Saturday, October 3, 2015

The Alleged Limitations of Olfactory Language

That smells can be difficult to name is a commonplace observation. Almost as commonplace as the observation that there exist many specialized vocabularies for smell, such as those used by perfumers, wine tasters, brewers, coffee roasters, tobacconists, potheads, etc., etc. In this battle of off-setting banalities, those who downplay our ability to verbalize odors are often ceded the victory, in keeping with the pessimistic Greco-Freudian view that the human sense of smell is a poor thing, rendered vestigial from lack of use, and substantially inferior to that of other animals.

A more optimistic view is that humans are quite competitive in terms of odor sensitivity (often exceeding that paragon of scent detection, the dog) and that a remarkable amount of information regarding other people (emotional, physiological, and health status, for example) is received and processed via the nose. This positive outlook has been gaining support steadily in recent years but science journalists and assistant beauty editors have been slow to recognize the trend. This is not surprising; they are, after all, science journalists and assistant beauty editors. What is surprising is that a pair of credible scientists have now thrown in with the nasal nay-sayers and offered a theoretical account of why humans must necessarily suck at naming smells.

That might seem a rather rude way to characterize a paper decorously titled “The muted sense: neurocognitive limitations of olfactory language,” but I think it captures the essence of what Jonas Olofsson and Jay Gottfried are attempting to do.

Olofsson and Gottfried begin with three papers from the 1970s that find when you bring people into a psychology lab and have them sniff odors absent any contextual information (visual, auditory, or otherwise), they have a hard time coming up with the correct name. Provide them multiple-choice odor names and they generally choose the correct one. For good measure, Olofsson and Gottfried also reference studies showing that under similar laboratory conditions people suck at picking out individual components from a bouquet of scents.

Atop these rudimentary observations, O&G construct a “biologically informed framework for olfactory lexical processing.” Being neuro-imaging specialists, they sketch connections between piriform cortex, orbitofrontal cortex, and all the other neuroanatomical waystations on the route from nostril to naming. You will enjoy the discussion if this sort of thing appeals to you:
Importantly, odors are already integrated with lexical representations at the third synapse from receptor neuron input. This could put olfaction at a disadvantage compared with the visual system, where multiple subcortical and cortical sites create object representations before lexical–semantic integration by integrating features at different spatial scales.
My concern here is not with O&G’s theoretical edifice, but with their presumption that the difficulty in generating a verbal tag for a context-free odor is somehow fundamental to our understanding of human olfaction, and with their view that this phenomenon benefits from a convoluted account drawing upon “recent behavioral and neuroimaging data.”

Take the laboratory task upon which their entire argument is based: could there be anything more remote from the universal, everyday experience of smell than being confronted with a sniff-bottle and asked to name its contents by smell alone? What real world setting does this resemble? The answer is none.

Smells always occur in a context, and it is only within this context that we try to make sense of them. At the fish market, for example, we sniff to see whether the fish is fresh. Whether we can summon up the name “trimethylamine” is irrelevant. Smells may confirm our visual expectations (“it seems to have rained here recently”) or draw our attention to something that warrants exploration (“what’s burning?”) all without resort to specific lexical representations.

Tagging a smell with a specific lexical term requires high-level abstraction. In contrast, odor identification and description are broader abilities that are exercised more often and with greater functional impact. When olfactory naming happens in real life it also happens in a natural context and the language processing is tuned to an appropriate (and useful) level of generalization. Here’s a non-laboratory example of olfactory language in action:
“Umm. Is someone grilling dinner?”
“Yeah, it smells like hamburgers.”
To me, that is an example of rapid, precise, and biologically useful neurocognitive olfactory processing. But in Olofsson and Gottfried’s model it simply doesn’t exist.

In my view, the O&G model is an elaborate neurocognitive account of a laboratory artifact. It has little bearing on the broader role of olfaction in human behavior and communication. Does this sound extreme? Then ask yourself: does the near-universal inability to name the musical key of a song imply that “people are poor at describing sounds?”

The study discussed here is “The muted sense: neurocognitive limitations of olfactory language,” by Jonas K. Olofsson & Jay A. Gottfried, published in Trends in Cognitive Sciences, 19:314-321, 2015.

