She Works in the Olfactory

It's always pleasant to talk to someone who loves her work--and my recent chat with Pam Dalton was no exception. Her enthusiasm was palpable (nay, contagious) as she gaily described the easiest way to brew up the smell of rotting meat in a lab, then moved on to talk about her never-to-be-forgotten field trip to a pig farm.

Dalton, a psychologist by training, was not being perverse--she's a scholar of "odor perception" at the Monell Chemical Senses Center in Philadelphia. (Even the military is interested in her work, with a mind to creating a super-powerful stink bomb.) She got interested in studying smells for a host of reasons--to find out why we like some, why we hate others, how they affect our mood, trigger memories and more.

"The field was ripe for asking lots of interesting questions," she says.

"Ripe," too, describes the kinds of smells Dalton opted to study--nasty, stinky ones. Her specialty is scents that waft from putrid cheese, rotting carcasses, old drains and rancid armpits--odors she brews up in her very own lab. To get a rotting mouse smell, for instance, Dalton allowed a dead one she'd found in a trap to age gently in a glass jar. But often she resorts to analytical chemistry, combining smelly chemicals into medleys that she tests on volunteers.

(These lab mixes, of course, will not tell the whole sensory story, but the concoctions will at least invoke the essence of a smell. For instance, just one chemical--called skatole--does a very good job of capturing that je ne sais quoi of raw sewage.)

To do her studies, Dalton either presents people with nasty smells on bits of filter paper or exposes them to stinks in fancy masks or observation rooms. Then she measures their responses--asking them questions and scoring their facial expression for that characteristic frown of disgust. She measures breathing and heart rate (which change when someone's disgusted). She even attaches electrodes to people's bellies and records the telltale increase in stomach activity that signifies the onset of nausea.

It's hard to know, says Dalton, if people are born with innate disgust for certain odors--though it would certainly make sense, she reasons. (Human waste has probably long been associated with disease-causing germs.)

But even if we do have pre-set preferences, they're very plastic, Dalton says--depending on all kinds of factors such as memories and experience.

Among the things she's learned:

* If you're constantly exposed to a smell, you're apt to stop smelling it. (I've wondered, from time to time, why people entering my house often wrinkle their noses and ask me if I've got cats.) Folks back in Elizabethan times were used to pretty rancid streets and probably wouldn't bat an eyelid at reeks that would send us running.

* Our aversion to a smell depends on context. People given a cheesy smell aren't put off if they're told it's a food--they may even start debating which fine French cheese it is. But tell them instead that they're dealing with a bodily odor and they are apt to think stinky feet and blanch.

* Familiarity's important as well. One particular smell that Dalton positively hated made a Chinese student simply shrug his shoulders. He was used to the sulfurous, fermented odors that hung around some of the back alleys of restaurants back home.

And when Dalton visited South Africa, she discovered that people there strongly disliked the smell of cinnamon--it was nothing they used in their cooking and smelt medicinal, poisonous, weird.

* Our smells are also tightly wrapped up with memories. Dalton couldn't stand the smell of modeling glue for a spell: She'd been mugged by a man who'd been using it. (She bought a tube of glue and took whiffs of it till the association faded.) Smells may be particularly evocative because the smell-processing parts of the brain lie very close to those that deal with emotional memories.

There's so much more to learn, Dalton says, and always some new, bad odor beckoning round the corner. Her husband is used to making detours so she can get a whiff of chicken farms, smokestacks or paper mills.

"If there's an odor source anywhere within 20 miles, I want to go smell it," she says. "It's what I do. It's my professional curiosity."

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