It has long been thought that animals facial expressions are involuntary displays of emotional states—rather than an attempt to communicate with others. For example, we know a dog is happy when it sees food. This would be described as an involuntary reaction. Food good. Dog happy. Tail wags.
Dogs have been living with humans for over 30k years and offer an interesting example of the possibility for more explicit communication between the two species. There is currently no evidence that facial expressions in animals (excluding primates) are effecting by the attention of an audience. However,
In the current study, Human attention affects facial expressions in domestic dogs, Kaminski and a team of researchers set out to test whether a dogs facial expressions are subject to “audience effects”—or having the humans attention. The alternative explanation is that a dogs facial expressions are the involuntary reflex based on emotional response and state of arousal.
To test which of these is true a person presented a piece of food (non-social and arousing stimulus) in different conditions—back turned v. looking. As the author notes “human attentional state affected the production of dogs’ facial expressions. Dogs produced significantly more facial expressions when the human was oriented towards them, than when the human had her back turned to the dog (specifically more inner eyebrow raises and sticking out their tongue). So, while dogs produce more facial expressions when the human is oriented towards them and in a position to communicate, the visibility of non-social but arousing stimulus (the food) did not alter their facial movements in the same way.”
The researchers conclude that the “visibility of the human’s eyes might be important for dogs for the production of facial expressions. This might be evidence that dogs produce facial expressions as a flexible signal and that its production depends on the attentional state of the receiver of the signal.” This suggests some degree of voluntary control and an active attempt to communicate with people.
Human attention affects facial expressions in domestic dogs
Juliane Kaminski, Jennifer Hynds, Paul Morris & Bridget M. Waller
Scientific Reports, 2017