A Sensory Analysis of Marijuana Volatiles: Not Such Great S***

The chemistry behind the scent of marijuana is a compelling topic for a number of reasons. First off, it’s a big technical challenge. Pot consists of an extraordinarily complex mixture of volatile compounds and sorting them out is a big job. (Paradoxically, the main psychoactive ingredient tetrahydrocannabinol is odorless.) Secondly, it is of forensic interest: law enforcement seeks to detect the scent while smugglers try to cover it up. Finally, legalization has spurred increased interest in the aromatic qualities of pot as a consumer product. Here in Colorado, it has been fascinating to observe the industry grapple with branding and struggle to formulate edibles that consumers find acceptable.

So I was psyched to find a new paper in PLoS ONE titled “Characterizing the smell of marijuana by odor impact of volatile compounds: an application of simultaneous chemical and sensory analysis.” It is written by a pair of researchers at Iowa State, who use the latest methods of sampling (solid phase micro-extraction) and chemical analysis (multidimensional GC-MS) to characterize the concentration of various volatile molecules in samples of fresh marijuana. They also bring a sensory element to their analysis: they compare chemical concentrations to odor threshold data available in the literature, and have someone sniff and evaluate the various molecules as they emerge from the gas chromatograph. So far, so good.

Based on their results, authors Somchai Rice and Jacek Koziel conclude that when it comes to characterizing the smell of marijuana, “more attention should be focused on highly odorous compounds typically present in low concentrations.” (They mention nonanal, decanol, o-cymene, and benzaldehyde.) This, in principle, is a reasonable and potentially useful conclusion. Unfortunately, it is limited by the paper’s shortcomings in exposition and experimental design.

Rice and Koziel claim to add 200 new molecules to the list of previously known marijuana volatiles. But take a closer look at how they phrase their claim:

Over 200 compounds are being added to the list of what is currently known to be emitted from illicitly packaged marijuana.

They refer to “illicitly packaged marijuana” because they based their analysis on three samples of pot (of unidentified strain), all obtained from the evidence room of the Iowa Division of Criminal Investigation. One of the samples was a gram of pot analyzed along with the plastic baggie it was zipped up in. Another consisted of approximately 50 kilos of pot stuffed into a “US military-style duffel bag.” Thus the chemicals analyzed by Rice and Koziel are not exclusively marijuana-based—they include molecules off-gassing from the packaging.

In this research, the authors are not differentiating between VOC emitted from marijuana samples and VOC emitted from packaging.

Indeed. So Rice and Koziel have now muddied the scientific literature on pot volatiles with who knows how many irrelevant chemicals. It will be up to future researchers to sort through the mess they have created.

What about Rice and Koziel’s conclusion that certain chemicals found in low concentration may have a major impact on the smell of pot? It’s a reasonable idea. Perfume chemists have long known that the most common molecule in a mixture is not necessarily the smelliest. A highly potent odor molecule can impact the overall scent if present even in trace quantities. Despite Rice and Koziel repeatedly patting themselves on the back for being the first to apply the concept to marijuana, one might say that it is the first rule of chemosensory analysis.

The authors use the concept of Odor Activity Value (OAV) to make their point. OAV is an attempt to relate a chemical’s concentration to its sensory impact. One calculates OAV by dividing the chemical’s concentration in the sample by its olfactory threshold concentration (i.e., the lowest limit of detectability to the human nose). If a chemical is present at less than its threshold concentration (OAV < 1.00) it is unlikely to contribute to a mixture’s smell. Rice and Koziel use OAVs to identify potentially important odor components of pot. This is fine as a first pass through the data, but when the authors use OAVs in statistical analyses, they stretch the concept almost beyond its limits.

Why? Because every smell molecule has its own concentration-intensity curve. For every step increase in concentration of molecule A, for example, its odor intensity might increase dramatically. For molecule B, in contrast, it might take many step increases in concentration before its odor intensity is noticeably stronger. Therefore, samples of A and B, set at the same OAV, could have very different odor intensities. This makes OAVs useful as a first pass to identify the smelly ingredients in a mixture, but it is perilous to use OAVs as a measure of comparative odor impact.

Finally, this paper is poorly written and would have benefited from closer editorial attention (yes, I’m talking to you, John Glendinning). The introduction wanders all over the map. It begins by mentioning odor as probable cause for search and seizure, but the ridiculous S1-Table is a random grab-bag of U.S. legal cases which completely omits the fact that at least nineteen states have search and seizure rules for marijuana based on the “in plain smell” doctrine. The intro then discusses analytical techniques, veers into a consideration of drug dogs and scent training, and then into the subject of human olfactory abilities. Like wow, man, everything is connected to everything else, you know?

The chemical and sensory analysis of marijuana scent is an increasingly important topic, and while Rice and Koziel have made a preliminary effort I expect that much better work will be done in the near future.

The study discussed here is “Characterizing the smell of marijuana by odor impact of volatile compounds: an application of simultaneous chemical and sensory analysis,” by Somchai Rice & Jacek A. Koziel, published in PLoS ONE 10(12):e0144160, 2015.

