Can animals really smell fear in humans?

2024-02-28 19:10:29Lifestyle SHKRUAR NGA REDAKSIA VOX
Can animals really smell fear in humans?

By Jennifer Nalewicki*

It has long been debated whether animals are able to sense fear in humans. Unfortunately, the answer to this age-old question is not so simple. But what do scientific studies say? Can animals really smell people's fear?

To get to the root of this question, researchers have largely removed the human presence from the equation, as animals such as dogs are known to respond to our expressions and body posture. Therefore, experts have focused on how animals, including horses and dogs, react to different scents released by people watching happy versus fear-inducing videos.

In a study with several horses, published in 2023 in the journal Scientific Reports, researchers asked participants to watch clips from a comedy one day and a horror movie the next. After the participants watched each of the videos, the researchers collected sweat samples from the viewers' armpits using cotton swabs, and asked the participants to report how much joy or fear they felt while watching each of the clips.

The researchers then presented the two samples from the same human to a specific horse, to see if it could distinguish the scents produced by humans during times of happiness and distress. "At first we weren't sure if horses could distinguish scents," study lead author Plotine Jardat, PhD student at Tours University in France, told Live Science.

But the horses reacted differently depending on which swab they were exposed to. "When horses smelled sweat samples from happy people, they used only their left nostrils. This shows which part of the brain they are using to analyze the smell. In all mammals, the two hemispheres of the brain have different functions and in an emotional context, it seems as if the smell from the samples of joy was perceived as more positive by the horses" - says Jardat.

But when the horses were shown the samples taken by humans while watching the horror movie, the animals reacted very differently and not only sniffed the sample longer, but used both nostrils to pick up any smell, the expert points out.

However, Yardat was quick to point out that this does not necessarily mean that horses know what fear is. "It's not like when horses smell another animal, the word fear comes to mind. But now we know that horses can distinguish scents from different emotional states in humans."

And it raises a question: What specific compounds do humans produce in their sweat that causes a change in horse behavior? Researchers suggest that chemosignals, which are chemicals produced by animals that can influence another animal's behavior, may also explain the horses' reactions.

In humans, there are certain compounds in sweat, such as adrenaline or androstadienone (a pheromone-like protein), that can cause a change in smell during moments of fear. These compounds can carry "emotional information" from one species to another, the researchers wrote in the study.

In a future study, the scientists plan to examine whether smelling fear can cause a fearful response in horses, and what kind of impact this might have on the animals emotionally, by prompting them to perform a series of tests after smelling the samples. .

"We want to understand if fear will modify their reactions to the tests" - says Jardat.

Meanwhile, in a 2018 study in the journal Animal Cognition, scientists asked Labrador retrievers to sniff samples taken from the armpits of male participants after watching a scary or happy video. The researchers placed the sample inside a box with one side opening, and placed it inside a closed room with two people: a stranger and the dog's owner.

As with the horse study, the researchers found that the dogs reacted differently depending on whether they smelled the scent of a fearful or happy human. "When the dogs smelled the scent of a happy person, they increased their interactions with the stranger in the room," lead study author Biagio D'Aniello, professor of zoology at the University of Naples Federico II in Italy, told Live Science. .

"When they smelled fear, they either went to their owner or went to the door and tried to get out of the room," study co-author Anna Scandurra, a post-doctoral researcher at the University of Naples Federico II, told Live Science.

The researchers reached a similar conclusion as the scientists in the horse study: The dogs' reactions were likely due to chemosignals, suggesting that "emotional communication between two different species" was at play, the authors wrote in their study.

*Source: Live Science