AS HAPPY as a pig in – well, you know the phrase. But when we see a hog rolling in muck, a dog racing after a stick or an elephant reunited with a long-lost relative, how do we know what these animals are feeling?
One thing we can say is that many non-human animals do experience emotions. Today, biologists are increasingly accepting of the idea, once dismissed as mere anthropomorphism, that certain other species have a range of emotional states. Which doesn’t change the fact that a pig’s true feelings at any given moment are nigh-on incomprehensible to us, not least because it doesn’t share our capacity for language.
In the past few years, however, researchers have been figuring out creative ways to discern when animals are pessimistic, bored or gleeful. “We’re not just looking for signs of pain, fear or anxiety,” says at the University of Bristol in the UK. “We’re looking for signs of joy, the potential for happiness and fulfilment.”
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What they are discovering isn’t just that animals reveal their emotions in subtle ways, but also that they seem to be surprisingly delighted by mental challenges – and might even enter a “flow state” when deeply immersed in an activity they enjoy.
All of this adds fresh impetus to the ongoing campaign to move from merely reducing suffering in animals we keep in farms and zoos to doing everything we can to ensure they lead happy lives. “People will soon start to realise that emotions are the main part of welfare, even more important than health,” says at the University of Copenhagen, Denmark.
For much of the past century, scientists were sceptical about the idea that non-human animals have emotions. In recent years, just as we have come to realise that animals are more intelligent than we thought, we have arrived at a new awareness of their emotional capacities. As outlined in his 2019 book Mama’s Last Hug, it is a bigger leap of faith to believe that humans are exceptional in this regard. Observations of other mammals’ behaviour, and the shared roots of our neurological systems, have convinced de Waal, a primatologist at Emory University in Atlanta, Georgia, and others that many species experience the full spectrum of emotion, from fear and pride to hope, joy and happiness.
That isn’t to say these animals feel emotions in the same way we do. De Waal was careful to distinguish between feelings, which are internal, subjective states and therefore unknowable to others, and emotions – bodily and mental states we can recognise through their effects on behaviour and physiology. “Anyone who claims to know what animals feel doesn’t have science on their side,” writes de Waal.
The trouble is that it is also tricky to reliably detect animal emotions – especially positive ones. “We can observe them and infer how they might be feeling, or we can look at physiology, see if they might be stressed by how their hormone levels go up and down, but the connection to how it feels is a bit tenuous,” says Clark. “We’re very, very far away from being able to detect if an animal is happy or not – we can only make big assumptions.”
In striving to do better, the obvious place to start is facial expressions. For species such as horses, cows and rabbits, researchers have identified . Positive emotions are more difficult, says at the University of Natural Resources and Life Sciences in Vienna, Austria. “There is a lot of work looking at positive emotions in facial expressions, but this research is in its infancy.”
Animal welfare
Researchers have had more success with vocalisations. For a study published in 2022, Briefer and her colleagues . They trained it on more than 7000 recordings from a variety of contexts. In situations thought to be positive, such as when they were running free, nursing or expecting a reward, the pigs tended to make sounds like grunts and barks. In negative scenarios, such as when they were fighting or being handled by humans, their grunts and barks were longer in duration and lower-pitched – or they unleashed high-pitched squeals and screams.
Briefer and her colleagues found that their algorithm could correctly classify 92 per cent of calls as positive or negative. They are speaking to several interested companies about developing a tool that farmers could use to monitor pig welfare. She reckons that, in future, systems that combine analysis of vocalisations with that of facial expressions and body movement might give us more precise ways to measure animals’ emotions – to gauge if they are distressed, but also to identify signs of something akin to happiness.
For the moment, one of the best ways to gauge an animal’s emotional state is to set them tasks designed to reveal, in human parlance, whether they see the glass as half full or half empty. Researchers call these cognitive bias tests, and their use stems from studies showing that, if humans are depressed or anxious, they have a more pessimistic outlook. This seems to be the case for animals, too. “If they’re in a situation where you might expect they would be anxious, they tend to interpret things more negatively,” says at Dalhousie University in Canada.
The animals must first be trained to understand that a certain signal indicates a reward, while another indicates no reward. For example, the animal presses a button to start the test, then a door on the left opens, enabling them to access a tasty morsel of food. Alternatively, the door on the right opens and there is nothing. Once they have learned this association, they are given an ambiguous stimulus they haven’t seen before – a door in the middle opens, for example. If they approach the door, this suggests they are optimistic. If they press the button to start the test again, this suggests they are pessimistic.
When Hintze did this for dairy calves, she found that they were . Optimism isn’t the same as happiness, of course, but humans’ long-term emotional states, or moods, have an impact on how we process information and make judgements. These sorts of experiments do at least suggest that we can detect positive emotions in captive animals through their effects on decision-making – and therefore we can begin to get a grip on what they like.
Coming at this from a different angle, one big question about the emotional welfare of captive animals is whether they can experience boredom. Meagher and Georgia Mason at the University of Guelph, also in Canada, have studied this in farmed mink by assessing their interest in novelty. They found that when the mink were housed in conditions where they had less to do, they were more likely to seek out things that would be scary or unpleasant. “Our conclusion was that the if they are in boring conditions,” says Meagher.
