Imagine a species that lived in a world of smells and didn’t pay a lot of attention to what things look like. What would members of that species use for a mirror?

Would they even want a mirror?

Yes, of course, we are talking about dogs, who usually don’t seem to understand the mirrors humans use. Sometimes they ignore them. Often they bark as if the dog in the mirror were a stranger.

Scientists use mirrors to find out if animals recognize themselves, to see if they have some sense of self. Chimpanzees do very well on what is called the mirror test.

A chimp will notice a mark on his face and perhaps even use the mirror to aid in removing it. He might use the mirror to examine parts of his body he can’t normally see, like the inside of his mouth. Researchers have reported that dolphins, one elephant and a magpie have also passed this test.

Dogs have not, and that has raised questions about whether dogs might recognize themselves if another sense were tested.

Alexandra Horowitz, a psychologist at Barnard College who studies the behavior of dogs and has written several books about them, decided to give dogs a chance at showing self-recognition on their own, smelly terms. In a recent study, she concludes that they do recognize the smell of their own urine.

While some researchers find the study intriguing, the scientist who first developed that mirror mark test doesn’t think the evidence supports her conclusion. Still, even the idea of a smell mirror is mind (nose?) boggling.

“I had always flirted with the idea in my head that there should be an olfactory mirror,” Horowitz said, acknowledging that “it could be horrifying for humans.”

Marc Bekoff, a biologist and animal behavior specialist at the University of Colorado, Boulder, broke the ice, or actually the snow, in this kind of research around 20 years ago with what has become known as the “yellow snow” study.

He found that his dog, Jethro, recognized his own scent. The evidence was that Jethro was more interested in snow marked by another dog’s urine than in snow marked by his own, even if it had been surreptitiously moved — by Bekoff.

The research had its down side. “People who saw me move the pee around thought I was weird, and someone wrote a letter to the editor of the local paper” that questioned what he was doing, he said in an email.

Horowitz took the testing a bit further, adding something like the mark on a chimp’s face: She set up dishes with different smells.

A dog’s own urine. An unfamiliar dog’s urine. A dog’s own urine along with another scent. And, in some control tests, no urine and just the unfamiliar added scent.

She tested 36 pet dogs to see how long they spent with the different scents. In many behavior tests, the time spent on a scent or a sight is taken as evidence of interest.

As she reported in Behavioral Processes, the dogs were least interested in their own urine, somewhat interested in another dog’s urine, and most interested in their own altered urine.

What that means, of course, is a matter for discussion. She says it shows that the dogs recognize their own scent, finding it less interesting unless it has been altered.

“I don’t think it’s precisely parallel to the mirror mark test,” Horowitz said. In an odor test, you can’t “use the mirror to restore what you think you should look like.”

But, she said, her test and the mirror tests “all show that there’s this selective sensory investigation of something that comes from yourself, but is changed.”

The scientist who developed the mirror mark test, Gordon Gallup, disagrees. “I don’t think the results support the conclusions,” he said. He defines the self-awareness assessed in the mirror mark test as “the ability to become the object of your own attention.”

If you present a familiar odor and a modified version of that familiar odor, he said, that will increase a dog’s attention. The same would happen when a dog is presented with the odor of the owner who lives in the same house.

A definitive test would need to have a component in which the animal identifies the source and refers to it, the way chimpanzees point to the mark on their own faces.

Gallup also questions the tests of dolphins. They twist their body around to look at a mark, but can’t point to it as chimpanzees and other apes and human children do.

Laurie Santos, director of the Canine Cognition Center at Yale, said the study was “a really important innovation.” She said that by using a mirror test based on smell, Horowitz “was able to observe cognitive capacities that we didn’t realize dogs had.”

Because the mirror mark test depends on visual ability, many researchers, including Gallup, have been interested in extending testing to other senses.

Frans de Waal, a primatologist at Emory University, said by email: “We need to move away from the mark test as sole source of information. My view is that all animals have some level of self-awareness, they need to, and that the mirror mark test taps into a special kind, perhaps a rare kind, but we need more ways of testing.”

Horowitz plans further tests, including using the scent of familiar dogs and modifications to that scent. The testing methods may vary, but one thing is likely: There will be urine.

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