Susan Hanson's dog, AnnieIt’s easy to forget that beyond her soulful eyes, velvety ears, and comical nature, the dog in my living room is a biological marvel. Like all canines, she inhabits a world that humans can know only partially—the world of scent.

Estimates vary, but according to the Sensory Research Institute at Florida State University, “canines' sense of smell is generally 10,000 to 100,000 times superior to that of humans.” The reasons for this lie not only in the structure of the dog’s nose—what Whole Dog Journal describes as “a veritable maze” where scents are “trapped in mucus and processed by the sensory cells”—but also in the animal’s brain, approximately one-third of which is devoted to interpreting smells. 

Once a scent reaches the dog’s brain, the Journal continues, it travels beyond the frontal cortex and into “centers for emotions, memory, and pleasure.” How a dog “reads” a scent, then, is far more complex than we might imagine.

Thanks to their uncanny sense of smell, dogs have long been used for tracking, sometimes successfully following trails as much as eight weeks old. More recently they’ve been employed for locating victims of disasters—both the living and the dead—and detecting the presence of drugs, firearms, and explosives. Perhaps most exciting of all, though, is the dog’s potential as a diagnostic tool to “sniff out” cancerous tumors in human beings.

Put another way, the dog in my living room—when I look at her with fresh eyes—reminds me that what I know is indeed partial. There are other realities beyond what I can see and hear. The world and its creatures have much to teach me, and I have much to learn.