Woof! Dog Social Intelligence / Human Social Intelligence

[MKSheppard]

Link

Monday, Sep. 21, 2009
The Secrets Inside Your Dog's Mind
By Carl Zimmer

Brian Hare, assistant professor of evolutionary anthropology at Duke University, holds out a dog biscuit.

"Henry!" he says. Henry is a big black schnauzer-poodle mix--a schnoodle, in the words of his owner, Tracy Kivell, another Duke anthropologist. Kivell holds on to Henry's collar so that he can only gaze at the biscuit. (See pictures of dogs learning new tricks.)

"You got it?" Hare asks Henry. Hare then steps back until he's standing between a pair of inverted plastic cups on the floor. He quickly puts the hand holding the biscuit under one cup, then the other, and holds up both empty hands. Hare could run a very profitable shell game. No one in the room--neither dog nor human--can tell which cup hides the biscuit. (See a video on how dogs think like us.)

Henry could find the biscuit by sniffing the cups or knocking them over. But Hare does not plan to let him have it so easy. Instead, he simply points at the cup on the right. Henry looks at Hare's hand and follows the pointed finger. Kivell then releases the leash, and Henry walks over to the cup that Hare is pointing to. Hare lifts it to reveal the biscuit reward. (See TIME's photo-essay "Puppies Behind Bars.")

Henry the schnoodle just did a remarkable thing. Understanding a pointed finger may seem easy, but consider this: while humans and canines can do it naturally, no other known species in the animal kingdom can. Consider too all the mental work that goes into figuring out what a pointed finger means: paying close attention to a person, recognizing that a gesture reflects a thought, that another animal can even have a thought. Henry, as Kivell affectionately admits, may not be "the sharpest knife in the drawer," but compared to other animals, he's a true scholar. (See TIME's photo-essay "Color My Dog!")

It's no coincidence that the two species that pass Hare's pointing test also share a profound cross-species bond. Many animals have some level of social intelligence, allowing them to coexist and cooperate with other members of their species. Wolves, for example--the probable ancestors of dogs--live in packs that hunt together and have a complex hierarchy. But dogs have evolved an extraordinarily rich social intelligence as they've adapted to life with us. All the things we love about our dogs--the joy they seem to take in our presence, the many ways they integrate themselves into our lives--spring from those social skills. Hare and others are trying to figure out how the intimate coexistence of humans and dogs has shaped the animal's remarkable abilities.

Trying to plumb the canine mind is a favorite pastime of dog owners. "Everyone feels like an expert on their dog," says Alexandra Horowitz, a cognitive scientist at Barnard College and author of the new book Inside of a Dog: What Dogs See, Smell, and Know. But scientists had carried out few studies to test those beliefs--until now.

This fall, Hare is opening the Duke Canine Cognition Center, where he is going to test hundreds of dogs brought in by willing owners. Marc Hauser, a cognitive psychologist at Harvard University, recently opened his own such research lab and has 1,000 dogs lined up as subjects. Other facilities are operating in the U.S. and Europe.

The work of these researchers won't just satisfy the curiosity of the millions of people who love their dogs; it may also lead to more effective ways to train ordinary dogs or--more important--working dogs that can sniff out bombs and guide the blind. At a deeper level, it may even tell us something about ourselves.

Hare suspects that the evolutionary pressures that turned suspicious wolves into outgoing dogs were similar to the ones that turned combative apes into cooperative humans. "Humans are unique. But how did that uniqueness evolve?" asks Hare. "That's where dogs are important."

The first rule for scientists studying dogs is, Don't trust your hunches. Just because a dog looks as if it can count or understand words doesn't mean it can. "We say to owners, Look, you may have intuitions about your dog that are valuable," says Hauser. "But they might be wrong." (See TIME's video "The New Frugality: Doggie Day Care.")

Take for instance the kiss a dog gives you when you come home. It looks like love, but it could also be hunger. Wolves also lick one another's mouths, particularly when one wolf returns to the pack. They can use their sense of taste and smell to see if the returnee has caught some prey on its journey. If it did, the licking often prompts it to vomit up some of that kill for the other members of the pack to share. The kiss dogs give us probably evolved from this inspection. "If we happened to spit up whatever we just ate," says Horowitz, "I don't think our dogs would be upset at all."

