When a dog growls at you, is it angry? When a squirrel flees up a tree at your approach, is it fearful? When an elephant stands for days on a spot where another has died, is it grieving? If you live with an animal (the non-human kind) you might think the answer is obvious, but the scientific question remains tantalisingly open.
Let’s start with some well-established findings. Every animal’s brain regulates its organs, hormones and the other systems of its body via electricity and swirling chemicals. Inside your own body, these processes keep you alive and also, somehow, produce your general mood in ways that scientists are still puzzling out. Your mood is kind of a summary of how your whole body is doing. It ranges from pleasant to unpleasant and from still to activated. Mood is not emotion – it is always with you, even when you’re not emotional.
Do other animals consciously feel mood as we do? They cannot tell us, so we can’t know for sure. Philosopher Peter Godfrey-Smith, in his book Metazoa, proposes three behaviours that may provide clues. Does the animal tend to and protect its injured body parts? Many do, including birds, mammals, octopuses and crustaceans, but flies can lose a limb and carry on as normal. Does the animal appear to consider costs and benefits? Crabs will tolerate electric shocks in order to remain in place if the smell of a predator is wafting about. Does the animal seek pain-killing chemicals after an injury? Chickens do – they choose drug-laced feed over the regular stuff when they’re hurt. Some fish will swim in shallower waters, where predators may lurk, to reach and consume opioids. Bees, however, don’t display these kinds of behaviours.
Moving from mood to emotion is trickier because the question of animal emotions depends on how you define “emotion” in the first place. Some scientists think emotions are specific feelings, such as the dread of fear, and ask if other animals feel them. Other scientists define them as behaviours with useful survival functions, such as actions that allow an animal to escape a predator. Still others define emotions as the brain circuits that correspond to those behaviours; for example, they search for a specific “fear circuit” that could trigger freezing in situations we would consider fearful.
Each of these definitions of emotion requires human inference – observing an animal’s physical state and guessing at its psychological meaning. To tackle this problem, let’s attempt to separate out the human perspective. Consider a fly, a rat and a person in situations that we’d think of as frightening. Sweep a fly swatter above the fly, and it rubs its legs together rapidly. Train the rat to associate an audio tone with a painful shock; play the tone alone and the rat freezes in place. Observe a man who is being followed by a stranger on a dark street and he widens his eyes, constantly looking back while his heart pounds in his chest.
A typical scientist observing these animals concludes that all three are exposed to a threat and are therefore in a state of fear. But here’s the curious thing: the three examples have virtually nothing in common physically. They involve different kinds of brains in different situations, moving different kinds of bodies in different ways. So, where’s the similarity that makes all three situations “fear”? It’s in the scientist’s own brain. You may well experience a world full of animals who cry in sadness, screech in terror and skulk in guilt but these are effortless inferences on your part – human perceptions that give meaning to cries, screeches and skulks.
I’m not saying emotions are imaginary. I’m saying our brains have evolved to instantly group things together as similar, even when they are physically different, such as leg-rubbing flies, freezing rats and wide-eyed humans. We categorise like this 24/7, most of the time without realising it. As an example from a different branch of science, Mercury, Earth and Jupiter are all planets, so they must be similar in some way, right? Well, Mercury is a tiny, hot, barren rock. Earth is three times larger and its surface mostly water, teeming with life. Jupiter is a gigantic ball of gas. Where’s the similarity? In our brains. We focus on abstract features such as “orbits the sun” and ignore immense differences in size and substance to group these heavenly bodies into the same category. A big rock in space is physically real but the category “planet” is a human creation.
Emotions that you see and hear in others are also human creations. When you experience another animal as fearful, you are not “detecting” fear in any objective sense. It is a construction in your brain that happens automatically, and faster than you can snap your fingers. Your brain groups different movements, sounds and other physical signals together, into the same category, to give them emotional meaning. If a fly beneath a looming fly swatter rubs its legs together on one occasion but freezes on another, a human brain can generalise across both cases to interpret the fly as being in a state of fear. But are fly brains equipped to go beyond physical features and construct this level of meaning? How about the brain of a cat or dog? The answer is probably no. Some animal brains, such as those of chimps, can categorise abstractly, but to the best of our knowledge only we have the wiring to compute abstractions of this magnitude. A non-human animal’s fearful state is real for human observers but not necessarily for the creature itself.
As scientists, we must be extremely careful to separate our physical observations from our mental guesses. When we don’t, it can be really problematic. If a scientist discovers a brain circuit that controls freezing behaviour in rats, calls it a “fear circuit” and discovers that a certain drug can suppress the circuit, it’s a mistake to assume that the drug tames the symptoms of human disorders such as PTSD.
When we slip off our lab coats, it might be beneficial to assume that other animals have the same emotions we do because it encourages empathy – it’s easier to admit them into our moral circle and protect them. Empathy is important but this view also tempts us to see other animals as inferior versions of humans, full of emotionality but lacking the rationality to tame it. And placing ourselves at the pinnacle of the animal kingdom in this way can lead us to mistreat creatures which seem less sophisticated than we believe ourselves to be.
Perhaps it’s more respectful and scientifically useful to contemplate animals on their own terms. Dogs can smell things we cannot. Birds can see colours we cannot. So maybe they can also feel things we cannot. When one elephant stands by the body of another for days, clearly something is happening, but why must it be a primitive version of human grief? How do we know the elephant isn’t guarding the body from scavengers, gloating over the death of a rival, or experiencing something else that we can’t possibly comprehend? The idea that other animals share our emotions is compelling and intuitive, but the answers we provide may reveal more about us than about them.
• Lisa Feldman Barrett is a professor of psychology at Northeastern University and the author of How Emotions Are Made (Pan Macmillan).
Further reading
Metazoa: Animal Life and the Birth of the Mind by Peter Godfrey-Smith (William Collins, £20)
An Immense World: How Animal Senses Reveal the Hidden Realms Around Us by Ed Yong (BBodley Head, £20)
Between Us: How Cultures Create Emotions. Author by Batja Mesquita (Norton, £24.14)
