Oxytocin and Emotional Tear in Dogs

In humans, tear volume increases in emotional arousal. No studies have investigated the relationship of emotional arousal and tear volume in animals. We measured tear volume in dogs before and after reunion with their owners. Tear volume increased significantly during owner, but not familiar non-owner, reunions but not during reunions with familiar non-owners. When oxytocin instillation was applied to dogs, the tear volume increased, suggesting that oxytocin can mediate the emotion-induced tear secretion in dogs. When the photos of dog’s face in which artificial tear was applied to the dog’s eyes, the positive impression of these photo increased. These suggest that emotional tear can facilitate human-dog emotional connection.