Your Cheating Scent

Tempo, an online news site in the Philippines, features advice columnist Manay Gina. Here’s a letter she posted yesterday:

Dear Manay Gina,

One day, while I was putting our clothes away for laundry, I found a shirt my husband had worn to work. Surprisingly, it was scented—a really strong one. I know that my husband does not go to work with cologne on. When I inquired about his change of habit, he got very defensive and asked if I was accusing him of something.

Do you think I should be suspicious?

Tarcy

Manay Gina takes a wait-and-see attitude. Here at FirstNerve we’re more like “duh.” [Yeah, but is he seeing a woman or a man?—Ed.]

Giving a New Meaning to Head Space

Every so often a client hires me to work on what I call the “dark side” of olfaction, products like underarm deodorant, kitty litter, feminine hygiene products, and adult incontinence garments. To get anywhere on such projects, the first item of business is to identify the malodors involved, at both the descriptive and chemical level. You need a know what you are dealing with in order to design sensory tests to measure progress, much less assign perfumers and chemists to work on solutions.

This is precisely the tack researchers at Firmenich’s R&D division in Geneva, Switzerland, took when they turned their attention to an important public health issue: designing free-standing toilets (i.e., latrines) that are safe and attractive to use. Flushable toilets require infrastructure—water supply, plumbing, sewerage—that is not always available or affordable. Lacking even field latrines, “more than 2.5 billion people defecate in the open.” So there is a big need for well-designed models that minimize malodor. The Firmenich team tackled the essential first step, a “qualitative and quantitative analysis of volatile constituents from latrines.” They published the results last month.

The group examined traditional models (i.e., a toilet seat over a pit in an outhouse) and “next-generation” designs that separate urine and feces. They did field research in Africa (Kampala, Nairobi, Durban) and India (Pune) in order to capture variation in climate and culture. Deploying the full array of modern analytic chemistry (SPME, GC-MS), they produced a “top 10” list of the key latrine volatiles. It includes sulfur-containing compounds, carboxylic acids, phenol, p-cresol, and those shitty old favorites indole and skatole.

I particularly enjoyed their matter-of-fact field descriptions. Here’s one from Durban, South Africa:

The pit latrines sampled contained various garbage, and the sludge was greenish gray. The odor of the sludge was typical sewage, methyl mercaptan, and rotten egg. In the proximity of the Durban UD [urine diversion] latrines, there was a strong urine smell, slightly ammonia, and animalic, typical of urinals. Inside the UD latrines, the smell was weak, slightly urinal, and farmyard. The collected sample was quite solid and had a weak smell, most likely due to the sandy red soil added to cover newly added feces, and the odor was reminiscent of manure, styrax, and asphalt.

By identifying the malodor volatiles involved and how they vary with physical factors of latrine design and use, Firmenich has made a valuable contribution to improving the well-being of people everywhere. Well done.

The study discussed here is “Qualitative and quantitative analysis of volatile constituents from latrines,” by Jianming Lin, Jackline Aoll, Yvan Niclass, Maria Inés Velazco, Laurent Wünsche, Jana Pika, and Christian Starkenmann, which appeared in Environmental Science & Technology 47:7876-7882, 2013.

Put Your Mouse Nose On

My first experiment on human odor perception asked whether people can smell the difference between strains of inbred laboratory mice. (Bottom line: yes, we can.) In addition to having test subjects sniff live mice from a Tupperware container, we utilized an, umm, alternative odor source of biological relevance.

Dry fecal pellets provided olfactory cues sufficient for subjects to discriminate between the males of two strains of mice differing at many genetic loci (AKR and C57BL/6) as well as between H-2 types (bb and kk) within each strain.

While the resulting article has been cited 53 times (according to Google Scholar), no one since has taken up the scientific banner of mouse turd odor. Until now.

A Japanese research team has sniffed and chemically analyzed the odor of mouse turds. Not just any turds—these were from mice exposed to four different stress conditions: no bedding chips, shaking, fasting, and movement restriction.

The sniff panel data indicate that all stressors except fasting result in stronger smelling feces. The chemical data (gathered by microscale purge and trap gas chromatography-mass spectrometry) revealed 17 odor compounds, including a bunch of aldehydes, two sulfides, and everyone’s favorite fatty acid, isobutyric acid.

Most, but not all, of these volatiles were present at concentrations detectable by the human nose. While the amount of some compounds varied significantly across the stress conditions, on the whole there was a lot of overlap in the chemical profiles. The researchers intend to use quantitative poop profiles to measure, and hopefully reduce, stress in lab mice.


The study discussed here is “Analysis of odor compounds in feces of mice that were exposed to various stresses during breeding,” by Kenji Sakuma, Susumu Hayashi, Yoshiyuki Yasaka, Hiroto Nishijima, Hisakage Funabashi, Masayoshi Hayashi, Hideaki Matsuoka, and Mikako Saito, published in Experimental Animals 62:101, 2013.

Amazing Human Tricks: Dundowran Beach Edition

A woman named Sandy Fletcher loses her watch while taking her daily walk on Dundowran Beach, about 160 miles north of Brisbane, Australia. An 11-year-old kid finds it, and his 9-year-old dog sister recognizes the owner—by smell.

