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Science

Human Sense of Smell Rivals That of Dogs, Says Study (theguardian.com) 143

One scientific analysis is arguing that the human sense of smell has not only been underestimated over the years, but that it may rival that of dogs and rodents. John McGann, a neuroscientist at Rutgers University in New Jersey and the paper's author, said: "For so long people failed to stop and question this claim, even people who study the sense of smell for a living. The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs." McGann has reached this unexpected conclusion after spending 14 years studying the olfactory system. The Guardian reports: McGann identifies a 19th century brain surgeon, Paul Broca, as the primary culprit for introducing the notion of inferior human olfaction into the scientific literature. Broca noted that the olfactory bulb -- the brain region that processes odor detection -- is smaller, relative to total brain volume, in people compared with dogs or rats. The discovery inspired Freud's belief that human sexual repression may be linked to our "usually atrophied" sense of smell. In the latest paper, published in Science, McGann points out that in absolute terms the human olfactory bulb is bigger than in many mammals and a literature search revealed that the absolute number olfactory neurons is remarkably consistent across mammals. McGann goes on to deconstruct other metrics that have been used to support the idea that human smelling abilities are limited. Humans have approximately 1,000 odor receptor genes, for instance, compared to 1,100 in mice, which some had taken as confirmation of mouse superiority. However, other work suggests there is not a tight relationship between the number of olfactory genes and smelling ability. One study found that cows have 2,000 such genes - far more than dogs.
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Human Sense of Smell Rivals That of Dogs, Says Study

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  • by Snotnose ( 212196 ) on Friday May 12, 2017 @08:30PM (#54408715)
    I can't smell my own BO, let alone a nice stash of coke, weed, or vodka 2 feet from my nose.
    • I can't smell my own BO

      I can smell your BO, too. Over the Intertubes, for Christ's sake. I use Irish Spring, maybe you should too.

      • Yeah well, spring's almost over, better use it again...

        And what the headline really meant was that some humans' smell rival that of dogs.

        And if you want to make your nose a bit more sensitive, just wet it a little, like theirs.

  • Really? (Score:5, Insightful)

    by MrLogic17 ( 233498 ) on Friday May 12, 2017 @08:33PM (#54408725) Journal

    Find me a human who can compete with a bloodhound or beagle in tracking a person, based on smelling a old shirt.

    • Re:Really? (Score:5, Insightful)

      by Chris Katko ( 2923353 ) on Friday May 12, 2017 @08:44PM (#54408765)

      Seriously. Just because one study (that hasn't been replicated yet, the fundamental requirement of science) say something, doesn't mean it invalidates ALL of our pragmatic knowledge and experience.

        - Police aren't using humans to track drugs and dead bodies buried under ground for 7 days.

        - As an engineer, it doesn't take a genius to look at the shape of a dog's nose verses other animals to notice the huge mass and evolutionary investment in their noses. We aren't using humans to hunt for truffles. Don't you think in the course of human history it would be easier to use our noses than DOMESTICATE AND TRAIN ANOTHER ANIMAL to learn what we want?

      I mean, all we know from this snippet is we MAY have more "oder receptor genes." DO more genes = more smelling ability? And what is ability defined as? Maybe dogs can't smell [as many] types of different smells, but they can smell them BETTER at smaller parts-per-million. They may also be able to smell the DIRECTION the scent is coming from a thousand times stronger than us. Our nose is pointed DOWN, theirs is pointed FORWARD. Evolution doesn't just design stuff like that for shits and giggles.

        I mean, there are so many questions that the only thing we can really do at this point is go "Huh. Interesting." and go about our days until some REAL science starts confirming this study and exploring the actual implications. This is just clickbait at this point unless some actual EXPERTS show up in the comment section to elaborate their experiences and research.

      • Don't you think in the course of human history it would be easier to use our noses than DOMESTICATE AND TRAIN ANOTHER ANIMAL to learn what we want?

        From the summary:

        One study found that cows have 2,000 such genes - far more than dogs.

        Cows were probably domesticated before dogs, so it stands to reason that we could have had bomb sniffing cows and cadaver cows.

        • by aberglas ( 991072 ) on Saturday May 13, 2017 @12:58AM (#54409491)

          According to Jim Corbet, 1930s Tiger hunter with a national park named after him (seriously -- he really understood wild tigers).

          In his book Corbet warned any readers that wish take up the sport of hunting tigers on foot through thick jungle that tigers do not realize that humans cannot smell. So if you are walking downwind you will be safe from an attack from behind. However, walking upwind can be extremely dangerous if there is a man eater nearby.

