Human Emotions Affect Animal Welfare for Horses, Pigs - Study Confirms

For cat and dog owners, talking to pets is a normal activity where the pet somehow knows if its owner is angry or happy. In recent studies, animals other than cats and dogs can also differentiate between positive and negative sounds.

Animals were tested to confirm if the subjects could tell the difference between positively and negatively charged sounds from humans and members of their species. The team of international researchers focused specifically on wild and domesticated horses and pigs.

Elodie Briefer, the study author and behavioral biologist from the University of Copenhagen's Department of Biology, stated that her team wanted to confirm if all of the species tested expressed emotions in the same way and if the animals could distinguish between them. Their research was part of a larger project looking into the evolution of emotional vocalization in hoofed animals or ungulates.

Another concern for their team, according to Briefer, was whether domestication influenced the vocal expression of emotions.

For the experiment, the team tested domesticated pigs and wild boars, as well as domesticated horses and wild Przewalski's horses by playing human voices that mimick positive and negative emotions.

Briefer explains that since the farm animals have constant interaction with humans, the farm animals are considered domesticated. This led to the team's hypothesis that the farm animals would also share the same abilities as the dogs, Treehugger reports.

She added that this concept is already common knowledge for horses, however, there are less data when it comes to pigs. The biologist pointed out that emotions are a big part of animal welfare, making talking to the animals very crucial.

Influenced by Emotion

Researchers analyzed the calls of domesticated pigs against those of wild boars and vice versa for the study. They also analyzed wild Przewalski's horses' calls against domesticated horses' calls and vice versa. Animals from parks and zoos were used to study the two wild species. Those animals were used to humans, but not to their domesticated species.

Then they played recordings of human voices talking gibberish but with positive or negative expressions.

Briefer explains that animals living around humans learn to associate words with consequences or contexts. She added that their study was aimed at testing how voice intonation o 'emotional prosody', in a similar way as changes occurring in animal calls, affect emotions.

Actors reciting nonsense words were used to rule out the possibility that animals understand certain words.

Their study revealed that domesticated pigs and horses and wild horses can tell the difference between sounds coming from distantly related species, as well as from human voices. Wild boars, on the other hand, reacted differently to domesticated pig calls, but not to sounds produced by other wild boars or humans.

Horses reacted by pointing their ears, stopping eating or walking, and moving their heads in various ways. The position of the heads of pigs and boars was used to determine whether they stopped walking or eating.

Read also: Scientists Discovered Octopuses, Mollusks, and Other Invertebrates Have Emotions 

Animal Welfare

Researchers wanted to confirm if animals could mirror human emotions, a phenomenon is known as emotional contagion. That would have been obvious in the study if animals had negative emotions when playing negative vocalizations, or positive emotions when playing positive vocalizations.

Briefer says explains that a challenge for the study is that the indicators of emotional valence, or whether the animals are experiencing negative or positive emotions, are very subtle and tricky to assess. These indicators include movement in the ears or tail.

The ability of wild Przewalski's horses to distinguish between positive and negative human voices astounded the researchers. They also discovered that wild boars did not change their behavior in response to humans but instead responded with more calls and "freezing" when they heard positive pig calls, and vice versa.

Briefer believes that the fact that so many of the animals reacted more strongly to a negative sound suggests that the way humans talk around animals may have an impact on their well-being.

The biologist shared the findings that the two species of horses and pigs discriminate between positive and negative speech and react stronger when they first hear negative speech. This means that the way humans speak around or to animals influenced the animals' emotions, and hence their welfare.

Related article: Animal Emotion: Here Are Several Ways to Know What Animals Feel