Call Off the Dogs

The space between the lost clinical art of olfactory diagnosis and Dr. McCoy’s tricorder of the future is filled with canine scent detection studies. These prove, ad nauseum, that a disease may have a distinctive scent signature. But to put this principle to work in a way that doesn’t involve teams of trained dogs we need a precise, chemically defined profile of each disease’s scent. Some new studies suggest we’re finally getting some traction on the problem.

My former Monell Center colleague George Preti, along with others at Monell and UPenn, has found a small set of volatile molecules that distinguish melanoma cells from normal melanocytes. The usual cautions apply—e.g., the volatiles were collected over cell cultures and not over the skin of actual patients—but the work is a significant step toward a device that can “smell” skin cancer. Preti et al. used sophisticated scent capture (solid-phase micro-extraction for GC-MS) supplemented by nanotubes coated with single-stranded DNA. Strictly speaking this isn’t an e-nose but an e-nose with nanosensors. The team then did a lot of heavy lifting to screen out volatiles not endogenous to the melanoma cells. (Earlier studies picked up traces of antiseptics and anesthetics from the hospital environs.)

The result: key differentiating compounds included isovaleric acid, 2-methylbutyric acid, and isoamyl alcohol, plus the sulfur containing compounds dimethylsulfone, dimethyldi- and trisulfide. None are exotic but the pattern allows discrimination of healthy and cancerous cells. Heightened production of these molecules is presumably to metabolic differences between the two cell types.

Meanwhile, researchers in the UK reported pilot data on detection of bladder cancer using a GC-sensor device that samples urine headspace. Using statistical algorithms the device correctly separates urine from cancer patients and that of healthy matched controls. Nice.

A leading member of the team is Professor Norman Ratcliffe, pictured below.



With necktie and fresh, unwrinkled lab coat he’s quite well dressed for an engineering professor. [Especially a British one!—Ed.] He appears to be holding a urine sample. Honestly, dude, glove up!

Prof. Ratcliffe presumably knows better than to bare-hand biofluids. He and his colleagues have previously done a lot of shitty work [Phrasing!—Ed.] using fecal volatiles to diagnose diarrhea, cholera, necrotizing enterocolitis, and irritable bowel syndrome.

From the Competing Interests statement of the PLoS ONE paper, it appears that team Ratcliffe has been granted one patent and has applied for another. To my inexpert eye, the granted patent seems rather broad—it covers the idea of a headspace collector and analyzer that can diagnose disease via odors. I don’t see how it would hold up in litigation, but then I’m not a patent attorney. [Or a patent troll.—Ed.] By publishing in PLoS ONE they certainly achieved plenty of free publicity for their patented device.

While human cancer studies make the headlines, olfactory diagnosis is advancing down on the farm. In Germany, a group of veterinarians and vet students was matched against an e-nose. The task: sniff post-partum vaginal discharge from a cow and judge whether or not the animal suffers from acute puerperal metritis. The humans performed adequately but they were completely dusted by the DiagNose device. The researchers note, however, that the e-nose is yet suitable for use in the field, er, barn.

The studies discussed here are “Volatile biomarkers from human melanoma cells,” by Jae Kwak, Michelle Gallagher, Mehmet H. Ozdener, Charles J. Wysocki, Brett R. Goldsmith, Amaka Isamah, Adam Faranda, Steven S. Fakharzadeh, Meenhard Herlyn, A.T. Charlie Johnson, and George Preti, published in Journal of Chromatography B 15:90-6, 2013,

“A pilot study combining a GC-sensor device with a statistical model for the identification of bladder cancer from urine headspace,” by Tanzeela Khalid, Paul White, Ben De Lacy Costello, Raj Persad, Richard Ewen, Emmanuel Johnson, Chris S. Probert, & Norman Ratcliffe, published in PLoS One, 8(7):e69602, 2013,

“An investigation of fecal volatile organic metabolites in irritable bowel syndrome,” by Iftikhar Ahmed, Rosemary Greenwood, Ben De Lacy Costello, Norman M. Ratcliffe, & Chris S. Probert, published in PLoS One, 8(3):e58204, 2013, and

“Evaluation of odor from vaginal discharge of cows in the first 10 days after calving by olfactory cognition and an electronic device,” by I. Sannmann, O. Burfeind, V. Suthar, A. Bos, M. Bruins, & W. Heuwieser, published online in Journal of Dairy Science, June 27, 2013.

Advice Columnist Steers Widower to Certain Disaster

Okay, so it’s not exactly I Smell Dead People—more like “I smell my late wife’s perfume on my new girlfriend and it’s a problem.” Advice columnist Jann Blackstone tells the guy to avoid being truthful because “rarely do women like to be compared to one another” and because it might look like problematic devotion to his late wife.

Hmmm.

Blackstone advises the widower to shop for a new perfume for the GF, and perhaps even “take her with you and actually spend some time together in the process.” This sounds good at a theoretical level: use the power of scent to create positive new associations. But at a practical level it is a recipe for disaster.