          Information that I am sure Slash Dot readers will find very useful.

          • by jafiwam ( 310805 )

            According to Jim Corbet, 1930s Tiger hunter with a national park named after him (seriously -- he really understood wild tigers).

            In his book Corbet warned any readers that wish take up the sport of hunting tigers on foot through thick jungle that tigers do not realize that humans cannot smell. So if you are walking downwind you will be safe from an attack from behind. However, walking upwind can be extremely dangerous if there is a man eater nearby.

            Information that I am sure Slash Dot readers will find very useful.

            Domestic felines seem to need to be reminded of human inabilities frequently. My cat gets stepped on in the dark about once a year, not realizing she can't be seen in the middle of the floor. Once it's done, she gets up and moves when humans walk in the dark.

            The main difference I see between "smelling" and "incidental smelling" animals is a distinct two directions to nostrils so bi-directional smell can be done close to something that you don't necessarily want stirred up. (dust). Cold enough to "see bre

      • by sodul ( 833177 )

        Well we do use human to develop new perfumes for women and men, and not really dogs or pigs, at least on the smelling part.

        In the same vein we also do not, or no longer in developed countries, use humans to transport humans, we use horses, donkeys in places where beasts are more practical than cars/trucks.

        I believe it is possible that while not as sensitive as a blood hound, our nose might be a lot more sensitive than assumed in the past but just not at a conscious level and we might not be as good at isola

      • Re:Really? (Score:4, Insightful)

        by rmdingler ( 1955220 ) on Friday May 12, 2017 @09:38PM (#54408953) Journal

        - Police aren't using humans to track drugs and dead bodies buried under ground for 7 days.

        You are correct, but they sure are using dogs trained by humans. You have to learn to delegate.

        • > You are correct, but they sure are using dogs trained by humans. You have to learn to delegate.

          Often, they are using dogs "trained by humans" much like horses have been trained to do math in the infamous case of "Clever Hans". There are many court cases about spurious canine search results, and a great deal of video and legal testimony that the dog alerts are manipulated by the officers handling the dogs. See https://nevergetbusted.com/201... [nevergetbusted.com] for more details.

          Examples of highly trained noses include sk

          • A Sheriff might set roadblocks with a Game Warden, since the Warden could search the vehicle for hunting violations without a warrant.

            The bottom line: People who enforce the law want to look through your stuff? They'll go to some length to make it look as legitimate as possible, but they'll be looking through your stuff.

      • As an engineer, it doesn't take a genius to look at the shape of a dog's nose verses other animals to notice the huge mass and evolutionary investment in their noses. We aren't using humans to hunt for truffles

        No, we use pigs to hunt for truffles. Additionally pigs are considered to have superior olfactory sense and yet their noses aren't all that specially shaped.

      • by mentil ( 1748130 )

        Human noses tend to be several feet off the ground, while dog noses are much closer (and often go to the ground to sniff stuff.) Even if a human puts their head to the ground the nostril points the wrong way to hoover up scents on the ground.

      • We aren't using humans to hunt for truffles.

        How about an experiment. [imgur.com]

        On a serious note, maybe nobody has really tried it. Dogs instinctively rely on their noses. People may have to train and practice. Being upright, we kind of have to go out of our way to sniff the ground a lot. It would take athletic training and conditioning to bend often, or use a shoveling device. Is that cheating?

        A handful of deaf people have learned to use echo location to navigate by making clicking sounds. I tried it myself and indee

      • by Evtim ( 1022085 )

        There is a story from "The man who mistook his wife for a hat" about a young student of medicine who [if memory serves, due to trauma] for a period of several months acquired sense of smell well beyond that of our everyday experience. It seems that the " hardware" is capable of doing this, but something in the head had to go click to re-enable it.

        It is argued that present sense of smell is weak because we do not need it so much for our survival. And a speculation that a more acute sense requires more comput

      • Re: Really? (Score:2, Insightful)

        by Anonymous Coward

        I, a human, smelled this article, which smelled like bullshit well before I opened it.

      • by MrL0G1C ( 867445 )

        As an engineer, it doesn't take a genius to look at the shape of a dog's nose verses other animals to notice the huge mass and evolutionary investment in their noses.

        Hmm, so what about small dogs, how do they compare?

      • by Megol ( 3135005 )

        Yes the title and blurb is misleading clickbait. However people do have a better sense of smell than many assume - part of smell not being used more by humans are that we don't need to. We have good general-purpose vision and hearing, we don't need smell to detect if a member of the opposite gender want to have sex, we don't mark territorial boarders with pee etc.

