sniff it.
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So, and this is perfectly timed.
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They go like this.
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Okay.
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So they're sniffing their hands.
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So this was an olfactory behavior, no doubt about it.
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I mean, we're quite confident.
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And there's an interesting thing going on here too, because people didn't only smell the hand that shook, They also smell the other hand.
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And we think that there's something going on here comparing self to other.
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And we think a lot of self -sampling might reflect that.
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There's a study we published by Einbal Rav Rebbe in our
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lab where Einbal came with this basic interest in this phenomenon that's loosely referred to as click friendships.
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So people you meet and you click right away.
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Everybody experienced this in their life, you know, to some extent.
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And the question is, what was there, right?
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What was it?
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Was it because you looked the same?
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Could be, was it because you had the same sports team that you liked?
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Or is there something deeper here?
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And Baal's theory was that a similarity in body odor may contribute to this.
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That people who smell the same will click in some way.
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And so to address that, she actually recruited click friends from all over Israel.
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She posted all over social media to identify pairs of friends.
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And so these are same -sex, non -romantic dyads.
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So these are friends, men and women, whose friendship started as a clique.
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And then she sampled their body odor.
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And we have a protocol for this.
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So they're given, you know, odorless shampoo and soap to use for three weeks or something.
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And then they sleep two nights in this T -shirt where they have to sleep alone.
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And then we extract the body odor from the T -shirt.
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And so we have a way to extract, a method to extract body odor.
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And then she first asked whether indeed click friends are more similar in their body order than you would expect by chance.
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And she first tested this with a device, a machine we call an electronic nose.
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So an electronic nose is sort of a very poor effort to mimic what the mammalian nose does.
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Basically, it's a bunch of sensors that respond to airborne molecules.
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In this case, sensors referred to as moxers, as metal oxide covered sensors.
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And so she used an electronic nose to sample these body orders.
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And she found that click friends are indeed more similar to each other than you would expect by chance by random dyads.
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And this was a significant difference.
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And after she found that a device could do this, she had other participants do this.
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So she had people smelling the click friends versus non -click friends.
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And they judged them as being more similar to each other than not.
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Now, again, you might wonder, is this causal or not, right?
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Because maybe click friends go to the same restaurant together all the time or whatever, live in the same neighborhood,
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and that's why they smell the same.
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So to address causality, she recruited total strangers
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and first smelled them with the electronic nose and then engaged them in a social interaction, something called the mirror game.
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So in the mirror game, one person moves their hands and the other person is really close to them,
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like right here, so they can smell each other and has to move their hands with the other person.
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And one prediction there panned out, but another didn't.
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The one that didn't, so she predicted
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that people who would smell more similar to each other would be better at the mirror game.
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That is, they would follow each other better.
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That did not pan out.
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However, she then also had, the interaction was completely nonverbal.
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They were not allowed to speak with each other and she did an entire round robin.
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So everybody played with everybody else.
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This was an insane experiment to run.
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She then, at the end of the experiment,
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each person rated each other person as to how much they think they would want to be their friends
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and also on a bunch of ratings, how nice they think they are, how affectionate they think, a bunch of ratings, okay?
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All of this was predicted by the electronic news.
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So people who smell more similar to each other think that the other person is more likely to be their friend,
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is more likely to be a nice person, et cetera, et cetera.
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So we could actually predict friendship using the electronic nose.
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So this is not a result of friendship.
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It plays into the causal elements of building friendship.
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People are constantly smelling themselves, constantly smelling others.
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I want to touch on some other so -called pheromone effects,
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whether or not it's a classic pheromone effect or whether or not it's olfaction or something else.
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This is chemosensory signaling between individuals.
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It all becomes semantics.
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Yeah, sort of like nerdy inside ball.
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It's all semantics.
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So in our publications, we don't use the term pheromone, because it would not help me and it would probably only hurt us.
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And so we talk about chemo signals, and humans definitely emit chemo signals from their body.
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And these chemo signals influence other humans and influence their behavior.
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The flavor of the month for the past 10 years in this field is what's referred to as the smell of fear.
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Humans emit a particular body odor when they're in a state of fear, and this body order influences other humans,
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in effect, increasing their autonomic arousal, their sympathetic state.
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So in effect, you could say that fear is contagious a bit.
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So the smell of fear is contagious.
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By the way, Culturally, we know for ages that dogs can smell fear in humans,
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but actually that was only really shown about a year and a half ago in a study.
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So it was always said, but it wasn't really shown effectively.
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It was shown about a year and a half ago in a study that dogs indeed can smell human fear.
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And humans can smell human fear.
