False Positive Indications? STOP! You have a Scent Detecting TRAINING problem!

Delphi indicating CORRECTLY on her target scent source!

A false positive indication is one where your dog indicates, or alerts, on something that is NOT her target scent source (Lehnert and Weeks, 2016). To all intents and purposes, it looks as though she’s correctly located the target odour but … she hasn’t! You’ve been misinformed.

At Scent : Detect : Find Ltd, false positive indications are an extremely rare occurrence. If they do happen, they’re easy to identify and quick to remedy. In large part this is because …

a) All dogs are trained to perform a highly reliable, passive indication with duration – a sustained nose touch, or point. This indication is easy to distinguish from any passing investigatory sniff – which the handler can confidently ignore. In contrast, the correct indication is clear and unambiguous and is always generously rewarded.

b) Importantly, all training is broken down – split – into its, tiny, constituent parts rather than being lumped together into one, large, unmanageable whole (Berg, 2018. Zerubavel, 1996). Splitting allows any training difficulties to be addressed immediately, including any false positive indications, before the problem has the chance to escalate further or become entrenched.

If you’d like to know a little more about Splitting and Lumping, simply follow this link 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.

Strangely, false positive indications seem to be an accepted part of Scent Detecting practice – “Just one of those things“. “Nothing to worry about“. “To be expected“. “Par for the course“. “It happens“.

Well, I’m here to tell you otherwise …

False positive indications are not just one of those things.

False positive indications are something to “worry” about.

False positive indications should never be an expected, or usual, part of Scent Detecting training or practice.

False positive indications are a symptom of one, or more, Scent Detecting training problems which need to be addressed rather than accepted!

What are the likely problems with false positive indications?

Well, if you’re “just having a bit of fun” with your dog, perhaps a false positive indication doesn’t matter too much to you. That said, it’s worth asking yourself why “just having a bit of fun” is any less deserving of careful training than any other activity you choose to participate in? Would you only half train a Sit? Are you happy with a Recall that only happens sometimes? Is it OK for your dog to choose her own route around an Agility Course? …

A dog who doesn’t understand what’s required of her, who hasn’t benefitted from careful guidance, who gets rewarded on some occasions but not on others (dependent on her handler’s whimsy on a particular day) … well … that’s NOT a dog who’s having “fun“. It’s far more likely that she’s confused and anxious. If you want to use Scent Detecting as a fun activity for your dog, there are plenty of ways to achieve this including scent trails, scatter feeding, treat searches, hiding toys and using Scent ‘n Snack mats. These type of scent-based activities can provide numerous behavioural benefits for your dog and require little, if any, training – your dog is a natural scavenger and comes pre-programmed to locate food!

If you’d like some more ideas on how to entertain your dog’s nose, look out for one of my next Blog Posts – Scent-Based Nose Games – Just a bit of fun!

In contrast, if you’re the handler of a working dog, or take part in competition style Scent Detecting, then the reliability of your dog is key to your success. Be under no illusion, a dog who gives false positive indications is an unreliable Scent Detecting dog. If you cannot trust her indication you’ll only know if she’s correct if you can see the target scent source yourself or watched where it was hidden at some earlier point in time. When faced with a truly blind search – one where the location of the target scent source is unknown to you – well … I wish you all the luck in the world!

What are the potential causes of false positive indications?

There can be numerous potential causes for false positive indications but, very sadly, the vast majority are handler and training related. The root cause of your problems may be just one, very particular, issue or could be the result of a combination of different issues.

Contamination / Residual Odour

This is probably the number one rationale offered by handlers to “explain” away their dog’s false positive indication – “The area must have been contaminated”. “The scent wasn’t handled correctly”. “My dog’s nose is just so good that she picks up on every little bit of residual odour”. Sound familiar? Well, what if I were to tell you that although a contaminated search area is a real thing – it does happen and it happens all the time – the root cause of your problem is not odour related, it’s training and handler related?

Your dog is what’s referred to as a macrosmat or, ‘keen smeller’. Her olfactory threshold, the level at which she can first start to detect an odour, is reportedly as low as 2 – 3 parts per billion (ppb) and, quite possibly, for some odours, as low as 2 – 3 parts per trillion (ppt) (Helton, 2009). Given this incredible degree of sensitivity to odour, it seems a little surprising that your dog doesn’t give you a false positive indication more often than she does. So, what’s going on?

As an aside, keep in mind that if your dog indicates on any residual odour or contaminated area, she’s actually correct! It isn’t a false positive indication. What she’s doing is indicating on a very low concentration of the target odour … something you may not have wanted or planned … nevertheless, your dog is correct. For clarity, I consider residual odour to be any odour “left behind” by the target odour source when it has been removed from a search area or container. In contrast, contamination occurs when the target odour source leaves a residual odour in an otherwise “clean” area or when the target odour source becomes contaminated itself by another odour. Given the “catch all” nature of the definition of contamination, this is what I’ll be referring to throughout the following discussion.