Horowitz and other scientists are now running experiments to determine what a behavior, like a kiss, really means. In some cases, their research suggests that our pets are manipulating us rather than welling up with human-like feeling. "They could be the ultimate charlatans," says Hauser.

We've all seen guilty dogs slinking away with lowered tails, for example. Horowitz wondered if they behave this way because they truly recognize they've done something wrong, so she devised an experiment. First she observed how dogs behaved when they did something they weren't supposed to do and were scolded by their owners. Then she tricked the owners into believing the dogs had misbehaved when they hadn't. When the humans scolded the dogs, the dogs were just as likely to look guilty, even though they were innocent of any misbehavior. What's at play here, she concluded, is not some inner sense of right and wrong but a learned ability to act submissive when an owner gets angry. "It's a white-flag response," Horowitz says.

While this kind of manipulation may be unsettling to us, it reveals how carefully dogs pay attention to humans and learn from what they observe. That same attentiveness also gives dogs--or at least certain dogs--a skill with words that seems eerily human.

Juliane Kaminski of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, began exploring the verbal gifts of dogs when she saw a television show about a border collie named Rico--an animal that to all appearances could fetch dozens of different objects in response to their names. Kaminski put Rico to a rigorous test and confirmed that the dog could learn names for more than 200 toys, balls and other items. "I think Rico is a highly talented dog," says Kaminski, "but we've also found new dogs that do what Rico did."

That doesn't mean that the dogs understand the words the way we think they do. When they hear "Frisbee," they may think only, Get the Frisbee. Unlike us, they may not be able to recognize that Frisbee is a word for a distinct object that can be combined with other words to create sentences like "Run away from the Frisbee."

Some scientists acquired their fascination with dogs directly, but Hare's grew out of his research on chimpanzee cognition in the late 1990s, when he was part of a team of primatologists led by Michael Tomasello, now at Max Planck. A chimp can follow the gaze of other chimps and figure out what they can and cannot see. That's a skill that seems to be limited to great apes and humans. Tomasello and his team wondered if such a rare ability extended to hand gestures and tested chimps to see if they could understand pointing. To their surprise, the chimps did badly, able to learn the meaning of a pointed finger only after lots of training.

The apparent explanation for these results was that pointing--and the social smarts behind it--required a humans-only level of intelligence and evolved in our ancestors only after they branched off from the ancestors of chimpanzees some 7 million years ago. When Tomasello suggested this idea to Hare, however, Hare demurred. "I said, 'Um, Mike, I think my dogs can do that,'" Hare recalls.

Hare's later research revealed that while chimps and even wolves lack an innate ability to understand what pointing means, dogs come by the knowledge naturally. They're not limited to reading hands and fingers alone. Dogs understand what Hare means if he points with his foot or sets a piece of wood on top of a container with food inside. Even puppies understand, which means it can't be a skill they need to learn. "This is something that dogs just do," says Hare.

To understand how dogs evolved this skill, Hare traveled to Siberia. In the 1950s, Soviet scientists set up an experiment on a farm outside the city of Novosibirsk to understand how animals were domesticated. They decided to study foxes, which are closely related to wolves and dogs.

The Russians began by breeding a group of foxes according to one simple rule: they would walk up to a cage and put a hand on the bars. Foxes that slunk back in fear and snapped their teeth didn't get to breed. Ones that came up to the scientists did. Meanwhile, the scientists also raised a separate group of foxes under identical conditions, except for one difference: they didn't have to pass a test to mate.

More than 40 generations of foxes have now been bred in Novosibirsk, and the results speak for themselves. The foxes that the scientists bred selectively have become remarkably doglike. They will affectionately run up to people and even wag their tails. In 2003, Hare traveled to Novosibirsk and ran his pointing test on baby foxes. The ordinary ones failed miserably. As for the doglike ones, "they did just as well as puppies right out of the box," Hare says. As the animals were bred for their affability, a new side of their social intelligence was apparently awakened.

If foxes are a guide, dog evolution may have begun with a similar shift in personality. Ancestors of dogs could cooperate to hunt, but the cooperation had limits. Wolves are fiercely competitive, as each one tries to claw its way to the top of the pack. Hare proposes that aggressive wolves evolved to have an easygoing personality thanks to a new opportunity: trash.

As humans became better at hunting, they left scraps around their gathering spots. When they departed, the ancestors of dogs could move in. At first, when humans and wolves came into contact, many of the animals ran away. Others lashed out and were killed. Only the affable animals had the temperament to become camp followers, and their new supply of food let them produce affable puppies. "They selected themselves," says Horowitz.

