Do animals dream? If you’re a pet owner, it may seem obvious that your furry friends dream. Most of us have seen dogs running in their sleep or cats meowing during a nap. But this is an academic podcast and really proving that animals dream isn’t so simple.
In his new book, When Animals Dream: The Hidden World of Animal Consciousness, philosopher David M. Pena-Guzman of San Francisco State University argues the science shows that animals really do dream, and that those dreams are evidence of consciousness.
(Episode published July 21, 2022)
Paul Rand: There are a few things in life that are more personal and more mysterious than dreams. Some have gone so far as to say that dreams are an example of what makes humans different from all other animals, that they’re evidence of our unique consciousness that no other creatures possess. But not everyone agrees.
David Peña-Guzmán: I think it’s deeply problematic that we tend to think about mind by beginning from the human case and then looking to see which animals fit into our framework of the human mind.
Paul Rand: That’s David Peña-Guzmán, a philosopher at San Francisco State University and the author of a new book, When Animals Dream: The Hidden World of Animal Consciousness.
David Peña-Guzmán: The human mind is only one of the many minds that nature has produced by the process of evolution. And even if we are particularly attracted to it because it’s the one that we have, there’s nothing objective that suggests that it’s the only one or even the highest one. You really see that diversity at the level of dreams.
Paul Rand: If you are a pet owner, it may seem obvious to you that your furry friends dream. We’ve all seen our dogs yipping in their sleep, or are cats meowing during a nap. But this is an academic podcast, and actually proving that animals dream isn’t so simple.
David Peña-Guzmán: Because, historically, the way that we know that other people dream has been because we ask them and they answer. “Oh, last night I had a really bizarre dream. Let me tell you about it.” And so, with animals, given the absence of that shared common linguistic schema, how do we get to the conclusion that, in fact, other animals also dream and maybe dream in ways that might be similar to the way we dream?
Paul Rand: The scientific community has been so agnostic on this that until 2020, almost no study of sleeping animals in the whole literature use the word dream.
David Peña-Guzmán: I told myself, “There’s no way that there are literally thousands and thousands of publications on the sleep of so many different species, and yet virtually none of them in the 20th century mention the word dream, dreams, or dreaming.” So you don’t find the verb, you don’t find the noun, you don’t find the gerund.
Paul Rand: Amazing.
David Peña-Guzmán: As I began digging deeper and deeper into the science, I began to realize that this absence was actually quite systematic to the point that it seemed like it almost might be symptomatic. It might be symptomatic of an attempt to avoid an issue. In many ways, the book is me trying to situate myself at the heart of that absence and asking, “Why is it missing?” and making the argument that that absence needs to be filled out.
Paul Rand: There are two arguments Peña-Guzmán makes. The first is scientific, that all these studies really do prove that animals dream. The second comes from his work as a philosopher, that animal dreams raise profound questions about our ethical relationship to these creatures.
David Peña-Guzmán: A lot of people think that dogs and cats and hamsters, they can definitely feel emotions for which there is a very clear evolutionary function. Like fear, it helps you escape from predators. But then there are other more complicated emotions that sometimes we’re not sure if animals really have them, and the book sheds light on some of those emotions.
Paul Rand: From the University of Chicago Podcast Network, this is Big Brains, a podcast about the pioneering research and the pivotal breakthroughs that are reshaping our world. On this episode, do animals dream, and if so, what that says about their consciousness? I’m your host, Paul Rand.
Paul Rand: Do animals dream? Well, it’s a simple question with massive implications. To answer it, Peña-Guzmán poured through thousands of animal sleeping studies from decades of research, and what he found surprised him. Although, none of them used the word dream, he saw evidence of dreams all over the place.
David Peña-Guzmán: We do have enough evidence to believe that other species have these nightly experiences of a fantastical, almost phantasmagoric world.
Paul Rand: And he divides that evidence into three different buckets. The first is electrophysiological evidence.