As Gadbois (2016) has pointed out, your dog’s olfactory abilities are so good that no amount of cleaning, or careful handling of the target scent source, or use of gloves, will reduce contamination sufficiently for her not to be able to detect it. In addition, those gloves that you’ve been advised to wear are a recognised contaminant in themselves (Learning Centre Valutek Blog, 2016). Dogs whose handlers use Nitrile gloves have been found to indicate on anything that the gloves have come into contact with! By now you’re probably starting to appreciate that, to a very large extent, attempting to avoid contamination is a waste of your time. Far better to acknowledge that contamination is a real issue and work with it.

Scent : Detect : Find Ltd adopts a number of different strategies to overcome any so-called false positive indications as a result of odour contamination.

1. Initial training is conducted using a large concentration of target odour

Dogs are rewarded generously for indicating the location of this “large” odour source. Although they are likely to notice contaminated areas in their search environment – dogs may hesitate and investigate areas of the room where the scent source has previously been – importantly, they aren’t rewarded for this behaviour. It doesn’t pay off. In short, they’re learning to ignore any contamination as they discriminate between the different concentrations of odour. Dogs will work with this highly concentrated odour source until they’ve gained considerably more experience. At this point, the odour concentration will be reduced – Diminished or Diluted.

Interestingly, according to Laing et al (2003.), a “change in concentration can actually modify the quality of … [an] … odor“. As Wilson et al (2006) point out, “for many odours, as the concentration increases, the perceived quality of the odour changes“. With this in mind, Goldblatt et al (2009) suggest that Scent Detecting dogs should be “trained and maintained on a range of intensities of [odours] that they may encounter in [their Scent Detecting work]”.

A recent pilot study by DeChant et al (2021), investigating the ability of dogs to both generalise across, and discriminate between, different odour concentrations, has provided further support for Scent : Detect : Find Ltd’s training approach to odour concentration. As described previously, all dogs begin their training with a very high concentration of their target odour and only after some considerable amount of Scent Detecting experience are they then introduced to the same target odour at much lower concentrations. This approach applies to all target odours used.

According to DeChant et al (2021), “dogs can be trained to actively not respond to concentrations of a trained odorant below a desired threshold“. Put simply, your dog can be trained to ignore contaminated search areas. In DeChant et als (2021) study, “false alarms decreased after Concentration Discrimination training. This may result from training dogs not to respond to the low, but detectable concentration odor”. Clearly, on this account, false positive indications cannot be attributed to issues of contamination. There’s a definite need to examine the training protocols in use and pro-actively train using varying concentrations of odorant.

2. On locating their target odour, all dogs are trained to give an unambiguous passive indication with duration

As already discussed, all dogs at Scent : Detect : Find Ltd begin their training by working with a large concentration of target odour. This is what they learn to indicate, or alert, on. 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. There can be no mistaking the precise location of the target odour source when the dog’s nose is either touching or pointing toward it. Adding duration to the indication adds even more certainty. A passive indication with duration allows the handler to “ignore” any small acknowledgements of contamination within a search area and simply wait for the added commitment – the duration – that comes when the dog is convinced that she’s located the highly concentrated target odour source. The dog is free to check out all areas of possible contamination because the handler can be confident that once investigated, she’ll dismiss these contaminated areas and move on.

Recently, I’ve noticed a growing trend toward relying on a dog’s change of behaviour (COB) to help the handler recognise that their dog has located the target 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. The dog may simply be checking out an area of contamination.

For further discussion of indications, you might like to follow this link to one of my previous Blog Posts – The Indication. It’s not an optional extra.

3. In very specific circumstances, it’s worth taking care to avoid any possible contamination

Although, generally, I don’t worry about contamination, there are a couple of very specific circumstances where target odour handling needs to be a little more thoughtful.

a) Storage – Keep your target odour in the most secure container you can get your hands on. Your dog needs “down-time”. Remember, if you’ve taken the time to familiarise your dog to the target odour it will have become a “motivational magnet” for her. If she can detect the odour she’ll be in “work mode”. Give her a break!

b) Frequently used containers – If you’re likely to use a particular container on repeated occasions, make sure you can identify it – label it in some way – and only use it to hold the target odour. Frequent contact with the target odour source will, over time, result in a heavily contaminated container closely matching the concentration of the target odour source itself.