Once dogs became comfortable in our company, humans began to speed up dogs' social evolution. They may have started by giving extra food to helpful dogs--ones that barked to warn of danger, say. Dogs that paid close attention to humans got more rewards and eventually became partners with humans, helping with hunts or herding other animals. Along the way, the dogs' social intelligence became eerily like ours, and not just in their ability to follow a pointed finger. Indeed, they even started to make very human mistakes. (See more about dogs.)

A team led by cognitive scientist Josef Topál of the Research Institute for Psychology in Hungary recently ran an experiment to study how 10-month-old babies pay attention to people. The scientists put a toy under one of two cups and then let the children choose which cup to pick up. The children, of course, picked the right cup--no surprise since they saw the toy being hidden. Topál and his colleagues repeated the trial several times, always hiding the toy under the same cup, until finally they hid it under the other one. Despite the evidence of their eyes, the kids picked the original cup--the one that had hidden the toy before but did not now.

To investigate why the kids made this counterintuitive mistake, the scientists rigged the cups to wires and then lowered them over the toy. Without the distraction of a human being, the babies were far more likely to pick the right cup. Small children, it seems, are hardwired to pay such close attention to people that they disregard their other observations. Topál and his colleagues ran the same experiment on dogs--and the results were the same. When they administered the test to wolves, however, the animals did not make the mistake the babies and dogs did. They relied on their own observations rather than focusing on a human.

One question the research of Topál, Hare and others raises is why chimpanzees--who are in most ways much smarter than dogs--lack the ability to read gestures. Hare believes that the chimps' poor performance is one more piece of proof that the talent is rooted not in raw intelligence but in personality. Our ape cousins are simply too distracted by their aggression and competitiveness to fathom gestures easily. Chimps can cooperate to get food that they can't get on their own, but if there's the slightest chance for them to fight over it, they will. For humans to evolve as we did, Hare says, "We had to not get freaked out about sharing."

Deeper understanding of the mind of the dog will come with more testing, and Hare and other researchers are planning it--on a grand scale. They're designing new experiments to compare different breeds and to search for genes that were transformed as the animals' social intelligence evolved. Plenty of dog owners are signing up for the studies Hare will be launching this fall. "We'd be happy with thousands," he says.

The biggest challenge to the new experiments, Hare says, will be not the giant pack of dogs he'll be studying but their anxious owners. "When a puppy does badly, people get upset," says Hare. "You have to emphasize that this is not the SATs."

Perhaps that's the most telling sign of just how evolved dogs are. They have us very well trained.

[The Spartan]

My dog can do that. Understand a pointed finger that is. I trained her to do it by putting her in a position as though I'm standing at the plate and she's on the pitcher's mound and telling her to stay. Then I would throw a ball to first base, so to speak, and then point in that direction and tell her to go get it. Once she figured that out I taught her to run to third. And then I did something similar for second, just with a different hand signal.

Now, if she's in the way or I want her to go somewhere I can point and say, "Shadow, go that way" and that's exactly what she'll do. It also gave rise to a game she loves where I'll hold up a ball and tell her to, "Go back," and she'll back up and sit and then catch the ball I throw at her.

[Eleas]

I love cats, but it's a fact that not just my cats (who seem almost retarded in terms of intelligence) but every cat I've ever heard of will interpret a pointed finger to mean "hey, look! a finger!"

[Knife]

My dogs even recognize the emotional element of it. When and if I tell them to get out of a specific room they sometimes are defiant about it (in a passive aggressive way) until I point out of the room, when they sulk and leave.

[The Spartan]

My dogs even recognize the emotional element of it. When and if I tell them to get out of a specific room they sometimes are defiant about it (in a passive aggressive way) until I point out of the room, when they sulk and leave.

With me it's my voice that conveys that. The finger point simply provides a direction, but if she's defiant, my voice gets raised and then she does move.

[Darth Wong]

It seems almost intuitive that dogs rely heavily on human feedback, and are really good at picking up details in it. The way a dog looks at you is almost worshipful. They pay very close attention to our moods, our cues, our intents.

Razor always knows when we're near the end of a car trip, even though he can't possibly know where we're going. It could be a mall, a restaurant, somebody's house, it doesn't matter. When we get close to the end of the trip, he knows. There's some cue that I give off which says "we're getting out of the car soon" and he somehow always knows. Neither my wife, my kids, or even myself can tell what that cue is.