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So several labs starting from Denise Chen and Haviland Jones, and then in our lab and in other labs,
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if you collect body odor from people in a state of fear,
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and collect body odor from the same people when they're not in a state of fear,
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other people can determine which is the state of fear or not, and this influences their behavior.
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And they just highlight again, you know, that we're incredibly olfactory animals.
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We had a guest on this podcast who I'm sure you're familiar with, Charles Zucker.
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Yeah.
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A professor at Columbia has done incredible work in vision and olfaction and thirst sensing.
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And I talked a little bit about this, that there's something in the breath of romantic partners that's hopefully appetitive, not aversive.
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As well as in children, he was talking about the smell of his grandchild, the back of their neck,
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and how he misses that smell because when he thinks about missing his grandchild or children, it's that smell that's associated with that feeling.
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Hexadecanal.
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Hexadecanal?
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Yes.
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This is a study ran by Eva Michore, who was a graduate student in our lab.
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Eva was interested in aggression.
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And so when she started off, we said, okay, let's do chemo signaling of aggression.
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She actually was going to like MMA clubs and collecting body odors.
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And we had all sorts of ideas going.
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And she worked on that for quite a bit.
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It never went anywhere, really.
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At the same time, Heinz Breer, he was studying in his lab a molecule,
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hexadecanal, that was a chemosignal in mice that promotes social buffering.
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So when lots of mice are together, they feel good about being in a group, and that's social buffering.
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And it's promoted by hexadecanal, which they emit in their feces.
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So Breer and his colleague, Storzman, they discovered the receptor for this, and then they went and discovered that the receptor is very highly conserved
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throughout mammalian evolution and therefore they hypothesized that maybe this is a universal mammalian signal.
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Now, which is unusual because in chemo signaling, typically you tend to think of things as being very species specific.
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So he approached us and said, look, you got to study this stuff in humans, right?
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Because he knows us as the human people, right?
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I mean, we go to these olfaction conferences where lots of people study mice and zebrafish and whatnot, and we're the human group.
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And eventually he just FedExed us hexadecanal.
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And Eva was not going anywhere with her aggression studies with sweat from human participants.
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And yet she built the entire paradigm to study human aggression.
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So they're standard paradigms.
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This is a paradigm known as the TAP, the Tyler aggression paradigm.
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And what's nice about this is that it then allows you to quantify aggression.
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And so you have a measure of aggression.
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Again, the Tyler aggression paradigm, obviously invented by Tyler, very well validated, studied all over, you know, a very standard protocol.
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So we brought in participants and had them play the Tyler,
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the tap, either under exposure to hexadecanal or control.
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And I'll first tell you the result with men, which is that hexadecanal consistently reduced aggression.
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People were less aggressive under hexadecanal.
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The effect size was quite meaningful compared to the effects seen in the aggression world in research.
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Really, really strong effects, so unusually strong.
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So hexadecanal lowered aggression in men, and we were like, cool, this is sort of what we were hoping to see,
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consistent with the hypothesis and consistent with what it seems to do in mice.
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But then we looked at data from women, and hexadecanal increased aggression equally significantly.
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Is this thought to be something related to maternal protectiveness?
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We're getting there.
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So she went and did the entire experiment again.
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And this time she did it within the fMRI magnet so that we can also track brain activity while this was happening.
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And first of all, it replicated again.
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So once again, hexadecanal made men less aggressive and women more aggressive.
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And yet I was telling you, Eva, you know, but this makes no sense to me.
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And then her insight, which of course afterwards is like, duh, is no, there's a place where this makes perfect sense.
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And that is if you're a mammalian offspring, because paternal aggression is often directed at you.
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There's infanticide all over.
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And sadly, there's male aggression towards human children as well.
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And maternal aggression is often protective.
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So if you're an offspring, if you have a molecule that will make your mother more aggressive and your daddy less aggressive,
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both of those are good for you.
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So you're winning.
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So the bottom line of all this is that hexadecanal is the most abundant semi -volatile in baby hits.
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It's tons of it coming out of baby hits.
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Babies are conducting chemical warfare, right?
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They're reducing aggression in their fathers or males around them and increasing aggression in their mothers or females around them.
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And both of those things are good for them.
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What is the relationship between odors and hormones and in particular, crying?
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Tears are a bodily liquid,
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emotional tears that we emit in emotional situations where these are situations where nonverbal communication is critical and key.
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The most influential text, I think, till this day in emotion research is Darwin's book, The Showing of the Emotions in Man and Animals,
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I think is the full name of the book.
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and an entire chapter, chapter six, is devoted to tears.
