The prevalence of aggression in UK dogs varies depending on the definition of aggression, the population studied, and the method of assessment. Studies that use strict criteria for aggression often find lower rates of aggression than studies that use broader criteria. Additionally, rates of aggression can vary by breed, sex, age, and other factors.

A 2016 study published in the journal "Preventive Veterinary Medicine" found that 8.9% of UK dogs displayed some form of aggression towards humans or other animals in the previous year. The study was based on a survey of over 13,000 dog owners. However, it is important to note that this study did not use a strict definition of aggression, and some of the behaviors included in the definition may not be considered aggressive by all experts.

Another study, published in the journal "Applied Animal Behaviour Science" in 2017, found that 5.1% of UK dogs exhibited aggression towards humans. This study used a stricter definition of aggression, which required that the dog had bitten or attempted to bite someone in the past.

Overall, aggression is not uncommon in UK dogs, but it is important to note that the prevalence of aggression can vary depending on the definition of aggression and the population studied. Additionally, there are a number of factors that can influence the likelihood of a dog displaying aggression, including breed, sex, age, socialization, and training.