2. Handler Pressure and the Clever Hans Phenomenon

As Galambos et al (2021) point out, “dogs are unmatched amongst non-human animals regarding their inter-species social skills … thousands of years of domestication [have] enabled them to excel at the reading of and responding to human social-communication signals” … and here lies the problem … our dogs, and their performance, are affected by us!

Two potential Scent Detecting problems arise from this.

1. Our dogs will be aware of our mood and emotions and respond accordingly

As Galambos et al (2021) states, our dogs have a “human-like susceptibility to social influence” and demonstrate a “spectacular level of social sensitivity“. This is likely to be a particular problem within competition-style Scent Detecting circles where handlers can place enormous “pressure” on themselves to do well and gain rosettes. Unintentionally, the handler’s “pressure” is then “transmitted” to their dog.

Scent Detecting videos, available freely on various social media platforms, are well worth checking out. Make your focus of attention the dog and his body language rather than the actual Scent Detecting task itself. Watch for any Calming Signals (Rugaas, 2006) – lip-licking, yawning, turning away from the task, hesitancy, slowing down – and link these behaviours to the handling skills that you observe. Mariti et al (2017) consider these signals as having “a communicative role” – they can help you identify how your dog is feeling. More often than not, this will be a reflection of how you’re feeling! Custance and Mayer (2012) refer to this phenomenon as “emotional contagion“.

And the consequences for your dog’s Scent Detecting performance? If she’s becoming uncomfortable in the search area because of the way you’re feeling and the demands you may be placing on her, the quickest way to end the experience is … you guessed it … to indicate. Unfortunately, more often than not, this will be a false positive indication. Again, without a doubt, this is reflective of a training issue. Are you and your dog ready for this Scent Detecting challenge? Have you put in the necessary preparatory work? Do you both have the requisite level of experience? Do the expectations you have of your dog’s performance outstrip their current level of ability?

2. The Clever Hans Phenomenon

The Clever Hans Phenomenon, or Clever Hans Effect, refers to any situation where a person or animal can be influenced by the subtle and unintentional cueing of another (Jackson, 2005). Your dog is able to recognise and respond to the cues delivered by those around her … including you, her handler! Problems arise when those cues misinform her. Importantly here, cues that misinform her about the location of the target scent source resulting in a false positive indication.

In a study by Szetei and Miklosi (2003), almost 50% of the study dogs would go to an empty bowl indicated to them by a person pointing at it rather than to a bowl in which the dog had previously seen and smelt food! The dogs appeared to place greater weight on the human cues than their own senses and experience.

In another study by Lit et al (2011), 18 drug / explosive detection dog and handler teams were given a number of detection tasks to complete. None of the tasks contained drug / explosive scent. In other words, they were all blank searches. Any alerts / indications that the dogs gave would be incorrect; false positive indications. Two of the detection tasks included a small piece of paper that falsely marked a scent location and two other detection tasks contained a decoy scent (toy / food).

In the detection tasks that included the false paper markers the handlers reported that their dogs alerted more at the marked locations than in other parts of the search area. According to Lit and her co-authors, when the handlers believed that there was scent present in the search area (paper markers) they were more inclined to claim that their dogs had indicated on a target scent; a false positive indication. As Lit et al (2011) state, this would seem to confirm that “handler beliefs affect outcomes of scent detection dog deployments“.

As Udell et al (2010) point out, with “increasing evidence for an acute sensitivity to human gestures and attentional states“, guarding against the Clever Hans Phenomenon in our dogs can be highly problematic but an essential consideration in the development of a reliable scent detecting dog. Again, any false positive indication in these circumstances is a training issue rather than simply “one of those things“. Suggestions for reducing the Clever Hans Effect include;

Practice more blind searches – If you don’t know where the target scent source is located you’re less likely to influence your dog.

Keep an OPEN mind – Try not to “second-guess” where the target scent source might, or might not, be. Chances are you’ll be wrong and, in the process, misinform your dog resulting in a false positive indication.

Allow your dog to work independently – Giving your dog the space and freedom to work by herself helps to reduce any tendency she might have to watch for cues from you rather than search the environment carefully herself. If you start to show interest in a particular part of the search area it’s highly likely that your dog will too. As soon as this happens, believing that your dog has located the target scent source, you’ll start to look harder yourself. A vicious circle with the almost inevitable result – a false positive indication from your dog prompted by inadvertent cues from you.

Beware of your audience – Keep in mind that your dog will be sensitive to cues from your audience as well as from you, her handler. Encouraging your audience to talk to one another can be helpful here. The more attention they’re giving one another the less attention they’ll be paying to your dog as she searches the area. Be particularly alert to ‘audience silence’ and ‘breath-holding’ as your dog comes close to her target scent source. Without a doubt, your dog will notice it even if you don’t!

