From the BBC:
Scientists have shown just how much dogs rely on seeing their owners faces in order to recognise them.
Participants in the study crossed paths with a stranger several times in a room. Each participant’s dog was watched to observe its ability to track its owner. Scientists found that most dogs had trouble keeping track of their owner when the owner’s face was obscured by a bag.
The article continues:
Wild dogs rely on body signals and on cues from other animals in their social groups, but studies including this one suggest that domestic dogs are so attuned to human social groups that they are even able to recognise some human facial expressions.
The study isn’t exactly groundbreaking. Nonetheless, it definitely shines additional light on the remarkable adaptations dogs have made as they became the best friends of so many people.