Significance: Although the positive impact of social bonds on individual’s fitness has recently been demonstrated, the mechanisms underlying the motivation to form long-term associations remain largely unknown. Current evidence shows that oxytocin modulates social behavior but evidence of its effects in bond maintenance remains scant, especially in nonreproductive contexts. We provide evidence that in the domestic dog oxytocin enhances social motivation to approach and affiliate with conspecifics and human partners, which constitutes the basis for the formation of any stable social bond. Furthermore, endogenous oxytocin levels increased after dogs engaged in affiliation with their dog partners, indicating a stimulation of the oxytocin system during social interactions. Our findings highlight the important role that oxytocin has in the expression of sociality in mammals.

During the domestication process, dogs were selected for their suitability for multiple purposes, resulting in a variety of behavioral characteristics. In particular, the ancient group of breeds that is genetically closer to wolves may show different behavioral characteristics when compared to other breed groups. Here, we used questionnaire evaluations of dog behavior to investigate whether behavioral characteristics of dogs were different among genetically clustered breed groups. A standardized questionnaire, the Canine Behavioral Assessment and Research Questionnaire (C-BARQ), was used and breed group differences of privately-owned dogs from Japan (n = 2,951) and the United States (n = 10,389) were analyzed. Results indicated that dogs in the ancient and spitz breed group showed low attachment and attention-seeking behavior. This characteristic distinguished the ancient group from any other breed groups with presumed modern European origins and may therefore, be an ancestral trait.

A potential association between pet ownership and mental well-being is suggested, but there is a shortage of high-quality longitudinal studies that consider probable differences among different species. We aimed to examine whether ownership of the most popular pets (dogs and cats) would predict mental well-being. The Tokyo Teen Cohort (TTC), a prospective population-based birth cohort study, had dog and cat ownership data at age 10 and mental well-being score at ages 10 and 12 from 2584 adolescents. Linear regression analysis with adjusting for covariates showed that dog ownership had a positive effect on mental well-being compared to no dog ownership, however, cat ownership had a negative effect compared to no cat ownership. Two-factor mixed-design analysis of variance showed that dog ownership predicted maintained mental well-being, while cat ownership predicted progressing decline of mental well-being. Thus, dog and cat ownership may have different effects on adolescents’ mental well-being, implying that the underlying mechanisms that are activated by these types of ownership may differ.

Dogs (Canis familiaris) and cats (Felis silvestris catus) have been domesticated through different processes. Dogs were the first domesticated animals, cooperating with humans by hunting and guarding. In contrast, cats were domesticated as predators of rodents and lived near human habitations when humans began to settle and farm. Although the domestication of dogs followed a different path from that of cats, and they have ancestors of a different nature, both have been broadly integrated into—and profoundly impacted—human society. The coexistence between dogs/cats and humans is based on non-verbal communication. This review focuses on “gaze,” which is an important signal for humans and describes the communicative function of dogs’ and cats’ eye-gaze behavior with humans. We discuss how the function of the gaze goes beyond communication to mutual emotional connection, namely “bond” formation. Finally, we present a research approach to multimodal interactions between dogs/cats and humans that participate in communication and bond formation.

Breastfeeding behaviours can significantly change mothers' physiological and psychological states. The hormone oxytocin may mediate breastfeeding and mothers' emotion recognition. This study examined the effects of endogenous oxytocin fluctuation via breastfeeding on emotion recognition in 51 primiparous mothers. Saliva oxytocin was assessed before and after the manipulation (breastfeeding or holding an infant), and emotion recognition tasks were conducted. Among mothers who breastfed daily, mothers with more increased levels of oxytocin after breastfeeding showed more reduced negative recognition and enhanced positive recognition of adult facial expressions. These oxytocin functions accompanying breastfeeding may support continued nurturing behaviours and also affect the general social cognition of other adults beyond any specific effect on infants.