So you think your dog is detecting the odour of mobile phones …

Discovering which chemicals might be involved in the manufacture of mobile phones can be a surprisingly difficult task. According to Compound Interest (2014), “there’s actually remarkably little easily accessible information out there that details the specific compounds used” and even less information regarding any associated odours.

That said, there seems little doubt that mobile phones “smell” – our dogs can find them – but what odour, or odours, are they actually latching on to? What produces the odour that is significant to our dogs? Possibilities include chemicals associated with the phone’s memory chip, touchscreen and rechargeable lithium ion battery and probably a lot else besides.


Memory Chip

Triphenylphosphine oxide – a flame retardant used to protect the memory chips in electronic devices including memory sticks, hard drives, SD cards and mobile phones.

Touchscreen

Lithium Niobate used in surface acoustic wave (SAW) devices. These convert electric signals to acoustic waves.

Lithium Ion Battery

Dimethyl Carbonate – produces an alcohol-like odour.

Diethyl Carbonate – has a nail-polish-like odour.

Lithium Niobate – used in electrodes of the lithium ion battery.


But how do we know whether our dogs are using any of these chemicals to find mobile phones?

A few months ago, one of my client’s reported that her dog, without any specific training, was able to locate hidden memory sticks. The client had discovered this ‘natural talent’ a few weeks previously when she’d asked her dog to find another, already trained, odour source. Instead, her dog found a memory stick that, earlier in the day, had been hidden for another dog!

Abel locating a mobile phone – But what odour, or odours, are significant to him?

So, was this evidence that her dog was searching for memory stick odour – perhaps one, or more, of the chemicals listed previously – or was there something else going on?

Given that her dog had received no previous Scent Detecting training with memory sticks – there had been no familiarisation process – and that memory stick odour is unlikely to be an Unconditioned Stimulus (UCS) for any dog (as far as I’m aware, no dog is naturally attracted to memory stick odour), it seems highly unlikely that her dog was locating memory sticks because of their very specific, chemical, profile and associated odour.

If you’d like to know a little bit more about the familiarisation process and unconditioned stimuli, take a trip over to one of my previous Blog posts, Smoothing out the Lumpy Bits; Why it might be wise to teach the indication before the search and all that back chaining stuff.

So, what was going on?


The simplest explanation is usually the correct one

During the 12th Century, a Franciscan friar – William of Ockham – argued that “the simplest answer – that is, the answer that requires the fewest assumptions – is generally the correct one” (Salter, ?date). “Ockham’s Razor”, as it has become known, or the “Law of Parsimony”, is the view that “of any given set of explanations for an event occurring, the simplest one is most likely the correct one … [it] is a vital tool in rigorous thought. By reducing the number of unsupported assumptions in an explanation, you reduce the likelihood of being wrong” (Salter, ?date).

So, rather than my client’s dog demonstrating some sort of ‘natural’, or ‘super-natural’, Scent Detecting ability, might there be a simpler, more straightforward, explanation? An explanation that fits better with the current knowledge of odour, olfaction and learning?


Contamination

Rather than being an example of ‘natural talent’ at work, the simplest explanation for this dog’s apparent ability to locate memory sticks (with no previous training) is provided by … contamination. In all likelihood, the memory stick had been contaminated with an odour that the dog had previously been trained to detect alongside human scent and, if they were used, the odour of gloves. Yes, those gloves you’ve been told to wear to avoid contaminating your scent source are a potential contaminant themselves (Learning Center, 2016) … an odour that your dog learns to detect! 

As Gadbois (2016) has pointed out, our dogs olfactory abilities are so good that no amount of cleaning or careful handling of the scent source or use of gloves will reduce contamination sufficiently for our dogs not to detect it. So, throw away your gloves and tweezers and work with contamination rather than against it! 


Mobile phone odour vs A N Other odour

In addition to some of the possible chemical sources of mobile phone odour (as listed previously), the overall “smell” of a phone is likely to comprise of a number of additional odours – plastics from the casing and human scent from handling the device. With the possible exception of a mobile phone straight from the factory, human scent is very much part of the mobile phone odour picture. It may be a contaminant but it’s also part of the mobile phone cocktail of odours.  

So, here are your first two, of many, potential difficulties. Is your mobile phone Scent Detecting dog using human scent or plastic odour to detect the phone rather than any of the previously listed chemicals? If so, just as my client didn’t have a memory stick Scent Detecting dog, you don’t have a mobile phone Scent Detecting dog.  


