Lift and wiggle brows.
We think we can read a dog by its tail, but its facial expressions are a much more powerful indicator. In a recent study in Japan, dogs were presented to their parent, a stranger, a dog toy, and an object they disliked.
Seeing their parent, the dogs immediately raised their eyebrows (especially their left), and when they saw a stranger, there was much less facial movement except for movement of the right forehead. Yet when they saw an object they knew and had bonded with, the dogs moved their left ear back.
But if it was an object they didn’t like, their right ear moved. According to the study, this suggests the dog is more reserved when engaging someone he doesn’t know or something he disapproves of.