Why some animals develop a sense of humor – 02/27/2024 – Science

When we think about what differentiates our species from other animals, the sense of humor usually appears near the top of the list.

We like to laugh so much that comedy seems to be ingrained in our species. Human babies smile and are amused when their parents make faces as early as three months old.

By eight months, babies know how to use their own faces, bodies and voices to make adults laugh.

And before long, parents watch their children become “full-time comedians,” deliberately messing around, with a cheeky smile on their faces.

But a new study shows that humans may not be the only ones who like to play. Animals can also make others laugh.

Postdoctoral researcher Isabelle Laumer, from the University of California at Los Angeles (UCLA), in the United States, watched more than 75 hours of videos of great apes interacting with each other with her colleagues.

Great apes are our closest living relatives. They include orangutans, chimpanzees, bonobos and gorillas.

All of the chimpanzees in the study lived in zoos and were filmed going about their daily routines. And members of all four species have been observed playing with each other.

The researchers identified 18 different types of provocation. The top five included poking, hitting, making movements difficult, hitting with the body and pulling a part of the colleagues’ body.

Some chimpanzees have even dangled parts of their bodies or objects in front of their colleagues’ faces or, in the case of orangutans, pulled each other’s hair.

Playful behavior

“We often saw young people hide behind an adult who was busy caring for another chimpanzee and start poking or hitting him on the back, sometimes even surprising the adults,” says Laumer, who is the study’s first author.

“They would then wait and watch the adult’s reaction. Typically, he would simply ignore them and they would continue to disturb him, with behaviors that were increasingly elaborate and difficult to ignore, until, sometimes, they ended up hitting the adult with all their might. the body.”

The playful behavior was similar to that adopted by human children, according to the researchers. It was intentional, provocative, persistent and included elements of surprise, play and checking the other’s reaction.

The human equivalent might be to stick your tongue out at someone and run away to gauge their reaction. This style of play can even be the basis for more sophisticated forms of humor.

“Poking, among humans, requires quite complex cognitive abilities,” according to Laumer. “You need theory of mind [a capacidade de imaginar o mundo do ponto de vista de outra pessoa]knowledge of social norms, ability to anticipate the reactions of others and appreciate the breach of the other’s expectations.”

Since all four species of great apes are capable of teasing each other, this suggests that a sense of humor may have been present in our last common ancestor, who lived 13 million years ago.

But many scientists believe that humor is much more widespread across the animal kingdom. In his book “The Origin of Man and Sexual Selection” (Ed. Garnier, 2019), biologist Charles Darwin (1809-1882) suggests that dogs may have a sense of humor, when he writes: “If a small stick or other If an object is thrown towards one of them, it will often carry it a short distance; and, then crouching in front of the object, it will wait until its master comes very close to catch it. The dog will then grab the object and run away in triumph, repeating the same maneuver and, evidently, enjoying the game in practice”.

Anyone who has a dog may have also noticed that, when playing, they produce a kind of snoring sound with their breathing that almost sounds like laughter.

In a 2005 study, animal behavior scholar Patricia Simonet played this sound to dogs at a rescue shelter. She concluded that hearing the dog’s “laugh” reduced the shelter dogs’ stress.

Evolutionary biologist and professor emeritus of ecology Marc Bekoff, from the University of Colorado in Boulder, in the United States, says he has collected decades of data showing dogs engaging in playful behavior, similar to that demonstrated by Laumer and his colleagues.

When trying to get a reluctant dog to play, for example, another dog may jump closer before running away. “I’ve seen it in wild dogs, foxes, coyotes and wolves,” he says.

In fact, Bekoff claims that, throughout his career, he has heard stories about many species that act as playful comedians, including horses, bears, Asian black horses and scarlet macaws.

Other researchers have observed that dolphins apparently make sounds of joy when they are playfully fighting and that elephants trumpet in excitement when they are playing.

It is also known that there are parrots that playfully tease other animals, either by whistling or confusing the family dog.

And there is evidence that even rats enjoy a good laugh. Research professor Jeffrey Burgdorf, from Northwestern University in the United States, has been making a living for about a decade by tickling rats.

When rats are tickled, they squeal happily in a loud tone, similar to laughter.

They ask for more and more and can even be taught to play hide and seek for a “tickling reward”, according to a study by another group at Humboldt University in Berlin, Germany. Now, Burgdorf and his team are using these findings to search for treatments for depression.

“What we are learning is that animals are more attentive when they are making these vocalizations,” says the professor.

“My supervisor [o neurocientista Jaak Panksepp (1943-2017)] I always said that play is fertilizer for the brain — and it’s true”, says Burgdorf.

“Their brains are connecting. They’re making new synapses and new neural connections. And I think that tells us that when we’re in that playful mood, we’re actually performing at our best and being ourselves.”

Rats clearly love being tickled, but is their high-pitched laughter really evidence that they have a sense of humor? After all, most evidence for animals’ sense of humor comes predominantly from isolated cases, as few large-scale studies have been carried out.

It’s also difficult to know why an animal adopts a specific behavior. The primates in Laumer’s study, for example. Are they simply making a concrete joke or are they trying to calm tension, start a game or simply get attention?

“Do I think animals have a sense of humor? Yes, I think they do, but it’s difficult to prove,” admits Bekoff.

“I’ve known homes with two dogs, for example, where, when it’s time to eat, one of the dogs runs to the front door and barks,” he says. “The other dog then runs to see who is there, while the first dog comes back and eats both of their food.”

“So you could say he’s showing a sense of humor, but the first dog may have simply learned how to get more food.”

There is also the question of what the evolutionary purpose of humor in animals would be.

In humans, laughter is believed to have emerged during evolution as a way to help connect individuals. After all, what other way would be better to make friends than sharing a good joke?

Could it be possible that humor plays the same role in animals?

“In humans, humor can serve as an icebreaker, breaking down social barriers and strengthening relationships,” says Laumer. “We don’t know if the same thing happens in chimpanzees or other animals, but it’s possible.”

“To know for sure, we would need to test and observe more groups of primates and other species.”

_{Read the original version of this report (in English) on the BBC Future website.}