Most owners think their pup’s face lights up when telling their dog they’re a good boy or girl. But are the expressions dogs make meant for humans?

Researchers in England wanted to find out. They tested 24 pups by having each dog’s owner do a series of actions while recording the dog’s expressions. The owner first faced their dog with a treat in their hand, then without a treat. They then faced a wall while holding a treat, then without one. Dogs’ facial expressions changed more when they could see their owner’s face—whether or not a treat was involved.

This means dogs likely use facial expressions to communicate with their owners. Even though they mainly react when we’re watching, “we get the impression that dogs understand everything we say to them” says Juliane Kaminski, an animal psychologist who was part of the study.