David Peña-Guzmán: Yes, electrophysiological evidence just refers to what we’ve learned about the animal brain in the state of sleep by looking at brain activity. So here we’re talking primarily about EEG studies.
Paul Rand: Basically, measuring the electrical activity of brains and creating correlations between different states to figure out what that activity signifies.
David Peña-Guzmán: If you compare what the brains of many animals are doing when they are asleep and when they are awake, so if you just hold them side by side and try to juxtapose them, you realize that there is a significant difference. However, in the middle of the sleep cycle, typically there is a moment when the electrical activity, the patterns of neuronal activation that we see coming out of the animal brain begin to resemble those of the waking state. They don’t just begin to resemble them, in fact, they match them. They match them one to one to the point where we can start making some pretty impressive inferences.
Paul Rand: Is that the same thing in humans, by the way? Does that occur just like that in humans?
David Peña-Guzmán: That’s correct. We look at what the brain of human sleepers are doing. By now, we have enough data to try to map or match certain sleep experiences with waking ones.
Paul Rand: For instance, a study of zebra finches from 2000 showed that the same electrical activity that happens when they sing their bird song while awake on occasion will also happen when they sleep. The same exact parts of the brain light up in the same exact order. Peña-Guzmán argues that this means we can safely infer that they’re dreaming about singing. Interestingly, the researchers in this study all said this was only evidence of an algorithmic implementation.
David Peña-Guzmán: As a general rule, scientist never use a high level psychological concept, let’s say like belief or memory or imagination, to explain the behavior of non-human animals if you can explain the behavior just as well, only appealing to lower processes that have a deeper evolutionary history.
Paul Rand: The rule is called Morgan’s canon, and many scientists adhere to it. As Peña-Guzmán writes in the book, researchers believe that birds don’t experience the song anymore than my laptop experiences running Adobe Reader. Of course, Peña-Guzmán disagrees, and he points to the fact that the zebra finches’ throats moved exactly as though they were singing during these events. So could the electrical activity and the embodiment combined confirm that they’re actually experiencing a dream? Other electrophysiological studies provide further evidence. For instance, we can also learn about animal dreams by looking at the way electrical activity cycles during sleep.
David Peña-Guzmán: We know that in humans and a lot of other mammals, the two phases are what are known as non-REM sleep, or deep sleep, which is when you first fall asleep and you go into that very deep, restorative sleep. And then the second phase of the sleep cycle is what is known as REM sleep, rapid eye movement sleep. And that’s when you see that spike in neuronal activation that starts giving you those parallels across the waking/sleeping divide.
Paul Rand: One of the most important studies on this had to do with another kind of zebra, this time, zebra fish.
David Peña-Guzmán: The zebra fish study that I looked at is a publication that shows two things. On the one hand, it shows that fish, like zebra fish, they have the same biphasic sleep cycle that we find in mammals. At some point, when they’re asleep, it’s almost as if there is a neuronal revolution that erupts in the brain, and you start seeing the brain lighting up like a Christmas tree and lighting up in patterns that are comparable to the way in which the brain lights up in you and I.
Paul Rand: That’s remarkable.
David Peña-Guzmán: And so, it really extends the possibility of dreaming to species as different from us as a tiny, tiny little fish.
Paul Rand: The second set of evidence Peña-Guzmán points to has to do with the behavior of animals while they sleep.
David Peña-Guzmán: I look at research from the 1990s conducted by the primatologist, Kimberly [Mukabee 00:09:04], who decided to look at what chimpanzees do when they fall asleep. And so, she conducted an experiment at the University of Washington in which she mounted a bunch of cameras inside the sleeping quarters of a group of chimpanzees, just to see what they do. Many of these chimpanzees began signing in their sleep using American Sign Language.
David Peña-Guzmán: Now, these chimpanzees had already been taught ASL as part of their upbringing. And so, they were used to communicating with human researchers but also with one another for a long time using ASL. And so, for them, ASL was a mode of communication. And so, the fact that you suddenly see the emergence of signing behavior when the chimpanzees are passed out and asleep becomes indicative that they are having a dream experience in which they are signing.
