ARUN RATH, HOST:
If you're a dog owner, this question may have crossed your mind. Does she really love me, or is she just looking at me that way to get a treat? New research out this week in the journal Science may provide some clues. NPR's Geoff Brumfiel has this report on puppy love.
GEOFF BRUMFIEL, BYLINE: Just up the street from NPR's headquarters, I found Myrna Charles walking her Great Danes.
MYRNA CHARLES: This is Peace and Quiet. This one's quiet. What, you're going to say hi?
BRUMFIEL: Peace and Quiet are a lot of dog to handle.
CHARLES: He's 185 pounds and she's 140 pounds.
BRUMFIEL: But they're also nice doggies.
CHARLES: They're pretty good. The only time they're running is really if there's a squirrel.
BRUMFIEL: And what do you do when there's a squirrel?
CHARLES: I let the leash go because if not, I'm in a tree or I'm being dragged with them.
GEOFF BRUMFIEL, BYLINE: Part of the reason Peace and Quiet are so well behaved is because of domestication. For thousands of years, humans have bred dogs for obedience. But what about affection?
EVAN MACLEAN: Well, it's a harder one to get at, partly because emotions are so subjective.
BRUMFIEL: Evan MacLean is at Duke University's Canine Cognition Center. He says sometimes human project emotions.
MACLEAN: I think a common one is that people always talk about dogs looking guilty. You know, you come home from work and there's a mess in the house. And you look at your dog and you knew they were feeling guilty about what they did. And, you know, there have been good studies to show that actually, what's happening in those situations our dogs are actually just responding to people.
BRUMFIEL: The dog looks guiltily at you because you look angrily at the dog. A team at Azabu University in Japan has now found a more quantitative measure of emotion. They let owners and dogs interact, and rather than just watching them, the team took urine samples.
MACLEAN: And what they did is they measured oxytocin, which is a hormone that has been very associated with trust and social bonds.
BRUMFIEL: Oxytocin is the same bonding hormone that gives parents warm fuzzies when looking at their infants. Researchers found that when dogs stared into their owner's eyes, oxytocin levels rose in both the people and the dogs. The same was not true for wolves, who were observed with their handlers.
MACLEAN: That suggests that what they observed in dogs might actually be something special about dogs and not just a general feature of interaction between humans and any other animal.
BRUMFIEL: Now, not everyone is buying this hormonal connection. Clive Wynne is a psychologist at Arizona State University who studies how dogs and people interact.
CLIVE WYNNE: There is a fashion in science at the moment to identify changes in hormone levels with changes in emotional and feeling state.
BRUMFIEL: In fact, oxytocin is not always associated with love. The hormone can also be linked to feelings of emotional isolation, even aggression in some animals. And Wynne says the wolves didn't make a lot of eye contact. If they had, their oxytocin might have gone up too. But honestly, Wynne believes dog owners shouldn't worry.
WYNNE: I think the best evidence that any dog lover has that their dog loves them, it's what the dog does when it's around them.
CHARLES: No. No...
BRUMFIEL: Back outside, a passing doggy gets Peace and Quiet excited.
(SOUNDBITE OF GREAT DANES BARKING)
BRUMFIEL: Owner Myrna Charles settles them down. Then she tells me she's got no doubt about their love for her.
CHARLES: Look in his eyes. You're not even his owner. Look in his eyes, wouldn't - like, oxytocin levels, oxytocin levels.
BRUMFIEL: Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.