In this episode of Tiny Show and Tell Us, we cover work scientists have done to understand what’s going on in dog brains and how attached to us they really are. We also discuss a polymer called hemoglycin that hitches a ride on literal tons of space dust and may have played a big role in how life on Earth got started.
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Transcript of this Episode
Sam Jones: Welcome to Tiny Show and Tell Us, the bonus series where you write in with your favorite science story, fact, or piece of news. We read your email aloud and then dive deeper. I'm Sam Jones, the exec producer of Tiny Matters, and I want to give a big, big thank you to science writer and chemist Anne Hilden for doing the research for this episode. All right. Today I'm psyched to be here with science communicator and producer, George Zaidan. George, hi and welcome!
George Zaidan: Hey. Hey. Happy to be here hosting a few of these with you and diving into some show and tells from listeners. Before we get into things though, just a reminder that Tiny Matters is always looking for you to write in, because that's what makes future episodes possible. You can email us at tinymatters@acs.org or click the Google form link that we put in the episode description. All right, let's do this. And Sam, since I'm a first timer, I will let you kick things off.
Sam Jones: How kind of you. So my tiny show and tell us is from listener Cecilia, and this is a really feel good one. So I'm excited actually to kick things off today.
George Zaidan: Excellent.
Sam Jones: So Cecilia wrote in and said, "When dogs see humans, their brains react scanned via MRI in the same way for love."
George Zaidan: Aw.
Sam Jones: Yeah.
George Zaidan: That's so feel good.
Sam Jones: I know. So I love this. And we actually have an episode from November, 2023 called We Don't Deserve Dogs, the Science Behind the Human Canine Relationship. So if you want to dive more into, not just love from canines, but a bunch of other things, that's episode 46 if you want to check it out.
George Zaidan: Do the people know that you are a dog owner, Sam?
Sam Jones: I feel like they probably should know, at this point, because I can't shut up about it. No. I am a dog owner. I have two dogs. I'm obsessed with them. George, you're also a dog owner.
George Zaidan: I am a dog owner and also obsessed with my dog. Just one, not two though.
Sam Jones: Yeah, it's a little out of control for me, at moments. But I've accepted my role as a crazy dog lady. Okay, so let's talk a little bit about this. There have been a number of studies using fMRI to see what's going on in canine minds and the canine brain. So functional magnetic resonance imaging, or fMRI, it's noninvasive. It just really measures brain activity by detecting changes in blood flow.
Some fMRI studies have focused on activity in the caudate nucleus. So this is a structure that's involved in the brain's reward system. So while the caudate nucleus assists in a bunch of different things, like learning, motor functions, goal-directed actions, it is strongly activated by dopamine, and it's involved in attachment behavior. And so in animals, this correlates with motivation to engage with different objects or targets, depending on what species you're talking about. In humans, it's also said to correlate with romantic love.
And so in her research into this topic, Anne came across a group of researchers who have done a lot of experiments in this area in working with dogs. And so I'm going to talk about some of the work that they've done. I'm talking about mainly this guy named Gregory Berns, who's a psychologist at Emory University, and he teamed up with a bunch of different colleagues as well as a dog trainer, very important-
George Zaidan: Oh, yeah. That's key.
Sam Jones: ...named Mark Spivak. The first task, in all of this, is to train dogs to lie perfectly still in an MRI machine.
George Zaidan: That's very, very easy, as we all know, to get a dog to stay still.
Sam Jones: Yeah, I know. I know. So they were able to do this and then confirm that they could actually detect caudate nucleus activation in dogs when they saw a hand signal that meant that a food reward was coming, versus a signal that meant no reward.
George Zaidan: Oh, interesting.
Sam Jones: I'm going to really quickly... George, I'm going to share this with you.
George Zaidan: Okay.
Sam Jones: But if you just scroll down here, you can actually see a very cute photo of a dog named Callie lying in a fMRI machine.
George Zaidan: We should actually note for everybody that the journal link you sent me is PLOS One, which is open access. So anyone can go and see this picture.
Sam Jones: Yes, yes, yes. I will link to this in the episode description.
George Zaidan: Oh my God. That is adorable.
Sam Jones: Yeah, she's so cute. She's so cute. My dogs would never, ever-
George Zaidan: Oh, no. No, no, no. Also, MRIs are loud as you are, no doubt, aware.
Sam Jones: So loud.
George Zaidan: Yeah. So this is impressive that she's just so focused on... Is that the trainer in Figure B?
