They're often referred to as'man's best friend', but a new study suggests that when it comes to communication, not all dogs are equal. Researchers from George Washington University have revealed the dogs that give humans the most expressive stares. Their findings suggest that it's not about breed, and it instead comes down to dogs' facial markings. Those with one, solid colour face are perceived as more expressive than those with multi-coloured faces, according to the researchers. 'Knowing what dogs are trying to tell us and what they might be thinking or feeling can really enhance both their experience and ours when we're together,' said Courtney Sexton, lead author of the study.