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So Darn systematically went through the expressions of emotions, and for each one went to their functional antecedent and explained everything very nicely.
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And then he got stuck with tears, right?
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Because tears are an obvious emotional expression, and he could not find a functional antecedent.
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So he ended up saying, this is an epic phenomenon.
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So we thought, well, maybe the function is a chemical signal.
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So with that in mind, we harvested emotional tears.
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So we collected tears and we exposed participants to these tears.
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First of all, the tears are completely odorless.
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You cannot detect them at all.
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Completely odorless.
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And yet, when you sniff them,
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you have a pronounced reduction in testosterone within about 20 minutes, half an hour.
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This is men and women smelling women's tears, but not perceiving any odor.
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Nothing.
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Just sniffing them.
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And you have about a 14 % drop in free testosterone.
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And people who study testosterone, which is not me, but they tell me this is a really strong effect.
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Like it's hard to even pharmacologically get an effect like that that fast.
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I mean, no one in pharmacology.
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Yeah, years ago I spent time studying endocrine effects of this sort.
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And that's a tremendously sized effect.
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And so here I'll point out in passing
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that one of the concerns we had
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because of the effort to run this study is that nobody would ever try to replicate it.
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And to our joy, about two years later, an independent group from South Korea, O et al., who I don't know at all,
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replicated the testosterone effect to a T.
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I mean, like same numbers.
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So it lowers testosterone.
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And we then also looked using MR at the effect on brain activity and saw pronounced effect on activity,
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a dampening, a lowering of activity under an arousing state,
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a lowering of activity, both in the hypothalamus and in the fusiform gyrus for whatever reason I don't know.
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Face recognition area.
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Amongst other things, yes.
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And we don't know why, but pronounced.
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So usually in our chemo signaling work, we look at what happens in ruins and we see if the same thing is happening in humans.
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This was a rare case where after we did this work more or less identical effects were discovered in rodents.
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So a paper published in Nature two years later found that mouse tears,
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mouse pup tears, lower aggression in male adult mice towards them.
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In a smell -dependent way.
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Yeah, yeah.
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And they also actually found the actual component in tears that, so the tear pheromone that lowers aggression, right?
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So, you know, this has us thinking of tears, It's tears,
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as you can think of tears as like a chemical blanket in a way that you're covering yourself up again with,
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you know, to protect against aggression, right?
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Smell being such a rich source of behavioral and hormonal and other sorts of deep, deep information.
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What is your experience with generating smells in silico in computers?
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And here, folks, for those of you that aren't catching on to this, and I don't expect that everyone would
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because what we're really alluding to here is the idea
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that you'll put into a search engine blueberry pancakes recipe and
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that not only will you get photos of those blueberry pancakes and a recipe, but you will get the hopefully validated odor of those pancakes
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and that recipe coming at you in real time through the computer
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so google had an april fool's spoof oh right
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and they put out this video of google smell okay and
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and it had all these like classic like sales images of you know holding up your phone to a rose
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and it generating rose and and and all these things right
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so google is now trying to do that you know to digitize uh smell
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and there are other companies that are trying to do this as well
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And recently in our lab, we've had, and I hope this doesn't come across as overly arrogant,
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but we've had a sort of mini breakthrough on this front.
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To call something a mini breakthrough is far from arrogant.
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And this is a paper led by Aaron Ravia from our lab and Kobe Snitz, also a major contributor there,
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a paper published in Nature.
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And in this paper,
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we develop an algorithmic framework where we can predict the perceptual similarity of any two molecular mixtures with very,
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very high accuracy.
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So if you give me two molecular mixtures, I can predict how similar you will smell them to be.
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Okay?
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Not only could we predict that, but we could design it so we can generate mixtures with known similarities.
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The result was highlighted, and you'll appreciate this coming from vision, is that using our algorithmic solution, we generated olfactory metameras.
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So we measured mixtures completely non -overlapping in their molecular structure, but they smell exactly the same.
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Now, if you would come to a classic perfumer
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or most classic perfumers and tell them that you can generate two mixtures with zero molecules in common, but smell exactly the same,
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they would tell you no. And yet we did and anybody can recreate them.
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This is simple, actually.
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And in the paper, we do a few things like we generate a metamera for
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Chanel No. 5 with no component from Chanel No. 5 in it.
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And to wake up feeling completely refreshed and energized, you actually want your body temperature to be increasing in the final hours of your sleep.
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Eight Sleep automatically regulates the temperature of your bed throughout the night
398
and is monitoring your sleep and dynamically adjusting the temperature of your sleep environment
399
so you get the maximum amount of deep sleep and rapid eye movement sleep.