Sam Jones: That's not the trainer that I was mentioning. I am not sure who that is. That could be one of their colleagues who they're working with, but she's so cute.
George Zaidan: Yeah, so cute.
Sam Jones: Okay, so back to the studies-
George Zaidan: Back to the science.
Sam Jones: Yeah, we had to take a moment to look at that. Okay. So then, they went on to measure whether the response was different depending on if the dogs receive the hand signals from their handler versus a stranger. So does it make a difference if it's the dog's owner? The reward response was always bigger for food than no food, obviously.
George Zaidan: Good. Yeah.
Sam Jones: So they found that the response was bigger when looking at a stranger in dogs that are more aggressive, actually.
George Zaidan: Really?
Sam Jones: But for less aggressive dogs, bigger when looking at their handler, which I thought was really interesting. In dogs who are aggressive, you're seeing more of this brain activity when there's someone that they don't know, there's a stranger. Versus dogs that are less aggressive, they're seeing the biggest change when they're looking at their owner.
George Zaidan: How do you interpret that? What does that mean?
Sam Jones: Their main point in this is that response depends on canine temperament as well. I think that was their big, big message there. But I would think that you are seeing just as much intense brain activity in that region as a response, like a protective response, as you are a love response. And it just depends what is the dog's default mode maybe.
George Zaidan: Oh, interesting.
Sam Jones: I don't know. That's sort of my armchair expert interpretation of it a little bit. But it is really interesting. And also I'm like, "Thank goodness for the canine handler," because if a dog is supposedly a bit more aggressive, how do you train that dog to be in an MRI machine to begin with?
George Zaidan: Yeah, seriously. Actually, yeah. That's a good question. How did they know which dogs were more aggressive than I guess... The owner would tell them, I guess.
Sam Jones: I think that was part of it. I didn't go super deep into all the methods of that article, but this is just kind of interesting. I'm a little off the topic of love at this point, but I think it's also just interesting to know, generally speaking, what kinds of experiments people have done to try and understand what's going on in a dog's brain. So I have a couple more of those, and then I'm going to talk about... I guess I can say love specifically, but it's still a bit of a reach. But I don't know. I think it's real. I think dogs love us. We love them. Case closed. No.
Okay. So then this researcher, Berns, and his colleagues also tested dog's caudate activation when smelling the sense of familiar and unfamiliar dogs and humans. What they found was that the dog's reward response was the strongest when smelling a familiar human-
George Zaidan: That makes sense.
Sam Jones: As opposed to an unfamiliar dog or a familiar dog.
George Zaidan: That makes sense. Yeah.
Sam Jones: Yeah. Yeah. My dogs are so obsessed with each other that I wonder if they'd be more excited to smell each other than me.
George Zaidan: When we were getting our dog, I was told not to get two dogs from the same litter, because they would bond to each other more than they bond to you. So that would be an interesting experiment to run, too.
Sam Jones: That would be interesting, because mine are not from the same litter. They're like a year and a half apart. But I feel like our older dog is like, "This is my best friend/baby," a little bit. Anyways... And then they actually did an experiment where they measured caudate activation in response to signals that meant that the dogs would receive food or praise, and they showed roughly equal or greater activation to praise versus food. That totally checks out with my dogs, because they're really not very motivated by food. They're much more motivated by our response to them. But again, this is still... It's kind of a mixed bag with this.
So all of this definitely indicates that dogs can have this very positive association toward their human, specifically. And seeing them, smelling them, makes them very happy a lot of the time in a similar way that food makes them happy, and that there is still this varying level of attachment depending on the dog.
But there is one study that I feel like is the closest thing to being able to say that dogs feel love. And so in it, the researchers tested the effects of looking into your dog's eyes. So this is a study done in 2015. And I feel like my dogs stare into my eyes sometimes, and it's like, I love it so much. And so what these researchers found was that when people look into their dog's eyes for 5 to 10 minutes-
George Zaidan: Minutes?
Sam Jones: Yes. Prolonged eye contact.
George Zaidan: Wow, okay.
Sam Jones: So I mean, I'm sure you're looking around a little bit, but you're really trying to maintain that eye contact. What they find is that both dogs and people experience a surge of oxytocin.
George Zaidan: Wow.
Sam Jones: Oxytocin, of course, often called the love hormone, the cuddle hormone, the bonding hormone. And there's no touching. It's just looking.
George Zaidan: Oh. You're not even holding your dog's head tenderly as you gaze into it.
Sam Jones: No, which is usually the case. It's like me holding my dog, kissing her face, looking in her eyes on repeat for five minutes until she's like, "I'm good."