        However there are people that have trained to use their sense of smell like wine tasters, perfumers etc. and there have been enough research to sh

      • Dogs can tell the direction of smells because, unlike humans, they have "stereo smell". Their nostrils are sensed separately by their left and right hemispheres. Ours are not.

        I can watch my dog sniffing a treat I am holding out for him, and he definitely samples it with one nostril, then the other, back and forth, until he has satisfied himself that It's acceptable for consumption.

      • by sjames ( 1099 )

        We also have to distinguish raw capability from ability. Perhaps if parents spent as much time showing baby scratch and sniff books and saying "What is THAT smell?" as they do with picture books, we might do better. Of course, we also confound our sense of smell on a regular basis. The products that aren't actively scented often have compounds meant to damp down the sense of smell as a cover-up (sometimes they have both). Practically nothing we learn encourages us (or instructs us) to use our sense of smell

      • by hey! ( 33014 )

        Also, it depends on how you define and measure "performance". It seems to me there are at least two relevant axes here: detection sensitivity and discrimination ability.

      • Yeah. we are just tuned into different things, dogs and humans. For instance, my dog needed to get really close to a turd to smell it. He needed to be only a few microns from the surface of the poop. I am capable of detecting poop on the ground from several feet away.
    • Find me a human who can compete with a bloodhound or beagle in tracking a person, based on smelling a old shirt.

      Also a cow. TFS makes it sound like since cows have a poor sense of smell. That is not true at all. Pigs also have superb smelling ability. They can locate potatoes and other root vegetables even through frozen ground. Pigs are sometimes used for tracking instead of dogs. Dogs have the drawback that they will only work with one handler, who they consider their master. But a pig will work with any handler, and will consider any human to be their equal.

    • This reminds me of a field-test, ten years ago, where researchers had volunteers follow a scent trail on all fours. It turns out that most did surprisingly well, even getting better at it with repetition. So we, humans, are actually pretty good at this. It’s just that we’re no longer quite comfortable putting (and keeping) our noses smack against the ground to take a really good whiff of whatever was down there.

      See this article (from 2006) in Nature: People track scents in same way as dogs [nature.com].

      In th

    • Exactly. I've owned 2 beagles. They are nothing short of amazing. One liked french fries in his later years. On walks he would pull me up to a block away if he smelled fries someone had tossed into the road. My 2nd was more of a hunter. At night he would bay at the tree and I'm thinking what? After awhile I got it. There was a field rat in the tree. I'd get a flashlight and see beady eyes staring back at me 10-15 feet in the air. He was right every single time. On walks, he'd scent a rat hole in tree roots

    • I agree. I've been in pristine areas in the Sierra Nevada mountains where I could smell the trees and vegetation but nothing made by a person. Been to Death Valley too, the heat and solar radiation would destroy any scent. Have you smelled a rock lately?
    • A sniffer dog at an airport, trained to find drugs and banknotes, flagged my travel bag positive. The dog handler searched the bag and found nothing. When I unpacked the bag at my destination I found a squeaky-clean 5 euro note in the pocket of a shirt that had been through the washing machine.
      Of course, my being a human, I could smell it all along.

    • by Anonymous Coward

      Yes, my wife managed to throw our dogs frisbee into a field of oil seed rape once (the tall yellow flowers you see in fields) which have a very strong scent and managed to lose it.

      I took the dog back there two days later with an identical frisbee and pretended to throw it for him then hid it behind my back, he knew it was behind my back because he was looking at me like "Oh, ha ha, I know it's there" but I said "Go get your frisbee a few times" and got a look of "Oh, fine, we'll play this stupid game then"

    • I disagree, counting receptors is not enough just like counting retinal cones does not tell us anything about color quantization in the brain. Was this study made on a differential population of Africans vs Humans? I contend the sense of smell is almost disabled in Human beings, while it functions better than Human in Africans. In my experience Africans are always complaining of smells I and other people simply do not perceive and are very happy within clouds of dandruff while I find it disgusting. But ther
  • I know of drug and bomb sniffing dogs, I don't know of any drug or bomb sniffing humans.

    Maybe we have as much processing hardware dedicated to smell as dogs, but we still don't do it as well as them. Maybe our sensors in the nose are worse, maybe our software running on that processing hardware is inferior. The end result ist: dogs do it better.

    • "I don't know of any drug or bomb sniffing humans."
      Any cop with an attitude.