400
I've been sleeping on an 8sleep mattress cover for nearly five years now, and with each new iteration of 8sleep,
401
it gets better and better at figuring out what my body needs in order to get the best possible night's sleep.
402
If you would like to try 8sleep, go to 8sleep .com slash Huberman to get up to $200 off their new Pod 6.
403
8sleep ships to many countries worldwide, including Mexico and the UAE.
404
Again, that's 8sleep .com slash Huberman to save up to $200.
405
In a way, we've generated the infrastructure for digitizing smell because...
406
Again, what our algorithm predicts, our framework predicts is similarity.
407
But in a way, that's enough for you.
408
Why is that enough?
409
We have a map of 4 ,000 molecules.
410
For each one, we know they're a perceived smell.
411
Now you can make up any mixture you want for me.
412
I can project it into that map and measure its pairwise distance from all the points in the map.
413
If it falls on lemon, then what you generated smells like lemon.
414
And if it falls on tomato, then what you generated smells like tomato.
415
So we now solve that problem.
416
We can predict the odor of any molecular mixture.
417
We can see how it's going to smell.
418
What we can do is then find a set of components, which we call odor primaries,
419
that can be used to mix any odor that you can perceive.
420
And that's what we're working on now.
421
So this is in collaboration with a lab of Jonathan Williams and Max Planck in Munich.
422
Jonathan Williams is an atmospheric chemist, but he's really good at using GCMS, these tools that measure molecules.
423
So Jonathan Williams measured odorants in Germany, transmitted the information to us over IP.
424
We fed that into our algorithmic framework and recreated it from a device that mixes primaries.
425
And we tried to do four different odorants in our proof of concept test.
426
One of them was rose, and we failed at recreating rose.
427
We, in fact, recreated something that had a precip, but most people perceived it as bubblegum.
428
The second one we tried to do was anise, and we failed at recreating anise.
429
And most people said it was cherry, which is not very far, but it failed.
430
The third was gasoline.
431
And we were slightly but significantly better than chance at recreating gasoline.
432
And the fourth was violets.
433
And 15 of 16 people said violets.
434
So the first odor ever transmitted over IP is violets.
435
Don't hold your breath for this to be on your table tomorrow.
436
All we have in hand is this very initial proof of concept.
437
But we're on the path.
438
And we're talking now of trying to achieve the olfactory equivalent of circa 1956 black and white TV,
439
okay, basically, right?
440
I mean, you know, I'm not dreaming, let's say, of being able to transmit to you the difference between a Cabernet or a Merlot, right?
441
But if I can generate something that's vaguely wine, that will be an amazing success from my perspective, right?
442
But jump ahead in your imagination to 4K odor transmission, then medical diagnostics is what you want to be talking about.
443
Because this is over extension, but you can almost say that every disease will have an odor.
444
I mean, every disease is a specific metabolic process.
445
Metabolic process have metabolites, metabolites have a smell, olfaction, once it's digitized, and high resolution,
446
which again, in our hands, it's not going to be.
447
I mean, we're talking, you know, in my retirement, maybe I'll read about this one day if I'll still have vision.
448
I mean, this is not close.
449
But when olfaction digitization is brought to the equivalent of 4K vision and audition that you have now,
450
then it will be in medical diagnosis.
451
Excuse me for the imagery, but you will have an electronic nose in your bathroom.
452
Each one of us will have in the toilet and it will be doing diagnostics all the time.
453
And, and that's, that's where it's going to go.
454
But again, not anywhere in the very close future.
455
Noam, I, I want to say thank you for your time today.
456
First of all, this was a tremendously interesting conversation.
457
I mean, We touched on so many things, hormones, smells, the architecture of the olfactory system.
458
I know that people listening to this are realizing, but I'm going to say it anyway, what an incredible gift you've given us.
459
Thank you.
460
As an expert in this field, giving us this tour of the work that you
461
and others who you credit so generously have done and the spirit that you bring to it.
462
Whatever drives that spirit, as the great late
463
Ben Barris used to say, keep going because we are all benefiting tremendously.
464
And I also just want to say that, you know, for people listening to this, that the spirit of science is one of,
465
as you mentioned, there's complex politics and all these things, but it's absolutely clear that you delight in the work you do.
466
And so I delight in it.
467
I'm grateful for it.
468
I'm grateful for your time today.
469
And so on behalf of me and the many, many people listening to this, I just want to extend a huge debt of gratitude.
470
Thank you so much.
471
Thank you so much for very warm words.
