IRA FLATOW: This is Science Friday. I’m Ira Flatow. If you’ve looked down while you’re eating and saw two big dog eyes longingly stare at you– I have seen this many times with my granddogs– you know the full power of “puppy dog eyes.” You might have even been compelled to share a piece of your steak or your pizza. Who can say no after a dog has activated its sad eyes? 

My next guest is here to talk about how dogs evolve to have puppy dog eyes and why they are so important to the human-dog bond. Anne Burrows is a professor of anatomy at Duquesne University in Pittsburgh. And she joins us via Skype. 

And if you have any questions about how dogs have evolved to be our animal sidekicks, our number is 844-724-8255. You can also tweet us at @scifri. Welcome to Science Friday. 

ANNE BURROWS: Thank you so much for having me. 

IRA FLATOW: So you have a study about how dogs make puppy dog eyes. What did you find? 

ANNE BURROWS: What we found was that a large range of dog breeds all had this muscle around the eyebrow that lifts that eyebrow up, except for the husky. And then we found that none of the wolves that we looked at had this muscle. So that result with the husky not having it was really interesting, because they’re considered to be an ancient breed, more closely related to the wolf than many other dog breeds. 

IRA FLATOW: Why would they not evolve it? Why would the wolf not have it? 

ANNE BURROWS: Well, they probably have some very tiny representation of this muscle that I just couldn’t see with my naked eye. Because you typically don’t evolve something from nothing. 

IRA FLATOW: Yeah, yeah. 

ANNE BURROWS: So they must have something there that just doesn’t function in the same way as it does in the dog. 

IRA FLATOW: We normally think of evolution as taking thousands and thousands and thousands of years. So if we’re talking about people and dogs together and the dogs evolving over time, it must have not been that long ago? 

ANNE BURROWS: Well, it seems like around 30,000 to 35,000 years ago, across the globe people started domesticating these dogs. And they were probably choosing first for traits that were non-aggressive. So maybe this cute, little eyebrow lift kind of came along with those non-aggressive behavioral traits– the smaller teeth, the smaller snout– and just kind of rode along with it. But it is a fast selective breeding evolution, for sure. 

IRA FLATOW: And so it stayed with the dogs? Because I guess people, then, bred more dogs who raised their eyebrows at them? 

ANNE BURROWS: Sure. It seems that over selective breeding, that people did with these dogs, that whether we were conscious of it or not, we were selecting for that really cute eyebrow lift. And it sort of reminds me a little bit of what it was like looking at my infants when they would lift their little eyebrows up. It just triggers this nurturing, care-giving response when we see it. 

IRA FLATOW: Is there any breed or breeds of dogs that do it more– have mastered this more than other dogs? 

ANNE BURROWS: That’s a good question. And that’s what my psychology colleagues are doing now, is looking at a broader range of dog breeds. 

We only really looked at the mutts, the Chihuahua, the toy breeds. We didn’t really get a broad representation. But if the results of the husky not having this muscle are applicable to most ancient breeds, that would be really interesting to get that footage and see if they do this movement or, more likely, they don’t do this movement. 

IRA FLATOW: That’s a great idea. I’d like to bring out another guest who is an animal behavior researcher. Sarah-Elizabeth Byosiere is director of the Thinking Dog Center at Cuny Hunter College here in New York. She’s here with me in the studio. Welcome to Science Friday. 

SARAH-ELIZABETH BYOSIERE: Hi. Thank you for having me. 

IRA FLATOW: Just tell me what the Thinking Dog Center is for. 

SARAH-ELIZABETH BYOSIERE: It’s a canine cognition center. So we ask New York City dog owners to come in, bring in their pets, and they play our problem-solving and training games, get fun certificates. It’s pretty enriching. 

IRA FLATOW: Now, so you study animal behavior. 

SARAH-ELIZABETH BYOSIERE: Yes. 

IRA FLATOW: Why do you think dogs have evolved to have these muscles? 

SARAH-ELIZABETH BYOSIERE: Well, dogs are extremely unique in the sense that they interact with us on a daily basis. And that’s different from a lot of other animals. They live in the home with us. We take them for walks. We have this really cool and unique bond with them. And so it makes sense that they have certain physiological features or traits or behaviors that would help them facilitate interaction with us. 

IRA FLATOW: Let me go to the phones, because we have a question that’s leading up to what I would like to ask. Michael in Oakland, California, welcome to Science Friday. 

MICHAEL: Hi. So if there is a special muscle required for this– maybe this is somewhat sideways, but I had heard several years ago that the fact that the young of most or all mammalian species have these adorable, sort of big eyes relative to the size of their faces and so forth is actually itself an evolved thing so that we will pay attention and bond to them, and that we have a similar reaction to animals of other species as we do to our own young, because we’ve all evolved this same response to this same set of features in all of our young. 

IRA FLATOW: Yeah, yeah, yeah. Sarah is nodding here head yes. 

SARAH-ELIZABETH BYOSIERE: Yes. No, exactly. We have these cool features that dogs and other animals have– so large eyes, large forehead. We often call them “pedomorphic features,” meaning that they look like infants. And they’re probably somehow hitching a ride or a hijacking an emotional response that we have already for our young, but just exacerbating it with other animal species. 

