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Human Sense of Smell Underestimated
Posted by
kdawson
on Tue Dec 19, 2006 01:31 PM
from the we-got-something-of-a-hounddog dept.
from the we-got-something-of-a-hounddog dept.
Benjamin Long writes to note a study, by a team of neuroscientists and engineers, that demonstrated that humans can follow a scent trail — an ability that most had assumed only animals possessed. Furthermore, the study demonstrated for the first time that humans make use of differential information from the two nostrils. The researchers blindfolded college students who crawled through grass to sniff out a chocolate-scented trail. Here is the abstract of the paper in Nature Neuroscience. From the article: "The humans, however, still sniffed much more slowly than dogs, which may partially account for canines' greater efficiency at scent tracking. [A commentator] says that despite their relatively sluggish speed, the fact that subjects improved with training is noteworthy. 'I think that shows the effect of our distinctively different behavior in actually using this sense,' he says. 'The dog [has] been doing this its whole life, and humans [were] just asked to plunge in the first time they've ever done it.'"
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Student Dignity (Score:5, Funny)
Re:Student Dignity (Score:4, Funny)
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Re: (Score:3, Funny)
I hope it went down like that with these kids too.
Re:Student Dignity (Score:5, Informative)
I hope it went down like that with these kids too.
Most police dogs are trained to think of work as a 'game' and as such they only respond to the games commands. "Lets go to work" is the police-dog equivilant to telling your dog "Lets go play" and everything after that is a 'game' to them.
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Re:Student Dignity (Score:5, Interesting)
before i settled on computer science i took a couple of pysch classes. We were required to participate in a couple of experiments each semester so that's probably why they did it.
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Re:Student Dignity (Score:5, Funny)
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Re:Student Dignity (Score:4, Funny)
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Re:Student Dignity (Score:5, Insightful)
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We all volunteered (Score:4, Insightful)
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Re:Student Dignity (Score:4, Funny)
I'm not proud of it, but I've dated girls that'd crawl through grass on the scent of chocolate.
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Re:Student Dignity (Score:5, Funny)
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Re:Student Dignity (Score:4, Funny)
Oh, did I say dated? To be accurate, I followed them.
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Worst. Smell. Ever. (Score:4, Funny)
Re: (Score:3, Insightful)
Re:Worst. Smell. Ever. (Score:5, Funny)
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No surprises (Score:5, Funny)
Most women can follow a chocolate scented trail, oddly enough the scent trail left by diamonds and currency works just as well. On the flip side most men are able to scent track women so I guess there's balance in nature.
Agree no surprises. Richard Feynman documented it (Score:5, Interesting)
Many people who suspect their spouses of affairs also observe this ability too (knowing in which rooms a guest's been in).
This shouldn't be a surprise to anyone; and it's pretty sad that the obvious gets passed as new, novel research.
Parent
Duh? (Score:5, Insightful)
that demonstrated that humans can follow a scent trail -- an ability that most had assumed only animals possessed.
Err, I recently smelled something burning. I walked through my house using my nose to follow the scent trail, and locate the single light bulb in the chandelier that had a tiny piece of plastic stuck to it that was burning (from a Christmas decoration).
How do these researchers think I performed this amazing feat? Got out my hound dog and had him sniff around?
Re:Duh? (Score:4, Informative)
As I understand it, the prevailing idea was that you had to walk around or move your head to identify the smoke gradient, whereas these new results suggest that you can get directional information just from nostril separation, the way you determine the direction of sounds.
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Re:Duh? (Score:4, Informative)
That's the point -- the question is whether you can identify the direction without following it! (Which, apparently is also possible.)
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Re:Duh? (Score:5, Interesting)
Most people underestimate their sense of hearing as well. Have you ever seen any of those blind people who can use echolocation to scan an area? Pretty impressive. When I first saw a video of it, I decided to experiment around. I spun around in my (then apartment) to disorient myself, with the intent of "clicking" to orient myself. However, I found something odd: I couldn't disorient myself. There was a faint electrical hum in one corner of a room on the opposite side, and that was enough that my mind automatically reoriented me, even though that sound was undoubtedly bounding off of all sorts of surfaces to get to me. Our sense of hearing provides an excellent direction-finding ability, so the only extra components for echolocation is the ability to A) get a good echo, and B) to be able to handle more complex echo returns.