Paul Rand: And these weren’t just easy-to-interpret hand twitches. As Peña-Guzmán writes in the book, “These were elaborate signs that the probability of this happening by pure chance is astronomically small.”
David Peña-Guzmán: So sometimes she talks about one chimpanzee signing asking for coffee. That particular example stood out to me because I thought to myself, “How would a chimpanzee even know what coffee is? That doesn’t even make sense.” And so, I sent an email to Professor Mukabee who responded to me saying, “Well, we actually used to give them coffee. And over time, they learned what coffee was and they learned to ask for it.”
Paul Rand: Man. Okay.
David Peña-Guzmán: And so, I think some of these chimpanzees were dreaming of having coffee. In itself, that already raises a lot of questions about the cognitive capacities of these animals, but it also raises an interesting point about the nature of dreaming more generally. Animals like chimpanzees, they don’t just dream of scenarios that are evolutionarily significant, like how do I kill a prey, or how do I escape from a predator? But rather, they dream of things that they pick up in the course of experience. So their dreams are, I would say, social and cultural. They have to do with the specific experience that this particular animal has had. Because, of course, you’re never going to find a chimpanzee who dreams of coffee and who signs for it using ASL in the wild. And so, it brings the importance of individuality, of personality, of personal experience into the picture in a way that I think is highly suggestive.
Paul Rand: The final argument for animal dreaming comes from looking at the neuro analytical studies, the actual anatomy of animal brains, and the most prominent study involves cats.
David Peña-Guzmán: Yes, the study from the 1960s involving cats is very famous in the field of dream science because it was conducted by one of the founders of modern dream research, a French neuroscientist named Michel Jouvet. Michelle Jouvet had this idea that there must be a reason why when we dream we don’t physically act out our dreams, right? So we are horizontal. We are immobile for the most part. So what is happening in sleep that prevents us from really physically acting out our dreams? And so, he came to the conclusion that there is a particular part of the brain that is in charge of producing that state of atonia, or lack of bodily movement, during the dream state such that even though our minds think that we are actively engaged in the world, physically we are not. He asked himself, “What would happen if I removed the part of the brain that keeps the body in a state of atonia?”
David Peña-Guzmán: And so, he essentially did that with cats. He grabbed a group of domestic cats, and he intervened surgically into their brains and removed the part of the brain that brings about that state of atonia. What he found was nothing less than revolutionary in its time and I think today. He found that, indeed, the cats that had been surgically affected suddenly would perform the spectacle of their dreams from top to bottom. There are videos of this on YouTube for those who might be interested. If you Google Michel Jouvet cats, you can find some of the original footage of the cats in his laboratory.
Tape: This remarkable film shows a cat in the middle of a night’s sleep.
David Peña-Guzmán: And these are cats that start literally fighting with imaginary enemies in the lab while they’re asleep, but they’re moving around, they’re walking, they’re jumping.
Tape: Now, believe it or not, the cat is still asleep. But because some of its nerve pathways have been cut, it’s acting out its dreams.
David Peña-Guzmán: They’re attacking the air with their paws.
Tape: Its brain shows all the signs of REM sleep, but its muscle activities suggest an exciting dream life chasing flies and mice.
Or they’re also cats that start displaying fear behaviors. The ears go down. They start receding. They start showing the teeth as a mode of defense. And so, you can see the spectacle of their dreams played out for you as a motoric performance.
Tape: If our muscles weren’t paralyzed, we too would probably act out our dreams in this way. Perhaps it’s fortunate for our partners that we don’t.
David Peña-Guzmán: And so, this research from the 1960s helped establish that there is, in fact, this period of the mammalian sleep cycle, which Jouvet called paradoxical sleep, where there is indeed a paradox, because the body seems to be inactive yet the mind is fully active. What he did is he reactivated the body during that phase of sleep as a way of letting that mental reality that was playing internally manifest itself outwards.