Want to know more about this subject? Just follow this link to False indications, Clever Hans and You.

3. Target Odour is not a “Motivational Magnet” for your dog

Familiarising your dog to the target odour refers to the process of Classical or Pavlovian conditioning that helps her form positive associations with the scent. What starts out as a completely irrelevant odour, something that your dog would not normally be attracted to, will, after conditioning, start to become highly relevant. The presence of the odour will predict that good things will follow. According to Hall et al (2014), the process of familiarisation enhances odour discrimination training and can reduce overall training time.

During the familiarisation process the target scent becomes what Berridge et al (2009) describe as a “motivational magnet” – something that has to be approached, often compulsively. This fits well with the notion of “scent obedience” – the idea that the target scent itself will act as a cue to your dog to search it out and stay with it.

For more information on the odour familiarisation process, you might like to follow this link to Smoothing out the Lumpy Bits: Why it might be wise to teach the indication before the search and all that back chaining stuff .

Self-evidently, if the target odour is not important to your dog – if you haven’t turned it into a motivational magnet for her – then she has no real reason to search it out or indicate to you that she has found it. Pair this situation with a reliance on a change in your dog’s behaviour (COB) – rather than a fully trained indication – to show you where the target odour might be located and you have the recipe for a Scent Detecting disaster. To clarify, any passing sniff at the “olfactory messages” left by another dog, or the odour of food crumbs dropped on the floor, will look like (and is) a COB and, as such, will be considered an indication. Unfortunately, it’s a false positive indication.

The simple take-home message – review your training. Take the time to familiarise your dog to the target odour and train a reliable, unambiguous, indication!

4. Your dog has not learnt what you thought you had taught her

Recently, I came across a video clip of a dog working a “Line-Up” comprising a number of identical containers. Apart from considerable hesitancy on the dog’s part to both start, and continue, working (which points strongly to issues of Handler Pressure and Incomplete / Inadequate Training), it was very obvious that the dog did not fully understand the task in hand. On approaching the Line-Up, the dog gave false positive indications on multiple containers before, eventually, arriving at the correct container – the one that actually held the target odour source. If the handler had not placed the target scent source there herself, her dog’s multiple false positive indications would have completely misled her. Unfortunately, on the evidence provided by this video clip, this is an unreliable Scent Detecting dog.

Although this type of issue can become evident during many different types of Scent Detecting challenge, it’s probably most obviously identifiable in Line-Up tasks. In this particular case, the handler obviously believed she had taught her dog to deliver a passive indication, with duration, when she located the target scent source. In reality, her dog had learnt to deliver a passive indication, with duration, when it encountered any of the containers. The dog had learnt a visual cue – the containers – rather than the intended target odour cue.

Again, in common with other false positive indications, this is a training issue. One that needs to be addressed by the handler if her dog is to progress any further.

156719588_231339938661889_913839513036941995_n — Frodo CORRECTLY identifying the location of his target odour source in a Line-Up Scent Detecting Task

5. Incomplete / Inadequate Training

A few things to consider when training your dog …

1. Do you have a plan?

Do you have a clear picture of what you want to achieve? Have you thought about the steps you might need to take to achieve this end goal? Do you have realistic expectations of just how long this goal might take to achieve? Have you assessed your dog’s current level of ability and used this as the starting point for your training? Are you prepared to take one, or, possibly more steps back in your training plan to ensure that any new training is building on firm foundations? Have you considered your dog’s current level of health, fitness and emotional well-being? Have you considered how long your training sessions should be to optimise learning? What about rewards? Is your training plan Evidence Based? Without a doubt, these are only some of the questions you should ask yourself before starting to formulate your training plan or schedule.

2. Have you split your training?

As discussed earlier, when it comes to Scent Detecting training, I’m a big advocate of splitting rather than lumping. Splitting requires you to break your training down into tiny, incremental, steps. Speed of progress is dictated by your dog rather than any pre-determined time-frame decided by you, her handler. This forces you to consider your dog’s understanding of the particular training task in hand, and her ability to perform the element reliably, before attempting to move on with your training. If you move on too quickly, poor understanding, or performance, of a particular training element will result in false positive indications as your dog struggles to work out what is expected of her.

3. Are you training or testing?

If you ever find yourself saying something like, “let’s just see if she can do this” then it’s highly likely that you’re testing your dog rather than training her. If your dog does happen to succeed at some challenge you’ve set her, this will have far more to do with luck than any carefully considered application of training skills on your part. Why should that matter? Well, it matters because, next time, your luck might just run out. As the saying goes, “It takes more than one Swallow to make a Summer” and it takes more than one lucky success to make a RELIABLE Scent Detecting dog.

and in conclusion …

False positive indications should never be an accepted part of Scent Detecting practice. Without a doubt, the most likely culprit will be a training issue. If you want a reliable Scent Detecting dog … STOP. ANALYSE and ADDRESS the issues even if that requires you taking many steps back in your training.