So, I went online to see what experiments were out there. Apparently, they've done experiments in which humans are blindfolded and told to walk as close to an object as possible without running into it. They vary its distance with each run. At first, people either run into it or are way off. However, with successive runs, they become quite good at avoiding collision, ending up right next to the object. However, if you muffle their footsteps and plug their ears, they lose their ability to do this. The echoes from their footsteps are enough for them to find the object.
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Re:Duh? (Score:5, Interesting)
At first I thought "OK, what the hell kind of bogus ninja crap is this?" And at first there were many cheeks getting tapped. But before too long, most of us found that we could in fact block the punches. Not fast ones (I moved away shortly after this so I don't know what the others achieved in the end), but it was still pretty weird. Even in a room full of rustling gis, you would still be able to get enough audio cues (and at first, tactile ones from the touching knees) to tell more or less where the hit was coming from.
It was pretty cool. I'd love to know how far that could be taken.
Torben
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Re:Duh? (Score:5, Funny)
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Re: (Score:3, Interesting)
you could have used your eyes to look for the burning plastic.
I could have, but didn't. And that's a bit impractical looking at every square inch of the room to identify something small and burning (if you can even see what's burning).
And since you knew that the light bulbs were on (and hot), you could have used your powers of deduction to guess that the chandelier was a likely place to look.
Actually, I was predisposed to look for electrical shorts to find the burning source. It was only by follow
On the Internet... (Score:5, Funny)
sense of smell first to develope (Score:3, Interesting)
I, for one, can't even smell my own breath.
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say what's on your mind - online confession and send anon email at my website http://www.sayitt.com/ [sayitt.com]
Re:sense of smell first to develope (Score:5, Funny)
There's an easy experiment to demonstrate that humans have the ability to distinguish smells very finely. The point is, humans (at least the ones I know) don't mind the smell of their own farts, but can't stand the smell of others. This means that humans have the ability to distinguish between their own farts and the farts of everyone else. Now there are three obvious classes of mechanism for this:
(1) Humans can distinguish between their own farts and every else's - ie. they can partition fart smells into self and non-self
OR
(2) Humans can distinguish between everyone's farts.
OR
(3) Various shades in between.
Now consider hypothesis (1). This is pretty preposterous. Chemical sensors in our nose that can only distinguish fart smells into two classes, self and non-self, would be ridiculously specialised. So we're left with (2) or (3).
Now consider (3). To the extent that you can't distinguish self from non-self, there are people's whose farts you can't distinguish from your own. In other words, (3) implies there are other people whose farts you don't mind. This is simply too disgusting to contemplate and no benevolent deity could have created a universe like this.
So we are led to conclusion (2).
Anyway, I think more experiments are needed. I think this is an example of low hanging fruit if someone is seeking an Ig Nobel prize.
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Maradona's nose (Score:3, Funny)
We Smell in Stereo (Score:5, Interesting)
Richard Feynman did a number of smell experiments with his first wife, Arlene. He would leave the room and she would handle bottles and books then he'd return and see if he could determine which ones she'd touched. He was able to find them. It's detailed in Surely Your Joking, Mr. Feynman [gorgorat.com].
There! And I didn't make any smelling cracks about misunderestimating or Uranus or "once you get past the smell it tastes all right".
Re: (Score:3, Interesting)
Dogs have to learn to use their scenting ability too, and the more native
Individuals' scents, subconsciously different (Score:4, Interesting)
I remember reading (somewhere) a scent-related experiment which was suggested for kids. The purpose was to demonstrate that people can differentiate the odors of other individuals even though they don't consciously smell anything at all.
