Self-awareness might seem like the most basic part of life to us humans, but it's a surprisingly rare concept when it comes to other animals. While great apes, dolphins, orcas, rhesus macaques, Eurasian magpies, and a single Asiatic elephant have all passed the self-recognition test, everything from pandas and pigeons to sea lions, gorillas, and several species of monkey have failed to show signs of consciousness.

Dogs were also on that list of failures - until now. Traditionally, self- consciousness is evaluated via the 'mirror test'. If an animal uses its own reflection to examine or touch a red mark that's been applied to its body without its knowledge, scientists can confirm that they possess some sense of self. But what if the animal isn't that visually oriented?

"I believed that because dogs are much less sensitive to visual stimuli with respect to what, for example, humans and many apes are, it is likely that the failure of this and of other species in the mirror test is mainly due to the sensory modality chosen by the investigator to test the self-awareness and not, necessarily, to the absence of this latter," says evolutionary biologist Roberto Cazzolla Gatti from Tomsk State University in Russia.

Gatti was prompted into this line of thinking by the fact that in past mirror tests, dogs have shown no interest in looking at their reflection in the mirror, but they will go ahead and sniff the area and possibly even urinate around it. While this got them a big old "fail" in previous studies, Gatti thought the behaviour warranted a closer look. 

Back in 2001, renowned animal behaviour expert, Marc Bekoff, investigated the 'mirror sniffing' phenomenon via an experiment dubbed the 'yellow snow test'. Yep it's exactly what it sounds like. Over a five-year period, Bekoff took his dog Jethro on walks during the winter months, and timed how long he would sniff clumps of snow soaked in his own or other dogs' urine. 

The AnimalWise blog explains:

"Bekoff would wait until Jethro or other known female and male dogs urinated on snow, and then scoop up the clump of yellow snow as soon as Jethro was elsewhere and did not see him pick it up or move it (Bekoff used clean gloves each time and took other precautions to minimise odour and visual cues). 

Bekoff then moved the yellow snow varying distances down the path so that Jethro would run across the displaced urine: (i) within about 10 seconds, (ii) between 10 and 120 seconds later, or (iii) between 120 and 300 seconds later. After Jethro arrived, Bekoff recorded how long he sniffed at the yellow snow, whether he urinated over it using the typical male raised-leg posture, and whether urination immediately followed the sniffing ('scent marking')."

Not surprisingly, Jethro paid a lot less attention to his own urine than he did to that of other dogs, so Bekoff concluded that his pet had to have some sense of self to be able to distinguish between scents. But with a sample size of one, the experiment wasn't exactly going to set the scientific community on fire.

Gatti decided to come up with something a little more convincing. Called the Sniff Test of Self-Recognition (STSR), the experiment involved collecting urine samples from four stray dogs and systematically exposing them to the scents. He repeated this four times a year at the beginning of every season. 

"I placed within a fence five urine samples containing the scent of each of the four dogs and a 'blank sample', filled only with cotton wool odourless," he says. "The containers were then opened and each dog was individually introduced to the inside of the cage and allowed to freely move for 5 minutes. The time taken by each dog to sniff each sample was recorded."

Just like Jethro, each dog spent way more time smelling the urine samples of other dogs than their own, which supports the hypothesis that they know their own scent and aren't that interested in it. The result was stronger the older the dog, which suggests that self-awareness develops with age. 

It might seem obvious that dogs would know their own scent, but if you've ever seen a dog bark at its own reflection, or completely ignore it - totally unaware of its own appearance and movements - you can see the significance.

"I demonstrated that even when applying it to multiple individuals living in groups and with different ages and sexes, this test provides significant evidence of self-awareness in dogs and can play a crucial role in showing that this capacity is not a specific feature of only great apes, humans, and a few other animals, but it depends on the way in which researchers try to verify it," says Gatti. 

The findings are published in the journal Ethology, Ecology and Evolution.

Now, I know what you're thinking: that sample size of four is pretty crap. And yep, it is, so we can't really call this an official "pass" just yet. But the fact that we may well need to rethink the mirror test and figure out how to better align it with how certain species see the world is certainly worthy of a proper investigation. Certain behaviours such as empathy have been linked to self-awareness, and thanks to the 'yawn test', there's evidence that dogs feel empathy towards their owners.

We'll just have to wait and see if scientists are prepared to conduct a giant yellow snow test to put this conundrum to bed once and for all. In the meantime, here's dolphins passing the mirror test adorably: