November 08, 2016

Neurobiological Basis of Dogs' Social Responses to Humans

A review article discusses the neurobiological factors that affect dogs’social-cognitive responses to humans.
 
By Laurie Anne Walden, DVM, ELS
Why do dogs become attached to people and seem to understand what they are feeling? In a review article published in Neuroscience and Biobehavioral Reviews, Alicia Buttner, of the University of Nebraska at Omaha, discusses the neurobiological factors that affect dogs’ social-cognitive responses to humans. She suggests that the ability of dogs to connect with people is influenced by genetics and biochemical mediators of stress responses, such as oxytocin.
 
The term social competence describes the way dogs respond to human cues. Previous research has suggested that social competence in dogs is a function of species-to-species communication rather than learned behavior. Domestic dogs are generally better than other species at following human cues (like pointing, gazing, or turning the head) to find a hidden object. They are also able to recognize some human emotions. “This breadth of human-directed social-cognitive and emotional capacities allows dogs to engage in multifaceted social interactions with humans unlike what is seen with any other interspecific relationship,” writes Buttner.
 
Dogs’ social-cognitive abilities are analogous to those of humans, says Buttner, partly because of the length of time dogs have been domesticated (as long as 33,000 years, according to one study). Because domestic dogs evolved in close contact with humans, their social skills and behaviors became adapted to human society. The social-cognitive abilities of the two species are similar enough that some researchers are now using dogs as models for studies of social cognition in people.
 
Domestic dogs are genetically predisposed to interact with humans by selection for docility and the blunting of fear-related stress-response systems, says Buttner. The sympathetic-adrenomedullary system is responsible for the release of epinephrine in response to a perceived threat, the “fight or flight” response. The hypothalamic-pituitary-adrenal axis regulates the body’s response to stress via the release of adrenocorticotropic hormone and glucocorticoids. These stress-response systems are typically less active in domesticated than in wild species, writes Buttner, and genes involved in their activity are expressed differently in wolves and dogs. Reduced activity of the hypothalamic-pituitary-adrenal axis in dogs has also resulted in an extended period during which puppies are open to socialization with people. These changes have predisposed dogs to form attachment bonds with people, Buttner says. “By selecting for reduced [hypothalamic-pituitary-adrenal] axis activity, dogs became less reactive and their sensitive windows of socialization were altered, thereby enhancing human-directed eye gaze and allowing them more occasions to form attachments bonds with humans,” she writes.
 
Research into the neuroendocrinological basis of social behavior has identified several neurochemicals involved in social cognition, says Buttner. Oxytocin is a neurotransmitter that regulates social attachment, maternal bonding, and stress. It also reduces activity of the hypothalamic-pituitary-adrenal axis, she writes. Oxytocin levels are elevated with social interaction in various species, and Buttner describes various studies that have explored the relationship of oxytocin (both endogenous and exogenously administered) on dogs’ social responses to humans. Although oxytocin appears to have a clear influence on social behavior in dogs, she cautions that the mechanisms are complicated, involving many neurotransmitters and systems.
 
Buttner proposes a model of canine social competence that links three main factors:
  • Influencing variables: genetic predisposition to human attachment, extended socialization period in puppies, and actual social interaction with people during the socialization period
  • Biological mediators: feedback loop involving oxytocin-mediated attachment, reduced stress reactivity, and increased emotional regulation
  • Expressions of social competence: sensitivity to human cues and more complex expressions like empathy
This model may help explain some inconsistencies in previous social cognition research in dogs by including the effects of biological mediators and stress response systems, she says. The model also takes into account the effects of interaction with humans. Wolves, for example, lack domestic dogs’ innate predisposition to connect with humans and have more active stress response systems, but in some studies, wolves with extensive human contact and training were able to follow human cues as well as dogs could. Shelter dogs might not have a history of early human socialization, but their performance on social-cognitive tasks involving people could also be greatly influenced by stress.
 
“The cascading effects of down-regulated stress response systems as a result of domestication in combination with their wolf-inherited social capacities have allowed dogs to form unique attachment bonds to humans, facilitating their complex social competence,” concludes Buttner. “Exploring the neurobiological and hormonal aspects of social cognition will further enlighten us to the complicated mechanisms that influence cognitive processes underlying social interactions not only in dogs, but in humans as well.”
 
Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC. She works as a full-time freelance medical writer and editor and continues to see patients a few days each month.
 

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