Paul Rand: And like those defensive cats, not all animal dreams appear to be good. There’s just as much evidence of animal nightmares as animal dreams.
David Peña-Guzmán: I also talk about research that we have from field studies on elephant communities showing that many elephants experience terrific nightmares, especially in the wake of trauma.
David Peña-Guzmán: When young elephants, in particular, experience a deeply traumatic effect such as witnessing human poachers murder one of their family members and cut out the tusks, those young animals remember that scene. It just gets burned into their memory.
Paul Rand: Oh gosh.
David Peña-Guzmán: And later when they are asleep, because they’ve been traumatized, they begin replaying that over and over again. They replay it so much that it can become a problem for their mental wellbeing. What I try to do is paint a picture of the emotional depths of other animals, just all the complex, deep, revealing, emotional states that they can experience and how sometimes those come out in various kinds of dreams. They can be negative dreams like nightmares, but they can also be extremely positive dreams where you see not so much fear and terror and trauma coming to the foreground, but desire and aspiration and hope as well.
Paul Rand: Putting all of this research together, Peña-Guzmán shifts from science to philosophy, and he says that the evidence of animals dreaming should raise all sorts of philosophical and ethical questions about animal consciousness. That’s after the break.
Paul Rand: If you’re getting a lot out of the important research that’s shared on Big Brains, there’s another University of Chicago Podcast Network show that you should check out. It’s called Capitalisn’t. Capitalisn’t uses the latest economic thinking to zero in on the ways that capitalism is and, more often, isn’t working today. From the debate over how to distribute a vaccine to the morality of a wealth tax, Capitalisn’t clearly explains how capitalism can go wrong and what we can do about it. Listen to Capitalisn’t, part of the University of Chicago Podcast Network.
Paul Rand: All right, you’ve made a real case about animals dreaming. That, of course, leads to this next thought of consciousness and where does that lead us? In your book, you talk about three levels of consciousness when it comes to animals, and I wonder if you could just talk about, well, what is consciousness and why are we having three levels of that consciousness?
David Peña-Guzmán: One thing that anybody who has read any articles or books in the philosophy of consciousness knows is that if you ask 10 people to define consciousness, 10 experts, you’re going to get at least 11 answers. There is very little agreement about how to define this term. It’s just very slippery. It’s very tricky. Since we can’t really agree on what consciousness is, why don’t we just start cutting it up into pieces? That way, we might make a little bit more progress. And so, in the book I argue that we should think about consciousness as having three different phases or three different dimensions. One of them is what I call subjective consciousness, and that refers to that egological, phenomelogical self that is at the center of a world, being a self in the world and being an ego that finds themselves at the center of a phenomenal or phenomenological field. And what that means is simply seeing the world from a perspective and moving through that world with a sense of agency.
David Peña-Guzmán: One of the arguments that I make in the book is that this kind of consciousness is inherently connected to dreaming. You cannot dream and not have this kind of consciousness, because by definition, a dream is the manifestation of a world or the disclosure of a world of experience to an ego that is the center of that world. So let’s try to think about what a completely egoless dream would be, and it just makes no sense. I mean, whose dream would that even be if there is no ego in it? Even that minimal dream of here I am surrounded by absolute whiteness, even that is a world that has an ego at the center. The act of seeing that whiteness and looking around and moving around in it refers to that egological structure of that experience, that it cannot be understood without reference to an ego that ground sets.
Paul Rand: And if animals dream, they must have egos. There must be a self within the chimpanzee that experiences the coffee it’s drinking in the dream. And Peña-Guzmán builds further with his second level, effective consciousness.
