Humans have been found to have the surprising ability to understand doggy talk and differentiate between different growls.

A study invited 40 volunteers to listen to different growls recorded from 18 dogs that were guarding food, facing a threatening stranger, or playing a tug of war game.

Participants were able to correctly classify 63% of the growl samples – significantly more than would be expected by guesswork alone, researchers said.

The “playful” growls were identified by 81% of listeners, but the food-guarding and threatening growls proved harder to distinguish. Women were also found to be better than men at identifying a playful or threatening dog.

During the game of tug of war, the dogs produced a larger number of shorter, less separated growls than when they were aggressive or fearful. The “play” growls and food-guarding growls had distinctively different pitch characteristics.

As well as identifying growl contexts, the volunteers also had to rate the growls on a sliding scale according to five emotional states – aggression, fear, despair, happiness and playfulness.

The scientists concluded: “Our results indicate that dogs communicate honestly their size and inner state in serious contest situations, where confrontation would be costly, such as during guarding of their food from another dog.

“At the same time, in contexts with assumedly more uncertain inner states, such as in a play or when threatened by a stranger, they may manipulate certain key parameters in their growls for an exaggerated aggressive and playful expression.

“According to our results, adult humans seem to understand and respond accordingly to this acoustic information during cross-species interactions with dogs.”