Social Behavior and Cognitive Bias in the Domestic Dog (Canis familiaris)

Abstract

Investigation of individual differences in behavior has increased in recent decades, with implications for both applied and basic science. Research with species that have evolved alongside humans presents an opportunity to improve understanding and welfare simultaneously. This dissertation first examines the potential applications of personality research with nonhuman animals of any species, before shifting focus to a species that is ubiquitous in the lives of humans around the world; domestic dogs (Canis familiaris). I discuss the development and validation of a pictorial questionnaire designed to measure three dimensions of canine body language during interactions with conspecifics: Aggression, Arousal, and Boldness. Results indicate that these three dimensions are correlated, with body language identified as higher arousal associated with being more aggressive and more shy/fearful when rated by experts as well as when reported by owners. Observer ratings of dogs’ body language during an introduction to a live dog correlated with owner responses on the Arousal and Aggression dimensions, but not Boldness. Subsequently, I compare dog behavior in a live dog introduction to three other conditions (control, a novel object, and a model dog) to evaluate the validity of using a model dog as a proxy for a live dog when assessing dog-dog sociability. In general, dogs treated the model dog as intermediate between the live dog and a novel object. Dogs’ scores on Aggression in an owner survey correlated with their behavior in the experiment. Dogs that were higher in aggression stared longer and oriented their bodies more directly toward the model dog and live dog compared to the novel object and control conditions. Dogs with lower Aggression scores did not treat the conditions differently in this regard. Finally, I investigate potential cognitive underpinnings of canine aggression toward conspecifics. I compared dogs’ judgement bias (the tendency to treat an ambiguous stimulus as predicting a positive vs. negative outcome) in a spatial discrimination task to individual differences assessed by owner survey, including aggression toward other dogs and general fearfulness. Increased dog-directed aggression was associated with a more positive judgement bias, while higher levels of fear predicted better discrimination of stimuli.