David Peña-Guzmán: Yes, effective consciousness refers to effects and sentiments and emotions. The idea here is also that there is a very close connection between dreaming and this kind of emotional consciousness or effective consciousness. The reason for this is because all of our dreams are fundamentally emotional to some degree. It’s not as if we relate to that dream as completely disinterested spectators that could care less about that reality. Rather, when we are dreaming, we become invested in the scene that is unfolding before our eyes. In the book I talk about this emotional, hedonic dimension of dreams, and I develop it, in particular, through, as I mentioned earlier, animal nightmares. Because I think that in animal nightmares, that’s where we see coming to the foreground the emotions of other animals most clearly in the context of a dream.
Paul Rand: Your last bucket that you got into in terms of levels of consciousness is metacognition. Play that out for me.
David Peña-Guzmán: Metacognition refers to cases in which the mind starts thinking about its own thinking.
David Peña-Guzmán: In the history of philosophy, people have been fascinated by metacognition. In fact, people have used metacognition as one of these concepts that are used to police the boundary between humans and other animals. So it’s not uncommon for philosophers, for anthropologists, for scientists to argue that what differentiates humans from the rest of the animal kingdom is that, well, we have metacognition. Interestingly, since the 1990s, there has been an explosion of research on animal metacognition.
David Peña-Guzmán: One of the most common research paradigms for this is what is known as metacognitive monitoring. In short, the way it works is this: let’s say that you give an animal, let’s just choose, let’s say, a rhesus monkey, as an example, a very simple task where the monkey has to look at two pictures and decide which one is a friend and which one is a stranger. Over time, the monkey learns the test, and they start performing pretty well. And you reward them with something that they like every time they get it right. Let’s say that you give them a grape. Now, researchers have realized that if you start increasing the level of difficulty of the test, let’s say that you start decreasing the resolution of the picture so they start getting a little bit blurrier and blurrier with time so that you can’t really tell the difference between the two as easily, the monkeys will start hesitating. They’ll start taking a step back and essentially wondering, “How sure am I of my decision right here?”
David Peña-Guzmán: And on top of that, if you add an option so that they’re not just choosing left or right, but suddenly they have a third option, a third button that they can press, that essentially means I don’t know, and then you give them, let’s say, half a grape for saying I don’t know when they really don’t know, many of these animals will, in fact, start pressing the I don’t know button right at the moment that the pictures start getting a little bit too difficult for their perceptual systems to discriminate, indicating that these animals do what is known as metacognitive monitoring. They monitor their own level of certainty before making a decision.
David Peña-Guzmán: The connection to dreams here, I’m sure you’ve had a very bizarre dream where there are elephants flying or there is water moving upwards, things that just don’t even make sense from the standpoint of physics.
Paul Rand: Yes. Right.
David Peña-Guzmán: And yet, when you are in the middle of that dream, you don’t question it. That’s because we know that our cognitive guards are lowered when we are in the dream state. And so, typically, dreams are not the best place to go if you really want to study cognition. With one exception, and that is lucid dreaming.
David Peña-Guzmán: There are certain dreams that are very specific in which suddenly you regain all your cognitive capacities and you start realizing, “Wait a minute, I’m pretty sure this is a dream.” Lucid dreams are a very good example of human metacognition, because it’s a case in which you are thinking about your own thinking. You’re saying, “Wait a minute, this thing that I believe is real is in fact not real.” Now in the book, I try to connect this to animals. I have to say for our listeners that this is probably the more speculative section of the book. While lucid dreaming is a kind of metacognition, and if other animals are metacognitive agents, then it’s possible that they could have lucid dreams. We do, in fact, know that there are some animals that have metacognitive capacities. And so, I draw a weak conclusion, but it’s a conclusion that really boggles the mind and that really pushes the limits of our thinking about the minds of other animals. And that is that there might be some other species, in particular, some birds and also the great apes, that might have lucid dreams.
David Peña-Guzmán: I mean, how shocking is that, the idea that an Orangutan could fall asleep, have a dream, and then in the middle of the dream say, “This isn’t real,” that they would pass judgment on reality itself? And that’s another thing that philosophers have for a long time used as a marker between humans and animals, that we’re the only ones who can tell the difference between reality and appearance, but maybe not.
