Olfactory 3-D sense in dogs

Factual Questions
1

OK. Dogs smell well. Cites at hand:
Dogs have large folds of mucous membranes inside their nose containing more than 200 million scent receptors compared to smaller areas of mucous membranes containing about 5 million in humans. Their olfactory bulbs are also about 4 times larger than ours.andIt is estimated that dogs in general have an olfactory sense approximately a hundred thousand to a million times more acute than a human’s. That is, they have a greater acuity. This does not mean they are overwhelmed by smells our noses can detect; rather, it means they can discern a molecular presence when it is in much greater dilution in the carrier, air. Scenthounds as a group can smell one- to ten-million times more acutely than a human, and Bloodhounds, which have the keenest sense of smell of any dogs[citation needed], have noses ten- to one-hundred-million times more sensitive than a human’s.

and God knows how much more processing goes on in the disproportionally large part of their doggie brains devoted to it. [Interestingly, far more research has been done on animal echolocation than animal olfactory location. Something to do with more signal-process folks than molecular-process folks, perhaps.]

Dogs can spot fix the scent geographically in its memory–like when they dig up bones they’ve buried.

[The following are ideal assumptions]

  1. Smell dissipates the further away it is in air. For the sake of argument, assume that there are no air currents or extraneous scents to a group of scents, that, to the dog taken all together that stand for “tree.” [Which I do believe in fact.] By the sequence of more-and-more-dissipated scents, standing in front of a line of trees receding from it, does the dog have a kind of depth-perception–despite the “non-parallax” scent-field of the single-nose dog–via the two non-parallax clues of a) depth of field and b) smaller objects appearing more distant?

  2. Even more cool on 3-D smell: everyone sees dogs’ noses constantly twitching to catch the tiniest scent change (what of course to us is “invisible”). Could this be the equivalent of saccadic motion or, perhaps, with what I do with my one eye, which is bend down to look at a pot, say, then look at it from a different angle while keeping the original view in my head, and then synthesizing the two for a pseudo-parallax view?

2

As a note, while humans can typically differentiate two or sometimes three smells at a time, dogs can distinguish many more individual smells.

While standing in a room, you might smell a flower and maybe the chilli being cooked in the next room, the dog will smell the flower, the chilli in the next room, the garbage in the next room, the spot on the couch where the baby’s diaper was changed, your perfume and the scent of the laundry detergent you used.

As for the rest of your post – I’m confused… what? I don’t think dogs can get a 3D vision from their scent, I think they can simply follow the air currents to the objects in question.

3

I apologize to you and to (hopefully) other people who will join this thread. The OP took over a half an hour to write even to get it into this form, and it’s now 3:10 AM where I live and the dog has even stopped farting he’s so asleep.

So you’re saying that by “following the currents” means they don’t fix them for a micromoment (no more than we do visually in order to see), and then synthesize the sensory data?

4

I believe that the correct analogy would be akin to touch.

Imagine you were in a room and felt a hot air current blow by you… You’d search for it’s origin by feeling out the source of the current, but you cannot actually determine it’s source without tracking it down physically.

Now, smell is a bit more nuanced than that, and dogs can (theoretically) determine a lot more about the origin of a smell than you or I can from an air current, but that doesn’t embue their olfactory senses with any clairavoiant abilities (but how cool would that be, of it did?).

5

To some extent at least dogs probably can locate the direction and distance to an odour. It’s well established that dogs can detect the time since an odour was released, presumably due to oxidation and other reactions with the air.A dog will be able to get at least a rough fix on the distance to an odour source simply by working out how long ago it was released and how far it would diffuse/blow in that time. If there is a breeze then the animal can also work out direction.

How accurate that would be I have no idea, but I would be surprised if they couldn’t get at least a rough fix on many odours.

6

Yes, but that is really how vision works too, except that we are so good at it, and the exploratory movements it involves happen so quickly and automatically, that we are usually not aware of them.

Foveal vision, where we can register fine detail and full color, is only about 2° of visual angle at the center of our visual field, and the ability to detect detail and color falls off rapidly from there towards the edges of the retina. The sense people have of a wide field of view is essentially an illusion generated by the speed with which we move our eyes. Peripheral vision is essentially an alerting system, that tells you when there is something going on (usually involving a movement) somewhere sort-of-over-there. In order to see both what it is and precisely where it is, we move our eyes to bring it into foveal vision, but this is so fast and automatic that we don’t notice we are doing it.

Depth vision is also largely dependent on motions of the head that produce motion parallax. Although the fact that we have two eyes with overlapping fields of view provides some depth vision independently of this, in practice, one eyed people can judge distances almost as well as the two eyed, provided they are able to move their heads. Much the same considerations apply to hearing: although having two ears enables one to get a vague sense of the direction from which a sound is coming, if you want to get an accurate fix on it you have to actually turn your head to find the direction from which it seems loudest, and if you want to get a sense of the distance of the sound source you will probably need to actually walk towards (or away from) it.

