What’s your dog really thinking?

The research showed that volunteers could correctly spot when a dog was happy, sad, angry, surprised or scared, when shown only a picture of the animal’s face, suggesting that humans are naturally attuned to detecting how animals are feeling.

Dr. Tina Bloom, a psychologist who led the research, said: “There is no doubt that humans have the ability to recognize emotional states in other humans and accurately read other humans’ facial expressions. We have shown that humans are also able to accurately – if not perfectly – identify at least one dog’s facial expressions.

“Although humans often think of themselves as disconnected or even isolated from nature, our study suggests that there are patterns that connect, and one of these is in the form of emotional communication.”

The study, published in the journal Behavioural Processes, used photographs of a police dog named Mal, a five-year-old Belgian shepherd dog, as it experienced different emotions. To trigger a happy reaction, researchers praised Mal. The result was the dog looking straight at the camera with ears up and tongue out.

They then reprimanded the dog to produce a “sad” reaction, causing the animal to pull a mournful expression with eyes cast down.

Surprise, generated using a jack-in-the box, caused the dog to wrinkle the top of its head into something akin to a frown. Medicine that Mal did not like was produced to stimulate disgust – flattened ears – and nail trimmers, which Mal also disliked, were brandished to create fear, causing the ears to prick up and the whites of the eyes to show.

For anger, a researcher pretended to be a criminal. Mal’s teeth were bared in the beginnings of a snarl.

The resulting photographs were shown to 50 volunteers, who were split into two groups according to their experience of dogs.

By far the easiest emotion they recognized was happiness, with 88 per cent of the volunteers correctly identifying it. Anger was identified by 70 per cent of participants.

About 45 per cent of volunteers spotted when Mal was frightened, while 37 per cent could identify the relatively subtle emotion of sadness.

The canine expressions that were hardest for humans to identify were surprise and disgust, with only 20 per cent of the volunteers recognizing surprise and just 13 per cent recognizing disgust.

The study by Dr Bloom and Prof Harris Friedman, both from Walden University, in Minneapolis, found that people with minimal experience of dogs were better at identifying canine disgust and anger, perhaps because dog owners convinced themselves that their dog was not aggressive and so the associated facial expression was just playing.

The researchers believe the ability of inexperienced volunteers to sometimes be better judges of emotions may be because reading dogs’ faces comes naturally, rather than being a learned skill.

Dr Bloom said she hoped further research might determine whether this apparent natural empathy with canines was something we shared with all mammals, or could be explained by humans and dogs evolving side-by-side for the past 100,000 years.

As a dog lover — who was “very confident” in her ability to read the faces of her two Dobermans and two Rhodesian ridgebacks — she admitted such unproven theories were emotionally appealing.

She added: “If I adopted a cat, or a snake or a turtle, I don’t think it would be as emotionally attached to me and watching my face as much as a dog would. There is something different and special about a dog — I’m not sure what it is, but it’s there.”

Beverley Cuddy, the editor of Dogs Today, said dog lovers would feel vindicated by the research. “I am not at all surprised that science has finally accepted what we knew all along — dog and owner communicate perfectly well without words.”