Size, skull shape and age influence the temperament of domestic dogs

Studies have investigated the relationship between dogs' morphological characteristics and behavioural dimensions, but little is discussed about this relationship in the context of dogs' responses to emotion eliciting stimuli and temperament. Based on the assumption that the developmental trajectory of behaviour and emotion processing is impacted by the interaction between organisms and environment, we analysed whether dogs' characteristics - that determine how they perceive and interact with their surroundings - affect temperament profiles. We looked at size, height, weight, skull morphology, age, sex, reproductive status, and breed of a sample of Brazilian domestic dogs' and their temperament (measured as Positive and Negative Activation), obtained via the PANAS questionnaire for dogs. We tested possible main effects and first-order interactions in linear mixed models. Younger dogs showed higher positive activation (i.e. sensitivity to positive stimuli; play and treats). For short snouted dogs, the older the dog, less was the negative activation (i.e. sensitivity to negative stimuli; punishment). And for long snouted dogs, larger dogs showed lower negative activation. Weight alone also showed an effect, with heavier dogs having less sensitivity to negative stimuli. Overall, our study demonstrated how morphology and age are important factors that influence temperament expression and emotional reactivity in dogs.