Biology Reference
In-Depth Information
human noses, rather than bear noses, into a laboratory. Even while we tend to denigrate it,
the human sense of smell is getting more deserved attention. Humans can detect thousands
of different odors. Even Linda Buck, Nobel olfactory biologist par excellence, hems and haws
over some details: “It is estimated that humans, for example, can detect from 10,000 to over
100,000 different volatile compounds.” That's a difference of a factor of ten, less than some
of the variations I've seen used with dogs, but hardly a rounding error.
While smell isn't entirely a lost subject for research or practice, for most Westerners, it is
a deeply underappreciated sense compared to vision. It wasn't always so. Smell used to be a
critical tool for physicians. Hundreds of years before we started exclaiming over the miracle
of dogs being able to detect diabetes or lung cancer, doctors were using their noses to do the
same thing. “Evaluating effluvia” was considered a basic diagnostic skill: Sweat on a rubella
patient smelled like “freshly plucked feathers”; life-threatening diabetic ketoacidosis made a
patient's breath smell like “rotting apples”; a certain bacterial condition made the skin smell
like “over-ripe Camembert.” Now we leave that job to lab tests and litmus paper.
Vestiges of human scent skills do survive in pockets in the West. For instance, “odor mit-
igation” expert Larry Sunshine will fly into a city, tilt his head, open his nostrils, and identify
specific foul odors in subways, including mildew and chemicals venting off plastic seats. Luca
Turin, a perfume expert and biophysicist, can deconstruct a perfume down to its exact com-
pounds and describe it in terms that make you want to laugh and weep and even buy that
particular patchouli: “The smell was at once beguiling, salubrious, and toxic, and felt like a
perfume composed for a fiercely intelligent librarian.”
Research is starting to blossom in this world of human olfaction, and it's taking some in-
teresting turns—ones that working-dog handlers can relate to. Certain scents turn humans
into the kinds of tracking machines whose accomplishments seem to rival those of trained
scent dogs. If chocolate is involved. Scientists took a group of Berkeley undergraduates,
showed them a video of canine scent-tracking, and then took them out on a lawn that had
been laced with essential oil of chocolate. Scientists gave the students blindfolds, thick gloves,
knee and elbow pads, and let them loose, off-lead. Could they track the chocolate using their
noses, crawling on their hands and knees? Absolutely. The track they followed looked like the
zigzag of a dog's trail.
The Berkeley scientists loved the students for more than their noses. Unlike rats or dogs,
they could be debriefed afterward. The students could even say which nostril they tended to
depend on: “Humans are an appealing animal model for addressing such questions because
they can follow task instructions and accurately report behavioral strategies,” noted the article
in
Nature Neuroscience
.
Fortunately, that's one aspect of olfaction that a few researchers are starting to focus on
moving forward, both in humans and in dogs: the importance of training. Olfactory scientist