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Vocabulary and speaking notes for this lesson
This speaking lesson is built on the video “Essentials: How Smells Influence Our Hormones, Health & Behavior”. This video has 471 sentences and 5904 words to shadow. The speech runs for 34:51. The speaker talks at a natural 169 words per minute, close to everyday conversation. Only 80% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
15 words from the video worth learning, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| aggression noun | /əˈɡɹɛʃən/ | The act of initiating hostilities or invasion. |
| tear verb | /tɛɹ/ | To rend (a solid material) by holding or restraining in two places and pulling apart, whether intentionally or not; to destroy or separate. |
| receptor noun | /ɹɪˈsɛp.tə/ | A protein on a cell wall that binds with specific molecules so that they can be absorbed into the cell in order to control certain functions. |
| generate verb | /ˈd͡ʒɛn.ə.ɹeɪt/ | To bring into being; give rise to. |
| predict verb | /pɹɪˈdɪkt/ | To make a prediction: to forecast, foretell, or estimate a future event on the basis of knowledge and reasoning; to prophesy a future event on the basis of… |
| molecule noun | /ˈmɑ.lɪ.kjul/ | The smallest particle of a specific element or compound that retains the chemical properties of that element or compound; two or more atoms held together by… |
| mouse noun | /maʊs/ | Any mammal of the many rodent families (especially Muridae) that have a small body and a long tail. |
| mixture noun | /ˈmɪkst͡ʃɚ/ | The act of mixing. |
| chemotherapy noun | /ˌkiːməʊˈθɛɹəpi/ | Any chemical treatment intended to be therapeutic with respect to a disease state. |
| molecular adjective | /məˈlɛk.jə.ləɹ/ | Relating to, or consisting of, or produced by molecules. |
| participant noun | /pɑːɹˈtɪsəpənt/ | One who participates. |
| experiment noun | /ɪkˈspɛɹ.ə.mənt/ | A test under controlled conditions made to either demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy or likelihood of… |
| aggressive adjective | /əˈɡɹɛs.ɪv/ | Characterized by aggression; highly combative; prone to behave in a way that involves attacking (especially if unjustly) or arguing. |
| flavor noun | /ˈfleɪvə/ | The quality produced by the sensation of taste or, especially, of taste and smell in combined effect. |
| bulb noun | /ˈbʌlb/ | The bulb-shaped underground portion of a plant such as a tulip, consisting of a shortened stem and many fleshy scale leaves, from which the rest of the plant… |
Phrasal verbs you will hear
| Word | Meaning |
|---|---|
| end up verb | To bring to a conclusion. |
| go through verb | To travel from one end of something to the other. |
| put out verb | To blind (eyes). |
| start off verb | To begin. |
| come across verb | To change sides; to cross over to work for the opposition. |
| figure out verb | To come to understand; to discover or find a solution; to deduce. |
| get up to verb | To do something, especially something that is forbidden or improper. |
| give away verb | To make a gift of (something). |
Sentences worth repeating
Short, complete lines from the video that you can reuse in everyday conversation:
- I've been a huge fan of your work.
- That's considered almost something you're supposed to do.
- I mean, we're quite confident.
- It's also important that you get adequate electrolytes.
- Was it because you looked the same?
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Conditional sentences if + clause, will/would + verb — a condition and its result | if I was a dog, what would I · if you have a molecule that will make |
| Present perfect continuous have/has been + -ing — an action that started earlier and is still going on | I've been taking · I've been sleeping |
| Passive voice be + past participle — the focus is on what happens, not who does it | is referred · is devoted · are docked |
| Relative clauses who / which + clause — extra information about a person or thing | skull, which is · brain, which is · people who come |
Pronunciation to watch
The speaker uses 85 contractions and reduced forms, such as I'm, we're, don't. Say them the short way, as you hear them.
- The “th” sounds: chemotherapy /ˌkiːməʊˈθɛɹəpi/, breakthrough /ˈbɹeɪk.θɹuː/, algorithmic /ˌælɡəˈɹɪðmɪk/, epithelium /ˌɛpɪˈθiːlɪəm/
- The “sh” and “zh” sounds: aggression /əˈɡɹɛʃən/, friendship /ˈfɹɛn(d)ʃɪp/, sheet /ʃit/, shake /ˈʃeɪk/, interaction /ˌɪn.təˈɹæk.ʃən/
- Long words — get the stress right: chemotherapy /ˌkiːməʊˈθɛɹəpi/, molecular /məˈlɛk.jə.ləɹ/, participant /pɑːɹˈtɪsəpənt/, experiment /ɪkˈspɛɹ.ə.mənt/, testosterone /tɛˈstɑ.stəˌɹoʊn/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
- Record yourself and compare with the original, paying attention to words like aggression, tear, receptor.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.