Choosing a fragrance for another person is difficult enough; add the emotional undercurrents of this relationship and it’s fraught with peril. Secondly, Blackstone is directing the guy to the women’s fragrance counter: seldom a comfortable situation for a male. All we know is that the widower liked his wife’s perfume, not that he is knowledgeable about or even interested in women’s perfume in general, much less at ease browsing for it. So Blackstone is recommending that the guy give style advice, no matter how indirectly, to a woman he doesn’t know that well yet, and do it in the live-fire zone of a fragrance counter.

This strike me as well-intentioned but terrible advice.

On Second Thought Who Needs Lassie?

Cal Tech’s Heather McCraig

Is it time to send your diabetes scent detection dog back to the animal shelter? In a blog post on MIT’s Technology Review, David Zax takes a look at the possibility of diagnostic e-noses embedded in smart phones.

Bottom line: a neat idea that needs a lot of work to reduce to practice.

Zax embeds what he oxymoronically calls a “cool video from the American Chemical Society.” The video is about chemical vapor sensors and features a Cal Tech nerdette named Heather McCraig—a graduate student in Nate Lewis’s lab—and some really silly 1950’s-style background music. [Don’t be so square. It’s ironic post-modern nerd music.—Ed.] [Okay, okay.]

One of Ms. Craig’s talking points needs work: the canary in the coal mine is a good analogy for chemical vapor sensors but a bad one for e-noses. (Canaries detect odorless methane gas.) Still in all, she’s good on camera and is working in probably the premier chemical sensor lab in the country. [And her safety glasses are way more fashionable than yours.—Ed.] [Bite me.]

Hat tip to Instapundit.

A Boy and His Rat

It seems like every few months we’re treated to another heart-warming story about scent-detecting service dogs. Lately it’s been dogs for diabetics. You know the drill: Fido alerts one way when Johnnie’s blood sugar is too low, and another way when it’s too high.

The latest entry is Ben Ownby, a middle-schooler from San Antonio, Texas, and his Labradoodle Dakota. Before them it was another Texan, Katie Jane Brashier, and her Labrador Retriever mix named Shots.

This is the adorable public face of the scientific enthusiasm for training dogs to detect various human diseases by odor. I was skeptical of it in What the Nose Knows:

So, yes, dogs can smell odors associated with bladder-cancer. But this is a far cry from “What’s that Lassie? Timmy has bladder cancer?” To make use of this canine talent, your local hospital would have to maintain a half dozen dogs and their trainers, supply copious medically-certified human urine samples, and provide ongoing statistical support and chemical analysis. At which point 6 out of 10 bladder cancers would go undetected.

Recently published studies report more impressive success rates. A French group used a Belgian Malinois shepard to sniff urine sample from patients with prostate cancer. The dog correctly chose cancer samples in 30 of 33 cases, for a detection sensitivity of 91%. Detection specificity was also 91%. (In other words the dog correctly identified 91% of cancer samples, and correctly rejected 91% of non-cancer samples.)

This is a pretty impressive performance, but keep in mind that it came after 16 months of training, and that “training was a full-time job for the team, who worked with the dog 5 d/wk over the study period.” No wonder the authors caution that

the present work is a proof-of-principle study, and the use of these dogs is not supposed to be generalized. We tested a limited number of subjects in a costly, long study that makes it difficult to conceive of an extended use for this test in clinical practice.

Meanwhile, a German research group claims 71% sensitivity and 93% specificity for dogs trained to detect odors associated with lung cancer.

If you’re going to use animals for routine disease detection in the clinic, you need a species that is less expensive and less demanding that the dog. And now, thanks to a multi-national research team led by Georgies F. Mgode, we have a candidate—a rodent, less. Allow us to present Cricetomys gambianus, the African giant pouched rat. (It weighs in slightly more than one of Paris Hilton’s dogs.)

Mgode et al. have previously trained the giant rats to detect odor associated with tuberculosis. Now they use lab culture samples to ask whether the animals can discriminate TB samples from non-TB bacterial samples using artificial laboratory cultures. Which brings us to this classic line from their methods section:

Negative sputum samples from TB clinics in Dar es Salaam, Tanzanai, were used for spiking test microorganisms.

Mmmmmm . . . make mine a Rhodococcus!

Having obtained the necessary sputum, the next step was to train the animals.

during training sessions, rats were rewarded with food (mashed banana mixed with crushed commercial rat food) when they paused for 5 s at known TB-positive sputum samples. They did not receive food for pausing at known TB-negative samples. With extensive training the rats learnt to consistently pause at TB-positive samples but not at TB-negative samples.

Here’s a photo of co-author Maureen Jubitana, two trainers, and the study animals.

Mgode and colleagues tested the trained rats on sputum samples containing either TB culture or cultures of other, nontuberculosis mycobacteria. The rats responded only to the TB-spiked samples, indicating that there is an odor profile specific to TB, and not to other pulmonary bacterial infections. Interestingly, the detection rate for the TB-spiked sputum samples was lower than that for naturally occurring TB-positive sputum. And the spiked samples were more detectable when the spiking dose was taken from certain growth phases of the bacterial culture. Evidently, the exact character and intensity of the TB-associated scent depends on the biological context and growing condition of the bacteria.

Dogs, African giant pouched rats, whatever. What I want to know is, why don’t any of the labs just straight-out run a sniff test with human odor judges?