[Aaron]

It seems almost intuitive that dogs rely heavily on human feedback, and are really good at picking up details in it. The way a dog looks at you is almost worshipful. They pay very close attention to our moods, our cues, our intents.

Razor always knows when we're near the end of a car trip, even though he can't possibly know where we're going. It could be a mall, a restaurant, somebody's house, it doesn't matter. When we get close to the end of the trip, he knows. There's some cue that I give off which says "we're getting out of the car soon" and he somehow always knows. Neither my wife, my kids, or even myself can tell what that cue is.

Suesse is the same way. I saw a show a number of years back that had a segment on a Newfoundland that served as a rescue dog on a tour boat. He could apparently tell when a person was going to drown by smelling his/her breath, he would swim around the group sniffing faces and would drag anyone who was starting to weaken back to the boat.

So I figure that Suesse does something similar, a large portion of their brains are given over to smell after all.

[Alferd Packer]

Razor always knows when we're near the end of a car trip, even though he can't possibly know where we're going. It could be a mall, a restaurant, somebody's house, it doesn't matter. When we get close to the end of the trip, he knows. There's some cue that I give off which says "we're getting out of the car soon" and he somehow always knows. Neither my wife, my kids, or even myself can tell what that cue is.

The same thing happens with our chihuahua. She absolutely loves my dad, and accordingly loves it when we take her with us when we go visit him. Invariably, when we get within, say five minutes of his house, she starts whining excitedly and pawing at one of us. I have no idea why; my only theory is that the altitude change is so pronounced(my dad's house is at over 1200 feet above sea level, and we're less than 100) that she feels the different air pressure and has learned to associate that with my dad's house. That, or since we spend the vast majority of the trip at freeway speeds, she takes the slowdown as a cue that we're almost to our destination. It's tough to say, because she starts getting excited at different points in the drive.

[PeZook]

The same thing happens with our chihuahua. She absolutely loves my dad, and accordingly loves it when we take her with us when we go visit him. Invariably, when we get within, say five minutes of his house, she starts whining excitedly and pawing at one of us. I have no idea why; my only theory is that the altitude change is so pronounced(my dad's house is at over 1200 feet above sea level, and we're less than 100) that she feels the different air pressure and has learned to associate that with my dad's house. That, or since we spend the vast majority of the trip at freeway speeds, she takes the slowdown as a cue that we're almost to our destination. It's tough to say, because she starts getting excited at different points in the drive.

I think it's actually a clue the passengers give away, like DW said. Pay close attention to the behavior of a car's occupants near the end of a long trip. The mood inside the car changes significantly: people start talking less, they get more relaxed, their voices take that soft texture that says "Oh, man, we're almost there. We made it!", there's suddendly more talking, rehashing of plans, checking pockets etc.

If a human can pick up on it, I'm sure dogs can, too.

[andrewgpaul]

Razor always knows when we're near the end of a car trip, even though he can't possibly know where we're going. It could be a mall, a restaurant, somebody's house, it doesn't matter. When we get close to the end of the trip, he knows. There's some cue that I give off which says "we're getting out of the car soon" and he somehow always knows. Neither my wife, my kids, or even myself can tell what that cue is.

The same thing happens with our chihuahua. She absolutely loves my dad, and accordingly loves it when we take her with us when we go visit him. Invariably, when we get within, say five minutes of his house, she starts whining excitedly and pawing at one of us. I have no idea why; my only theory is that the altitude change is so pronounced(my dad's house is at over 1200 feet above sea level, and we're less than 100) that she feels the different air pressure and has learned to associate that with my dad's house. That, or since we spend the vast majority of the trip at freeway speeds, she takes the slowdown as a cue that we're almost to our destination. It's tough to say, because she starts getting excited at different points in the drive.

This might sound silly, but are you sure she doesn't just recognise the neighbourhood?

[Gil Hamilton]

It seems almost intuitive that dogs rely heavily on human feedback, and are really good at picking up details in it. The way a dog looks at you is almost worshipful. They pay very close attention to our moods, our cues, our intents.

Razor always knows when we're near the end of a car trip, even though he can't possibly know where we're going. It could be a mall, a restaurant, somebody's house, it doesn't matter. When we get close to the end of the trip, he knows. There's some cue that I give off which says "we're getting out of the car soon" and he somehow always knows. Neither my wife, my kids, or even myself can tell what that cue is.