Sunday, September 13, 2015

Summer's Bounty: An ISDP Cornucopia

We were stuffing pages from an old copy of the Guardian into our wet boots the other evening when we noticed a piece by our pal, the winsome Katie Puckrik: “Bottling the smell of dead people won’t capture their essence.” Our first reaction was, “the hell it won’t.” But then we realized she was talking about Olfactory Links, a French enterprise based on the idea of “olfactory comfort” or capturing the scent of a departed loved one. Katie riffs on the idea in her characteristic style. For example, the company’s method is “a high-tech variation of boiling dad down to a reduction sauce.”

A million people write about fragrance. What sets Katie apart is the thoughtfulness and vividness she brings to it:
family smell associations are both more nuanced and more abstract than anything produced by an enfleurage of my parents’ senior-style velour tracksuits. I don’t know that I’d find their literal smell more comforting than that of cut grass (Dad mowing the lawn), or of leather ballet slippers (Mom driving me to dance class), or even of the lung-shrivelling damp that crept up from the cellar as their house aged along with them.
Katie is firing up her Katie Puckrik Smells blog again and it’s worth stopping by. We will as soon as we hack into our neighbor’s WiFi.

Meanwhile, it appears that we may need to open an ISDP news bureau in Japan to cover the rising epidemic of what are called “solitary deaths”
(孤立死 or koritsu-shi).
According to data made public by the Tokyo coroner’s office, in 2013, the latest year for which figures are available, some 2,733 people over the age of 65 were found dead while living alone in Tokyo’s 23 wards. The figures showed a continuous increase over the previous decade. The office also had data on the average number of days that had passed from the dead person’s last human contact. Compared with six days for women, the average for men was double.
Underlying the phenomenon is Japan’s population structure—fewer young people to look after an increasing proportion of elderly—and perhaps changing cultural norms, in which a preoccupation with social media takes precedence over family obligations. On the bright side, Japan Today notes that the increase in koritsu-shi has created a commercial niche for specialized clean-up crews.
Finally, blogger Maki notes how use of the related terms koritsu-shi and kodoku-shi reflect recent changes in language and in the Japanese attitude towards deaths that take place in social isolation.

This month’s ISDP summary is swollen to grotesque proportions by the heat of August. We begin with an item from Brooklyn that should have been included in last month’s edition.
Police found a man’s decomposing body inside a Brownsville apartment, authorities said. The grim discovery was made Saturday night after neighbors reported a foul odor coming from inside an apartment at the Chester Street home near Dumont Street, cops said.
Upstate in Batavia, New York, a body found in Kibbe Park turned out to be that of a missing 49-year-old man. His body was discovered “after workers at the park noticed a foul odor, and then discovered him in Tonawanda Creek.”

More news from Philadelphia, the city that let ghoulish butcher M.D. Kermit Gosnell thrive for years: A “terrible stench” leads neighbors to discover corpses from a funeral home stored in a garage. The funeral home director, Janet Powell Daley, had an expired business license and an expired license as a funeral director. She had not responded to citations regarding either one.

A decomposed body was found in the back set of a car parked next to a supermarket in West Covina, California “after someone noticed a foul odor coming from the car and peered inside.” The body was that of an Uber driver, a 36-year-old woman from Irvine.

In Youngstown, Ohio, police found the decomposed body of a man in a wooded area behind a home, after a citizen reported “a foul odor coming from a vacant home.”

In Blairsville, Georgia, neighbors of Randy Ray Siggers on Highway 325 “reported a foul odor coming from his residence.” His body was found inside.

The headline from Forest Lake, Minnesota: “Foul odor in Forest Lake apartment leads police to body; man held.” The body was that of a woman; the man was her boyfriend. Officers were called by the landlord who “reported a foul smell coming from the south end of the building.”

In San Antonio, Texas, police found a body inside a vacant home after a neighbor called about a foul odor. It appears the victim had been kidnapped several days earlier.

Lingering After Effects

In Topeka, Kansas, a woman complains that “she can’t escape a foul odor coming from a neighbor’s home.”
Kim Boyd says the odor’s been around ever since a decomposing body was removed from the house next door to her in the 1200 block of SW 25th. (. . .) Boyd says the smell is so bad, her son won’t go outside and play.
Sounds like a job for Taiichi Yoshida's cleanup crew.

There are none so anosmic as those who will not smell . . .

