Small dogs may suffer from a canine equivalent of short man syndrome, researchers believe, making them more aggressive and prone to mount people and objects.
Regardless of breed, the smaller the dog is, the more likely it is to be unruly, aggressive, noisy and prone to "humping", according to a study by the University of Sydney.
"Our research shows that certain physical characteristics in dogs are consistently associated with certain types of behaviour," said Professor Paul McGreevy from the Faculty of Veterinary Science.
"Essentially, the shorter the dogs the less controllable their behaviour is for their owners.
"Undesirable behaviours such as owner aggression, or mounting, occur more often among small dogs."
The study, published in journal PLOS One, examined owners' reports of 8000 dogs from across 80 breeds. It found that 33 of 36 undesirable behaviours in dogs could be associated with height, body weight and skull shape.
"When average body weight decreased, excitability and hyperactivity increased," said Professor McGreevy.
Further studies will address whether these bad behaviours seen in small dogs are a result of nature or nurture.
"This suggests that, in small dogs, these behaviours are tolerated more than they would be in larger dogs where such behaviours are more unwelcome and even dangerous."
"Equally, such behaviours in small dogs may be a result of their being overindulged and over-protected," he said.
