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posted by janrinok on Saturday June 08, @02:47AM   Printer-friendly
from the my-dog-has-no-nose.... dept.

Dogs trained to detect scent may be able to identify significantly lower concentrations of odour molecules than has previously been documented:

A study carried out by the University of Helsinki's DogRisk research group, the University of Eastern Finland and Wise Nose – Scent Discrimination Association in Finland investigated the threshold for scent detection in dogs.

The study revealed that dogs can learn to identify concentrations of eucalyptus hydrolate that are clearly below the detection threshold of sophisticated analytical instruments used today. The concentrations were also far below previously reported levels. Dogs' extraordinary sense of smell can be exploited, for example, in search and rescue operations and in medical detection.

The 15 dogs that participated in the study had different training backgrounds. Some dogs had experience of nose work, which is a hobby and competitive dog sport, while some had been trained to identify diseases, mould or pests.

In the study, the dogs were to differentiate samples containing low concentrations of eucalyptus hydrolate from samples containing only water. The focus was on determining the lowest concentration that the dogs could detect for certain. The study included three different tests where the concentrations of the hydrolate were diluted gradually until the dogs could no longer identify the scent. This determined the threshold for their scent detection ability.

"The dogs' scent detection threshold initially varied from 1:10⁴–1:10²³ but narrowed down to 1:10¹⁷–1:10²¹ after a training period. In other words, the dogs needed 1 to 10 molecules per millilitre of water to detect the right sample. For perspective, a single yeast cell contains 42 million molecules," describes the principal investigator of the study, Anna Hielm-Björkman from the University of Helsinki.

Journal Reference: Turunen, S.; Paavilainen, S.; Vepsäläinen, J.; Hielm-Björkman, A. Scent Detection Threshold of Trained Dogs to Eucalyptus Hydrolat. Animals 2024, 14, 1083.

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  • (Score: 3, Insightful) by DrkShadow on Saturday June 08, @03:53AM (3 children)

    by DrkShadow (1404) on Saturday June 08, @03:53AM (#1359774)

    I tried looking that up, but it's more practical to look up water molecules in a milliliter..


    So, they need 10-1000 molecules of eucalyptus per milliliter of water.

    How do enough of those molecules even get from the water into the air to be detected by the dog's nose? They're literally responding to _one_ molecule, which just *happened* to waft to the dog's nose after random-chance evaporation from the water sample.

    The correct answer is: these dogs only need 1 to 3 molecules of a substance in their nose for detection. That seems like *way* better than my eyes function.

    • (Score: 4, Interesting) by krishnoid on Saturday June 08, @04:14AM (1 child)

      by krishnoid (1156) on Saturday June 08, @04:14AM (#1359776)

      Your eyes, maybe, but the threshold for light detection in the human eye is on par []. Makes me wonder what birds are capable of.

      • (Score: 4, Interesting) by DrkShadow on Saturday June 08, @04:43AM

        by DrkShadow (1404) on Saturday June 08, @04:43AM (#1359779)

        Wow, thank you for that link. I had no idea.

        It really changes my perspective a bit - during the day, everywhere you look, there are photons. Every *thing* throws off (or reflects..) enough photons to be seen, in detail, from any direction. It's truly magnificent just how many photons are flying around, all around us. Even in a room lit only by the light of a monitor (I'm very familiar with that..) there are *so many* photons that a great many things are tossing photons in my direction, wherever I may be standing.

        Looking up in the sky, even in the dark of night, you can see the stars and the band of the galaxy. At a surface area with a radius of however-many light years, the stars are producing a *continuous* stream of photons that we can actually detect them with just our eyes. (At least, the ones that we can see.)

        That is amazing to me. Though, this article makes it a little less amazing -- maybe we're only picking up single-digit photons from those sources. :-) Still, for something the diameter of a half-centimeter, at 4-400 light-years radius surface area, that's an _incredible_ number of photons. (either to make it to that small a spot, or produced, leading to so-many photons over the whole surface area)

    • (Score: 3, Interesting) by Beryllium Sphere (r) on Saturday June 08, @04:40PM

      by Beryllium Sphere (r) (5062) on Saturday June 08, @04:40PM (#1359842)

      I did read an estimate that after prolonged dark adaptation a human eye can fire a neuron for a single photon. Certainly the case for high energy photons. Cosmic gamma rays give astronauts little flashes in their eyes.