In San Antonio, Texas, police received a late-night call about a foul odor coming from a vacant house. They found a decomposed body in a bathtub on the second floor.
Roger Aguilar, who works as at church across the street, heard about the disturbing discovery and drove by the area. He said he has noticed a lot of activity around the house in the past, but didn’t notice anything unusual lately. “I never smelled anything. I never noticed anything,” Aguilar said. “We always see traffic in and out of there, people coming out, so we don’t know who’s the actual person that lives there.”
Doth he protest too much? Police say the body had been there for a week. They are treating it as a homicide.

At the Penn Plaza Apartment in the East Liberty neighborhood of Pittsburgh, PA, a man’s decomposed body was found in his unit.
“The man lay inside his apartment for seven or eight days, by the door, and where was security at? Why didn’t security officials walk the halls and report any foul odor to management?” said resident Gayle Williams.
In Brockton, Massachusetts, the body of a 24-year-old homicide victim was found in the backyard of an abandoned home on Boylston Street.
Susan Russo, who lives on nearby Winona Street, told the Enterprise she started smelling a foul odor on Wednesday.
“I started smelling it Wednesday but it was also trash night so I thought it was just trash,” Russo, 54, said. “My neighbor, it smelled really bad in her yard and as you walked into her yard and the next yard it smelled disgusting.”
Later, Ms. Russo complained to The Patriot Ledger that she was troubled by the discovery.
Susan Russo didn’t get much sleep after finding out that the foul odor she had been smelling in her neighborhood this week was coming from the body of a man in a nearby backyard.
“I just couldn’t sleep knowing that. It’s really bothersome. This is a decent neighborhood and it’s really bothersome that they found a body here,” Russo, 54, said Friday.
Talk about bothersome. Who is this “they” that found a body? You smelled it first, lady.

In contrast to these dispiriting reports, here’s a reminder that concerned citizens can and do rise to the occasion. In California, Calaveras County Sheriff’s deputies responded to reports of a foul odor and “located the remains of an adult male off the roadway.” The remains were found “off Winton Road near Lily Gap Road in a sparsely populated area several miles east of West Point, between Highways 4 and 88. A person driving through the area reported the foul smell to the Sheriff’s Office.

Annals of Marketing

The FOX Connecticut TV channel manages to needlessly piss off at least two potential advertisers:
WEST HARTFORD – Police are investigating the discovery of a dead body in a car outside the Red Robin restaurant near Best Buy at the Corbin’s Corner shopping center. A call came in to police at about 4 p.m. Sunday from a shopper who reported a foul odor and possible body.
Down in Putnam County, Florida, the body of a young woman was found in a cemetery. According to an initial story, it was discovered by a local pastor.
“I noticed a foul odor,” said the Rev. Christopher Coleman. Coleman said he was preparing a grave for an upcoming service Thursday morning at the remote Gethsemane Cemetery.
In a subsequent story, Rev. Coleman is identified as the owner of Coleman Mortuary. Would it be to cynical to suggest that he gave reporters his commercial bona fides after he realized the PR opportunity provided by the new coverage? Yeah, probably.

Minutes of the Rules Committee

Long-time readers know that to qualify as an ISDP incident, the stench of decay must lead to the discovery of human remains; odor noticed in the course of investigating a welfare check or a missing person complaint does not qualify, and we don’t bother posting such cases. So this case from Lake Worth, Florida presents a difficult case for the Rules Committee.
While Palm Beach County Sheriff’s detectives were handing out missing person fliers today on South L Street, they smelled a “foul odor” that led them to human remains, PBSO reported. After noticing the stench in Lake Worth south of Lake Avenue, the deputies investigated and found what the medical examiner’s office later confirmed were human remains.
We don’t yet know that the discovered remains were those of the person in the flyer. If they were not, it’s clearly an ISDP incident. If they were, we’re still inclined to credit the Palm Beach County Sheriff’s detectives for olfactory alertness and follow-through.

Postscript: It turns out the remains did, in fact, belong to the missing person.

On the other hand, this case from Butler County, Missouri is an easy call. A sheriff’s deputy on patrol spotted an abandoned car in a ditch. As he approached the vehicle “he immediately detected a foul odor.” On inspecting the car, he found the decomposed body of a 48-year-old murder victim in the trunk. That’s good police work but it doesn’t qualify as ISDP.

