There is a great article over at the blog "The Science Dog" that investigates the science behind the notion that small dogs are yippy, overly excitable, nippy and untrained brats.
As it turns out, owners of small and toy breeds have indeed found this to be true when compared to larger dogs.
The article is based on a large study of more than 1300 owners and measured the dog trait factors of "Obedience", "Aggressions/excitability" and "anxiety/Fearfulness". The dogs were broken into two categories -- they were "small" if they weighted less than 44 lbs and large if they weighed more than 44 lbs.
The results were significant, although not at all surprising.
Small dogs were reported by their owners to be significantly more excitable, anxious/fearful and aggressive than were larger dogs.
However, as also would be expected, it appears that the owners were an important contributing factor as to the creation of these undesireable behaviors.
Based on the research, there was a significant correlation (not proving causation, but strong correlation) that owners of small dogs were less likely to train their dogs, less likely to engage in play interaction and had less consistency in training interactions than the owners of larger dogs.
It tends to lead one to believe that small dogs are often ill-behaved because owners are less likely to provide consistent training, interaction and play with their dogs than owners of larger dogs. This could be because owners are less likely to see aggressive behavior in small dogs as a threat or that the bad behavior is "cute", or because large dog owners are more likely to engage in activities such as hiking, running, frisbee, regular walks, etc.
Also of note (and I know I'm opening a can of worms here), but there is also differences between training methods used.
Probably not surprisingly, owners of small dogs were found to use punishment less frequently than large dog owners. However, it's important to note that frequent use of punishment during training was strongly correlated with aggressive behavior in both small and large dogs.
However, greater reliance on punishment during training was also associated with greater anxiety/fear in small dogs, but NOT in large dogs.
Again, there is probably nothing here that would likely surprise most of my readers. Trainers, behaviorists and experts for years have been preaching the importance of owner behavior and the importance of training on dog behavior. While often these conversations happen in the context of dog bite incidents and aggressive behavior, it should be noted that this is also an issue for small dogs and that as a whole, we need to put greater emphasis on teaching responsible dog ownership -- regardless of what type of dog people choose to have.
Because whether the dogs are large, or small, the impact on the owner's training (or lack of training) is a major influencer on the behavior of the individual dog. Which is why when we talk about canine behavior, we must look at dogs as individuals who have been formed not only by their genetics (among and within breeds) but also by their life experiences and the owners that trained them.
H/T: The Science Dog