The articles discussed here are “Olfactory detection of prostate cancer by dogs sniffing urine: a step forward in early diagnosis,” by Jean-Nicolas Cornu, Géraldine Cancel-Tassin, Valérie Ondet, Caroline Girardet, and Olivier Cussenot, which appeared in European Urology 59:197-201, 2011, and “Ability of Cricetomys rats to detect Mycobacterium tuberculosis and discriminate it from other microorganisms,” by Georgies F. Mgode, Bart J. Weetjens, Christophe Cox, Maureen Jubitana, Robert S. Machang’u, Doris Lazar, January Weiner, Jean-Pierre Van Geertruyden, and Stefan H.E. Kaufmann, which appeared in Tuberculosis (Edinb), 92:182-186, 2012.

Does This Condom Make Me Smell Slutty?

Good grief. Canadian sex-advice columnist Sasha provides the . . . uh . . . low-down.

P.S. Just a thought, but another solution is for correspondent Pretty Pony to exercise some restraint in filling her social calendar.

P.P.S. Should Mr. Two actually detect the tell-tale scent, what are the odds he will be (a) surprised, or (b) offended?

P.P.P.S. If Mr. Two takes offense, doesn’t that make him a priggish, uptight jerk? In which case, why would Pretty Pony be interested in what he thinks?

Olfactory Tips from the Free Clinic

So you’ve exchanged a few text messages with that guy you met on VeganSingles.com, you’ve carefully chosen an outfit that’s alluring yet not Jersey Shore-ish, and you’re heading out the door for your first face-to-face, hoping for the best.

Remember one thing: get a good sniff of Mr. Eligible before taking things to the next level.

That’s the net-net from a new paper in the Journal of Sexual Medicine. Extending to humans a finding that has been well established in rats and mice, a team of Russian scientists has found that guys battling an infectious disease smell, uh, somewhat “putrid” in the armpits. And since the disease in question is gonorrhea, rank BO is another thing to watch for, along with whether he pays for the drinks and holds the door.

Mikhail Moshkin and colleagues from scientific institutes in chilly Siberia used the now-classic cotton-pads-pinned-into-T-shirts technique to collect axillary odor from young men. The odor donors included guys with current gonorrhea infection, guys cured of same, and guys who were never infected. A group of young women rated the BO samples for strength and pleasantness, and described them using a list of adjectives.

The results in a nutshell: infectious disease reduces a person’s odor attractiveness, and

The odor of infected persons was more often associated with a putrid smell. The odor of recovered persons was more often associated with a floral smell.

Moshkin et al. observed the usual experimental niceties: the odor donors refrained from eating spicy food for two days before the study, the odor judges did not use hormonal contraceptives, and the BO samples were stored at -20°C. The judge’s menstrual cycle phase made no difference to the outcome.

Saliva sample from the male odor donors were analyzed for testosterone, cortisol, and immunoglobulins A and G. None of these measures differed significantly among the three test groups. However,

while salivary IgA and IgG concentrations were insignificantly higher in the infected persons, they correlated negatively with pleasantness scores and positively with prevalence of putrid associations. A high level of the nonspecific salivary immunoglobulins reflects activation of the defensive mechanisms due to general antigenic pressure on the immune system. Several studies on laboratory animals demonstrate that antigen-induced immunoenhancement leads to reduction of male scent attractiveness.

Another small victory for the human sense of smell. Forget about electronic noses, trained service dogs, or hacking into private medical records. Just use your nose.

The study discussed here is “Scent recognition of infected status in humans,” by Mikhail Moshkin, Nadezhda Litvinova, Ekaterina A. Litvinova, Alena Bedareva, Andrey Lutsyuk, and Ludmilla Gerlinskaya, published in the Journal of Sexual Medicine, ahead of print, on December 6, 2011.

A Dog’s Life: Canine Olfaction Put to the Test

In What the Nose Knows, as well as here on FirstNerve, I’ve questioned the conventional wisdom about the dog’s sense of smell, namely that it is amazingly better than our own. Recent evidence suggests that the human nose, in terms of its sensitivity as an odor detector, is quite competitive with the canine nose. The dog’s ease in odor tracking may have more to do with differences in sniffing behavior, nostril design and the amount of brain devoted to analyzing olfactory information.

Still, the conventional narrative gets a boost with every report of dogs smelling termites, bedbugs, abnormal glucose levels in diabetics, bowel cancer, ovarian cancer, and so on. Just because a trained scent dog is handy in a pilot study (“does disease X have a smell?”) doesn’t prove that dogs alone are able to make this discrimination. And unless tight controls are built into the experimental design, we still have to rule out that subtle, unintended cues from the dog’s handler are giving us a false result.

This was brought home by a new study that examined the role of human handlers in the response of working scent dogs. Conducted by Lisa Lit and her colleagues at the University of California at Davis, the experiment looked at canine scent-tracking behavior without using any scent at all. It’s a trans-species examination of what social psychologists call “demand characteristics”, i.e., cues that study participants use to glean the aim of an experiment and behave accordingly.

In this case, 18 dog-plus-handler teams—all trained, certified, and experienced in the detection of drugs or explosives—search four rooms in a church for contraband. In view of the teams, an experimenter set down a metal box of gunpowder or marijuana samples. The samples, however, were never opened; this was a ruse to make the room searches believable.