Here’s a final one for the Rules Committee: “Boyfriend suspected in death of woman found in trunk of her father’s car” The details, provided by the New York Post, are ambiguous:
The vehicle was found at the corner of Murray Street and 22nd Street around 8:30 p.m., emanating a foul odor, cops said.
Did a citizen report a foul smell coming from the car (ISDP)? Or did police find the car because they were looking for a make, model and license plate (not ISDP)? Committee decision: withhold judgment pending clarification.

Thursday, August 27, 2015

F. Scott Fitzgerald: An Olfactory Archaeology

A wonderful literary use of smell to illuminate the thick layers of human detritus that accumulate with time in a New York apartment building. Climbing up the scented stairway is like descending through the layers of an archaeological dig.
Then he would trudge homeward, enter the dark hallway, and climb three rickety flights of stairs covered by an ancient carpet of long obliterated design. The hall had an ancient smell—of the vegetables of 1880, of the furniture polish in vogue when “Adam-and-Eve” Bryan ran against William McKinley, of portières an ounce heavier with dust, from worn-out shoes, and lint from dresses turned long since into patch-work quilts. This smell would pursue him up the stairs, revivified and made poignant at each landing by the aura of contemporary cooking, then, as he began the next flight, diminishing into the odor of the dead routine of dead generations.

Eventually would occur the door of his room, which slipped open with indecent willingness and closed with almost a sniff upon his “Hello, dear! Got a treat for you to-night.”
F. Scott Fitzgerald
“Oh Russet Witch!”
From Tales of the Jazz Age (1922)

Friday, August 14, 2015

ISDP: In the Heat of the Summer

It’s peak summer—the zucchini are plump and the corn is ripening. So too are the remains of certain unfortunate souls who expired this past month; only the grim olfactory residuum of decomposition allowed them to be found. Here in the ISDP nerve center at FirstNerve Manor we have been collecting reports from all across the nation—we were so busy we missed our traditional 13th of the month deadline last night, something that happens only once in a blue moon. So without further ado, here is our latest compendium of the most grotesque smell in the world.

An Ordinary Evening in New Haven

Two severed legs were found near the State Street train station in New Haven, Connecticut. Then things got weird:
After the discovery of the severed legs, someone noticed a foul smell and upon searching two severed arms without hands in a garbage bag were found under the bridge.
“It’s a little creepy,” local resident Marge Vallee told WTNH-TV.
We’re inclined to agree.

Olfactory Irony Alert

In DeBary, Florida, a man notices a foul odor coming from a residence on Jasmine Drive, and alerts the town rescue unit which discovers the bodies of an elderly couple who had been having trouble with their air conditioner. But you know the rules, people! Since the man had been checking the house at the request of the couple’s daughter, this fails the basic requirement of ISDP: discovery of the decedents via the smell of decomposition.

The helpful neighbor did provide these words of wisdom to News13:
“I don't know if you've ever smelled death before, but once you smell it, you never forget,” Bartlett said.
Other People’s Money

Speaking of rules, this incident from Pahrump, Nevada, also fails to qualify as bona fide ISDP: the family of an elderly woman asked the Nye County Sheriff’s Department to look in on her, as they hadn’t heard from her for some days and they noticed unusual activity in her bank account. Longtime ISDP readers will not be shocked to learn that deputies noticed “an extremely foul odor” at the house, and entered it only to find the lady’s decomposed remains. The stepson of the deceased, one Robert Marygold, “arrived home” while officers where still on the scene and admitted to shooting his stepmother dead a few days earlier, then using her debit card at a casino. It is unclear from reports whether Mr. Marygold was, in fact, living with his stepmother at the time of the murder. If so, he may be eligible for a Norman Bates Award™ nomination.

Maryland, My Maryland

Based on the lede, you’d think you know where this story is headed:
On July 21, 2015, Deputy Lawrence responded to the 21000 block of Great Mills Lane in Lexington Park, after witnesses reported a foul odor coming from the vacant residence.
But SURPRISE! Deputies found a man and a woman (of “no fixed address”) asleep in the basement. The couple was charged with burglary. The source of the telltale foul odor remains unexplained.


In Williamsport, Pennsylvania, a guy stabs his girlfriend to death and stashes her body in a closet in the apartment. After a few weeks the stench triggers odor complaints. The guy blames it on a toilet problem and is told he’ll have to vacate while the place is fumigated. He attempts to dispose of the remains that night but bungles the job and is arrested. Congratulations to Hasan Gooden-Reid on his nomination for the 2015 Norman Bates Award™.

Car 54 Where Are You?