Animal welfare scientists have long recognised the importance of making living environments more stimulating, or enriching. But the evidence that animals get bored suggests that the key to making sure that captive animals are happy as well as healthy is to provide them with mental challenges.
Clark’s research suggests that some animals enjoy a puzzle as much as we do. In 2018, she and her colleagues designed a maze for gorillas in which they could push a peanut through a series of wooden boxes with their fingers or a stick and retrieve the reward when it reached the exit. During six 1-hour trials at Bristol Zoo Gardens in the UK, five out of six gorillas played with the game and it was in use for almost all of the time available. Some of the gorillas played for up to 45 minutes, even though they seemed uninterested in the food reward. “When the nuts came out, they would just leave them to the side,” says Clark. “So that’s a really good indication that there’s a positive impact of doing this challenge and it’s not just to get the food.”
Thanks to a built-in camera, Clark even spotted facial movements that corresponded with how well the gorillas were performing. “You get these lovely little expressions, as you would in a human face, that might indicate a little flash of positive emotion,” she says.
Some animals will even work for a reward when the same prize is available for free. Back on the farm, . And goats will choose to push open a sliding door to access food over taking it from an open door. Scientists call this “contrafreeloading” as it contradicts the assumption that animals should optimise their foraging efficiency by minimising their energy expenditure.
But it makes sense because challenges are a ubiquitous part of life for wild animals, and positive emotions have presumably evolved to reward animals for solving them, says Clark. “The better you are at solving your challenges, the more likely you are to thrive, to go on and breed and find the best food,” she says. “So there’s this really interesting link between challenges and emotions.”
There is also evidence that farm animals find learning intrinsically rewarding. For a study published in 2020, Meagher and her colleagues , so they could choose the food they wanted by recognising the lid. Another 10 cows were given the same food, but without learning to predict or control what they would get. The cows in the learning group subsequently approached the testing area more quickly, suggesting they were more motivated to take part in the experiment.
Perhaps the most surprising claim, however, is the idea that animals, like humans, might enter a “flow” state – in which they are completely absorbed in a stimulating activity.
Flow has been studied in human psychology for decades, and it is strongly linked with positive emotions. To be clear, it has never been observed in animals. But Hintze argues that there is no reason to think it is unique to humans on the basis that animals are likely to have similar motivations to us to acquire skills and work towards a goal. In a published in 2022, Hintze and Jason Yee at the University of Veterinary Medicine, Vienna, proposed that for predatory animals, for example, we might be able to induce flow by simulating hunting behaviours, while a flow-inducing task for pigs might involve challenging their acute sense of smell.
Flow state
Hintze and Yee suggest that one way to assess whether animals really do experience flow-like states is to measure their perception of time. The idea stems from the fact that when we experience flow, we perceive time to pass more quickly. So, for example, you might train an animal to press a red button when they hear a long tone and press a blue button when they hear a shorter tone. If you then play them an intermediate tone, their response might tell us how quickly they are experiencing time. “If we can induce flow, assess flow and find out what it means for animal welfare, it might be a new dimension for how to study positivity and improve ways of life,” says Hintze.
That would be a boon for the campaign for positive welfare, which seeks to promote better lives for captive animals. In recent years, the movement has begun to spill over from the research community into the wider world. Welfare assurance schemes in the European Union, for instance, are now looking to , says Hintze. “There is a change. Society doesn’t accept just preventing suffering anymore,” she says.
At which point, the question becomes: how can we incorporate what we are learning about positive animal emotions and what elicits them into how we treat the animals we keep by the thousands in farms and zoos?
For at the Swedish University of Agricultural Sciences, a key area to focus on is animals’ early life experiences. She draws a parallel with child psychology: children who are insecure at a young age avoid taking risks, whereas children who feel secure enough to take risks learn that doing so can be rewarding. “If you rear an animal in an environment where there’s more choice, then it helps improve their cognitive abilities –they are better at problem solving, they’re better at handling situations, they cope with stress better,” she says.
The other thing to keep in mind when it comes to providing a pleasingly challenging environment is that it isn’t always easy to find the sweet spot between too easy and maddeningly difficult, says Clark. “This might be why cognitive enrichment is not being taken up as much as I would like. Sometimes, it takes a bit of training.”
And yet there is a huge and potentially very grumpy elephant in the room. To put it bluntly, it is hard to imagine that these insights will lead to meaningful improvements in animal welfare unless there is a radical shift away from industrial-scale farming. “I really hope farms will move to a much smaller scale, where the animals have more space, more resources and more natural behaviours, which would mean less production,” says Briefer.
That might sound unrealistic at first blush, but the researchers working in this field are hopeful that what they are revealing about captive animals’ cognitive and emotional lives might force a shift in how we think about our relationship with them. “If people started giving animals a little more credit for what they actually can do, then maybe we will be more motivated to change how we keep them,” says Meagher.
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