Why Is Your Dog Laughing?

March 24, 2013— -- Does your pet talk to you? Probably, but there's a problem. You don't speak the same language.

That's a little inconvenient when it comes to the family mutt, but it could pose a major problem for researches around the world.

The workhorse in scientific laboratories is the lowly rodent and it has helped illuminate everything from diseases to drugs to human emotions, but new research suggests scientists have not been getting the full story. It turns out that rats speak a language that, until now, was understood only by other rats.

They sniff, but not just to detect odors. They sniff to warn a potential rival to back off, because this is the baddest rat in the cage. It's a way of enforcing hierarchy.

We've all known for years that many animals, including the ubiquitous family dog, sniff to collect information. But new research from the Case Western Reserve University School of Medicine shows that the same process can also transmit information -- and thus is a form of two way communications -- at least among rodents, and probably among dogs and all sorts of animals.

"I'm certain this research has never been done before on rodents," neuroscientist Daniel W. Wesson, author of the study, published in Current Biology, said in a telephone interview. "There might be a little more going on than we previously thought."

Is it possible that some research projects -- especially experiments that use animal models to study human emotions -- have been compromised by the fact that we don't know what the animals are saying to each other? This finding is not likely to undermine most projects, but there are probably a few researchers out there who are feeling a bit uncomfortable.

A study last year from Stanford University raised questions about a standard practice in the pharmaceutical industry's search for drugs to treat human depression. Rodents are commonly put under stress, thus inducing depression, so drugs can be tested.

One technique is a "forced swim" test. A mouse is thrown into the water and when it gives up trying to swim it is presumed to be in a state of despair, leading to depression. That assumes that mice experience a common human condition, despair, but scientists noted that no one can be sure because the mouse can't talk about it.

Steven Hyman of MIT and Harvard University, a leading researcher on psychiatric drugs, who commented on that study when it was released, raised this question: "Who interviewed the mouse?"

Maybe the mouse quit swimming not out of despair, but to conserve energy, Hyman suggested.

No one interviewed the mouse, because no one speaks the language.

That's what Case Western's Wesson set out to do. Wesson is an animal lover, and he often noticed how much his dog likes to sniff other dogs when he takes it for a walk. Dogs love to sniff, as we all know, but Wesson suspected there was more going on than just collecting information on the other animal.

"When my dog approaches another dog, they sniff each other face to face (as well as other regions of the anatomy,)" he said. "Sometimes that can result in my dog's mouth being around the other dog's head, and there was nothing I could see that would tip me that was about to happen. There is no growling or barking.

"That makes you think there are other signals being conveyed between the two animals that we are just not aware of."

Wesson decided to take a closer look. But it's difficult to study two animals interacting, because they must be wired to sensors and computers and all those wires would become entangled as they rolled around on the floor.

So Wesson teamed up with a computer expert and the two developed a wireless system using today's near-microscopic technology. A sensor was placed in one nostril in each of two rats, and linked wirelessly to a receiver and computers. The sensor detected each sniff.

Four million sniffs later, Wesson had his answer. One of the rats clearly outranked the other, and that rat sniffed quickly and furiously until the subservient rat reduced its sniffing and backed away.

The message was clear: Sniffing was a form of communication that had nothing to do with detecting odors. A subsequent experiment proved that. When the rats were fed oxytocin, the so-called "love hormone," the animals didn't sniff at all, and there was no sign of aggression. The rat with high status apparently forgot to sniff, so the sniffing clearly was a form of communication that no one -- except the rats -- knew was there.

This finding fits nicely with a discovery in the 1970s that rats also communicate through vocal ultrasonic frequencies, which we can't hear.

But sniffing may turn out to be even more important. In the canine world, odor is king. Dogs have a sense of smell that is vastly superior to humans, and when your pooch sticks his nose into another dog's business he's picking up a lot of information, from the other dog's health to his diet to his gender. And probably stuff we don't even know about.

We humans don't do that, of course. At least not overtly. But the multibillion dollar perfume industry is banking on the fact that to humans, smells matter. Our recent predecessors probably depended a lot on smelling.

No less an authority on human evolution than Paul Ehrlich, the president of the Center for Conservation Biology and Bing Professor of Population Studies at Stanford University, suggested recently that we would probably still be sniffing each other if we hadn't changed to walking upright.

By the way, one reason we don't speak the same language as our pets is we don't want to. We want them to learn ours -- which to a degree they do -- and we actively suppress some of their attempts to communicate. As in "don't bark."

That's what a dog does.

But back to rodents. One experiment from a major university, published in a major science journal last year, sought to prove that rats have empathy -- the care among most humans for others that is so intense we do more than sympathize, we actually feel their pain.

One rat was constrained in a trap while another wandered freely around the pen. The trapped rat was suffering so much that the free rat finally figured out how to open the trap and set it free. Thus, rats have empathy.

Maybe the trapped rat promised to lead the free rat to a secret stash of peanuts. Then it wasn't empathy. It was bribery.

But of course we will never know because nobody there interviewed the rats.