Couple of deputies make a routine traffic stop in Polk County, Florida. They pull the violator into a Walgreen’s parking lot, and while there notice a foul odor leaking from another car in the lot. In the driver’s seat they discover the body of a 52-year-old suicide victim.

In Butler, Pennsylvania, a pizza shop employee noticed a foul odor behind the business and discovered the body of a 29-year-old local man lying in the grass.

In Norcross, Georgia, a landscaper mowing the lawn at a rental property noticed a foul odor coming from the house. He flagged down a police officer who entered the house and found two bodies: an apparent brother-sister murder-suicide.

In Pueblo, Colorado, someone strolling near the Pueblo Mall “smelled a foul odor” and discovered a dead body near Fountain Creek. Authorities believe it is that of a homeless man and they do not suspect foul play.

Technically speaking, this incident in Pacific Palisades involves neither smell or the discovery of a dead body. But since it bears a superficial similarity to many previous cases of DBs found in cars, it caught our interest. Plus there are some headlines that were impossible to ignore:
Mystery Man Found Decomposing In Car Had More Than 1,200 Guns, Cash, Underwater Car
Dead LA gun stash owner described as alien hybrid, govt. spy
And then there are the names, right out of a Carl Hiaasen novel: the deceased was Jeffrey Alan Lash. His longtime fiancée was Catherine Nebron, and her employee Dawn VadBunker. Nebron and VadBunker believed Lash to be a CIA and/or FBI spy and possible human-alien hybrid. When he collapsed and died they left his body in his car—he had told them people from the government would retrieve his remains—and went on a ten-day-long trip. They say they were surprised to find his body there upon their return. So they had an attorney contact police. Bottom line: no smell, no discovery of remains, and, perhaps even more disappointingly, no Norman Bates Award™ nomination. But Mr. Lash was clearly a glorious, major league weirdo. RIP.

Turning to other vehicular events, we find this item from Escondido, California. Police were called to an apartment complex to check on reports of a foul odor. Inside a van they found the body of a 46-year-old man. His death does not appear to be suspicious.

The Nostrils of Texas are Upon You

In Houston, Texas, male remains were discovered at 53 East Parker Road. The circumstances were classic:
“A neighbor to the east of the residence smelled a foul odor coming from the above address and went to investigate. Upon walking up the driveway, the neighbor found the victim in a heavy stage of decomposition.”
Up in San Antonio, police found a decomposed body in a grassy area on the West Side of town. It had evidently been gnawed on by animals. According to KSAT ABC-12, “neighbors in the area reported smelling a foul odor for weeks.” Apparently they couldn’t be bothered to call police or take a look themselves.

Dead People Make People

The headline from “Florida Woman Killed Her Father and Her Daughter So She Could Be with Her Boyfriend: Cops.”
The investigation started when 25-year-old Cheyanne Jessie called police on Saturday morning to report that her father and 6-year-old daughter had vanished. When police arrived at Jessie’s home, they say, they smelled a foul odor. Jessie allegedly attributed the smell to a dead raccoon.
[Dead raccoon? Not bad!—Ed.]

According to People, police think Ms. Jessie left the bodies in the house for days until the smell forced her to move them to a storage shed 200 feet away. That period of co-residency means Cheyanne Jessie is nominated for the 2015 Norman Bates Award™. Congratulations!

Tuesday, July 21, 2015

Stepping in It: How Journalists Perpetuate the Myth that Dogs' Sense of Smell is Superior to Our Own

We’ve been hearing a lot about dog noses recently and how they are far more sensitive than ours. Liz Bestic kicked things off with a July 1 story in New Scientist called “The cancer sniffers: Dogs could be the best tool for diagnosis.” She covers some studies showing that dogs are able to sniff out specimens from patients with various types of cancer. An infographic accompanying her story states
“A dog’s sense of smell is between 1000 and 100,000 times more sensitive than that of humans.”
Next up was Rachel Pannett, the Sydney-based Deputy Bureau Chief for The Wall Street Journal in Australia and New Zealand. Her story appeared on the front page of the July 16, 2015 edition: “Forget drugs, these dogs sniff out a different kind of evil weed: Australia tries using spaniels to hunt for invasive plants called orange hawkweed, a.k.a ‘Grim the Collier’.” Pannett’s story includes this line:
A dog’s nose can be over 10,000 times more sensitive than humans, according to academic studies.
Zounds! Those are some impressive numbers. No wonder those dogs can sniff out cancer—their sense of smell is soooo much more sensitive than ours.