Be Systematic – Rule things out!

After familiarising my dogs to the odour of mobile phones – I have a huge collection of old, well-used, phones that I use for this purpose – I then begin to make sure that they’re searching for the cocktail that is the mobile phone odour as opposed to human scent, or plastics, more specifically.

Human Scent

As well as hiding mobile phones, I hide other, similar sized, items that I, and other people, have handled thoroughly. What I want to see is my dog either checking these items out, or ignoring them, before moving on to locate and indicate on the mobile phone – the target odour.

Rather than relying on a change of behaviour (COB) to tell me when my dog has located the scent source, I train a rock-solid passive indication, with duration. This gives me the confidence to let my dog check things out, dismiss things and move on to the correct location before letting me know that they know they’ve found the correct scent source – the mobile phone. My dog has shown me that he’s differentiated between human odour (more generally) – mine and other peoples – and human odour (more specifically) – mine and other peoples – associated with the mobile phone. 

If you’d like to know more about the power of the passive indication, follow this link to one of my previous Blog posts – The Indication. It’s not an optional extra!

Plastics

If you take a look at your mobile phone you’ll notice just how much plastic is used in its construction. Again, in order to confirm that my dog is using the whole cocktail of mobile phone odour to find its location rather than focusing on one odour in particular – plastic – I hide a variety of other, similar sized, plastic items – Spectacles. Plugs. Spectacle cases. Pencil cases. Backs off mobile phones – alongside the mobile phone. I want my dog to demonstrate to me that he can differentiate between plastic items (more generally) and plastic items (more specifically) that are part of the mobile phone odour cocktail.

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L differentiating between a variety of plastics during the early stages of her mobile phone training

Interestingly, last week, BB demonstrated very clearly that he was searching for mobile phone odour as opposed to any other associated odours. The mobile phone had been thrown into a wooded area and, as it landed, part of its plastic casing fell off and came to rest a few feet away from the remaining phone and its contents. BB located the area, checked out the separated piece of plastic casing before dismissing it and moving on to indicate, correctly, on the main part of the phone. Embrace these moments of happenstance


Elemental vs Configural Odour Cues

As Thomas-Danguin et al (2014) point out, “smelling monomolecular odors hardly ever occurs in everyday life, and the daily functioning of the sense of smell relies primarily on the processing of  complex mixtures of volatiles that are present in the environment”. The mobile phone is just one example of a scent source that is comprised of a complex mix of odours.

Some Scent Detecting trainers attempt to address this issue by taking an elemental approach. That is, they identify each odour molecule within a mixture of odours and train their Scent Detecting dog on each of these separate odours. According to an article by Chammah (2016), this is the approach taken by the California Department of Corrections and Rehabilitation when training their mobile phone detecting dogs. They work on each element of the phone – its battery, its SIM card – before training on the whole phone. 

But here’s a question for you. Take a look at this picture …

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What do you smell?

Do you smell roast chicken (A) or broccoli (B) or beans (C) or cauliflower cheese (D) or the whole roast dinner (U)? 

Interestingly, but not surprisingly perhaps, “an odor mixture can carry, beside the elements, another stimulus that is unique to the combination of those elements … usually noted U (unique cue)” (Thomas-Danguin et al, 2014). This mixed odour – U – “can stimulate cortical neurons that are not stimulated by their individual component odorants. This complex combinatorial coding system is consistent with the fact that often a mixture of odorants gives rise to novel perceptual qualities that are not present in each component” (Thomas-Danguin et al, 2014).

And this is why I train my dogs on the whole mobile phone rather than dissecting it into individual olfactory parts. I want my dogs to find mobile phones rather than mobile phone batteries or SIM cards or circuit boards or touch screens. If I want my dogs to find these individual parts, I’ll train them to find these individual parts – a completely separate exercise. As Hall et al (2018) state, “mixtures tend to be perceived configurally, such that the mixture produces a unique percept distinct from the constituent elements, and this may vary depending on the chemical similarities of the components in the mixture”.

Interestingly (and importantly), in a study by Lazarowski et al (2014), “most dogs trained with pure PC [potassium chlorate] did not correctly signal the presence of one or more PC-based explosive mixtures, despite having demonstrated the ability to reliably detect a trained amount of pure PC”. According to Lazarowski et al (2014), possible explanations for a dog’s inability to detect a previously trained substance when presented to him in a mixture include the way in which two or more chemicals might interact with one another making them unrecognisable to the dog. This is referred to as mixture suppression.