  • (Score: 3, Interesting) by gnuman on Saturday June 08, @08:10AM (4 children)

    by gnuman (5013) on Saturday June 08, @08:10AM (#1359781)

    In other words, the dogs needed 1 to 10 molecules per millilitre of water to detect the right sample. For perspective, a single yeast cell contains 42 million molecules,

    How did he do that count? Let's assume that the molecules per milliliter is correct.... the problem is that partial pressures are vastly different in actual AIR where the dog does the detection.. So, what you need is actual concentration in the air, not water.

    And secondly, where you don't actually need a degree to argue, the single yeast cell is exactly ONE particle for smelling purposes and counting purposes. You can say, yeast PARTICLES in the air per milliliter. And with ONE yeast, it's ONE particle. Comparing other things is ridicules. Like maybe we could count number of electrons in that eucalyptus hydrolate and write that down? It would make as much sense as his comment.

    Anyway, I will not blame him too much on this because this was mostly done by School of Pharmacy, Faculty of Health Sciences. But then doing these press releases is kind of crappy. Maybe that's thanks to the non-scientific associations with this small study.

    Wise Nose-Finnish Odor Separation Association, 00790 Helsinki, Finland

    Nose Academy Ltd., 70780 Kuopio, Finland

    Like, ok, but these don't exactly scream "hard science"

    However, the diluted target solutions were not measured using the NMR spectroscopy technique, as such low concentrations cannot be detected with this kind of analytical technique (see text of Figure 3). In the future, when studying dogs’ threshold to detect the pure odor of eucalyptol, it would be preferable to utilize a commercial product of 99% of eucalyptol

    They could have tried Time of Flight spectroscopy for that. But yes, using pure products instead of what you get at a store is generally more predictable when it comes to quality ;) Also, measuring the AIR concentration and not the WATER concentration is probably what they wanted to do instead?

    So, I would not trust these numbers further than I can throw the server this was published on.

    • (Score: 1, Interesting) by Anonymous Coward on Saturday June 08, @10:13PM (3 children)

      by Anonymous Coward on Saturday June 08, @10:13PM (#1359881)
      There might also be contaminants that the dogs are detecting that are correlated to the compound to be detected, but which are at higher levels.
      • (Score: 2) by Reziac on Sunday June 09, @02:58AM (2 children)

        by Reziac (2489) on Sunday June 09, @02:58AM (#1359906) Homepage

        And we already know that about 70% of the time, drug detection dogs are responding not to the scent of drugs, but to their handler's expectations.

        Also, "dog noses" are not monolithic. Some are spectacular, some are severely lacking. Watch a scent discrimination exercise; the good nose causally IDs the correct item as it zips past; the poor nose has to work at it.

        Probably the most bizarre exercise of scenting ability... lived in a place that had seen, um, better days. Dogs decided to dig little pits along the fence. What were they going after? individual beer cans from some years previous, under a foot of blown-in dirt.

        And there is no Alkibiades to come back and save us from ourselves.
        • (Score: 0) by Anonymous Coward on Sunday June 09, @06:32AM

          by Anonymous Coward on Sunday June 09, @06:32AM (#1359911)

          It's a bit like those people criticizing homeopathy by claiming that after X dilutions there isn't even one molecule left. At the same time they are rubbishing the "science" they are also assuming perfect lab practices. Half those drongos are probably using the same pipette each time.

        • (Score: 0) by Anonymous Coward on Monday June 10, @10:13AM

          by Anonymous Coward on Monday June 10, @10:13AM (#1360008)
          The thing is many dogs can smell ALL sorts of stuff. From detecting bladder/lung cancer to land mines.

          But how do the humans actually ask the dog to detect a specific chemical compound?

          That's like a blind man trying to ask someone to see whether a photo contains a particular item.

          And both of them don't speak the same language.

          The training is by showing that someone photos with or without the item.

          It works well enough in some cases. But there are many ways it can fail.