Weird Science | What puppy dog eyes and cat’s (trembling) whiskers really mean
Researchers have identified 276 facial expressions in cats. To convey the same kind of emotion, a cat may present one expression to a human and another to a cat
Anyone who has had a pet dog or a cat knows that the expressions on their faces may convey an emotion, such as anger or pleasure. For example, when a dog makes the familiar “puppy dog eyes”, raising its eyebrows and presenting a mournful face, it is understood to be signalling that it wants the human’s attention. In fact, mammals in the wild too may wear their emotions on their faces, though those might be less understood.
Charles Darwin took all this as evidence of evolution: if an animal and a human make similar expressions to convey a similar emotion, they must have evolved from a common ancestor. Many facial expressions, on the other hand, have evolved species by species, and these have been the subject of research for years.
A recent study on cats, published in Behavioral Processes, adds another dimension to such research. So far, scientists have largely tried to understand what pets making different facial expressions were trying to convey to humans. The new study, in contrast, examines how domestic cats use facial expressions to communicate with each other.
In the process, researchers not only uncovered a diverse range of expressions but also raised an intriguing question: To what extent has domestication by humans influenced these expressions?
Cats and communication
Facial communication in domestic cats is sophisticated, with the researchers identifying 276 different facial expressions, most of them generated during friendly interactions with other cats. Many other facial expressions can vary depending on context.
To convey the same kind of emotion, a cat may present one expression to a human and another expression to a cat. In certain instances, their expressions made before other cats look different from expressions that cats produce towards humans, said Dr Brittany Florkiewicz, an evolutionary psychologist at Lyon College who, along with her student Laura Scott, conducted the study.
“During non-friendly interactions with other cats, the ears are rotated backwards, the pupils are constricted, and the lips are licked. During non-friendly interactions with humans, the ears are rotated backwards but the mouth is opened widely to expose both rows of teeth,” Florkiewicz said over email.
During friendly encounters with other cats, on the other hand, they shut their eyes and push their ears and whiskers forward.
There is a lot more to learn here: A nuanced understanding of each of the expressions, and the human influence. “We are planning to conduct follow-up studies with wildcats to discern which facial expressions are the result of evolutionary continuity and which are the direct result of domestication. We can see evidence for evolutionary continuity in some facial expressions though,” Florkiewicz said.
Dogs interacting and reacting
A lot has been researched about the facial expressions of dogs, especially when communicating with humans. In one of the more recent studies on puppy dog eyes, researchers in 2019 found that a small muscle, which allows dogs to intensely raise their inner eyebrows, is not present in wolves. Although wolves and dogs come from a common ancestor, the emergence of that muscle indicates that it evolved to enable dogs to communicate with humans.
Just as in the case of cats, however, knowledge about dogs’ facial communication with other dogs is limited. One study that examined this aspect, if indirectly, was published in PLOS One in 2016. Researchers from the Helsinki and Aalto universities in Finland examined the reactions of 31 domestic dogs, representing 13 breeds when they were shown photographs of dog and human faces representing different emotions: pleasant, threatening and neutral.
What this study examined was not the dogs’ own facial expressions, but how they gazed at what kind of face. Whether they were looking at dog or human pictures, the dogs looked longer at the eye area compared with the mouth area, irrespective of the expression. There were, however, some interesting distinctions in other respects. For example, they looked at the eyes of pleasant dogs longer than at the eyes of pleasant humans, but at the mouths of pleasant dogs shorter than the mouths of pleasant humans.
Overall, the dogs looked longer at the faces of threatening dogs compared with the faces of pleasant dogs. In fact, it was only in the case of threatening faces that the dogs gazed longer at dogs’ pictures than at humans’.
The road ahead
There is a lot to facial expressions, and the key to studying them in greater detail could lie in using artificial intelligence to identify each expression and then figure out what it means.
“Our current study does not make use of AI. However, we are collaborating with research labs around the world to help automate the process of recognising and categorising cat facial expressions,” Florkiewicz said.
Florkiewicz and her co-author plan follow-up studies for more information on the meaning of each facial expression they detected in cats.
Florkiewicz referred to the work of Anna Zamansky, a professor of information systems at Haifa University, Israel. Most recently, Zamansky and colleagues published a paper in Nature in June this year describing methods to recognise pain in cats by using AI to analyse their facial expressions.
Kabir Firaque is the puzzles editor of Hindustan Times. His column, Weird Science, tackles a range of subjects from the history of inventions and discoveries to science that sounds fictional, but it isn't.
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