Each dog/handler team searched the four rooms twice. An observer noted when and where the dog signaled an “alert.” Of course the correct response in every trial was “no alert,” as there were not drugs or explosives present. What were present, on some trials, were decoys: a red sheet of paper (for the handlers to notice) or a new tennis ball and a couple of Slim Jims (for the dog to notice), or both. Lit and her team were interested in how alerts by the scent dog (i.e., false alarms) were distributed across the experimental conditions.

The great majority of false alarms happened in rooms with a red sheet of paper; this included trials with and without a scent decoy. To Lit and her team,

this suggests that human influence on handler beliefs affects alerts to a greater degree than dog influence on handler beliefs.

Lit et al., consider and dismiss the possibility that handlers were calling alerts in the absence of corresponding behavior from the dog. Instead, they suspect that the dogs were responding to subtle cues from the handler, who in turn was influenced by the apparent location cue of the red paper. This would be an instance of the Clever Hans Effect. (Dig up your Psych 1 notes, people.)

Even without formal training, dogs respond to human cues such as pointing, nodding, head turning and gazing. The mental pull of these cues is powerful, to the point that a companion dog looking for food will ignore a bowl full of food and head to an empty bowl if directed there by his owner. Highly trained scent-detection dogs don’t fall for obvious distractions; clearly, however, they are not immune from subtle, even unintended, influence from their handlers.

Scent-tracking dogs have proven useful in search and rescue missions, detection of contraband, and tracking of criminal suspects. Whether the results of so-called scent lineups conducted by police dogs should be admitted as courtroom evidence is another question altogether. Radley Balko wrote about a recent case in Texas that brought these issues to the forefront.

Research on the olfactory ability of dogs are becoming increasingly sophisticated. While some results, like Lit’s, raise important cautions, another new study adds to the positive side of the ledger. It involved a rigorous and well-designed assessment of the dog’s ability to distinguish identical human twins (aka monozyogtic or MZ twins) by smell. Previous studies (in 1955, 1988, 1990 and 2006) have been a mixed bag. It has been claimed that MZ twins can be distinguished, cannot be distinguished, cannot be distinguished when they share a similar diet, and can be distinguished by some dogs but only if the twins don’t live together.

The new study, by researchers in the Czech Republic, starts on a strong note by using a single breed of dog with similar levels of training, namely ten German Shepherds, each a trained and proven scent-detection animal employed by the Czech Republic Police. The key body scents were provided by pairs of kids living together: two sets of MZ twins and two sets of DZ twins. Their MZ/DZ status was confirmed by DNA testing. BO was collected according to Czech Police forensic protocols (cotton pads in glass jars) and presented to the dogs in a seven-jar “lineup.” The dog signaled a scent match by lying down next to the jar that smelled like the target his handler gave him at the start of each trial. Various combinations of target and lineup scents were used; on trials when the target scent was not in the lineup, the correct response for the dog was to not lie down.

Remarkably, every dog made the correct judgment in every trial (10 dogs, 60 trials each). It seems the mixed results of earlier studies were due to variable skill levels among the dogs tested. Still, not one single incorrect response in 600 trials? (Experimental data with zero statistical variance is, uh, a little unusual.) On the other hand, if it’s this easy for dogs, I bet that humans are able to smell the difference between MZ twins living together.

The studies discussed here are “Handler beliefs affect scent detection dog outcomes.” by Lisa Lit, Julie B. Schweitzer, & Anita M. Oberbauer, published in Animal Cognition 14:387-394, 2011, and “Dogs discriminate identical twins,” by Ludvik Pinc, Luděk Bartoš, Alice Reslová, & Radim Kotrba, published in PLoS One, 6(6):e20704, 2011.

The Erotic Laundry Hamper: T-shirts and Testosterone

He held the panties in his hand and continued to kiss her, leaving her moist and panting. Then he turned away and buried his face in the panties, in the nightgown, wrapped the stockings around his penis, laid the black silk dress over his belly. The clothes seemed to have the same effect as a hand. He was convulsed with excitement.

[From Delta of Venus by Anaïs Nin.]

It’s tempting to think of the Basque’s response to the scent of Bijou’s clothes as nothing more than a personal kink, another odd sexual habit that Anaïs Nin was directed to write about by her lubricious pornographic patron.

But the arousing effect of feminine body scent is a resonant theme in literature and locker room—it seems to address something fundamentally biological in a vaguely primate way.

Sensory psychologists—much to the distaste of a certain perfume snob and his pedestrian second spouse—have given lots of attention to the links between smell and sex. Direct olfactory evaluations show that female body odor varies across the menstrual cycle. Men find BO from women in the luteal phase of the cycle less pleasant than BO from women in the follicular (i.e., fertile) phase.

The possibility that men can sniff their way to tactically useful information about a woman’s reproductive status throws a wrench into the conventional wisdom that human females are, in the technical jargon, “concealed ovulators.” But that’s a story for another day.

We focus here on the first study to examine the physiological effect of female BO on men. It’s by Florida State University psychologist Jon Maner and his student Saul Miller and is set for publication in the journal Psychological Science.

