Can you tell me how these dogs feel? Research shows that breeds with a flat face are more difficult to read. Do you think these puppies are happy or sad?

They are often referred to as 'man's best friend', but if you have a dog, do you really know how they feel?

According to a new study, the answer will likely depend on the shape of their face.

Researchers from the Czech University of Life Sciences in Prague say that flat-faced dogs, including pugs, Boston Terriers and French Bulldogs, are more difficult to read than dogs with a 'normal' head.

“Flat-faced dogs are often seen as cute, attractive and almost comically expressive, with their big eyes and short noses,” said Petra Eretová, the study's lead author.

“But contrary to the stereotype, it is actually more difficult to read the facial expressions of flat-faced dogs, compared to normal dogs.”

The characteristics of flat-faced or brachycephalic dogs did not evolve naturally and are instead the result of selective breeding.

Previous studies have shown that this facial structure puts them at high risk for a range of health problems, including breathing problems, childbirth difficulties and excessive skin folds.

Despite these problems, French Bulldogs, English Bulldogs and Pugs are all extremely popular pets.

Experts have previously claimed that this is due to their expressive, childish features, which people are attracted to.

In their new research, the team wanted to test whether this is really the case.

The researchers recruited 350 participants, who were shown photos and videos of dogs in different contexts.

In total, the behavior of 23 dogs of two breeds was recorded.

Boston Terriers were selected to represent the flat-faced dogs, while Jack Russell Terriers represented 'normal' breeds.

The dogs were recorded in four situations: they were called by name, they played, they were separated and they were threatened by a stranger.

The participants were then shown images or photos of the situations and were asked which of the four they thought the dogs were in.

The results showed that participants were better at reading the facial expressions of Boston Terriers in the two positive scenarios (called by name and played with).

However, they had difficulty recognizing their expressions in the two negative situations (separation and threat from a stranger).

“We found that Boston Terriers were often misunderstood when expressing negative emotions,” said Dr. Eretova.

“People were actually more likely to assume the dog was happy, even if it was scared or anxious.”

The researchers acknowledge that one of the main limitations of the study was the use of only two dog breeds.

“Another avenue to explore is people's perception of inner states in dogs with different skull lengths, which will be presented in an upcoming study,” they wrote in their study, published in Applied Animal Behavioral Sciences.

The new study comes shortly after figures showed that flat-faced dogs have declined in popularity in Britain.

Overall, The Kennel Club says there was a 17 percent drop in registrations of all dogs in Britain last year.

However, registrations of flat-headed breeds fell by more than a third.

There were 42 percent fewer registrations of Pugs, 39 percent fewer of English Bulldogs and 34 percent fewer of French Bulldogs.

According to The Kennel Club, this is the biggest decline in popularity for these breeds in more than a decade in Britain.

“The decline in puppy registrations for these flat-faced breeds is a welcome step in the right direction, although it should be viewed with some caution,” said Dan O'Neill, chairman of the Brachycephalic Working Group (BWG).

'We hope this is a sign that more and more puppy buyers, owners and breeders are thinking about the serious health and welfare implications of flat-faced dogs.

'This is particularly important if these dogs are bought on impulse because they 'look cute', but without a proper understanding of their potential health problems or how indiscriminate breeding to meet demand results in poor welfare.'