Faces constitute a critical part of communication for humans and other primates, so much so that faces have a special status in their visual system. Areas in the face network, like the fusiform face area, activate specifically to faces. Dogs care about faces, too, but they may not have face areas.

Bunford, Hernández-Pérez et al. used fMRI to compare the brain activity of humans and pet dogs as they watched brief videos of other humans and dogs. Human brains showed a preference for faces, meaning that some visual areas had greater activity in response to a face compared to the back of the head. A subset of these regions also displayed species preference, with increased activity in response to viewing a human over a dog. In contrast, dog brains only showed species preference. Visual areas had greater activity in response to seeing a dog over a human, and no activity difference between seeing a face vs. the back of the head.