George Zaidan: That is fascinating. So surge in oxytocin, meaning they were doing blood tests during these?
Sam Jones: Yeah, yeah.
George Zaidan: Okay. Wow.
Sam Jones: Which is so interesting.
George Zaidan: It is interesting. And it's interesting. I'm glad they tested it in both the dogs and the humans, because that result makes a lot of sense. Because you get a lot of joy and satisfaction from looking at your dog's eyes.
Sam Jones: Yeah, absolutely.
George Zaidan: Yeah.
Sam Jones: And then this is kind of fun. It's not love-related, but I thought it was interesting. There are also fMRI tests that indicate that dogs can feel jealousy, which I think for any dog owner is like, "Okay." So in some dogs, they had a lot of amygdala activation while watching their caregiver give food to a realistic but fake dog when they put food in a bucket.
George Zaidan: Oh my God.
Sam Jones: Yeah. Some weird jealousy thing going on. And so the amygdala, it's a structure that's deep in your brain. It's known to play a really important role in regulating aggression as well as fear. And so I thought that was fascinating. And then also a different group of researchers detected activation in a dog's amygdala as well as a couple other brain structures when they saw their caregivers interacting pleasantly with another dog. So that is not shocking to me, because when I go and I'm out on a walk and I go pet another dog, immediately mine comes over and is like, "I'm going to lean against you. And don't forget I'm your number one."
George Zaidan: Yeah, my dog growls when I pet another dog.
Sam Jones: So funny.
George Zaidan: It's really funny. And I always playfully was like, "Oh, she's just jealous." But now, I'm like-
Sam Jones: She is.
George Zaidan: She is jealous. Yeah, that's proven.
Sam Jones: Yes. Yes. So yeah, that's it. Thank you so much to Cecilia for that, because that was a really fun one to learn more about, even more than I learned in that regard, I guess, for the dog episode that I worked on last year.
George Zaidan: That is a really fun one. So I'm going to take us from dogs here on earth all the way out to space.
Sam Jones: We have range.
George Zaidan: We have range.
Sam Jones: I like that.
George Zaidan: Miles of range. This one is from Ben, and Ben writes, hemoglycin is a space polymer, which just space polymer already exclamation point! Present in areas where stars and planets are forming. In addition to faraway galaxies, the polymer likely arrives on earth piggybacking on the 5,200 tons of space dust that lands on this planet each year. Biochemists believe hemoglycin is present on earth because stromatolites, possibly the first life forms on our planets, show traces of hemoglycin and likely used the polymer as an energy source. Now, using the James Webb Space Telescope, astrophysicists will try to detect hemoglycin as it forms, providing key information on the origins of life on earth and other planets. There's a lot to unpack there. Let's just start with 5,200 tons of space dust falling on earth every year.
Sam Jones: Oh, gross. No thanks.
George Zaidan: So these things are called micrometeorites. They're tiny meteorites. Then they're so small that you need a microscope to see them, and a lot of them look like asteroids under the microscope. You see a picture of it, and you're like, "Oh, that's an asteroid." And then you see the scale, and it's like 90 micrometers. And you're like, "Oh, no. That's a small speck of dust."
Sam Jones: Yeah. That's maybe a grain of sand, if we're lucky.
George Zaidan: Yeah.
Sam Jones: Yeah.
George Zaidan: And so 5,200 tons reaches the earth... Sorry, reaches the earth's surface. That's out of a total of 15,000 tons that hits the earth, and about 10,000 burns up in our atmosphere. So whoa. A cicada just landed on the window outside.
Sam Jones: I was like, "Oh, this is dramatic effect for whatever George is going to say next."
George Zaidan: Oh my God. And now, I'm just looking right at the underside of a cicada. So that is gross. Okay. So space dust, hold that in your head. We're going to come back to it later.
Sam Jones: Okay.
George Zaidan: So hemoglycin, as you can guess from the name, it contains iron. And glycin is for glycine. That is an amino acid. And this thing is a polymer. So it has a well-defined structure. It is 2 chains of 11 glycines each, each of which is connected to make a small sheet with iron atoms at either end. And then that little subunit can link together to form really surprisingly complex structures, like tubes, vesicles, things like that. And as Ben mentions, hemoglycin is found in space. We found it on six meteorites.
Sam Jones: Wow.