The experimental design is simplicity itself. Relevant odors were collected by having nubile women wear T-shirts to bed at different times in their cycle—ovulatory and nonovulatory. Male physiological response was measured by having a guy drool in a tube before and after plunging his face into one of the worn T-shirts. A standard radioimmunoassay quantified the testosterone in the spit.

The results of Miller and Maner’s first experiment were suggestive but not conclusive—post-sniff testosterone was higher in men who had smelled ovulatory T-shirts than in men who had sniffed nonovulatory ones. The data left open the possibility that the difference was due to nonovulatory shirts decreasing testosterone during the 15 minute course of the test.

The researchers ran a second study that included a clean (control) T-shirt condition and more precise estimation of menstrual cycle phase. Once again, post-sniff testosterone was significantly higher in men who smelled ovulatory T-shirts compared to nonovulatory and control shirts (which didn’t differ). Even more compelling: testosterone levels were a curvilinear function—an upside down U shape—of the odor donor’s ovulatory phase. In other words, post-sniff testosterone was highest for shirts worn exactly at ovulation, and it decreased with the number of days before or after ovulation.

Miller and Maner cautiously provide a laundry list of caveats, the most important being that the ovulatory odor cue does not increase a guy’s testosterone—it only prevents the decrease that happens after sniffing a fresh or nonovulatory shirt. Still, this first-ever demonstration of a sexually-relevant endocrinological response to female BO opens the door to some potentially cool work on scent-driven mate-seeking behavior and eroticism in men.

Somewhere out there Anaïs Nin is smiling.

Paging Oliver Stone

Juan Tomayo of the Miami Herald reports on Cuba’s use of scent samples and tracking dogs to repress political dissidents. The scent repository is modeled on one kept by the communist East German Stasi. The techniques are described this 2003 article by one Rafael Hernández de la Torre that reads like a parody of a scientific paper. Unfortunately it’s no joke—innocent people may be suffering the horrors of the Castro regime’s prisons thanks to Hernandez’s flimsy pretext of “odorología criminalística.”

Cinnamon Girl

I once knew a girl from Topanga Canyon who lived near Neil Young’s place. She said he used to beat his dogs.

A not so random recollection while mulling over the erotics of cinnamon.

Philip S., a reader of my book, sent me the text of Michael Ondaatje’s poem The Cinnamon Peeler because he thought it might appeal to me. He was right.

It begins:

If I were a cinnamon peeler
I would ride your bed
and leave the yellow bark dust
on your pillow.

Your breasts and shoulders would reek
you could never walk through markets
without the profession of my fingers
floating over you.

Read—or listen to—the whole thing. It’s an amazing interplay of the senses: a blend of the tactile and the olfactory in the service of Eros.

Necessary?

The English have a long and honorable tradition of tolerating eccentrics, but the Baltesz family of Bristol is really pushing the envelope. Together with their teenage children, Mr. and Mrs. Baltesz are peeing into bottles and spritzing the neighborhood with their urine. Why, you ask? To help their lost dog Simon find his way home, of course. They hope he’ll follow the scent trail.

Unlike their less fastidious contemporaries, however, members of the Baltesz family dilute their urine before leaving it in public places. Why, you ask? (What, are you dense?)

Because Jane Hayes, their finder-of-lost-dogs consultant, says that

A dog’s sense of smell is 3,000 times more potent than ours . . .

Three thousand times more potent? Ms. Hayes clearly hasn’t read What the Nose Knows, or she'd know that controlled studies find the human and canine nose are close to parity. In fact, I’ll bet her a warm bottle of recycled Sierra Nevada Pale Ale that she can’t come up with scientific evidence to support her claim.

British Healthcare Going to the Dogs

Take your diabetic grandmother to the clinic and they’ll tell you she can be seen by the corgi in five weeks or by the Yorkshire terrier in eight. But it’s the National Health Service, so it’s free!

Yes, You Can Take It with You

Thanks to psychologists at the University of Pittsburgh we know that absence makes the nose grow fonder. It was only a matter of time before some enterprising outfit turned this to commercial advantage. Turns out it was Laterooms.com, a UK-based hotel room reservation site.

As a special promotion, Laterooms is offering a “Home from Home” travel kit to a lucky few high-volume customers. The kits are intended to remind road warriors of the sensory pleasures of home, including a pillow case laundered in the traveler’s own brand of detergent, favorite biscuits and teas, etc. Topping it all off, according to a spokeswoman, is this:

We send an expert from aroma designer Dale Air round to their house who captures the different smells in their home then goes away copies it and puts it in a spray can to be used whenever the customer wants.

Cool idea, being able to carry the scent of home with you on the road. But the charm of returning home is that the various sensory pleasures of which you’ve been deprived hit you all at once. Will the Laterooms Travel Kit eliminate the homecoming effect?

Or, in the lyrics of the immortal Dan Hicks,

How can I miss you when you won’t go away?

[Hat tip to Mike T.]

Reality Czech: Frozen Smelly T-shirts

Back in graduate school a buddy of mine was doing a clinical psychology internship. One day he interviewed an elderly couple—the wife complained that her husband was getting forgetful and confused. “How so?” asked my friend. “Well,” said the wife, “last week I found a pair of his underwear in the ice cube tray in the refrigerator.”