In contrast, the ability of a dog to successfully identify individual components in a complex mix is referred to as figure-background segregation (Hall et al, 2018). If, for example, I only wanted my dogs to detect a specific component of a mobile phone or other electronic device – the memory chip – then I would start by familiarising my dogs to that odour alone. During later training I would secrete the memory chips with other substrates – the whole phone, perhaps, or other materials – and continue with figure-background segregation training. This will ensure that my dogs can detect memory chips in a variety of environments and under a number of different conditions. I’m training them to detect memory chips within a roast chicken dinner! This is generalisation in action.


Odour Categorisation

Another generalisation issue in scent detecting involves the concept of categorisation. According to Wright et al (2017), “categorisation is the ability to treat comparable but non-identical stimuli as equivalent by responding to them according to the category to which they belong. Thus, the ability to identify a novel stimulus as a member of a known category allows the organism to respond to it in an appropriate way”

For example, in Cablk et als (2008) study, dogs were able to detect tortoises of all sizes, age and sex, not only those that they’d encountered during training. And this is where my very large collection of old mobile phones comes into its own – different makes, models, styles, sizes, previous owners and colours. My dogs are able to generalise and categorise. Their initial training is conducted using a variety of mobile phones and then, during subsequent searches, they’re able to successfully detect mobile phones they’ve never encountered before. 

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A very small part of my well-used mobile phone collection

In contrast, our dogs are also able to discriminate between “individuals” within a target class. If you really wanted to, it is feasible to train your dog to only detect a certain type of phone. According to Pinc et al (2011), specially trained German Shepherds were able to distinguish the individual scents of identical twins who lived in the same environment and ate the same food! 

Decide what it is you want your dog to detect – an individual within a target class or a target class more generally – a certain type of mobile phone or all mobile phones. Train your dog according to this decision. For instance, if you want your dog to detect a specific type of mobile phone then reward successful detection of that specific type of phone amongst other mobile phones.

You might just be surprised by what your dog can achieve!


Different Search Environments

Training your dog in different environments would seem to be a given. In terms of generalisation, it’s something that we’re always advised to do – from a straightforward Sit or Down to, arguably,  some more complex Scent Detecting challenges. But with Scent Detecting it’s far more than simply a question of whether or not your dog can perform in different types of environment.

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Is the mobile phone acting as a big red flag in this type of environment?

Placing a mobile phone in an outdoor area is likely to act as an attractant to your dog – a big red flag in the environment drawing your dog towards it. I’ve seen many a novice mobile phone detecting dog being trained in outdoor environments. They appear highly successful. They seem (like my client’s dog) to possess some sort of ‘natural talent’. As Ockham would point out, the more likely explanation for their apparent success is that they’re attracted to the unusual in an environment. A mobile phone in woodland is unusual – but so is a rubber duck or pair of spectacles. Your dog may not be detecting what you think he’s detecting!

Environmental factors need to be considered when training your mobile phone detecting dog and that means … start your training indoors.


and in conclusion …

Short and sweet … train systematically! It’s highly unlikely that your dog has any natural mobile phone detecting talents but he does have a super-natural ability to learn. Don’t waste it.


Final Note

As with all of my blogs, I include a reference list. This allows you to investigate the topic a little further, check out the sources of my information and decide for yourself whether my interpretations of the literature represent an accurate reflection of the author’s work. Happy reading.


