Anyone who has had a small dog snapping at their feet will declare that the most dinky of pooches often are the most inclined to start a fight.
Now, a new study has found that smaller dogs are almost always more aggressive than their larger counterparts.
Miniature Poodles and Miniature Schnauzers top the list of most aggressive dogs in a new study, published in Scientific Reports.
Larger dogs including Labrador Retrievers, Golden Retrievers and Lapponian Herders were found to be the most docile.
Researchers from the University of Helsinki studied over 9,000 dogs to analyse aggressive behaviour, including growling, snapping and biting.
As well as breed, other factors which impacted aggression include fearfulness, age, the company of other members of the same species and the owner's previous experience of dogs.
Older dogs were more likely to be aggressive than younger, with scientists saying this could be because of the pain caused by health conditions, and male dogs were more likely to be aggressive than female. Smaller dogs within breeds were also found to be more ready to snap than larger counterparts.
"Understanding the factors underlying aggressive behaviour is important. In what kinds of circumstances does aggressive behaviour occur and what is the dog's motive for such behaviour? In normal family dogs, aggressive behaviour is often unwanted, while some dogs with official duties are expected to have the capacity for aggressiveness. At the same time, aggressiveness can be caused by welfare issues, such as chronic pain," explained doctoral researcher Salla Mikkola from the University of Helsinki.
The study investigated aggressiveness towards both dog owners and unfamiliar human beings. Dogs were classified as aggressive if they growled often and/or had attempted to snap at or bite a human at least occasionally in the situations described in the survey.
Although small dogs are more likely to be aggressive, the study found that the behaviour was less likely to be addressed by owners as they are not seen as a threat.
"Aggressive behaviour is a serious and common behaviour problem in domestic dogs," the study said.
"Aggressively behaving dogs can cause public concern by biting people and other pets, with medical or even lethal consequences for the victim."
They add: "The severity of aggressive behaviour varies from biting and snapping attacks that can even lead to the death of a victim to less severe, but more common growling and barking."
Prof Hannes Loi from the University of Helsinki added: "People who are considering getting a dog should familiarise themselves with the background and needs of the breed. As for breeders, they should also pay attention to the character of dam candidates, since both fearfulness and aggressive behaviour are inherited".
The most to least aggressive dogs
Spanish water dog
German spitz mittel
Coton de Tulear
Pembroke Welsh Corgi
Jack Russell Terrier
Staffordshire Bull Terrier