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 work. Happy reading.

References / Further Reading

Berg J (2018) Lumping and splitting. Science. 359. 6382. 1309
Berridge KC, Robinson TE and Aldridge JW (2009) Dissecting components of reward; ‘Liking’, ‘Wanting’ and Learning’. Current Opinion in Pharmacology. Feb. 9(1): 65-73
DeChant MT, Bunker PC and Hall NJ (2021) Stimulus Control of Odorant Concentration: Pilot Study of Generalization and Discrimination of Odor Concentration in Canines. Animals. 11. 362
Custance D and Mayer J (2012) Empathic-like responding by domestic dogs (Canis familiaris) to distress in humans; An exploratory study. Animal Cognition. September. Vol 15. Issue 5. 851-859.
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
Galambos A, Gergely A, Kovacs AB and Topal J (2021) Affect Matters: positive and negative social stimulation influences dogs’ behaviour in a subsequent situation involving an out-of-reach object. Applied Animal Behaviour Science. Journal Pre-Proof
Goldblatt A, Gazit I and Terkel J (2009) Olfaction and Explosive Detector Dogs. IN: Helton WS (Ed) Canine Ergonomics. The Science of Working Dogs. London: Taylor and Francis Group
Hall NJ, Smith DW and Wynne CDL (2014) Effect of odor pre-exposure on acquisition of an odor discrimination in dogs. Learning and Behavior. Jan
Helton WS (2009) Overview of Scent Detection Work. Issues and Opportunities. IN: Helton WS (Ed) Canine Ergonomics. The Science of Working Dogs. London: Taylor and Francis Group
Jackson J (2005) The Clever Hans effect – a horse’s tale. Critical Thinking. http://www.critical-thinking.org.uk/pdf/clever-hans.pdf
Laing DG, Legha PK, Jinks AL and Hutchinson I (2003) Relationship between molecular structure, concentration and odor qualities of oxygenated aliphatic molecules. Chemical Senses. 28. 57-69
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
Lehnert M P and Weeks E N I (2016) Trained Dogs in Insect Detection. IN: Jezierski T, Ensminger J and Papet L E (Eds) Canine Olfaction Science and Law. Advances in Forensic Science, Medicine, Conservation, and Environmental Remediation. London: Taylor and Francis Group.
Lit L, Schweitzer JB and Oberbauer AM (2011) Handler beliefs affect scent detection dog outcomes. Animal Cognition. 14: 387-394
Mariti C, Falaschi C, Zilocchi M, Fatjo J, Sighieri C, Ogi A and Gazzano A (2017) Analysis of the intraspecific visual communication in the domestic dog (Canis familiaris): a pilot study on the case of calming signals. Journal of Veterinary Behavior Clinical Applications and Research. Volume 18. March-April. 49-55.
Rugaas T (2006) On Talking Terms with Dogs: Calming Signals. 2nd Ed. Washington: Dogwise Publishing
Szeiti V and Miklosi A (2003) When dogs seem to lose their nose: an investigation on the use of visual and olfactory cues in communicative context between dog and owner. Applied Animal Behaviour Science. Sept 5. Vol 83. Issue 2. 141-152
Udell MAR, Dorey NR and Wynne CDL (2010) What did domestication do to dogs? A new account of dogs’ sensitivity to human actions. Biological Reviews. 85. 327-345
Wilson DA and Stevenson RJ (2006) Learning to Smell. Olfactory Perception from Neurobiology to Behavior. Baltimore: The Johns Hopkins University Press
Zerubavel E (1996) Lumping and Splitting: Notes on Social Classification. Sociological Forum. 11.3. 421-423.

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.

117912623_223060265768875_5879640540067516656_n — 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 …

64291246_497147157782583_3056615279808217088_n (1) — 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.

118615012_307102380518755_7340140840833491906_n — 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.

117956468_4479175328789160_324224961928398989_n (1) — 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.

www.scentdetectfind.co.uk

References / Further Reading

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
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
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
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
Hall NJ and Wynne CDL (2018) Odor mixture training enhances dogs’ olfactory detection of Home-Made Explosive precursors. Heliyon 4. 4. 12. December
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
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
Pinc L, Bartos L, Reslova A, Kotrba R (2011) Dogs Discriminate Identical Twins. PLoS ONE. 6(6)
Salter M (? date) Examples of Occam’s Razor. https://examples.yourdictionary.com/examples-of-occam-s-razor.html Accessed: 24.8.2020
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
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

Smoothing out the Lumpy Bits; Why it might be wise to teach the indication before the search and all that back chaining stuff

At its most basic, Scent Detecting requires your dog to search for, and locate, the source of an odour. On this simple description, your dog is engaged in Scent Detecting activities (entirely independent of you) for a very large portion of his day; finding a dropped crumb of food on the floor, discovering where a passing rabbit has left some tasty deposits, examining your clothes when you return home at night.

