If you are afraid of dogs, you may find yourself wary of large dogs such as Dobermans or Great Danes.
But the results of a new study could refocus your attention away from these breeds and toward tiny puppies.
Researchers from the University of São Paulo revealed that heavier dogs tend to be more obedient than lighter pets.
In contrast, small breeds with short snouts like pugs, bulldogs, and shih tzus are the most misbehaved breeds, according to the study.
If you are afraid of dogs, you may find yourself wary of large dogs like Dobermans or Great Danes (stock photo). But the results of a new study could refocus your attention away from these breeds and toward tiny puppies
In the study, the team set out to understand the factors that influence aggression in pet dogs.
They recruited 665 pet dogs across 57 breeds of different sizes.
Dog owners completed three online questionnaires — one about themselves, one about their pet’s characteristics, and one about the nature of any aggressive behaviour, such as barking or attacking.
The results showed that the heavier the dog, the less likely it was to show aggressive behaviors.
In fact, for every additional 2.2 pounds (1 kg) of body mass, aggressive behavior was found to decrease by 3%.
However, small dogs with short snouts were found to be the most aggressive.
“Aggressiveness towards the owner was 79% more likely among brachycephalic dogs than among medium-headed dogs,” said Flavio Arosa, first author of the study.
Small-headed dogs have short, compact faces and include Pugs, Bulldogs, Boston Terriers, and Shih Tzus.
In contrast, medium-headed breeds including Beagles, Golden Retrievers, and Labrador Retrievers have more intermediate skulls.
The sex of the pet also seems to affect its aggression.
“The likelihood of aggressive behavior towards the owner was 40 percent lower among female dogs compared to males,” Arosa said.
In addition, the team found a link between the characteristics of the owner and the aggressiveness of his pet.
Aggression in dogs was 73 percent more frequent among male owners than among female owners, while dogs who were walked every day by their owners were less aggressive.

According to the study, small breeds with short snouts such as pugs, bulldogs, and shih tzus are the most misbehaved breeds. Pictured: a French bulldog wearing a muzzle
However, the researchers caution that these findings are not cause-and-effect associations.
“We’ve found relationships, but it’s impossible to say which comes first,” explained Mr. Arosa.
In the case of the “walking the dog” factor, for example, it could be that people were walking their dog less because the animal was aggressive, or the dog might have become aggressive because the owner wasn’t taking enough of it.
Traits such as weight, height, craniofacial morphology, sex, and age influence the interaction between dogs and their environment.
“They may spend more time indoors because of them, for example.”
The researchers hope the findings will highlight that dog behavior is not unique to the animal, but rather is the result of the interaction between the animal and its disease.
“The environment and the relationship between the owner and the pet, as well as conformation, are all factors that influence how pets interact with us and how we interact with them,” said Professor Briseida de Resende, author of the study.
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