A new study reveals that the infamous puppy dog eyes expression isn’t a way that our beloved pets express sadness — in fact, it may be a clever ploy by the dogs to receive attention and affection.

Researchers from the University of Portsmouth’s Dog Cognition Center report that dogs mostly use facial expressions in the presence of a human, while very rarely adopting them when on their own.

The findings question the assumption that our canine pets‘ facial expressions are involuntary and tied to their emotional state. Rather, they might just be a medium to communicate and are usually a direct response to attention or a request for one.

What are puppy eyes?

Anyone who’s ever befriended a dog knows what the puppy dog eyes are all about. It’s quite simple to pull off — all the dogs have to do is raise their brow, making the eyes appear wider and (to a human) sadder.

But boy is it effective at getting them some attention from any human struck by the visage.

Which, according to a team led by Dr. Juliane Kaminski, is exactly the point. Following their study, aiming to understand if dog’s facial expressions are “subject to audience effects and/ or changes in response to an arousing stimulus (e.g food)”, the team reports that dogs don’t involuntarily strike facial expressions when aroused — rather, they do it to impress us.

“We can now be confident that the production of facial expressions made by dogs are dependent on the attention state of their audience and are not just a result of dogs being excited,” Dr Kaminski explains. 

“In our study they produced far more expressions when someone was watching, but seeing food treats did not have the same effect.

The findings suggest that dogs are sensitive to a human’s attention and, most excitingly, that their facial expressions are active attempts at communication, not involuntary emotional displays.

For the study, the team worked with 24 dogs, all family pets but of various breeds, aged 1 to 12 years. Each dog was tied by their leashes about one meter away from a human participant. The dogs’ faces were filmed through all test scenarios, from the person facing the dog attentively to being distracted, with his or her body turned away from the animal.

The team looked at three measurements to establish why dogs strike up facial expressions: attentive vs. not attentive, food present vs. food absent, and a trial run.

For this latter measurement, the experimenter “stood still and did not respond to any of the dog’s behaviors,” and was asked to look “at a predetermined spot at the opposite wall and […] not actively seek eye contact with the dog when she was oriented towards the dog.” The trial would last 2 minutes, after which the experimenter briefly interacted with the dog and then “changed her position according to the condition presented in the next trial.”

Puppy eyes — they’re all lies

Overall, the scientists report, the single most important factor dictating how likely the dogs were to show facial expressions was attention. Almost all human-dog interactions elicited a facial expression in response from the animals, and would drop them when a human was no longer directly watching the animals — this held true through the food and trial steps as well.

The “eyebrow raiser” (puppy dog eyes) and the “tongue show” were the two facial expressions that dogs produced “significantly more of” when a human was orientated towards them.

“Human attentional state also affected one of the dogs other behaviours, the frequency of vocalizations produced,” the team wrote. “The visibility of the food, however, did not affect dogs’ facial movements and there is also no conclusive evidence that it affected any of the dogs other behaviours.”

Boiled down, what this means is that dogs produced more facial expressions when a human was orientated towards them and in a position to communicate (i.e. not blatantly ignoring the dog).

It’s not just happenstance, either — the visibility of food (which is a powerful arousal stimulus) didn’t elicit a similar effect on the animals’ facial movements, suggesting these were intended specifically for the human and not a general reaction to an emotion or state of arousal. 

The findings further help to strengthen past research which suggests a person’s gaze is a key element of human-dog communication — for example previous work showed that dogs will follow a human’s communicative gestures like pointing or gazing, but ignore such gestures when the human’s eyes were not directed at the dog.

It’s possible that dogs picked up this communication trick as they were domesticated, Dr. Kaminski believes.

“Domestic dogs have a unique history – they have lived alongside humans for 30,000 years and during that time selection pressures seem to have acted on dogs’ ability to communicate with us,” she said. “We knew domestic dogs paid attention to how attentive a human is – in a previous study we found, for example, that dogs stole food more often when the human’s eyes were closed or they had their back turned.”

“This study moves forward what we understand about dog cognition. We now know dogs make more facial expressions when the human is paying attention.”

However, the team points out that while they found that a human’s attention did correspond to an increase in all facial movements in the dogs, there was no indication that the animals “specifically modulate their facial movements” according to the human’s level of attentiveness.

One final interesting observation regards the two most common expressions dog produced when interacting with humans. A relaxed open mouth with the tongue showing is generally described in the literature as a pose signifying attention — which would make sense in the context of the study.

The role of the “puppy dog eyes” expression, however, is less clear. Despite this, the team notes that it “may have had the greatest influence on [genetic] selection” during domestication, citing work that showed shelter dogs that produced this expression “more frequently were rehomed quicker”.

The team has two theories as to why this happens. First is that the puppy dog eyes expression resembles facial movements that indicate sadness in humans, “potentially making humans feels more empathic towards dogs that produce this movement more,” 

Secondly, by making the eyes bigger and more infant-like, the adorable facial expression could tap into our preference for paedomorphic characters (adults that retain infant features) “and/ or humans innate tendency to respond to ostensive cues, one of which is eyebrow-raising”

Regardless of the exact reason, humans seem to be particularly responsive to this facial expression in dogs. Resorting to the puppy-eye argument more often when interacting with humans would thus benefit the dogs by strengthening the bond between the two — a powerful selective pressure during domestication. 

Ultimately, it is impossible to say if the dog’s behavior is drawn from an understanding of a human’s mental state, or simply a hard-wired or a learned response to seeing the face or the eyes of another individual.

But one thing is for sure — the puppy eyes work, dogs know it, and they’re not ashamed of using it. Not that we mind.

The paper “Human attention affects facial expressions in domestic dogs” has been published in the journal Nature.