IRA FLATOW: Yeah. Anne, do you agree with that? 

ANNE BURROWS: I do. The eyes are just outgrowths of the brain. So mammals are classified partially by having much larger brains than reptiles. So those eyes, as Sarah said, are sort of hitchhiking along with the brain. But it really does hijack our emotions. And we think of that as cute. 

IRA FLATOW: 844-724-8255, 844-724-8255. You can also tweet us at @scifri. I have seen research in recent years about dog bonding with humans and how important the eyes are, for you to make eye contact with a dog, Sarah. 

SARAH-ELIZABETH BYOSIERE: Yeah. So we have these cool studies that have been done on oxytocin, this “love hormone.” And it seems to be, at least with dogs, that we have some evidence that when you mutually gaze at your dog– so you’re looking into their eyes– that your oxytocin increases. 

And we also have some evidence that suggests that the oxytocin levels in the dogs are also increasing. Whether or not this is a causal relationship or how this all works, we still have to figure out. But we do have this positive love feeling that we get from looking into the eyes of our dogs. And it seems like our dogs do, too. 

IRA FLATOW: There’s another question about that, Sarah, that the dog uses its eyes not just to sort of beg for food, the scraps at the table, but when it wants to ask you something, right. Take me for a walk. Let me outside. It has learned how to do that, also. 

SARAH-ELIZABETH BYOSIERE: Yes, it seems to be– I mean, I have my dog. And he certainly uses his eyes to communicate with me in a variety of different ways. And so maybe because we are such a visual species, the dogs have, in a sense, evolved these features or traits to hack into that. 

IRA FLATOW: Anne, what would you like to know more? What are you studying more about this trait in dogs? 

ANNE BURROWS: Well, what my lab is doing now is looking at the microanatomy of the musculature in the dogs and wolves to see exactly how it functions, whether they can hold their facial contractions longer than wolves or vice versa. So that’s specifically what my lab is doing now. 

But I wanted to mention that some years ago, we did the same study on horses and found that horses make this movement, too. So we are wondering if this movement is just part of domestication in general, whether we select a series of eye movements that we interpret as being cute when we domesticate mammals in general. So those are two different pathways that we’re aiming for right now. 

IRA FLATOW: So is it more the eyebrow that the dog is doing than movement of the eyes– sort of the forehead of the dog? 

ANNE BURROWS: Right. If you look in the mirror and make a worried face, you can see the inner part of your eyebrow go up. That’s where we’re finding this muscle and this movement in the dog. So it’s not the entire eye changing shape, but just this portion of the eyebrow. 

But when you look at a dog’s eyeball, it has typically a bigger white area to the eye than many other mammals. And that may help increase the color contrast to the eye and make you focus on the eye more, just like a person’s eye. 

IRA FLATOW: Mm. Sarah-Elizabeth, you agree with that? 

SARAH-ELIZABETH BYOSIERE: Yes, for sure. Definitely. It would be very interesting to see what other dog, kind of canid species like dingoes, for example, or a rewilded dog, how their eye morphology or eyebrow morphology maps on. 

IRA FLATOW: With dogs, you see them– they follow you with their eyes. They make sure to make eye contact. I understand that wolves don’t make eye contact, specifically. Is that one of the differences, Anne? 

ANNE BURROWS: We did find when we took the video footage of wolves and domestic dogs that wolves not only didn’t make this eye movement, they were hesitant– they just didn’t make eye contact with the humans doing the work in general. 

IRA FLATOW: We humans, we use our eyebrows, I think, without even thinking about it. When somebody says something weird, we raise our eyebrows. Or when we’re laughing, we do that. I guess that’s why maybe subconsciously we’re aware of when the dog does that. What do you think, Sarah? 

SARAH-ELIZABETH BYOSIERE: Yeah, for sure. It’s extremely interesting. And it might be the case that, for example, this is a feature that comes about from looking at us. So maybe by having to look up higher to look at a human, these muscles start to kind of come about. And then there are other features that link to this, for example, hacking onto these pathways. 

IRA FLATOW: Hm. Could dogs have chosen us for our eyebrows? 

SARAH-ELIZABETH BYOSIERE: Potentially. I don’t know. We can do some science. 

IRA FLATOW: Yeah, that’s an interesting idea. What do you think, Anne? Could they have chosen us because we reflect their own eyebrows? 

ANNE BURROWS: I think that would be a really interesting experiment, because clearly dogs and humans are co-evolved. They have influenced our social behavior, as well. 

IRA FLATOW: Hm. Let’s see if we can go to the phones, because a lot of dog people are phoning in. Kate in Langdon, New Hampshire. Hi, Kate. 

KATE: Hi. I’m really interested in this show, because I’ve had huskies for 45 years. And one of the things I really like about them is that they’re really independent. But they’re very hard to train, because they don’t care about approval. 

They don’t care if you tell them that they’re a good dog. And they don’t want affection. They’re not particularly wanting of affection. So the whole idea that they don’t have the eyebrow raise is really interesting in terms of that. 

IRA FLATOW: So you’re saying your huskies never look at you with their eyebrows and give that dog face? 