What's more eerie is when they figure out where they are going based on your body language.

For some reason, without discussing it or giving any hint on where he is going, Joey KNOWS if he's going someplace he likes (like the park) or going someplace he doesn't (like the vet). Note that he becomes more somber or more excited BEFORE he gets into the car, so he's not recognizing the route we are taking if its somewhere he's been before. He's clearly reading us.

[Duckie]

I've been told that Dogs follow human behavior so much that if you yawn, they'll occasionally imitate you like a person having a contagious yawn. I've also seen a dog that attempts to smile when it's happy, despite dog mouths not working that way.

[Adrian Laguna]

I love cats, but it's a fact that not just my cats (who seem almost retarded in terms of intelligence) but every cat I've ever heard of will interpret a pointed finger to mean "hey, look! a finger!"

I lived for a couple of years with a pair of cats who could read human signals. I could see the older one get tense when it was time to kick him out of a bedroom or lap when he did not feel like going. He would also come over to be petted if you stretched out your hand toward him at a height he could reach. Meanwhile, the younger one would leave your bedroom if you opened the door and stood there, but would wait for your return if you opened the door and left.

Both cats can also recognize some emotions by the tone of voice, especially if you direct your speech at them, and react appropriately. An angry voice will make them flinch and flee, while a happy one more likely to come over and hang around. The younger one also never failed to come over when his favourite person in the world called to him, though he rather pointedly ignored anyone else.

Obviously nowhere near as good as a dog (different league entirely), but hardly oblivious either. Though I admit these cats were unusual. They were both remarkably social, asking for attention from complete strangers when most cats will be cold, hostile, or frightful. The younger one had to be locked up during parties lest he make a nuisance of himself, so even crowds failed to bother him. The older one liked to play fetch and at dinner time would lay under the table at everyone's feet. He would also respond to abuse by bitching about it and staying in place, which is counter the typical cat behaviour of running away after violently telling you to fuck off.

So cats in my experience can have some social intelligence, which is not surprising since they are domesticated household animals.

[Winston Blake]

One question the research of Topál, Hare and others raises is why chimpanzees--who are in most ways much smarter than dogs--lack the ability to read gestures. Hare believes that the chimps' poor performance is one more piece of proof that the talent is rooted not in raw intelligence but in personality. Our ape cousins are simply too distracted by their aggression and competitiveness to fathom gestures easily. Chimps can cooperate to get food that they can't get on their own, but if there's the slightest chance for them to fight over it, they will. For humans to evolve as we did, Hare says, "We had to not get freaked out about sharing."

A natural question is: so can peaceful, gregarious bonobos understand gestures?

That seems to be a valid prediction from this hypothesis: social sharing => gesture reading.

[Molyneux]

I've been told that Dogs follow human behavior so much that if you yawn, they'll occasionally imitate you like a person having a contagious yawn. I've also seen a dog that attempts to smile when it's happy, despite dog mouths not working that way.

I don't know...the dog 'smile' expression seems roughly analogous to a human smile. How did this dog try to smile differently?

[jcow79]

We've all seen guilty dogs slinking away with lowered tails, for example. Horowitz wondered if they behave this way because they truly recognize they've done something wrong, so she devised an experiment. First she observed how dogs behaved when they did something they weren't supposed to do and were scolded by their owners. Then she tricked the owners into believing the dogs had misbehaved when they hadn't. When the humans scolded the dogs, the dogs were just as likely to look guilty, even though they were innocent of any misbehavior. What's at play here, she concluded, is not some inner sense of right and wrong but a learned ability to act submissive when an owner gets angry. "It's a white-flag response," Horowitz says.

My dog appears to know when she has done something she knows is wrong. During her potty training she quickly learned to not pee in the house and would always wait to go outside. Pooping on the other hand took a lot longer for some reason. The funny thing was she seemed to understand she wasn't supposed to poop in the house because whenever I would discover poo she would get scolded and put in her crate. After a while when I would discover poo and began to scold she would immediately slink off to her crate. Eventually, I wouldn't even have to find the poo. She would poop and as soon as she saw me even if I had no idea she pooped she would slink off to her crate which would immediately alert me to the fact there was poo somewhere. To me this was an obvious indication that she knew what she was doing was wrong or at least would result in her scolding and detention. I am happy to say she no longer poops in the house.

