The connection between humans and their dogs is fascinating and intriguing. I have many patients who are extraordinarily attached to their dogs, spend large sums of money on sick dogs, rejoice at their unconditional love and affection, and mourn when they die. How did dogs come to occupy this trusted friendship and powerful social attachment.
Dogs respond to pointing cues to find hidden food or other rewards. There are other social cues that dogs respond to such as gaze direction to which children also respond. Both children and dogs interpret eye contact as communication suggesting a similar or shared cognitive style.
What explains these human-like attributes in dogs? Genetic studies have established that dogs evolved from wolves; but, wolves do not seek human assistance in solving problems nor so they attend to social cues as dogs do. Since the dog's human-like tendencies do not appear to be genetic in origin, possibly they were shaped by domestication, i.e., selection based on temperament which allowed dogs to interact with humans like partners. If this is the case, then there should be underlying biological processes which support this social and cognitive evolutionary convergence.
In a prior blog I talked about the important role of oxytocin, a nonapeptide neuropeptide, in social interactions and formation of bonds between members of the same species. Can it also produce these effects in members of separate species? T. Romero et.al. and J. Oliva et.al. have studied the effect of administered oxytocin on dogs relative to other dogs and on the effect on dogs attending to human social cues. The results showed an increase in social contact between dogs, more social contact with humans, and more attendance to human social cues. Could this suggest that increased oxytocin in dogs leads to an increased oxytocin response in humans? Such a finding would suggest a dynamic similar to that found in a mother-infant bond.
Now comes Miho Nagasawa et. al. whose recent article in Science described an experiment in which the researchers watched 30 dog owners interacting with their dogs (varying breeds and ages) and measured the changes in urinary oxytocin before and after they interacted. The dogs that looked at their owners longest had the largest changes in urinary oxytocin. Their owners experienced a similar response. They could not replicate this with wolves. This supports the feedback loop described above and suggests that is transmitted partly by sustained eye contact between dog and human.
Is the relationship one of cause and effect? Nagasawa then administered oxytocin to another group of dogs before they interacted with their owners. They found an increase in mutual gaze between dog and owner. Strikingly they also observed an increase in oxytocin in the dog owners mediated by increase mutual gaze. This occurred in female dogs only.
These findings mirror findings in humans described by O. Weisman et.al. Nagasawa's results suggest that dogs have piggybacked on our parental behavior such as staring into our eyes to produce rewarding caretaking behavior. This phenomena is bidirectional and so dogs experience reward as well. These behaviors convey selective advantage with regard to human preferences. It appears that we are tuned into dogs in a similar way we are tuned into children. Our relationship to dogs thus appears to be based on human bonding pathways.