By Dr. Karen Shaw Becker
Researchers are often hesitant to describe animal communication in terms of language, preferring instead to describe their many communicative sounds as vocalizations. But it's becoming increasingly clear that not only do animals have "languages" of their own, these languages can often be decoded by humans. If we would just stop to listen, we might find that there's a bit of Dr. Dolittle — the children's book character with the ability to talk to animals — in all of us.
In fact, research published in Proceedings of the Royal Society B revealed just that.1 They played recordings of vocal expressions from various animals, from tree frogs and birds to pigs and monkeys, and asked study participants to determine which sample showed higher arousal (i.e., the animal was more upset versus calm).
The results showed that Darwin's hypothesis from more than a century ago — that vocal expression of emotion is ingrained in all of us and dates back to "our earliest terrestrial ancestors" — may be true after all, and a universal animal language may actually exist.
Humans Can Gauge Animals' Emotional States From Their Calls
For the study, 75 participants listened to animal vocalizations from nine species (including humans speaking Tamil). The participants spoke different languages as well (English, German or Mandarin), and were asked to identify which animal sounds showed high or low levels of excitement.
For example, a high excitement sound may be used when an animal is in danger, competing for a mate or confronted by a dominant animal. The participants were able to correctly identify the higher arousal sample in the majority of cases across all species. Specifically:2
Humans: 95 percent correct
Giant panda: 94 percent correct
Hourglass tree frog: 90 percent
African bush elephant: 88 percent
American alligator: 87 percent
Black-capped chickadee: 85 percent
Pig: 68 percent
Common raven: 62 percent
Barbary macaque monkey: 60 percent
Researcher Piera Filippi, Ph.D., of Vrije University Brussels in Belgium told The Washington Post, "Our study shows that humans are naturally able to recognize emotional arousal across all classes of vocalizing animals … This outcome may find an important application in animal welfare, suggesting that humans may rely on their intuition to assess when animals are stressed."3
The authors noted that the results also suggest vertebrates share fundamental mechanisms of vocal emotional expression, which may represent a universal "signaling system."4
Even Children Can Determine the Emotion Behind Different Dog Barks
If you're a pet owner, you're probably not surprised that people can decode the emotional states of animals based on their cries — most of us do it all the time with our own pets. Your dog likely makes unique barks or whines when he's excited, scared, hungry or in pain, for instance, and you probably know each one well.
If you have multiple dogs, you can certainly distinguish one dog's barks from the other's, as well. Indeed, it does appear as if this is an ingrained trait, as even children are able to accurately distinguish one type of dog bark from another.
Kids as young as 6 years old were able to identify angry dog barks in one study, while 10 year olds were also able to determine dog barks signaling playtime or an approaching stranger.5 "Overall we found only slight differences between the performances of preschoolers and adults," the researchers wrote. "This shows that the ability of understanding basic inner states of dogs on the basis of acoustic signals is present in humans from a very young age."6
It's been argued that so many years of domestication have enhanced dogs' ability to communicate with us, and vice versa, however the featured study suggests we may be able to decode non-domesticated animals' emotional vocalizations in a similar way.
Can Animals Read Human Emotions?
If we're able to understand when a frog or alligator is upset, is it possible they can read human emotions, too? At least in the case of certain animals, like dogs and horses, the answer is decidedly yes. Researchers from the Mammal Vocal Communication and Cognition Research Group at the U.K.'s University of Sussex and colleagues showed photographs of people with different facial expressions to 28 horses.7 They were able to spontaneously discriminate between happy and angry facial expressions in the photographs.
In dogs, meanwhile, viewing human faces triggers the same brain regions — those used to process facial cues — in both humans and dogs. The human images also led to increased activity in subcortical structures like the caudate, which is involved in reward processes. This suggests that, as you'd imagine, dogs found viewing the human faces to be more rewarding than viewing inanimate objects.8
The thalamus also showed increased activity when dogs were shown photos of human faces; this brain area has been related in humans to an emotional response toward faces.
There is hope that one day humans and nonhuman animals may be able to communicate beyond simple emotional cues, even carrying out two-way conversations. Dolphins, for instance, are known to communicate using a human-like language and researchers believe "humans must … creat[e] devices capable of overcoming the barriers that stand in the way of … communications between dolphins and people."9
For now, however, the idea that a universal animal language exists that unites all mammals, even humans, seems highly plausible, as it appears we are all genetically wired to make (and interpret) similar sounds in response to certain emotions.