The procedure went something like this:
Distribute a freshly-cleaned T-shirt in a zip-lock bag to all participants. Groups trying this experiment should be small, less than 10 people. Each person should bathe in the evening and wear the T-shirt overnight, placing it back into the zip-lock bag in the morning (no distinctive folding or rolling, just shoved in). When everyone is back together again, the bags are gathered while a non-participant draws numbers from a hat, writing the number on the bag and recording who brought it. The number correspondence is kept secret. Bags are then passed around and participants try to guess who wore each shirt.
The article I was reading said that you should expect "uncanny" accuracy, the difference in scent seeming like a "hunch" or a "feeling" rather than a conscious recognition.
Now the even weirder part. A similar experiment was done where the shirt-wearers were unknown to the sniffers. The people smelling the shirts were given a set of photographs, and asked which one the shirt seemed to belong to. Apparently, they scored correctly by a significant margin.
Now, since I'm busy I'll just leave it up to the reader (and Google, perhaps) to find the sources.
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Easy (Score:4, Funny)
Stereo smell. (Score:5, Insightful)
That comes as a surprise to me - our other stereo sense organs (eyes and ears) are placed just about as far apart on our heads as is structurally possible - but our nostrils are really close together. OK - we don't have a really great sense of smell and we don't rely on it at all - but dogs clearly do - and their nostrils are also very close together.
You'd think we (or at least dogs) would have nostrils mounted just below our ears.
Weird.
Re: (Score:3, Insightful)
Re: (Score:3, Interesting)
I'm curious if the researchers produced CFD models of different types of nose to compare the mechanics of different nose structu
Re:Stereo smell. (Score:5, Interesting)
For our eyes, that's not really true. Our eyes are placed slightly apart, looking forward so that their respective fields of vision overlap each other. Then our brain calculates how far away objects are from us by noticing how much inward each eye has to rotate to hold the object in focus.
Prey animals, like deer and cows for example, have eyes mounted on totally opposite sides of their heads, like our ears. Each of their eyes sees an almost complete separate image. Their total field of vision is almost 300 degrees. Owls are predators par excellance, and have stereoscopic ears set just below their eyes. Their entire face is bowl-shaped like a radar dish.
So, if we evolved solely as prey animals, we probably would have eyes on the sides of our heads, near our ears. If we evolved solely as hunters, we would probably have forward facing ears that we could rotate, like cats or wild dogs. There is some debate, but some anthropologists argue that our forward-facing eyes and stereoscopic vision comes from having to navigate in trees. This is also backed up by the fact that we have 3-color vision, which you need to see ripe fruit, where as hunters like cats and dogs see in black and white. There are vegetarian, tree-dwelling monkeys that have forward-facing eyes, stereoscopic vision, and have 3-color vision*.
It is interesting that smell, if it is truly a stereo sense, would have both nostrils so close together. Maybe that's because light and sound waves don't get mixed up as much as scents on the wind, so each input would be very different. Also, smell seems to be a short-range sense, whereas sight and sound are long-distance senses. I don't mean that prey animals don't smell things far away, but it's not as usefully accurate as long-distance hearing or vision. If you're relying on smell to tell you when things are sneaking up on you, it will probably be too late by the time you really get a good whiff. A sound or a sight really tells you where they are, and which direction you need to run in. My guess would be that the stereoscopy of smell would be useful when you are examining something up close, such as a plant or carcass.
*By 3-color vision, I mean that we have specific receptors cell in our eyes for 3 discrete wavelengths of light -- red, green, and blue. Some birds, for instance, have four.
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Following scent trail? My mom did it! (Score:5, Interesting)
When I was young I used to hate that stuff, especially because my mom would throw blocks of it in the curries without powdering them. One bite of that chunk, and you will curse everyone in sight. So enraged I was, that I once stole her entire stash of asafoitida. I wanted to throw it away in garbage, but I was young and scared and did not dare throw it all away. So I hid it in a trunk in the loft. And, yes as I said in the subject line, my mom sniffed it out and found the stash. So yes, humans can sniff out very aromatic substances. But faint traces like a dogs do [note the significant absence of the apostrophe after the s in dogs] ? I am not so sure.