    • by raymorris ( 2726007 ) on Friday May 12, 2017 @08:49PM (#54408783) Journal

      Talking about the number of genes is a bit silly, agreed. If you want to compare the two, compare them directly. There are humans and dogs trained in smelling things (in the fragrance industry, for example). Run a direct comparison test. Also of course you could directly test having untrained humans and dogs smell for food and other items.

      DRUG dogs, specifically, have not fared well in blind in blind tests. While *some* dogs are probably quite good, in testing the typical police dog consistently "alerts" on wherever the handler thinks the drugs are. Tests have been done in which the drugs are in box #1, nothing is in box #2, and the police handler is *told* the drugs are in box #3. A police dog is more likely to alert on #3, where the cop thinks the drugs are, then box #1, where the drugs actually are.

    • I personally know a at least two drug sniffing humans.
    • then why do they plant their faces into piles of dung? Can't they just get a whiff of the leavings of other animals from a distance?

    • Even if the number of neurons or brain size is similar between humans and dogs, it seems to me that the physical proportions of a dog's nose could also make a big difference. I'm guessing that a good-sized dog must have an order of magnitude more nose volume than an average human. Maybe this optimizes the exposure of each nerve sensor to incoming scents.

      • I am wondering about the connections of the olfactory centers in the brain and how they relate to conscious processing and accessibility. Basically, when the impulses from olfactory sensation are percolating up from the nose and through the olfactory center of the brain how much of that information is then passed and accessible to the conscious part of the brain?

        Also, how many of those 1000 genes related to olfactory sensation are actually activated and involved in proteosynthesis in your average western c

    • I know panty sniffing humans. Show me one dog that sniffs panties better than they do. Maybe we are just optimised for different smells.
  • If our sense of smell is so good, can we tell whose urine is whose by smelling it?

  • by Anonymous Coward

    In terms of absolute mass of brain dedicated to smell, yeah, maybe humans are the same as everything else. However, it's pretty well shown that dogs can distinguish individual scents massively better than humans. Their brain seems to divide the smells in to individual pieces whereas a human combines and b lends them all together. So a dog smells a specific bacteria, soap, cologne, and the each item in your lunch. Whereas a human just smells a college of mixed smells.

  • It could be that dog's superior tracking is no related to the nose at all.
    For example:

    1) Closeness to the ground/source is esesntial, which is one of the reasons that dogs with shorter legs and/or long floppy ears to gather scents near the nose are better scent trackers than other dogs

    2) More nuerons biologically programmed to process the results of the nose. That is, it's not the genes for the nose, but the genes that focus the brain's growth on scent rather than sight.

    3) Training - most scent dogs have

  • From sniffing arse to kissing ass.

  • Yeah, it could be true, elephants don't forget anything. But they don't have to remember much, so thats probably why they remember.

    You can count the neurons and talk about the absolute size of the olfactory bulb versus relative fraction of the brain volume/weight. But proof is in the pudding. We don't have famed Scotland yard detectives sniffing their way from the murder scene. But the bloodhounds do. Till I see a human who can smell the difference between his own pee and his rival's... we need to give th

  • My dog's got no nose

    How does he smell ?

    Just like you

  • really? (Score:5, Informative)

    by Goldsmith ( 561202 ) on Friday May 12, 2017 @09:16PM (#54408891)

    I've studied olfaction, and this just doesn't seem right. This olfactory bulb argument seems like a straw man that no one in the field has been using since... the 19th century. Digging in to the article a bit, it seems the authors of the actual study agree with me, and are using different odors for humans to balance out some of our... differences. Their main point (which is right) is that the human sense of smell is much better than most people realize, and that you can be trained to follow a scent trail, distinguish similar odors, and notice the cognitive effects scent has on you. Anyone who has experimentally studied olfaction for a few years will notice themselves gaining these abilities (it goes away quickly when you're not smelling things professionally several hours a day).

    So why is this summary so wrong?

    First off, humans only have 400 different olfactory receptors, it doesn't matter if genetics say you should have 1000, you only get 400 (genotype =/= phenotype). Second, you have less "sensor" surface area than other mammals in real terms, not scaled for size. Third, you lack the ability to concentrate scent molecules by varying your rate of breathing like other mammals (this can be overcome by varying breathing through your mouth and nose, but other mammals don't have to do this).