But wait. What’s that beeping sound in the distance? Why, it’s the alarm on the FirstNerve Bogosity Meter (hooked up to the battery of a rusty Ford F150 behind the tool shed). It seems there might be something dodgy about these doggy claims.

First off, let’s assume for the sake of argument that all the experimental results are correct and dogs can reliably sniff out a variety of human cancers. What does that prove about the relative sensitivity of dog noses and human noses? The answer is: nothing at all. Relative sensitivity is logically irrelevant to these results. But for some reason, journalists feel compelled to assert that dogs have more sensitive noses than we do. A competitive sniff-off between dogs and humans would address the point directly. It would be nice if a Deputy Bureau Chief or a “health journalist” asked cancer study researchers whether they had, you know, let human panelists evaluate the scent samples the same way the dogs did. Wouldn’t it be interesting if a bunch of orderlies, interns, and maintenance people could sniff out cancer? (Bestic mentions that doctors since Hippocrates have used smell as a diagnostic tool. She doesn’t explain why 21st century physicians have suddenly ceded the game to dogs.)

Hey! Will someone please turn down the alarm on the Bogosity Meter? It’s getting on my nerves.

The next fishy thing about these stories is the beautiful, quote-tastic simplicity of the numbers: dogs are 1,000 or 10,000 or 100,000 thousand times more sensitive than humans. Not 27,000 times more sensitive. Not 1,450 times. But more sensitive by nice fat powers of ten.

Bestic and Pannett are merely the latest journalists to run with these numbers. Here is Mary Bates, PhD, writing on the Animal Minds blog at in 2012 (“Cancer-detecting canines sniff out a diagnosis”):
Canines’ sense of smell is generally 10,000 -100,000 times superior to that of humans.
Stefan Lovgren (“Dogs smell cancer in patients’ breath, study shows,” National Geographic News, 2006) and Peter Tyson (“Dogs’ dazzling sense of smell,” scienceNOW blog at, 2012) use the same comparisons.

So where are journalists getting these numbers? Unlike their colleagues, Lovgren and Tyson attribute them to a specific person. Here’s Lovgren:
According to James Walker, director of the Sensory Research Institute at Florida State University in Tallahassee, canines’ sense of smell is generally 10,000 to 100,000 times superior to that of humans.
And here’s Tyson:
Dogs’ sense of smell overpowers our own by orders of magnitude—it’s 10,000 to 100,000 times as acute, scientists say. “Let’s suppose they’re just 10,000 times better,” says James Walker, former director of the Sensory Research Institute at Florida State University, who, with several colleagues, came up with that jaw-dropping estimate during a rigorously designed, oft-cited study.”
Now we’re getting somewhere—the 10,000 to 100,000 claim was made by a smell scientist. [Full disclosure: I met Jim Walker numerous times at the AChemS meetings long ago.] Walker and his colleagues were once active in designing new ways to measure olfactory sensitivity. In 2003, they published a paper in Chemical Senses called “Human odor detectability: new methodology used to determine threshold and variation.” Using their new technique, they estimated a value for human sensitivity to amyl acetate, a chemical that smells like bananas and is something of a standard odor in studies on olfactory thresholds. So far, so good.

In 2006, Walker and colleagues published “Naturalistic quantification of canine olfactory sensitivity” in Applied Animal Behaviour Science. They tested two dogs (a Rottweiler and Standard Schnauzer) for sensitivity to amyl acetate. The threshold value they found was lower than that reported previously by other dog researchers, presumably reflecting the more precise experimental methods used.

In discussing the results, the researchers wrote
Our recent investigation of human odor detectability (Walker et al., 2003) yielded thresholds approximately 10,000- to 100,000-fold higher than those we report here for the dog.
Again, so far, so good. But note: the “10,000- to 100,000-fold higher” statement applies only to amyl acetate (i.e., one specific chemical) and only to two studies (i.e., those coauthored by Walker). Yet Lovgren and Tyson quote Walker with the clear implication that dogs are 10,000 to 100,000 time more sensitive to smells in general. Either Walker did not mention these limitations when he was interviewed by them, or he mentioned the caveat and they chose to ignore it. In any case, journalists are now on notice that they should be cautious in how they quote Walker and/or his 10K/100K claims of canine smell superiority.