© Lesley McAllister – Scent : Detect : Find Ltd 2020

www.scentdetectfind.co.uk

References / Further Reading

  1. Cablk ME, Sagebrel JC, Heaton JS and Valentin C (2008) Olfaction-based Detection Distance: A Quantitative Analysis of How Far Away Dogs Recognize Tortoise Odor and Follow It to Source. Sensors. 8. 2208-2222
  2. Chammah M (2016) The Amazing iPhone-Sniffing Prison Dogs. Who knew cell phones had a smell? https://www.themarshallproject.org/2016/06/07/the-amazing-iphone-sniffing-prison-dogs Accessed: 25.08.2020
  3. Compound Interest (2014) The Chemical Elements of a Smartphone. https://www.compoundchem.com/2014/02/19/the-chemical-elements-of-a-smartphone/. Accessed: 20.8.2020
  4. Gadbois S (2016) Modern Dog Training and Science: Are We Doing it Right? Common Misconceptions and Pitfalls. The Science of Sniffer Dogs. Oxford: Two day Conference
  5. Hall NJ and Wynne CDL (2018) Odor mixture training enhances dogs’ olfactory detection of Home-Made Explosive precursors. Heliyon 4. 4. 12. December
  6. Lazarowski L and Dorman DC (2014) Explosives detection by military working dogs: olfactory generalization from components to mixtures. Applied Animal Behaviour Science. 151. 84-93
  7. Learning Centre Valutek Blog (2016) Odor and Color Determine the Quality of Your Cleanroom Gloves. https://blog.valutek.com/home/odor-color-determine-the-quality-of-your-cleanroom-gloves# Accessed: 27.8.2020
  8. Pinc L, Bartos L, Reslova A, Kotrba R (2011) Dogs Discriminate Identical Twins. PLoS ONE. 6(6)
  9. Salter M (? date) Examples of Occam’s Razor. https://examples.yourdictionary.com/examples-of-occam-s-razor.html Accessed: 24.8.2020
  10. Thomas-Danguin T, Sinding C, Romagny S, Mountassir FE, Atanasova B, Le Berre E, Le Bon AM, Coureaud G (2014) The perception of odor objects in everyday life: a review on the processing of odor mixtures. Frontiers in Psychology. June. 5. 504
  11. Wright HF, Wilkinson A, Croxton RS, Graham DK, Harding RC, Hodkinson HL, Keep B, Cracknell NR, Zulch HE (2017) Animals can assign novel odours to a known category. Scientific Reports. 21 August. 1-6

The Indication. It’s not an optional extra!

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Poppy clearly indicating the location of her target scent inside this person’s trouser pocket.

What is an Indication?

The indication or alert is the means by which your dog is able to communicate to you that he’s found the location of his target scent source. It’s a behaviour that, after training, your dog will perform “immediately and unprompted” (Cablk et al, 2006) and is usually categorised as being either passive or (pro)-active in nature. In large part this classification is dependent on the degree to which the indication behaviour involves contact, or direct interaction with, the scent source.

I tend to view passive indications as those where the dog makes minimal or no contact with the scent source. For example, your dog might sit or lie down beside the scent source or place his nose on it or simply stare at it. In contrast, the pro-active indication involves far more direct engagement with the scent source and may include behaviours such as scratching, grabbing, biting and retrieving (Hurt et al, 2009).

Barking is another very commonly used indication. As this behaviour doesn’t involve any direct contact with the scent source, it would seem to be just another type of  passive indication, however, as Hurt et al (2009) point out, as a fundamentally frustrative behaviour that “can accelerate into other frustration behaviors” it is probably better described as a pro-active indication. In explaining their position, Hurt et al (2009) cited the case of search dogs on the Island of Guam who were trained to detect brown tree snakes and indicate their location by barking. Unfortunately, before very long, this behaviour transformed into pawing and biting and, for the safety of the dogs and the welfare of the snakes, the dogs had to be re-trained.


Does my Scent Detecting dog need an indication?

My short answer to this question is YES and here’s why …

Successful Scent Detecting requires your dog to search for, and locate, his target scent source. Without an indication (either passive or pro-active), you’ll have no means of knowing – for sure – that he’s found it. As Scent Detecting is primarily all about finding, it makes little sense to overlook training the one unambiguous way that your dog has to tell you that he has done just that … his indication.


Why spend time training an indication when I can just watch for a COB?

Recently I’ve noticed a growing trend toward relying on a dogs change of behaviour (COB) to help the handler recognise that their dog has located the scent source. Typical changes in behaviour might include slowing down, speeding up, heightened interest in a particular area of a room, walking on tip-toes with head held high … the list of possibilities is almost endless. Each of these behaviours may help you narrow down the location of the target scent source but may also act to totally mislead you.

As an example of just how poor a COB can be as a means of helping you decide that your dog has located the target scent source, take a little look at this video of Dream working amongst farm machinery.

 

At 23 seconds Dream starts to show a heightened interest along the wall of the tractor shed. This extra interest, or COB – standing on tip-toes, head in the air, staying close to the wall, carefully investigating certain areas – continues until approximately 58 seconds into the video when she then moves on to investigate other parts of the building.

I think it perfectly reasonable to suggest that many handlers, seeing their dog showing this level of interest in a particular area, would be sorely tempted to keep their dog working there until something is ‘found’. That something being a false indication.