    • by Anonymous Coward

      I think humans use minute sent difference much differently than other creatures. We don't have to use sent for identification or finding food, we have very good eyes and ears for that. But we do use sent in particular for knowing good food from bad food. We stop and recognize small changes when other animals just woof bad food down and get sick. We also use awareness of scents for bonding and memory like how we can remember the smallest whiff of an old house we lived in or an old SO's sweatshirt.

    • Having a wet nose doesn't hurt though, right?

    • I was just thinking that sensor area would obviously matter more than the size of the processing region. If someone who knows more about the topic than I do agrees, then I must be awesome. So thanks!
  • by Anonymous Coward

    Bullshit.

  • A NOSE FOR ODORS
    What do dogs have that we don't? For one thing, they possess up to 300 million olfactory receptors in their noses, compared to about six million in us. And the part of a dog's brain that is devoted to analyzing smells is, proportionally speaking, 40 times greater than ours.

    from: http://www.pbs.org/wgbh/nova/n... [pbs.org]

    A dog's nose sure is longer than a humans...

    If you look at a dog looking out of the window of a driving car - the activity is mainly smelling, seems to me dogs live in a world of smel

    • A dog's nose sure is longer than a humans...

      It's also shaped so that air entering is not mixed with expelled air as much as a human's nose will do.

  • The "sensitivity of the nose" is measured by odor detection thresholds. [wikipedia.org]

    Here are some values for humans:

    http://www.tandfonline.com/doi... [tandfonline.com]

    And here are some values for dogs:

    http://www.barksar.org/K-9_Det... [barksar.org]

    As you can see, both dogs and humans can detect some chemicals at below one part per billion. So, it's hard to say conclusively that dogs have "more sensitive noses" than humans. Humans and dogs are probably just sensitive to different compounds because we use smell differently. So, humans can't track prey b

  • I recall reading a book authored by Richard Feynman where he recounted a party where he used that as a party trick. He had one of his guests lay an arm somewhere inside a book, and Feynman was able to smell which two pages the person lay his arm between.

    ~Loyal

    • by rew ( 6140 )

      Right!
      Besides the party trick, in the 1960'ies Feynman was aware of the discovery published now: Humans can (with a bit of training) smell almost as good as dogs.

  • While on our first rafting trip together on the Truckee River, my dog, a vizsla jumped out of the raft, cleared over 30' of water, ran up an embankment into some bushes and promptly returned with some old tennis ball that had been laying there -- that he clearly smelled from over 30' away and over moving water There is no way in hell our sense of smell rivals a dog with a nasal cavity larger than a pugs
    • by rew ( 6140 )

      What Feynman realized (see comments above), is that it takes some practice to develop your sense of smell to the level that dogs are capable of. We have been trained to IGNORE most smells.

      I'm a bit over-sensitive to cigarette smoke. I had an intern a long time ago who smoked in the train coming to work. Back then my company was located inside my home. So one day I say: I smell him coming... I look out of the window... nobody there. Huh? I was wrong? So I look again, and there he is, turning into the street!

  • "One scientific analysis is arguing that the human sense of smell has not only been underestimated over the years, but that it may rival that of dogs and rodents"

    Utter bullshit.

    If this was true they'd be using humans to sniff out drugs and bombs instead of dogs.

  • I'll just go ahead and ship out this paper with a catchy headline and use the buzz for my next grant application.
  • If the human sense of smell were as sophisticated as Dr. McGann believes, then we would never be in doubt about who "dealt it".

  • Dry dogs smell OK to me, but wet dogs definitely smell worse than wet humans.

  • http://www.nature.com/news/hum... [nature.com]

    A human nose has around 400 types of scent receptors. When the smell of coffee wafts through a room, for example, specific receptors in the nose detect molecular components of the odour, eliciting a series of neural responses that draw oneâ(TM)s attention to the coffee pot. But many details of that sequence are still unknown.

    âoeThe relationship between the number of odorants that we can discriminate and the number of receptors that we have is unclear,â says No

  • The problem with humans and scent is that we have no standards to describe what we smell. Compared to sight, for instance, where children learn the names of popular colors. Consider that the ancient Greeks had only a handful of colors available, for the simple reason that there were no names for the rest of the spectrum. Our dependence on language means that a thing without a name does not exist.

    If children were given standardized samples of each scent they are likely to encounter, along with a name for eac

  • Simple field test. Take a large cloth object used by a person. Person walks to a point, unknown to anyone, about a mile away. Tear the cloth in half, approximately. Give one to a human, let the other be sniffed by a blood hound. Wait to see which one finds the human first, using only the cloth sample. The House will favor the dog.

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