Temperament as a Window to Dogs’ Past and Future: Individual Differences in Behavior and Physiology Across the Lifespan

Abstract

An animal’s temperament is described as behavioral traits that are early emerging, stable over time, and related to biological or genetic predispositions. In dogs, temperament is assumed to influence behavior but has not been clearly demonstrated to align with these criteria. To investigate how temperament emerges and changes across early development in dogs, we conducted longitudinal assessments of behavior from 8 to 20 weeks of age, incorporating behavioral assays, physiological measures (cortisol), and comparisons between rearing environments (home-reared vs. Duke Puppy Kindergarten). Chapter 1 examines the stability of temperament traits across early development and into adulthood, identifying which early-life behaviors predict adult behavioral outcomes. Findings reveal that while some aspects of temperament, particularly emotional reactivity, remain stable over time, others are shaped by experience and socialization, highlighting both biological constraints and developmental plasticity of temperament. Chapter 2 explores neurobiological correlates of temperament and finds that salivary cortisol fails to validate as a measure of arousal. Chapter 3 introduces a novel method to assess human-directed sociability in dogs, the Canine Social Preference Assay, in which dogs are free to approach competing nonsocial and social stimuli. While some puppies exhibit a strong preference for human interaction, others show equal or greater attraction to conspecifics, suggesting that human preference is a dimension of individual variation potentially influenced by both genetic predispositions and early experiences. Taking all chapters together, we find compelling evidence that, like in humans, temperament traits are useful predictors of behavior in dogs, and we explore applications of these findings.