Paul Rand: So if Peña-Guzmán is correct, both that animals dream and that these dreams are further evidence that animal consciousness is much deeper than we may think, it raises a whole host of ethical questions.
David Peña-Guzmán: When it comes to animals, there has been a lot of debate about whether we can attribute or assign rationality to them or whether we can even assign cognition. The argument that I make is that in some ways that doesn’t really matter because the kind of consciousness that we should really pay attention to is not access consciousness or cognition and rationality, but phenomenal consciousness. In short, it refers to subjective states that maybe are not rational and that are not easily communicated. Think about something like color. When I see around me, for example, right now I’m in my house, and I see the color blue because I have a water bottle next to me, my experience of seeing the color blue is conscious. I am aware that I am seeing it. And yet, the experience of blueness itself, it doesn’t seem like the kind of thing that I can describe as rational necessarily. It’s more felt. It’s more effective. It’s more embodied. So if I talk to somebody who has been blind from birth, I simply cannot convey my experience of blueness.
David Peña-Guzmán: Now, the connection to dreaming here is that, as I mentioned earlier, the majority of our dreams with the exception of lucid dreams are not really cognitive activities. In fact, our cognitive abilities are decreased when we dream. But what we do know about dreams is that they are perfect examples of phenomenal states because you see things, you hear things, you feel things even if you’re not thinking rationally or using high-end sophisticated cognitive operations. And so, dreams are a very good example of a phenomenal mental state.
David Peña-Guzmán: And so, then I just draw all these pieces together in the form of a logical argument and I say, “If the reason that we ought to care about an entity is because it has phenomenal consciousness, since that’s the foundation of moral status, and if animals have phenomenal consciousness by virtue of dreaming, because dreams are phenomenal states, then it follows that animals have moral status and that they deserve to be included in our moral frameworks.” And so, learning that an entity has a mind raises ethical questions.
Paul Rand: You’re a vegetarian, I bet.
David Peña-Guzmán: Yes, that’s correct.
Paul Rand: I can’t imagine you would be anything but given what’s inside your head and what you’ve been studying.
David Peña-Guzmán: Yes. This is a moral question that anybody who works in this area faces at one point or another. We all navigate it differently. People end up in different places, but it’s difficult to avoid without, at some point, feeling a very heavy sense of cognitive dissonance. If you don’t translate it into action, it can become a little bit unbearable, really.
Paul Rand: On a very simplistic level, for people that are pet owners, what insights on a very practical level do you think people would be surprised knowing about their dog or their cat?
David Peña-Guzmán: Paradoxically, I don’t think pet owners would be all that surprised with some of the conclusions that I draw in the book, and it’s because, in many ways, this book is a defense of the intuitions that many pet owners have about their pets that scientists tend to be skeptical about. It’s actually the pet owner or the person who lives with animals or who shares their lives with animals that is the hero in the story insofar as they’re the ones that give the animal the benefit of the doubt. And it’s a benefit that I think animals are entitled to.
David Peña-Guzmán: In fact, one of the really interesting things that has happened ever since the book came out, and it only came out about two weeks ago, is that I’ve now started receiving several emails from people who are pet owners who start sharing the stories with me of their pets saying, “I never really felt comfortable talking about what I thought was going on until I read the book. It gave me the language to talk about it and to relate to the animal with whom I share my life on a new level.”
David Peña-Guzmán: The minds of other animals are already weird enough by virtue of being alien, but their dreams are even more alien because dreams are already bizarre. And so, I really want my readers to walk away from it and maybe look at an animal sleeping and just wonder, “I wonder what’s happening in the mind of this creature.”
Tape: Big Brains is a production of the University of Chicago Podcast Network. If you like what you heard, please leave us a rating and review. The show is hosted by Paul M. Rand and produced by me, Matt Hodapp and Lea Ceasrine. Thanks for listening.