It turns out there are reasons other than Alzheimer’s dementia for people to want to freeze underwear. Take body odor researchers, for example. A standard method for collecting BO is to have the odor donor wear a T-shirt for a couple of days. The BO-infused shirt is a handy scent source—test subjects can rate it for strength and pleasantness of smell, how masculine or feminine it smells, and so on. A popular alternative method is to have the donor wear cotton armpit pads to collect the perspiration.

In BO research one often wants to use multiple samples from the same donor and to have more than one set of judges rate the same odor. The logistics of this can get tricky—a couple of dozen panelists have to arrive at the same time as a group of odor donors delivers the dirty laundry. The easy way out is to store the smelly shirts for testing at a more convenient time. Researchers often put the shirts or pads in plastic bags and freeze them. The rationale is that freezing inhibits the bacteria that turn odorless fresh sweat into stinky BO.

Does this practice work?  Could it distort experimental results in some unexpected way? We had no direct answer to these questions until now. A pair of Czech BO scientists—Pavlina Lenochova and Jan Havlicek in Prague—along with S. Craig Roberts at Liverpool in the UK, examined how freezing—and repeated freezing-and-thawing—affect smell ratings of cotton armpit pads worn by male BO donors.

The upshot of the study, published in the journal Chemical Senses, is that the pleasantness, attractiveness, and masculinity of the samples were unaffected by two weeks or even six months of frozen storage. (The odor judges were 28 young women.) There were some variations in odor intensity but puzzlingly they were not related to storage time.

So the underwear-in-the-freezer gambit looks like an excellent solution to your BO storage needs. As a smell scientist, I can breathe easier knowing this.

Odorprints on a Wanted Poster

In Ray Bradbury’s sci-fi novel Fahrenheit 451, the fire department uses a hellish Mechanical Hound to track a person down based on his individually unique body odor. The “sensitive capillary hairs in the nylon-brushed nostrils” of the Hound pick up the scent. Its electronic brain is programmed to recognize ten thousand individual BO profiles. After cornering its prey the Hound dispatches it with a lethal injection from a retractable fang.

I thought of the Mechanical Hound the other day when I spotted a juicy headline on Drudge: ‘Odorprinting’ will identify people. I clicked on the item with my usual mix of emotions. Would this be a story about real technology or some type of National Enquirer nonsense?

The linked report from the Telegraph quotes Jae Kwak, a scientist at the Monell Chemical Senses Center in Philadelphia. According to Kwak, genetically-based body odors are as unique as fingerprints; he thinks it may be possible to build devices that identify people based on their BO.

Intriguing. But in world of science-by-press-release it pays to be skeptical of media stories. Kwak could be a quack. Far better to examine the actual study that brought him to the Telegraph’s attention: in this case a paper in the open-access, online journal PLoS ONE.

The needle on my Bogosity Meter twitched as soon as I began to read: the experiment has nothing to do with humans—it’s about two strains of highly inbred mice.

I’m very familiar with these mice: I studied them years ago when I was on the faculty of the Monell Center. Originally bred for cancer research, the strains are genetically identical except for a set of genes that controls immune response. These so-called MHC genes are associated with a strain-specific scent. Mice can smell the difference and prefer to mate with mice of the other strain (a case of “opposites attract”). In addition, the mousey BO is distinct enough that humans can smell the difference between the two strains. (An experimental result of mine that I published here.)

It is widely believed that diet alters body odor. If so, can diet obscure MHC-linked BO differences? This is the question Kwak and his colleagues set out to answer using the two mouse strains and two kinds of commercially produced mouse chow. They trained “sensor” mice to recognize the scent of urine from mice with a specific combination of MHC type and diet. Then they let them choose between mice differing in various combinations of genes and diet. The result? The sensor mice failed to pick out the MHC-linked scent. In a direct match-up, diet-related BO overwhelmed the differences in genetically-based BO.

Other mice were trained to recognize a particular MHC scent from mice fed the same diet. Once trained, they were able to pick out that MHC scent from mice fed another type of diet. In other words, the genetically-linked BO signal persists amid stronger dietary signals and properly trained mice can find it. Chemical analysis revealed forty-nine molecules in mouse urine that vary with diet and MHC type. From these, Kwak and colleagues were able to construct a statistical model that predicts MHC type as accurately as the trained sensor mice. Pretty cool stuff.

Kwak et al. go on to claim “it should be possible to develop a detector to identify individual odortypes that can ignore environmental perturbations such as diet variation.” Once again the needle on my Bogosity Meter bounces a bit. Why? Because the mice in question weren’t recognized as individuals (Bob, Jane, John, Wendy, etc.) but as members of genetically identical groups (the Smith-family clones versus the Jones-family clones). Clonal sibship is one thing, individual identity is another. A device to “detect individual odorprints in humans” is several leaps of logic away from the results of this study.

In Fahrenheit 451, the fugitive fireman Guy Montag successfully evades the Mechanical Hound by swapping clothes with an old man, dousing himself with whiskey, and floating down a river. If pursued by trained mice from Monell, he could simply have popped a breath mint and taken it easy.