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48368492_1203023753207380_9064012562441437184_n

48275084_377656909477847_6153742602412752896_n

A little bit of independent Scent Detecting.

As Horowitz et al (2014) point out, your dog’s Umwelt or “Self-World” is primarily olfactory; “Dog noses house hundreds of millions more olfactory cells than humans’ do, and their corresponding brain regions are much more developed relative to their visual areas than in humans“.

So, what differentiates your dog’s independent Scent Detecting activities from those that involve you, his handler?

One word … Training.

Well, two actually … Careful training.

Ok, three … Careful, thorough, training!

Careful, thorough, training

Given your dog’s natural Scent Detecting talents, it can be hugely tempting to simply let him ‘get on with it‘. Spend a few minutes browsing any social media platform and you’ll soon find plenty of examples of this laissez-faire approach to Scent Detecting training, often with highly questionable results.

Yes, olfaction is your dog’s speciality but he isn’t Lassie! He can’t read your mind, guess what you want or speak your language. If you want him to find a specific odour for you – truffles perhaps – then you need to find some way of harnessing his natural abilities … some way of communicating your particular scent detecting requirements to your dog that might just differ from his own! And this is where careful, thorough, training comes into play.

Splitting vs Lumping

I start by splitting my Scent Detecting training into three separate, but interconnected, phases;

Familiarising my dog to the target odour.
Training the passive indication.
Searching.

By splitting I am referring to the process of dividing the whole training task – in this case, Scent Detecting – into smaller, more manageable, training elements as opposed to lumping all three elements together and training them as a whole (Berg, 2018. Zerubavel, 1996).

According to Zerubavel (1996), “although the world in which we live is essentially continuous, we experience it as discrete chunks: strangers and acquaintances, fiction and nonfiction … Carving out of reality such ‘islands of meaning’ involves two contrasting yet complementary cognitive acts – lumping and splitting. The former entails grouping ‘similar’ things together in a single mental cluster. The latter involves perceiving ‘different’ clusters as separate from one another“.

In short, splitting makes our world, and our training, more manageable.

Why Split the training?

Well … the simple answer is … I like my Scent Detecting training to progress as smoothly as possible. I don’t like lumps!

I don’t like lumps in my Scent Detecting training!

If, as seems common practice, I were to lump my scent detecting training together and set my dog off to search an area before he’d been familiarised to the target odour and had a trained and reliable indication, how would I manage the following possible outcomes?

He seemed to search the area very well but he didn’t find the target scent source.
He definitely found the target scent but he pulled it out of the box, ran around the room with it in his mouth and chewed it up.
He didn’t move from my side.

How do I let my dog know which bits he did well and were exactly what I could have hoped for and which bits were (to my view) just plain wrong? How can I reward his thorough searching in outcome 1 even though he didn’t actually locate his target scent? How can I reward my dog for locating his target scent in outcome 2 when he then went on to chew it up? And what on earth do I do about outcome 3?

Tricky, isn’t it? …. and this is what lumpy “training” looks like. Messy. Confused. Frustrating. Directionless. Unreliable. If our dogs learn anything from this lumpy approach to training, it would seem to be despite us rather than because of us. In contrast, splitting allows us to work on one specific training element at a time, helping to ensure competence in that area before moving on to another training element and then, eventually, putting all the elements together in one Scent Detecting whole or Lump.

But Splitting the training is so time-consuming, isn’t it?

Well, NO … it isn’t.

Splitting your training into smaller elements allows you to simplify things for your dog, aids clear communication, reduces frustration and increases your chances of getting things right in the first place without the need to add in further, remedial (Sticking Plaster), training at some later point in time.

Splitting your training results in …

easily understood and manageable steps toward a larger end-goal.
tiny bits of behaviour that, when successfully achieved, will allow you to reward your dog immediately.
tiny bits of behaviour that, when things don’t go so well, will allow you to identify and address the problem rapidly with a revised training plan and approach.
no need for your dog to “guess” what is required of him → less frustration → increased likelihood of training success.
no wasted opportunity to reward a well executed behaviour because it’s been lumped together with a whole host of other, poorly executed, behaviours.

When you Split … always keep the Lumps in mind!

