Not so fast, however – the scientific jury is still out on whether or not animals can/do actually smile. It’s perfectly reasonable to expect that the smiles we see on these animals are a case of pareidolia – our tendency to see human faces in everything around us. And many animals have different complex visual cues to express their emotions that may preclude the need for smiling. Dogs already communicate with each other by raising their haunches, baring their teeth, changing their postures and raising, lowering or wagging their tales, so it would be reasonable to expect that smiles just aren’t a part of their already complex physical vocabulary.
However, scientists are increasingly warming up to the idea that animals may have a more complex range of emotions and that some of them may even have facial expressions similar to ours. In 2010, a controversial experiment held at McGill University determined that mice have distinct facial expressions to express pain, which can be used to monitor their discomfort during a given experiment.