Not all humans can (Score:5, Interesting)
My first job after graduating from college was working as a computer programmer at a US Air Force base. I worked in the main building for our section of the base and our colonel one day was having a VIP come by to visit him. He walked out to the main area and smelled something burning. Convinced that his canine sense of smell had saved the day and wanting to show off for his visitor, he promptly called the base fire department and demanded that they send a truck out to investigate "the burning wires smoldering within one of the walls". The base fire department dispatched a truck and the firemen investigated and told the colonel that what he smelled was burnt popcorn from the break room and there was nothing smoldering within the walls. The colonel then did the only thing that a military man who has just embarassed himself could do. He promptly banned microwave popcorn.
Re: (Score:3, Interesting)
smell (Score:5, Interesting)
My sense's of taste and smell are so actute now - it's amazing! I can smell people smoking a few cars in front of me - peoples aftershave and perfumes are most times extreme and putrid (I believe it must be animal urine in them)
The weirdest experience was the re-living of memories evoked through smell, that I had long forgotton. Apparently, smell is the sense most connected to memory, I literally feel younger than ever (36yrs old in reality) Now I can smell the deeper complexities within freshly cut grass that I had completely forgotton. Quit that damn cigarette - you really do get your life back (lots more money too)
Much of common life destroys basic senses. (Score:5, Interesting)
One thing I noticed, during bootcamp was that my sense of smell became incredibly accute. While, I'll award the reader with the fact that I was a prior smoker to bootcamp, I will say that non-smokers DEFINATELY noticed the difference as well.
While it's not likely we as a society will retort back to nature in a sense, I will say, the body naturally cleans itself and the only reason a "bum" stinks as bad as he does is in relation to all the non-natural environment surrounding him. Not only that, but we are so used to the man made scents, that natural scents tend to stand out even more.
For example... while some city women will think a man from the country is being a sexist pig who treats women like objects... the fact is, men CAN smell women and from a considerable distance away.
OK. Let me stress this, becuase this is when it hit me like a brick during boot camp. It was almost a "holy shit do I have a Marvel Comic superhero nose?", no I don't and you don't either. But, when at a club, a female can be practically touching you and you might smell her perfume. In the work place, a female sitting in the next cubicle might not make her presence known until she makes sufficient noise to catch your attention....
After five weeks into boot camp, a female division walked past the barracks we were at, and walked up stairs. I would accurately judge the distance to about 50 feet away, and every single guy in the barracks literally smelled the girls. We didn't have to hear them. We didn't have to see them. We could smell them and knew they were there. The scents were distinguishable too, not just a generic feminine hormone release into the air. If two girls were in the next room, the guys three rooms down could smell two different scents.
When I was a kid, females weren't allowed to go hunting, irregardless of what time of month or whatever they washed their bodies with. Until boot camp, I always thought it was a wives tale that women gave off that much odor... but I swear to you. Yes, if I am able to smell a female just as well as see her from 50 feet away... then a deer or buck with much better noses can certainly smell a human female from 100 yards away. A man could probably smell the presence of a female much further than 50 feet away, it's just that's the distance I know for a fact and even at 50 feet, the scent was unbelievably strong. How far away before it becomes a hint? The girl might as well have showered in perfume and stood two inches behind me.
Nowadays, away from the lack of everyday luxuries and eminties, inhalation of cigarette smoke, car exhaust, overwhelming stench of plastics and asphalt... no, I couldn't tell you if a girl with no perfume is sitting five feet over in the next cubicle. It's somewhat sad. But, you are capable of doing it. Most people who go on long hunting trips in the wilderness know what I'm talking about. Without all this crap we deal with, this man made crap, nature gave us some pretty interesting abilities that have been long taken for granted or the use is nolonger really needed.
The scent of the girls is what blew me away the most. So vivid, so strong so unexpected. But, I also realized that a lot of other things that might have been overlooked or not processed certainly was while in boot camp. Such as the bed of flowers outside the barracks... yeah, you can smell those things. In modern day life, much of those scents are still hitting our nose, but if they remain being processed it's either at a subconscious level or outright ignored altogether. Anyway, it doesn't surprise me that a group of college students was able to smell a trail of chocolate in the lawn. Doesn't surprise me one bit.