Although I’m a big advocate of splitting, it’s worth keeping in mind that there will always be connections between the different phases of training and the overall end goal. In other words, never lose sight of the training lumps! For example, the process of familiarising your dog to the target odour (Hall et al, 2014) acts … believe it or not … as the foundation for later searching!

Splitting … and even more splitting …

So, as mentioned earlier, I start by splitting my Scent Detecting training into three separate, but interconnected, phases;

Familiarising my dog to the target odour.
Training the passive indication.
Searching.

… but, my splitting doesn’t end there! Each of these three phases will be split further.

For example, the apparently simple phase of familiarising my dog to the odour – which takes approximately 30 minutes to conclude – is split, again, into the following elements;

Introduction to the environment – Physical and Psychological. If you’d like to know a little bit more about this particular element, follow this link to Scent Detecting and the Enriched Environment
Choice of equipment – Harness and Line.
Rewards – Food vs Toys (play?). Quantity. Timing. Look out for my forthcoming Blog post – Food, Glorious Food.
Selection of the Target Odour – Safety. Cost and Availability. Previous use. Single Odour vs Configural Odour. Quantity (Concentration) of Odour. There’ll be more guidance in my forthcoming Blog post – Selecting a Training Odour for your Scent Detecting Dog. Some Considerations.
Mechanics of Training – Classical (Pavlovian) conditioning. Development of a positive Conditioned Emotional Response (CER).

The devil is, very definitely, in the detail.

… and then there’s Back Chaining

According to Orr (2015), back chaining is a really effective way to build reliable behaviours. It’s a very efficient way to teach a specific behaviour, limits any potential errors and “leads to fluency with less training time” (Pryor, 2012).

Scent Detecting requires a whole series of individual behaviours that, together, form a particular behaviour chain. My dogs’ Scent Detecting behaviour chain looks something like this;

Cue to start work (Context. Harness. Scent in the Environment. Word) → Searching the Area → Locates the Target Scent Source → Passive Indication → Verbal Cue to move away from the scent source → Leaves the Scent Source → Click → Returns to me → Rewards

Your dog’s Scent Detecting behaviour chain may look very different to mine. It all depends on your training approach and your particular requirements … but I’m sure you get the idea; it’s complex and, for success, careful, thorough, training is required.

I teach Scent Detecting by starting at the end of the behaviour chain and working my way back to the beginning. As Orr (2015) states, “by teaching the last part first the learner [my dog] is always moving toward the part of the skill that he learned first and with which he is most confident“. For my dogs, this means learning about the target odour first – the familiarisation process.

Familiarising your dog to the target odour – the mechanics

Familiarising your dog to a specific (target) odour involves Classical, or Pavlovian, Conditioning. It’s about helping your dog form positive associations with the scent. What starts out as a completely irrelevant odour to your dog, or neutral stimulus (NS), will, after conditioning, start to predict that good things (rewards) will follow (McLeod, 2013).

Familiarisation does not mean leaving the target scent with your dog (amongst his bedding, perhaps) for a few weeks until he becomes “used to”, or “familiar with”, it … unfortunately, “mere exposure [has] no effect on the acquisition of an odor discrimination in dogs” (Hall et al, 2014). If only it were that simple.

Scent : Detect : Find uses a very adapted form of Hall et al’s (2014) familiarisation protocol. Unit 13 is not a laboratory! Firstly, your dog is introduced to his “working” environment – he’s allowed to explore (or not) as he wishes – and then the familiarisation process begins. Over a 20 – 30 minute time-frame, as your dog continues to investigate the environment, he’s given the opportunity to “sniff” the target odour followed, immediately, with food rewards. No other behaviour is required … no need to sit, stand, down or similar. This procedure is repeated approximately 6 – 10 times within the 20 – 30 minute time period.

As for the “sniff” … well … some trainers place huge emphasis on hearing the dog inhale – sniff – during this familiarisation process … nothing less will do. This view probably has its origins in the work of Craven et al (2010) who state that, during normal respiration, approximately 12-13% of inspired air will reach the chemosensory area of the nose – the ethmoturbinate region – and that during active sniffing this may increase by 2-3%.

I’m not worried about hearing your dog sniff. That 12-13% of normally inspired air will do just fine for me! Why? Well let me give you an everyday – olfactory – example. If you walk along a road … breathing normally … you’re likely to become aware of a multitude of different odours, from the smell of bad drains, to the odour of frying chips, to diesel fumes, to … no need to sniff. Interestingly, you’re only going to start sniffing when you encounter a very faint hint of an odour, one that you’re trying to identify and locate. As Mainland and Sobel (2006) state, “when the olfactory system encounters a concentrated odorant, sniff vigor is reduced in real time; when it encounters a diluted odorant, sniff vigor is increased in real time“. In short, as your dog explores the environment, he’ll be aware of the target odour regardless of whether he chooses to sniff or not!

