Until a human experiences life as a canine, it's unlikely that debates about the emotions of dogs can be settled. Most dog guardians, along with some scientists, argue emphatically that dogs can "love" and "hate" — in generally similar ways that humans do. Other researchers argue just as vehemently that dogs are incapable of complex emotions. And Mike Mendl, U.K.-based head of the University of Bristol's Animal Welfare and Behavior research group, points out that emotions are inherently private.
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Dogs can feel complex emotions.
Marc Bekoff, author of "The Emotional Lives of Animals: A Leading Scientist Explores Animal Joy, Sorrow, and Empathy -- and Why They Matter," is in the camp of researchers who argues that dogs do feel emotions. Bekoff says emotions are what cause animals, including humans, to behave in different ways in different situations. Those who agree with Bekoff say your dog's love is what causes him to wag his tail and lick your face when you come home. Your dog may hate -- or at least dislike -- your cat, who has scratched his nose at every opportunity for years, and that's why he growls at her when she crosses the room.
Dogs cannot feel complex emotions.
Pennsylvania-based veterinarian Fred Metzger is among the scientists who argue that dogs don't feel emotions, including love and hate. Dogs are simply doing what they need to do to get what they want or to keep away from what they don't want, according to Metzger. Your dog wags his tail because he knows you will give him food. He's learned that the more he wags his tail, the more his human responds with "gifts" that benefit him. The reverse is when your dog growls at your cat. He simply remembers the cat scratching his nose and he wants to keep his distance so that he doesn't get hurt.
Studying the emotional lives of dogs.
The brain chemistry and structure responsible for emotions, including love and hate, is similar in humans and dogs. Dogs' brains release dopamine, a chemical integral to the emotion of love, when they are happy. As do human brains, dog brains release adrenaline — the chemical integral to hate — when they are angry. Research at Eotvos Lorand University in Budapest has found dogs convey emotion in their barking, and even humans can decipher whether a dog's bark is expressing happiness or anger. And research at Goldsmiths University in London has shown that dogs are empathetic to human emotions.
Every dog owner probably has a story illustrating her dog's love or hate. Among them is the story of Rocky, the boxer who after two near-drowning experiences could not be induced to get anywhere near a body of water. When the girl who raised him fell into a lake, though, Rocky dove in after her and brought her to safety.
In her book Through A Dog's Eyes (excerpted here), Jennifer Arnold tells the story of a service dog named Nick who stayed with a dying child. When the child passed, Nick instinctively comforted the child's mother and kept his emotions in check until he left the hospital room. After leaving the grieving mother's presence, Nick collapsed, moaned and refused to walk for a few hours. A veterinarian could find nothing physically to explain Nick's behavior. Arnold attributes it to the sheer weight of his emotions.