People use similar facial expressions when communicating with babies and dogs

If you find yourself pulling the kinds of faces to your dog that you'd also pull to a baby, you are not alone. In fact, new research in Scientific Reports has revealed that there are six distinct facial expressions that adults rarely or never use with another adult but do use with either a baby or a dog.

Anna Gergely at Institute of Cognitive Neuroscience and Psychology in Budapest, Hungary, and colleagues recruited 42 participants from 22 Hungarian-speaking families for their study. All the families had both a child aged between one and eighteen months and at least one pet dog.

Gergely conducted the research in the participants' homes. She videoed them while they interacted in three different ways with their infant, their dog, and also with her. In the first task, they had to try to draw their partner's attention towards a small ball. In the second, they had to hide the same ball in their hand and ask their partner to find it. In the third, they recited nursery rhymes to their partner.

The researchers coded all the facial expressions captured in the video. They concluded that there were six expressions that their participants (both male and female) typically used when interacting either with the baby or the pet dog, but not with Gergely. Three of these matched expressions that have previously been identified in work on adult-baby interactions (see images below):

• 'Special happy' – an intense Duchenne (genuine) smile with an open mouth
• 'Fish face' – puckered lips, a moderate smile, and a brow raise
• 'Mock surprise' – an exaggerated raised brow, an open-stretched mouth with the hint of a smile (often accompanied with 'Oooh' noises)
   

But the team also identified three new expressions, which they argue are clearly distinguishable from the others as well as each other:

• 'Mock surprise brow' – similar brow raise as in mock surprise, but no smile
• 'Mock surprise mouth' – wide open mouth as in mock surprise, but no brow raise
• 'Mock surprise and special happy' – intense smile plus eyebrow raise

The 'special happy' expression was particularly common in interactions with both babies and dogs, the team reports. It is thought to express genuine, intense happiness and to signal a strong desire to interact. With a pre-verbal infant, it functions as a clear expression of engaged, positive feeling towards that child. Clearly, adults – or at least adults with both a baby and a dog – use it to try to signal the same thing to their non-verbal dog.

The team also note that although the participants used these expressions for both babies and dogs, they tended to use them more frequently and more intensely with babies, particularly during the attention-getting and task-solving tasks (there was no difference in the scripted nursery-rhyme task).  Perhaps, the team suggests, more frequent, more intense expressions help with aspects of adult/baby interactions that are not so relevant to dogs, such as the teaching of language and the creation of a shared emotional state.

It's long been known that parents speak differently to their babies than they do to older children and adults. More recent research has also shown that dogs prefer the high-pitched voice that people often use with babies — at least, when the words being spoken are obviously relevant to them.

This new work on facial expressions clearly advances our understanding of human-dog, as well as human-baby communication. However, there are a few points worth noting.

Firstly, the adults in this study all had a baby. Would people who do not routinely interact with a pre-verbal child – or who have never had children – use the same expressions with their pet dog? Also, Gergely was a stranger to these participants, while the baby and the dog were part of their family. Perhaps the use of these expressions was partly linked to how close the participant was to their partner, not just to whether they were interacting with a baby or dog versus an adult? Again, only further work will tell.

Still, the discovery that caregivers tend to use similar expressions with their dogs and their babies is fascinating. Clearly, dogs are not babies. But perhaps these expressions help to enhance the wellbeing of dogs, too. 'Special happy' is likely to be the most important for this. "There is no doubt that such a smile has the potential to enhance positive interactions with an infant and now we can extend this assumption to canine companions," the team writes.