Fellow humans may look alarm or move away when you show anger, but your dog will likely lick his mouth. Researchers trying to determine whether dogs truly had an understanding of human emotion discovered that yes, indeed they do – and they are consistently demonstrate that understanding by licking their mouths when human express anger.

https://firepaw.org/2018/01/13/dogs-lick-their-mouths-in-response-to-angry-humans-say-scientists/