George Zaidan: These are the types of meteorites that formed about the same time as the planets in our solar system formed. So it's old. And now when I'm reading this, I'm like, "Wait a second. Is this evidence of life in space?" Because it's an organic polymer. It has iron. Here on earth, we have organic polymers with iron proteins. But alas, it is not evidence for life. And the reason it's not, is actually really cool, is that it can form abiotically, which means it can form just spontaneously on its own. It's not produced by life. It is formed in the cold, nothing, darkness of space.
And also, as Ben points out, hemoglycin is found on earth. It's been found on many meteorites, but recently, researchers reported finding it in a roughly 2 billion year old fossil, a fossilized stromatolite in Montana. A stromatolite is a rock that was made by a microbe, which sounds super weird. Right? But you're nodding your head. You've heard of these things before?
Sam Jones: Yes.
George Zaidan: Okay. You correct me if I'm wrong, then. Basically, it's photosynthetic microbes congregate together in biofilms. Those biofilms trap sediment, and that sediment hardens to form a microbial mat. And you get layer, upon layer, upon layer, upon layer of that, over time, a lot of time. And eventually, you have a rock.
Sam Jones: Okay, yeah.
George Zaidan: Does that sound right?
Sam Jones: That makes sense. Yeah.
George Zaidan: So you can find them being produced on earth today. But there were lots more produced, many, many, I guess, millions, hundreds of millions, billions of years ago before more complex life on Earth took over. And they give us a peek at some of the earliest life forms on earth. So what is hemoglycin doing in a stromatolite? The answer is we don't totally know. It could be that the microbes used it as food. It's got an amino acid in there. It's got organic carbon. It could potentially be used as an energy source. But the researchers who wrote this paper came up with a super wild theory, which I'm going to tell you.
Sam Jones: Okay.
George Zaidan: Two billion years ago, there was the Great Oxygenation Event, which is when the Earth's atmosphere went from having no oxygen to having a lot of oxygen. Not as much as we have today, but a lot. And they noted that this stromatolite that they found was found right in the middle of this GOE, great oxygen event. And so they were like, "Hemoglycin can catalyze a transformation of water into hydrogen peroxide, which then breaks down to form oxygen. So maybe this stromatolite kicked off the Great Oxygenation Event."
Sam Jones: Oh, wow.
George Zaidan: That's just a... They did quantum mechanical modeling. They did no bench work to validate this. But it's super interesting. Maybe that is why we have oxygen on Earth today, or one of the reasons.
Sam Jones: I love a wild theory, because I feel like as long as there's... Okay, I'm not talking about wild, conspiracy theories. I'm talking about a wild theory that has some scientific basis to it, because I feel like at the very least, it gets people excited and thinking about it and thinking about how they might design better experiments to test that. I feel like it's more a way of getting people's minds going and leading to some research that wouldn't exist, unless someone came up with a semi wild theory about how the Great Oxygenation Event happened.
George Zaidan: Totally. So that's hemoglycin. It comes to us from Ben. So Ben also wrote that the James Webb Telescope would be looking at how hemoglycin forms. I wasn't able to find that, but I didn't do a ton of research. So Ben, if you're listening, send us the link, and we'll put it in the show notes.
Sam Jones: Perfect. Thanks, George.
George Zaidan: Thank you. Thanks for tuning in to Shiny... Shiny Toe and Tell. Nope, that's not right at all.
Sam Jones: Shiny Toes and Tell Us.
George Zaidan: Shiny Toes... Oh, man. Thanks for tuning in to Tiny Show and Tell Us, a bonus episode from Tiny Matters, a production of the American Chemical Society.
Sam Jones: To be featured in a future episode, send us an email with your tiny show and tell us at tinymatters@acs.org, or click the Google form link in this episode's description. See you next time.
- Caudate nucleus as a component of networks controlling behavior
- The neural basis of romantic love
- Romantic love: An fMRI study of a neural mechanism for mate choice
- Functional MRI in Awake Unrestrained Dogs
- Replicability and Heterogeneity of Awake Unrestrained Canine fMRI
- One pair of hands is not like another: caudate BOLD response in dogs depends on signal source and canine temperament
- Scent of the familiar: An fMRI study of canine brain responses to familiar and unfamiliar human and dog odors
- Awake canine fMRI predicts dogs’ preference for praise vs food
- Neural Responses of Pet Dogs Witnessing Their Caregiver’s Positive Interactions with a Conspecific: An fMRI Study
- Structural organization of space polymers
- 5,200 tons of space dust falls on Earth each year, study finds
- James Webb fact sheet
- Chiral 480 nm absorption in the hemoglycin space polymer: a possible link to replication
- Oxygen production and rapid iron oxidation in stromatolites immediately predating the Great Oxidation Event
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