[His Divine Shadow]

So cats in my experience can have some social intelligence, which is not surprising since they are domesticated household animals.

Cats in the wild (real wild cat and ferals) do live in social groups so they have the basics for that kind of behaviour.

[Eleas]

I love cats, but it's a fact that not just my cats (who seem almost retarded in terms of intelligence) but every cat I've ever heard of will interpret a pointed finger to mean "hey, look! a finger!"

I lived for a couple of years with a pair of cats who could read human signals. I could see the older one get tense when it was time to kick him out of a bedroom or lap when he did not feel like going. He would also come over to be petted if you stretched out your hand toward him at a height he could reach. Meanwhile, the younger one would leave your bedroom if you opened the door and stood there, but would wait for your return if you opened the door and left.

Both cats can also recognize some emotions by the tone of voice, especially if you direct your speech at them, and react appropriately. An angry voice will make them flinch and flee, while a happy one more likely to come over and hang around. The younger one also never failed to come over when his favourite person in the world called to him, though he rather pointedly ignored anyone else.

That's a good point. I'm not disputing it; even my cats are pretty adept at picking up on moods. When I'm at low points, they worry and keep an eye on me (which also happens when I take a bath, because that's clearly unnatural behavior; one of them will always be close enough to offer a helping paw in case I'd find myself drowning), and they do understand when a finger is held up to signal "bad kitty". I'm saying that I've yet to see a cat able to not just interpret the meaning of a raised finger, but parse it in spatial terms and deduce an inferred direction.

[Akkleptos]

Yeah, but I've seen dogs counter these points pointblank. A Dobermann my aunt used to have would understand the word "punishment" (castigo, in Spanish) as an indication to go to her room because she had done something wrong. But when some unadvised guest uttered the word, she would perk her ears up and whine, as if to say "Why? I didn't do anything wrong!" or, if you will, "I did nothing that has previously warranted castigo!". This also happened whenever my aunt said the word "castigo", without referring to the Dobermann's behaviour. That's why she resorted to saying the word in English anytime the dog was in the room.

She displayed many other human-like traits such as attempting to "brush" her teeth by rituallistically chewing on the toothpaste tube in front of the bathroom sink mirror.

Yes, our dogs are more of a wolf than we usually acknowledge (hell, zoologists don't even classify as a separate species anymore, but rather as a subspecies of wolves -that's why the dog was reclassified from Canis familiaris to Canis lupus familiaris)- but that doesn't mean they're not intelligent enough -or adaptively evolved enough- to behave in a very different way from wolves, at least when it comes to humans.

About 12,000 years ago hunter-gatherers in what is now Israel placed a body in a grave with its hand cradling a pup. Whether it was a dog or a wolf can’t be known. Either way, the burial is among the earliest fossil evidence of the dog’s domestication. Scientists know the process was under way by about 14,000 years ago but do not agree on why. Some argue that humans adopted wolf pups and that natural selection favored those less aggressive and better at begging for food. Others say dogs domesticated themselves by adapting to a new niche—human refuse dumps. Scavenging canids that were less likely to flee from people survived in this niche, and succeeding generations became increasingly tame. According to biologist Raymond Coppinger: “All that was selected for was that one trait—the ability to eat in proximity to people.”

At the molecular level not much changed at all: The DNA makeup of wolves and dogs is almost identical.

[Akkleptos]

The funny thing was she seemed to understand she wasn't supposed to poop in the house because whenever I would discover poo she would get scolded and put in her crate. After a while when I would discover poo and began to scold she would immediately slink off to her crate. Eventually, I wouldn't even have to find the poo. She would poop and as soon as she saw me even if I had no idea she pooped she would slink off to her crate which would immediately alert me to the fact there was poo somewhere.

This would be merely a Pavlovian response. Same as Pavlov's dog started salivating whenever it heard the bell signalling dinner, regardless whether there was food in sight. Dogs read a lot of human body language better even than most of us, since they rely pretty much solely on that to interpret our behaviour; unlike us, who rely mostly on verbal cues (especially us guys: think about a hypothetical case: upset girlfriend: "hrumph"... You, male: "Is there something wrong?"; upset girfriend *growls low*: No... You, male: "Oh, okay"). This is of course a caricature, but don't tell me you haven't experienced something similar.

[edit: usually]