Still, there exists a strong presumption that dogs have a sense of smell that is more sensitive than ours in general, i.e., for the vast majority of odors. Surely there are other studies on other odor chemicals that support the claim, no? Enter Matthias Laska, a professor at Linköping University in Sweden. Laska is far and away the current authority of olfactory sensitivity in mammals—he has conducted smell experiments with mice, spider monkeys, squirrel monkeys, pigtail macaques, elephants, and fur seals. At this year’s AChemS meeting in April, Laska gave a talk titled “Busting a myth: humans are not generally less sensitive to odors than nonhuman mammals.” (Abstract here.) I attended his presentation and found it compelling.

Laska put together a data base of all published odor thresholds for humans and nonhuman mammals (17 species tested across a total of 138 odors). This let him compare the relative performance of humans and other species on a chemical-by-chemical basis.
I found that human subjects have lower olfactory detection thresholds, that is, a higher sensitivity with the majority of odorants tested so far compared to most of the nonhuman mammal species tested so far. This includes species traditionally considered to have a highly developed sense of smell such as mice, hedgehogs, shrews, pigs and rabbits. Humans outperform rats with 31 of the 41 odorants tested with both species. Humans even outperform the dog, often considered as the undisputed super-nose of the animal kingdom, with 5 of the 15 odorants tested with both species. Based on these comparisons, and contrary to traditional textbook wisdom, humans are not generally inferior in their olfactory sensitivity compared to nonhuman mammals.
So according to the most recent, most comprehensive review of the topic, humans outperform dogs on 5 of the 15 odorants tested. Does that sound like total, across-the-board, doggy nose superiority to you? No, not really.

After the recent flurry of dog superiority claims, I checked in with Laska by email. He confirms that the canine odor threshold for amyl acetate (-5.94 log ppm) reported in Walker’s 2006 study is the lowest on record. However, he points out that the lowest reported human threshold for amyl acetate in his database is -7.02 log ppm. In other words, when it comes to amyl acetate humans are more sensitive than dogs.

Let me repeat that: According to all the available scientific evidence, humans are more sensitive to amyl acetate than are dogs.

Where does this leave us? With three take-home messages:

#1: James Walker’s narrow claim that dogs are 10,000 to 100,000 times more sensitive to amyl acetate than humans is simply incorrect. The fact is that humans, not dogs, are more sensitive to amyl acetate.

#2: The broader, and much-cited claim that dogs are 10,000 to 100,000 times more sensitive to smells in general is unsubstantiated. The fact is that dogs outperform humans on some but not all of the smells tested to date.

#3: The media ought to take a healthily skeptical approach to claims about the incredible superiority of the canine sense of smell. Some of us have expressed reservations about this before, and have noted that undue deference to the dog nose leads to some dubious outcomes in the criminal justice system. Even assuming that all the studies to date are valid and replicable, the practicality and cost-benefit ratio of cancer detection with sniffer dogs is not that impressive.

P.S. Don’t even bother coming back at me with the claim by one Dr. Lawrence Myers. “Dr. Myers has been quoted as saying dogs can smell a million times better than humans. He says that was a speculative (but possible) number he used in an interview to illustrate a narrow point. The reporter picked up the figure as science and quoted it out of proper context.”

P.P.S. Und danke schön, German dog fans, but don’t bother digging up this old bone from 1953: “The olfactory sensitivity of the dog is 1,000,000 to 100,000,000 times better than humans.” [My translation.] It’s a hand-waving, one-line summary of results, now superseded, that dates back to the dawn of olfactory psychophysics.

The studies discussed here are “Human odor detectability: new methodology used to determine threshold and variation,” by James C. Walker, Sandra B. Hall, Dianne B. Walker, Martin S. Kendal-Reed, Alison F. Hood & Xu-Feng Niu. Chemical Senses 28, 817–826, 2003; “Naturalistic quantification of canine olfactory sensitivity,” by Dianne Beidler Walker, James Cornelius Walker, Peter James Cavnar, Jennifer Leigh Taylor, Duane Howard Pickel, Sandra Biddle Hall & Joseph Carlos Suarez. Applied Animal Behaviour Science 97, 241–254, 2006; and “Über die Riechschärfe des Hundes für Fettsäuren,” by Walter Neuhaus. Zeitschrift für vergleichende Physiologie 35, 527-552, 1953.