Put simply;

The dog’s COB → Increased interest in the area by the handler → Increasing interest in the area by the dog → Further interest in the area by the handler → Increasing psychological pressure on dog to ‘find’ something → False (positive) indication by the dog!

This is just one example of  the ‘Clever Hans Phenomenon’ or ‘Clever Hans Effect’ at work – “where a person or animal can be influenced by subtle and unintentional cueing on the part of a questioner” (Jackson, 2005). If you’d like to know more about how the Clever Hans phenomenon can impact your scent detecting, just follow this link to False Indications, Clever Hans and You

At “Scent : Detect : Find” dogs are trained to search independently, following scent plumes and filaments back to source without undue interference from their human partners. This “hands off” approach to scent detecting goes a long way toward mitigating the Clever Hans Phenomenon. In addition, all dogs are trained an indication behaviour that is totally reliable and unambiguous …. so much so that it is easily recognisable, not only to the handler but, to anyone else who might be looking on.

If you review the video again, you’ll notice that throughout her search Dream’s handler remains out of shot. At all times, Nicky gives Dream the necessary space to work independently. Even when Dream shows heightened interest along the wall of the tractor shed (23 secs – 58 secs), Nicky stays clear of the area and waits for Dream to persuade her, by way of her indication, that her target scent source is there … or, as in this particular search … in a completely different area!

And this is why your dog’s indication is not an optional extra. Having a well trained indication allows Nicky to simply watch her dog until that indication comes.

… Nose Touch. Stillness. Duration.


So, what type of Indication is best – Passive or Pro-Active?

I favour the passive indication and train my own, and other handlers, dogs to place their nose as close to the target scent source as possible and hold it there for a minimum of 5 seconds or until their handler asks them to move away.

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Chewee accurately indicating the location of his target scent; a tiny sticky dot.

This type of indication fits well with your dog’s natural olfactory behaviour. Watch your dog when he’s pottering around the garden. What does he do when he catches an interesting odour? He gets his nose as close to it as possible and, more often than not, will stay fixed to it for a lengthy period of time.

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The Passive “nose touch” Indication; a very natural olfactory behaviour

If the scent source is inaccessible to your dog’s nose, for example, placed high up on a wall, or submerged under-water, then this nose touch is transformed easily and quickly into a sustained nose point.

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Bob using his nose to point to his target scent.

 

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Fynn pointing to his submerged target scent.

My reasons for selecting the passive indication and, more particularly, the

nose touch → nose point (if inaccessible)

include;

Safety – Passive indications help minimise any direct engagement with the target scent source. This can be important where either the target scent itself, or its location, may pose a danger to your dog.

For example, tobacco products such as cigarette and cigar butts, nicotine patches and gum and e-cigarette fluid are all harmful to our dogs (Novotny et al, 2011).

Whilst the target scent may be safe for your dog, its location may not be. Sadly, every year there are a number of reported dog fatalities from Acute Water Intoxication following a period of time playing in water (Toll et al, 1999). Typically, these dogs have been repeatedly diving into water to retrieve items thrown in for them whilst, at the same time, ingesting excessive volumes of water (Becker, 2013). Although the actual prevalence of this condition is difficult to confirm – Becker (2013) believing it to be a relatively rare occurrence – retrieving from water should be an activity that you monitor closely and / or consider restricting.

If your dog has a passive indication, all of these potential dangers are markedly reduced.

Precise and unambiguous – There is no mistaking the precise location of the target scent when your dog’s nose is either touching or pointing toward it. Adding duration to the indication adds even more certainty … your dog isn’t simply having a passing investigatory sniff!

Other passive indications such as a sit or a down cannot match this degree of accuracy particularly in situations where your dog is searching for tiny amounts of target scent, so tiny that you would be hard pressed to see it yourself.

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Brook using her nose to indicate on an invisible target scent

Can be used in all situations – No matter where the target scent is located – submerged under water, high up on a piece of furniture, buried underground, in an easily accessible position – it will be possible for your dog to either touch his nose to it or point toward its position.

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Abel using his nose touch to indicate “buried treasure”!

Preserves the integrity of the scent source – A nose touch, or point, minimises any possible damage to the target scent source. This is unlikely to be the case with a Pro-active indication.

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Luytje pointing out a bundle of cash whilst leaving it completely intact!