So, back to the familiarisation process and classical conditioning.

Before Conditioning – if your dog is offered food, an unconditioned stimulus (US), he’ll begin to salivate. It’s a physiological process resulting in an unconditioned response (UR). He just can’t help it.

Food (US) —> Salivation (UR)

Initially, if you let your dog smell what will eventually become his target odour, it’ll mean nothing to him. It’s a neutral stimulus (NS).

Target Odour (NS) —> No Salivation

During Conditioning – this requires you to allow your dog to smell the target odour and then provide him with food.

Target Odour (NS) —> Food (US) —> Salivation (UR)

After Conditioning – the target odour is now a conditioned stimulus (CS) and is associated with food. Smelling the odour in his environment will cause your dog to salivate in expectation of food rewards. Salivation in response to the target odour is now a conditioned response (CR).

Target Odour (CS) —> Salivation (CR)

According to Hall et al (2014), familiarising your dog to the target odour in this way enhances odor discrimination training and may reduce the overall training time. In short, it’s a worthwhile exercise to work through especially as it only takes approximately 30 minutes to complete.

Interestingly, and importantly, by classically conditioning your dog to the target odour, it will become what Berridge et al (2009) describe as, a “motivational magnet” – something that has to be approached, often compulsively. This is the foundation of all subsequent searching behaviour. Your dog WANTS to find the target odour. As Berridge et al (2009) explain, WANTING can apply both to unconditioned stimuli (US) such as food as well as conditioned stimuli (CS) such as the target odour after a classical conditioning procedure has taken place such as the one described here.

According to Litman (2005), WANTING involves dopamine activation in the brain and is thought to “motivate approach behaviour and to attribute incentive value to stimuli associated with reward” … the target odour!

But not only will your dog WANT to find the target odour, he’ll LIKE it too. After classical conditioning, your dog will have formed a positive conditioned emotional response (CER) to the target odour. As Litman (2005) states, LIKING involves brain opioid activity and “consequent states of pleasure“. Your dog will LIKE the target odour and WANT to find it. This phenomenon – your dog’s desire to get to the target odour – is sometimes referred to as Scent Obedience.

Familiarising your dog to the target odour and the notion of Imprinting

For clarity, in some scent detecting circles, the process of Familiarising your dog to the target odour (as described here, but often using very different training protocols) is frequently referred to as Imprinting. I prefer to avoid using this term in the context of scent detecting as it has its origins within the field of Ethology and is associated with the work of Konrad Lorenz and the rearing of Geese. Beware, terminology can be confusing and misleading!

and in conclusion …

If you’d like your scent detecting to progress a little more smoothly, consider splitting your training to avoid the lumps. Start where you’d like to finish – Back Chain!

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.

www.scentdetectfind.co.uk

References / Further Reading

Berg J (2018) Lumping and splitting. Science. 359. 6382. 1309
Berridge KC, Robinson TE and Aldridge JW (2009) Dissecting components of reward; ‘Liking’, ‘Wanting’ and Learning’. Current Opinion in Pharmacology. Feb. 9(1): 65-73
Craven BA, Paterson EG and Settles GS (2010) The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia. Journal of the Royal Society. Interface. 7. 933-943
Hall NJ, Smith DW, Wynne CDL (2014) Effect of odor preexposure on acquisition of an odor discrimination in dogs. Learning and Behavior. Jan
Horowitz A and Hecht J (2014) Chapter 9. Looking at Dogs: Moving from Anthropocentrism to Canid Umwelt. IN: Horowitz A (2014) Ed. Domestic Dog Cognition and Behavior. The Scientific Study of Canis Familiaris. Springer.
Litman JA (2005) Curiosity and the pleasures of learning: Wanting and liking new information. Cognition and Emotion. 19(6). 793-814
Mainland J and Sobel N (2006) The Sniff is part of the Olfactory Percept. Chem. Senses. 31: 181-196
McLeod S A (2013) Pavlov’s Dogs. http://www.simplypsychology.org/pavlov.html accessed; 22.12.2015
Orr J (2015) Back Chaining: The top secret teaching tool that is the key to professional success. TAGteach International. https://tagteachblog.com/back-chaining-the-top-secret-teaching-tool-that-is-the-key-to-professional-success/
Pryor K (2012) Back-Chaining “Retrieve”. Karen Pryor Clicker Training. https://www.clickertraining.com/back-chaining-retrieve Accessed: 3.8.2020
Zerubavel E (1996) Lumping and Splitting: Notes on Social Classification. Sociological Forum. 11.3. 421-423.