In the study published in the journal Behavioural Processes, 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.
"There is no doubt that humans have the ability to recognise 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," Dr Tina Bloom, a psychologist who led the research, said.
"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," Bloom said.
The study by Bloom and Professor Harris Friedman, both from Walden University, in Minneapolis, used photographs of a police dog named Mal, a five-year-old Belgian shepherd dog, as it experienced different emotions, The Telegraph reported.
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 also 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. The dog'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 recognised was happiness, with 88 per cent of the volunteers correctly identifying it.
Anger was identified by 70 per cent of participants.
Around 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 recognising surprise and just 13 per cent recognising disgust.