Dogs really do put on their puppy eyes to pull our emotional heartstrings, a new study found.

When they are being looked at they raise their brows making their eyes look bigger along with other facial expressions.

Puppy eyes was the most common expression observed by dog experts when owners looked at their pet.

Yet our manipulative four legged friends do not respond with more facial expressions upon seeing tasty food suggesting they change facial expressions to communicate and not just because they are excited.

Puppy dog eyes closely resembles sadness in humans so it may make us more empathetic or because their eyes are more infant-like tapping into our preference for child-like characteristics.

Regardless we find it impossible not to respond.

Previous research found some apes can also modify their facial expressions depending on their audience, but until now, dogs’ abilities to do use facial expression to communicate with humans hadn’t been systematically examined.

Scientists at the University of Portsmouth’s Dog Cognition Centre are the first to find clear evidence dogs move their faces in direct response to human attention.

Yet it remains unclear whether the dogs are aware of our perspective or if their behaviour is hardwired, or even a learned response to seeing the face or eyes of another individual.

Most mammals use facial expressions but it had been assumed some, including humans, are involuntary and dependent on an individual’s emotional state rather than being flexible responses to the audience

And it’s possible dogs’ facial expressions have changed as part of the process of becoming domesticated.

Dog cognition expert Dr. Juliane Kaminski said: “We can now be confident that the production of facial expressions made by dogs are dependent on the attention state of their audience and are not just a result of dogs being excited.

“In our study they produced far more expressions when someone was watching, but seeing food treats did not have the same effect.

“The findings appear to support evidence dogs are sensitive to humans’ attention and that expressions are potentially active attempts to communicate, not simple emotional displays.”

The study published in Scientific Reports involved 24 family pets of various breeds aged one to 12.

Each dog was tied by a lead 3 feet away from a person, and the dogs’ faces were filmed throughout a range of exchanges, from the person being oriented towards the dog, to being distracted and with her body turned away from the dog.

The dogs’ facial expressions were measured using DogFACS, an anatomically based coding system which gives a reliable and standardised measurement of facial changes linked to underlying muscle movement.

Co-author and facial expression expert Professor Bridget Waller said “DogFACS captures movements from all the different muscles in the canine face, many of which are capable of producing very subtle and brief facial movements.

“FACS systems were originally developed for humans, but have since been modified for use with other animals such as primates and dogs.”

Kaminski added: “Domestic dogs have a unique history — they have lived alongside humans for 30,000 years and during that time selection pressures seem to have acted on dogs’ ability to communicate with us.

“We knew domestic dogs paid attention to how attentive a human is — in a previous study we found, for example, that dogs stole food more often when the human’s eyes were closed or they had their back turned.

“In another study, we found dogs follow the gaze of a human if the human first establishes eye contact with the dog, so the dog knows the gaze-shift is directed at them.

“This study moves forward what we understand about dog cognition. We now know dogs make more facial expressions when the human is paying attention.”