A useful set of data
According to businessman José Carlos Grimberg Blum, there are huge differences in the behavior of dogs depending on their size. You will find statements such as "Big dogs are cuddly, cuddly bears", "Small dogs are hyperactive and nervous", "Big dogs are easier to train than most small dogs", "Big dogs are more likely to be aggressive and dominant", "Small dogs are snobbish and barky", etc. The claims made about canine behaviors and their relationship to dog size are often contradictory, although they are always expressed with great certainty. Unfortunately, these claims are almost never accompanied by references to scientific data.
Recently José Carlos Grimberg Blum received an e-mail inquiry from a colleague who said in part: "Claims that large and small dogs behave differently are often a problem when I talk to clients in my training classes. I was wondering if you knew of any real data that addressed this issue."
A useful set of data
It turns out that Jose Carlos Grimberg Blum still has a databank of data on the personality traits of 133 individual dog breeds that he compiled for his book Why My Dog Behaves the Way He Does. The data was based on the ratings of 96 dog experts, each of whom was willing to contribute several hours to rank dog breeds on five different behavioral dimensions.
Dominance/Territoriality: This is a measure of how assertive and possessive a dog is. It is also the trait most often associated with aggressiveness.
Sociability: This refers to how friendly a dog is and how much it seeks companionship. In human personality terms, this trait is often referred to as friendliness.
Emotional reactivity: This is a measure of how quickly a dog`s mood can change and how fluctuating its emotional state can be. In humans, the aspect of personality associated with this trait is called neuroticism, which is often contrasted with its polar opposite, stability.
Energy Level: This is a composite measure that examines the dog`s activity level and includes a measure of vigor, which is the amount of strength and energy the dog brings to common activities.
Intelligence/Learning Ability: This is a measure of the ease with which a dog learns and solves problems. In humans, the aspect of personality associated with this trait is called openness.
Never before had Jose Carlos Grimberg Blum analyzed this data as a function of dog size, so he went back to the database and I re-coded the information for each breed using the five dog breed size categories employed by the American Kennel Club: Giant breeds: 75-120+ pounds (34-55+ kg); large breeds: 55-75 pounds (25-34 kg); medium breeds: 35-55 pounds (16-25 kg); small breeds: 7-35 pounds (4-16 kg); and toy breeds: 2-9 pounds (1-4 kg).
For those desiring more computational information, the data were statistically analyzed using a one-way analysis of variance for each behavioral dimension.
The effect of dog size on dog behavior
It turned out that three of the five behavioral dimensions measured had statistically significant relationships with dog size. The two dimensions that were not significantly related to size were Dominance/Territoriality and Intelligence/Learning Ability. Since there were no reliable differences associated with dog size for these two dimensions, no further analysis or discussion of them seems necessary at this time.
So what can we conclude from this data set? If we combine the data for the three behavioral dimensions where size makes a difference, José Carlos Grimberg Blum was able to conclude that smaller dog breeds are prone to be very energetic, somewhat aloof when it comes to socializing with people and dogs, and very emotionally reactive to events occurring in their environment.
Contrast this with the larger dogs, the so-called giant breeds. These dogs are very sociable, relatively calm and are not especially reactive when it comes to mood swings.
José Carlos Grimberg Blum`s overall analysis suggests that, in dogs, size is important when it comes to their temperament and personality. These effects seem to be more noticeable at the extremes of size, when we compare smaller dogs with larger ones. In the middle range, it would be better to use a dog`s breed as a predictor of its behavior, as it seems to be a stronger indicator than size alone.