Dogs might have evolved to read your emotions
Emotional contagion between humans and canines comes from centuries of selective breeding, suggests a comparison with pet pigs
Selective breeding may have had the side effect of making dogs receptive to human emotions — and able to mirror them.Credit: David Baileys/Alamy
Dogs’ ability to feel your pain could be innate. It is the result of centuries of co-evolution with humans, suggests a community-science study that compared the responses of dogs and pet pigs to the sound of humans crying and humming. The results were published on 2 July in Animal Behaviour1.
Humans pay attention to how the animals in their lives are feeling, and it seems that this attentiveness is reciprocal. Researchers have found that horses will stop and listen longer to human growls than to laughter2. Pigs respond more strongly to sounds made by people than wild boars do3.
But studies testing whether the animals are just reacting to weird human sounds, or are capable of true emotional contagion — the ability to interpret and reflect people’s emotional states — are thin on the ground. Most animals can accurately echo the feelings of only other members of their species. But studies have shown that dogs (Canis familiaris) can mirror the emotions of the people around them4,5.
One question is whether this emotional contagion is rooted in ‘universal vocal signals of emotion ’ that can be understood by all domesticated animals, or is specific to companion animals such as dogs. To test this, researchers compared the stress response of dogs and pet pigs (Sus scrofa domesticus) to human sounds.
Pet sounds
Like dogs, pet pigs are social animals that are from a young age raised around people. But unlike dogs, pigs have been kept as livestock for most of their history with humans. So, if emotional contagion can be learnt through just proximity to people, pet pigs should respond in similar ways to dogs.
The team recruited dog or pig owners around the world to film themselves in a room with their pets while playing recorded sounds of crying or humming. Researchers then tallied the number of stress behaviours — such as whining and yawning for dogs, and rapid ear flicks for pigs — exhibited during the experiment.
As expected, dogs were “really, really, good at catching the emotional content of our vocalizations”, says study co-author Paula Pérez Fraga, an animal-behaviour researcher at Eötvös Loránd University in Budapest. Dogs became stressed when they heard crying and were largely unmoved by the sound of humming. However, although pigs did experience some stress when exposed to crying, their behaviour suggested that humming was much more stressful.
This could be because pigs don’t interpret crying as a negative emotion, says Natalia Albuquerque, a cognitive ethologist at the University of São Paulo, Brazil. Humming, however, could be “very weird” for pigs, who “don’t know how to process” it.
The findings suggest that, compared with livestock, companion animals might have stronger emotional contagion with humans, she adds. But she cautions that more research is needed. “Pigs are very sensitive,” says Albuquerque. “I was expecting to find that pigs would also show emotional contagion.”
Fraga agrees. “We don’t say that pigs can’t do [emotional contagion],” she says. “The story is really about how good dogs were, not how bad pigs were.”
doi: https://doi.org/10.1038/d41586-024-02320-w
This story originally appeared on: Nature - Author:Freda Kreier