Because humans have such excellent vision, and usually depend so heavily on it, sighted people sometimes get the idea that their sense of the spatial layout of the environment is dependent upon sight, and that spatial information from the other senses can only be interpreted if it is somehow overlain onto some sort of “visual map” of our surroundings. This is not the case. Even congenitally blind people are capable of attaining an excellent understanding of the layout of their surroundings (and of imagining the layouts of surroundings they are not currently experiencing) just from information that they get from the other senses (coupled with bodily motions, of course). There is nothing “clairvoyant” about it. Congenitally blind people even dream in 3D: that is, they have a sense of where things are in their dream, in what direction and how far away, but, as when they are awake, they do not experience purely visual qualities like color and brightness.

I suppose it is possible that dogs may be inclined to make the equivalent mistake to that often made by sighted humans, and think of spatial layouts as being fundamentally olfactory. (I have no idea how one might test that, however.)

Basically, all the senses depend on the sensor’s motion in order to get more than the most rudimentary information about the spatial layout of the environment. So, in essence, I think the OP has it right, although I am not sure whether there is really that much analogy between the twitches of a dog’s nostrils and eye saccades (they may serve an analogous function, but I think it is quite plausible that they might not). It also seems a bit unlikely (but not inconceivable) that having two nostrils provides dogs with anything analogous to the advantages that we (and dogs too) derive from having two eyes and two ears. It seems to me that to provide any useful degree of spatial resolution from smell the nostrils would have to be much further apart than they are.

7

does a hoarding animal have to remember where its cache is? maybe it just has to find it again or those of others? small mammals might continuously cache food, which allows for loss, and use smell or location types (hollows, holes, crevices) to find caches of theirs or others. maybe dogs don’t have to remember their locations they just need to follow the smell of rotting meat or whatever crap they feel the urge for.

8

I’ve read – somewhere – that dogs also sense odors in layers. Where we’d sniff a pizza and register “mmmm, pizza!” the dog would smell top layer, sausage, mmm, cheese under that, yum, tomato under that, bread all around and underneath, and so on. So when Fido’s sniffing that shrub for 5 minutes, he’s sensing who was just there 5 minutes ago, an hour ago, yesterday, and so on. And for each layer, he’s sensing species, sex, etc. and putting together a series of events that happened at that shrub.

9

[quote=“Leo_Bloom, post:1, topic:531827”]

[The following are ideal assumptions]

  1. Smell dissipates the further away it is in air. For the sake of argument, assume that there are no air currents or extraneous scents to a group of scents, that, to the dog taken all together that stand for “tree.” [Which I do believe in fact.] By the sequence of more-and-more-dissipated scents, standing in front of a line of trees receding from it, does the dog have a kind of depth-perception–despite the “non-parallax” scent-field of the single-nose dog–via the two non-parallax clues of a) depth of field and b) smaller objects appearing more distant?

IGNORE the following in my OP, consider it null and void:

[COLOR=Silver]2. Even more cool on 3-D smell: everyone sees dogs’ noses constantly twitching to catch the tiniest scent change (what of course to us is “invisible”). Could this be the equivalent of saccadic motion or, perhaps, with what I do with my one eye, which is bend down to look at a pot, say, then look at it from a different angle while keeping the original view in my head, and then synthesizing the two for a pseudo-parallax view?[/COLOR]

That paragraph was/is the basis of a ridiculously half-baked thought (you can take the boy out of the marijuana smoke, but you can’t take the smoke out of the boy).

It is not as strongly interesting to me as question 1), which is in a general way devoted to olfactory “cognition” at a spot in 3-D space: if a dog can locate a smell in the kitchen, and one higher up and more recent [+z] [+y] and closer in the bedroom, he has constructed a 3-D place. [Actually a slice of a 4-D construction.]

My example, which could have been written better, was to focus on a line of trees, merely to examine if a 2-D mental map could be construed while adding a time factor of scent dissipation, and with those clues might there be a “depth of field” effect (which is one clue to 3-D perception in the absence of parallax) via olfaction, and/or would a "smaller “size” [==more dissipated] be sensed, and could that information be “depth perception” as another clue to “3-D olfaction” w/o parallax.

I’ve thought about this for years.

10

I’m not sure I understand exactly what you are asking, but I’ve long been interested in dogs’ senses and perceptions. My understanding is that in tracking they are able to smell “time”, by discerning which of only a few footprints are more recent. And when hunting - for game or a misplaced ball - they circle, processing the increase and decrease in the strength of odors. So that certainly suggests some spatial element to their smelling, doesn’t it?

Also, the range of things they can smell is so huge compared to us. Combined with the fact that they rely most heavily upon scent, as opposed to our reliance on sight, it really makes it difficult to try to get an idea of how dogs really perceive the world.