KATE: I don’t see that. They do look at me. And especially when they get older and they’re more food-motivated, they want food and they look at me for food. But because I’ve only had huskies, I’m not really sure what the (LAUGHING) eyebrow raise is. 

IRA FLATOW: [LAUGHS] 

KATE: But I think it goes along with the fact that they’re not particularly driven by affection or approval or even food until they get older. You can’t bribe them with anything. 

IRA FLATOW: That’s interesting. Thanks for calling, Kate. What do you think of that? 

ANNE BURROWS: I can second that. I have a husky mix. And you cannot make her feel bad about anything. And she does not like to be held. 

IRA FLATOW: So she doesn’t put her head in your lap and raise its eyebrow and do all those things the other cute dogs do? 

ANNE BURROWS: Not very often. 

IRA FLATOW: Sarah? 

SARAH-ELIZABETH BYOSIERE: Well, that’s interesting. It also maps on a little bit with some of the oxytocin research that we’ve been seeing, that owners that report that they have a stronger bond or relationship with their dog also seem to have a greater magnitude increase of this oxytocin. So potentially, this is something that might happen. And maybe it is breed-specific. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios. Talking about dogs and their reaction to humans and how they use those eyebrows. Here’s an interesting tweet from Kip, who says, with regards to dog eyebrows, do dogs use this with other dogs? Or is the expression only to get human attention? Wow. Anne, have you ever seen dogs do it with other dogs? 

ANNE BURROWS: That’s one of our step 2 research agendas, is to film dogs interacting with one another. Anecdotally, I watch dogs very carefully in dog parks when I’m out there. And I’ve never seen a dog do this to another dog. I have seen dogs turn and look at their humans and do it, but never dog-on-dog. That’s not proof, but it’s anecdotal. 

IRA FLATOW: Sarah, you’re agreeing. 

SARAH-ELIZABETH BYOSIERE: Yeah. Vision is different in dogs. So potentially, there are different ways that they see the world. Their acuity is less refined than ours. So for something as minute as a little detail in the eyebrows to increase the white around the eyes, it may be more likely that it’s co-evolved with humans or for human use, rather than for interacting with other dogs. But they could still potentially still use it. 

IRA FLATOW: Mm-hmm. You also study dog bowing. 

SARAH-ELIZABETH BYOSIERE: I do. 

IRA FLATOW: What is dog bowing? What does that tell us about how they have evolved? 

SARAH-ELIZABETH BYOSIERE: Dog play bows are this position– you’ve probably seen it at home if you have a dog. The forearms go down. The back is curved. The butt goes up, and the tail starts wagging. And this tells us a little bit about how dogs play or mediate their social interactions, at least with other dogs. There is some research with humans, but I focus on dog-dog interaction. 

IRA FLATOW: Oh, you mean this is what dogs do to other dogs? Instead of the eyebrows, they do the bowing? 

SARAH-ELIZABETH BYOSIERE: They do the bow. 

IRA FLATOW: Huh. That’s interesting. Anne, have you heard about that? 

ANNE BURROWS: I have heard of that. And that makes perfect sense, the explanation about the small face movement. 

IRA FLATOW: Hm. Let’s see if I can get one more call in before we have to go. Let’s go to Tyler in Stockton, California. Hi, Tyler. 

TYLER: Hi. I had heard through either another podcast or another source that one reason that wolves have more upright ears than dogs is due to domestication causing a lowering of testosterone. And the earlier caller was referring to her huskies, which I know have more upright ears, not necessarily making eye contact, and that that might somehow be related. 

IRA FLATOW: Hm. 

SARAH-ELIZABETH BYOSIERE: In terms of the hormones, I’m not so familiar with that. But there are these really cool experiments happening in Siberian foxes where we’ve seen that, even over a short period of time, when you select for affectionate behaviors that you see morphological changes. You get floppy ears like you do in dogs. You get curly tails. You get color changes. So by selecting for certain behavioral traits, we are seeing that there are anatomical changes that are associated with that. 

IRA FLATOW: Mm-hmm. Well, anything else that you would like to know in your further studies, Sarah? 

SARAH-ELIZABETH BYOSIERE: I’d be interested to see if Anne has anything more to say in the future about feral dogs, as well. Do they have these eyebrows? How do they communicate with humans? Do you think they still need it? 

ANNE BURROWS: That’s a good– I mean, we’ve reached out and gotten some coyotes and foxes, but not feral dogs. That’s a really interesting question that I would like to put on my list. 

IRA FLATOW: And you’ll come back and tell us, because we’d like to know. 

ANNE BURROWS: Hope so. 

IRA FLATOW: And we’ve run out of time. 

ANNE BURROWS: [LAUGHS] OK. 

IRA FLATOW: Sarah-Elizabeth Byosiere, director of the Thinking Dog Center. And she’s adjunct professor at Cuny Hunter College here in New York. Thank you. And it’s very fascinating stuff that you’re doing. And also, Anne Burrows, professor of anatomy, Department of Physical Therapy at Duquesne University in Pittsburgh. Thank you. 

ANNE BURROWS: Thank you for having me.

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