Dogs’ noses are wondrous things. Their acute sense of smell enables them to be trained to detect bombs and drugs, and find earthquake survivors. But it also makes them fine-tuned to human emotions, strengthening the bond between dog and owner and helping them serve as therapeutic companions to those in distress. (This article was first published in Who Knew?)
A Nose of Two Halves
Dogs have a unique nasal system. Unlike our rather basic noses, where breathing in and out occurs through the same part of the nostrils, dogs’ noses have a clever slit at the sides, where the air passes out. This means they can build up the concentration of a particular scent by drawing more odor molecules into their nose more quickly. Inside their nose there are two separate areas—one for breathing and one for smelling. The smelling region features hundreds of millions of olfactory cells, compared to a human’s meager ten million. These cells are what help to send electrical signals to the brain.
Sense of Smell
It could be said that dogs are wired to smell. The portion of the canine brain dedicated to smell is significantly larger than the relative area used in a human brain. The damp, spongy surface area of the nose works to draw air molecules in. This, combined with the fact that dogs can smell through both nostrils separately, helping them to determine the direction a scent is coming from, makes for a nose of epic capabilities. It can detect and interpret smells at concentrations 100 million times lower than a human can.
How about Hormones?
On top of their super-sensitive sniffing skills, dogs are gifted with a particularly astute vomeronasal organ, which sits above the roof of their mouth. It is also known as the Jacobson’s organ, after its discoverer, anatomist Ludvig Levin Jacobson. Its primary function is to detect pheromones—chemical compounds, often without any discernible scent, that transmit signals between organisms of the same species. They help dogs to identify both potential mates and hostile threats from other animals. Studies have shown that dogs can also pick up on other animals’ pheromones, including those of humans. These pheromone scents can help a dog detect a person’s gender and age, and if a woman is pregnant.
Unfortunately, research into human pheromones is severely lacking. For example, while scientists have been able to identify two pheromones, androstenone and androstenol, that attract fertile female boars to their male counterparts, they’ve not been able to isolate a human equivalent. There is significant evidence from studies, such as babies being able to smell breast milk and adults being able to determine if a person is anxious or not by the smell of their sweat, that shows our pheromones give out signals, but apparently dogs are a lot more adept at reading them than we are.