Requires no further training or re-training in changed circumstances – Starting off your Scent Detecting training with a pro-active indication may seem like a good idea at the time … until you decide to introduce a new target odour. It may be potentially dangerous to you or your dog or very valuable. Ooops … now may be the time to start afresh with your training, this time with a passive indication.


But a Passive Indication is difficult and time-consuming to train, isn’t it?

Well, that all depends on your point of view …

It certainly requires careful, detailed and thorough training to ensure reliability. Training can take anything from just a few hours or, in a limited number of cases (and for some very specific reasons), a few months to complete and this should all happen BEFORE searching “proper” begins.

Without this careful, early, training you are likely to encounter indication problems further down the line. Far simpler to train a reliable passive indication in the first place than have to add in further, often complex, remedial training at some later point in time including “Show me” or “Where is it?” cues.

The “Show me” or “Where is it?” cue is used, predominantly, within competition scent work circles where TIME means POINTS means PLACES! For very obvious reasons, an indication with lengthy duration is rarely trained and, as a consequence, any indication that there is may be missed by the handler. The “Show me” cue is a way of asking the dog to return to the location of the target scent and indicate again. I’m afraid I’m not a great fan of this sticking plaster approach to training. Far better I’d say to train the indication behaviour thoroughly in the first place than add in this extra layer of training complexity.

And then there’s the thorny issue of being “just a pet dog owner”. According to this viewpoint, pet dog owners are rarely interested in training a reliable passive indication. … It takes time … It delays their dog from starting to search until the indication training is complete … They aren’t bothered about an indication … They don’t have the training skills … and so on. Certainly this has never been my experience. The vast majority of my clients are “just pet dog owners” with almost 60 of them having trained reliable passive indications and another 50 or more well on their way.

If you are “just a pet dog owner” … keep this in mind … In a study by McCulloch et al (2006), investigating the ability of dogs to detect early- and late-stage lung and breast cancer, it was a mix of pet dogs with only basic puppy training who (in a matter of weeks) were able to accurately identify breath samples from lung and breast cancer patients. Those of you who are “just pet dog owners” can, and do, achieve great things with your dogs.


So … in conclusion …

As Scent Detecting is all about finding, it makes little sense to overlook training the one unambiguous way that your dog has to tell you that he has done just that … his indication.

If you’d like to know how I train a Passive Indication, look out for a future Blog – one of a series of three – Smoothing out the Lumpy Bits; Why it might be wise to teach the indication before the search and all that back chaining stuff 

And  … NO … your dog’s indication should never be a scent detecting optional extra.


Final Note

As with all of my blogs, I include a reference list. This allows you to investigate the topic a little further, check out the sources of my information and decide for yourself whether my interpretations of the literature are an accurate reflection of the author’s original work. Happy reading.


© Lesley McAllister – Scent : Detect : Find Ltd 2018

www.scentdetectfind.co.uk

https://www.facebook.com/scentdetectfind/?ref=bookmarks


References / Further Reading

  1. Becker K (2013) Water Intoxication: Too Much of a Good Thing. https://healthypets.mercola.com/sites/healthypets/archive/2013/10/28/water-intoxification.aspx Accessed 15.12.2018
  2. Cablk ME and Heaton JS (2006) ACCURACY AND RELIABILITY OF DOGS IN SURVEYING FOR DESERT TORTOISE (GOPHERUS AGASSIZII). Ecological Applications. 16(5). 1926-1935
  3. Hurt A and Smith DA (2009). Conservation Dogs. IN: Helton WS (Ed) Canine Ergonomics: The Science of Working Dogs. Taylor and Francis Group: London.
  4. Jackson J (2005) The Clever Hans effect – a horse’s tale. Critical Thinking. http://www.critical-thinking.org.uk/pdf/clever-hans.pdf
  5. McCulloch M, Jezierski T, Broffman M, Hubbard A, Turner K and Janecki T (2006) Diagnostic Accuracy of Canine Scent Detection in Early- and Late-Stage Lung and Breast cancers. Integrative Cancer Therapies. 5(1). 30-39
  6. Novotny TE, Hardin SN, Hovda LR, Novotny DJ, McLean MK, Khan S (2011) Tobacco and cigarette butt consumption in humans and animals. Tobacco Control. 20. 17-20
  7. Toll J, Barr SC, Hickford FH (1999) Acute Water Intoxication in a Dog. Journal of Veterinary Emergency and Critical Care. 9. 1. 19-22.