Dogs can sense your pain, this could be innate. A community science study that compared the responses of dogs and domestic pigs to the sound of humans crying and humming suggests that this is the result of centuries of co-evolution with humans. The results were announced on July 2ndAnimal Behaviorpublished 1.

People pay attention to how the animals in their lives are feeling, and it seems that this attention is mutual. Researchers found that horses stop and listen longer to human growls than to laughter 2. Pigs react more strongly to human noises than wild boars 3.

However, there is a lack of studies that test whether the animals simply respond to strange human noises or are capable of experiencing true emotional contagion - the ability to interpret and reflect people's emotional states. Most animals can only accurately reflect the feelings of other members of their species. However, studies have shown that dogs (Canis familiaris) can reflect the emotions of the people around them 4, 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 whether it is specific to companion animals such as dogs. To test this, researchers compared the stress response of dogs and domestic pigs (Sus scrofa domesticus) to human sounds.

Animal sounds

Like dogs, domestic pigs are social animals that are raised around people from an early age. But unlike dogs, pigs have been kept with humans as livestock for most of their history. Therefore, if emotional contagion can only be learned through proximity to humans, domestic pigs should respond similarly 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 them crying or humming. The researchers then counted the number of stress behaviors – such as whining and yawning in dogs and rapid ear movements in pigs – displayed during the experiment.

As expected, dogs were "very, very good at detecting the emotional content of our moods," says study co-author Paula Pérez Fraga, an animal behaviorist at Eötvös Loránd University in Budapest. Dogs became stressed when they heard the crying and were mostly unfazed by the buzzing. Pigs, on the other hand, did show some stress when exposed to crying, but their behavior suggested that the 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. The buzz, on the other hand, could be “very strange” to pigs who don’t know how to process it.

The results suggest that companion animals may have greater emotional contagion with humans compared to farm animals, she adds. But she warns that more research is needed. “Pigs are very sensitive,” says Albuquerque. “I expected that pigs would also show emotional contagion.”

Fraga agrees. “We’re not saying pigs can’t do this,” she says. “The story is really about how good dogs were, not how bad pigs were.”