Re:Much of common life destroys basic senses. (Score:5, Insightful)
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Re:Much of common life destroys basic senses. (Score:5, Informative)
Great apes do not mark their territory with piss or pheromones. Great apes live in groups, so they don't need to smell each other to find each other -- they wake up with each other every morning, and go to sleep next to each other every night. They are all right in front of each other's faces.
Great apes attract and find mates based on vision, not smell. Have you ever seen a female chimp in heat? I have. Her hind end swells up to the size of a human buttocks. Here's [northrup.org] a picture. With baboons, the labia become swollen and cherry-red. It looks like the mother of all veneral diseases [abc.net.au].
This is true for out closest relatives -- gorillas, chimpanzees, orangutans, and bonobos. Sure, guys might be attracted to the scent of a woman, but what really gives you a boner is the sight of sexually mature breasts or a mature female butt with the wide hips. Porn is images, not smells.
When a human female menstruates, she is not leaking 'hormones'. It's not a stream of estrogen. The reason it's so exciting to wild animals is because she is bleeding and shedding endometrium tissue, and the animals are smelling blood.
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Wait a minute. (Score:3, Funny)
Sure... "researchers".
This is one of those weird Japanese game shows!
I was reading a book called (Score:5, Interesting)
Crystal Fire [amazon.com] and they had an interesting anecdote about the beginnings of semi-conductor research. In the late 1930's early 1940s the scientists at Bell labs were experimenting with silicon to see if they could build rectifiers and other electronic components out of it. At the time there really wasn't any theory about how these things might have worked. Some silicon rods showed semi-conductive behavior, some didn't. Finally they found one rod that showed strong semi-conductive behavior. They couldn't figure out what it was that made this rod special until the scientists and machinist who worked on it said that when it was cut or ground it gave off the same smell as one of the old carbide lamps that were used on many automobiles until the late 1920s. One of the chemists realized that what they were smelling was trace amounts of phospine gas, which meant that the rod has phosphorous in it. This was a surprise as the levels of phosphorous in the sample were so small that they didn't show up in a spectrographic analysis, it was the noses of the scientists and machinist that gave them the clue that the proper trace impurities in silicon would enhance the semi-conductive behavior.
Re:hey... (Score:4, Funny)
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Re:My Dog Has No Nose! (Score:4, Funny)
A beautiful girl gets on.
He says "Hey, can I smell your pussy?"
She says "NO!".
He says "Oh, must be your breath."
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Re:A dog is a million times better (Score:5, Informative)
So this may have nothing whatever to do with the sensitivity of our sense of smell and more to do with the shape of our head, neck and the length of our fore-limbs.
We mostly evolved to use our sense of smell for detecting whether food has gone bad or not - and for that, having nostrils right above our mouths is plenty good enough.
Dogs are evolved to track prey and find carrion - they need to be able to sniff and run at the same time.
Dog's noses are very impressive...it's incredible to see the kinds of tricks they can manage. But I wonder where that statement of "a million times more sensitive than humans" comes from - I bet it's something some journalist guessed at 100 years ago that we are all passing on as if it were the definitive answer. This study suggests to me that some simple practicing could narrow that gap considerably.
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Re:A dog is a million times better (Score:5, Funny)
For example, experienced sommeliers and cheesemongers probably have even more fined tuned senses of smell (at least within their areas of expertise) than most pet dogs. Not blood hounds, mind you, but especially sight hounds and working dogs. Being able to identify ten or twelve different aromas and tastes within one glass of wine is a distinct skill, and I doubt many dogs can do it.
At least, I know mine can't. But then, he can be a mean drunk, so maybe that's the real problem.
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Re:Taste == smell (Score:4, Informative)
The "tongue map" is a myth [wikipedia.org], and there is a fifth sensor, "unami" (MSG), and possibly a sixth for fats.
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