I talked about this a bit in the replies, but this is one of my like... micro special interests within my special interest of dog training and behavior so I'm going to add it to the post too, because why not? I like infodumping and talking about scent work and canine scent discrimination, sorry not sorry. This will probably be long af but if you're interested in the science and having a better understanding of scent work I promise it's interesting (and if you're not... feel free to scroll, I'm not judging, autistic infodumps aren't for everyone lol).
So to clarify what I mean by "cocktailing odors" here's a screenie from some random "detection training expert" that popped up first for me with a quick google on the subject.
Now, if you're someone new to scent work or detection then this might seem logical enough to you to not question it! People who are supporters of this method will often give this sort of reasoning and also emphasize how much time it saves and how extremely fast they can train with this method compared to imprinting one odor at a time (the person from the above screenshot claims they can fully imprint 6 different target odors in only one week this way, which is absolutely ridiculous, when normally it would be a week or more of training per odor). They are counting on less experienced trainers and owners not knowing better and buying that explanation without a second thought, especially when it's coming from someone who trains commercial detection dogs for a living or has advanced nosework titles. Some of them may also genuinely not know better themselves, and may have a biased view of their own results using this method and no experience with other methods done by knowledgeable trainers to compare it to which feeds into that bias (but in the case of people who are selling it as a way to massively cut down on time spent training specifically, I doubt it).
If you've known me or followed me for a while now you'll already know from my many rants on the subject and the type of training advice that I give out to people most often (start over and slow down) that I think you should always be extremely suspicious of anyone trying to sell you training methods that get things done really fast. That is usually a scam, and not how training tends to work in general. Whatever time you might save in the beginning will usually be spent later on cleaning up mistakes.
Anyway, I'm going to tell you why you should NOT expect this cocktail imprint method to work the way trainers like this one claim it does, and why science does not support this method of imprinting being as effective as single odor imprinting. First, though, my credentials to speak on this topic since I have the nerve to poke at other people's credentials:
I have personally assisted in the training of over a dozen police dogs for narcotics detection and human trailing in both wilderness and urban environments that were then sold to police stations and actively worked (ACAB though, also working with cops sucks, very abusive, -1000/10 do not recommend but it is unfortunately one of the only ways to get into this specific area of dog training), as well as one commercial explosives detection dog, one commercial narcotics detection dog, one cadaver dog (yes we had to use various actual human remains at different levels of decomposition for this), one bedbug detection dog (the live bedbugs we used had to be fed blood to keep them alive, and using blood from different people to make sure the dog didn't accidentally imprint on the scent of blood from a single person as part of the target odor was something that had to be taken into consideration), a truffle hunting dog, and many more dogs in various stages of wilderness trailing training (for Search and Rescue or for service work to help caregivers find SD handlers with disabilities that predispose them to elopement [running away/wandering off]).
Along with the hundreds of hours I spent directly hands on training dogs in scent work related areas I also spent classroom hours learning about the science of odor and canine sense of smell;
how strong canine sense of smell is and how little of an imprinted target material or residual target odor needs to be present for dogs to detect it (parts per TRILLION)
dogs' unique (compared to us) ability of scent discrimination and how dogs can perceive and learn odors elementally (meaning by detecting and learning individual compounds that make up odors) and not just configurally (as a whole single odor) the way we do
how we effectively teach them to discriminate for odors we want to focus on over other odors (by making the target odors themselves rewarding, which is the reason even police and military detection training is done almost exclusively with positive methods [and why I find it so amusing that protection sports people use aversives so much while training "tracking", which is already a thing I hate as a concept in general because it has no relation to real life manhunting or SAR work. TRACKING SUCKS. Using aversives for it sucks even more.])
the varying number of individual chemical compounds/elements that can make up a single target material odor (could be a few, could be hundreds)
the molecular size and weight of common compounds in the target materials and odors that we were primarily working with (explosives and narcotics, also human skin rafts)
how molecular size and weight of different individual compounds that make up a target odor impacts their shed rate from the target material which impacts a dog's speed of imprinting on/recognizing those compounds within that odor
how different volumes of target material shed individual compounds at different rates which can affect a dog's ability to recognize them
how much contamination and compound variance there is in different samples of real materials and why that makes real materials bad for imprint training purposes (more relevant for narcotics and explosives where quality synthetic materials for training are more available)
how different materials used for training to hold/hide odor present different levels of contamination to imprint training and how to minimize this and correct for it
and how things like humidity, temperature, weather, wind, storage/hide material, and different surface materials affect the way odor behaves and moves and therefore how a dog will be able to receive and follow it.
We also ran experiments on dogs being trained for narcotics detection specifically to test the difference in effectiveness of single odor imprinting vs cocktail odor imprinting. (Spoilers, the results were not good for cocktail imprinting.)
This classroom time and the imprinting experiments, as well as my personal studies of other more formal scent work experiments, are the parts that I think are actually more relevant to this topic - NOT the hands on experience. That is why someone having managed to title dogs in sports nosework or being involved in a detection industry does not automatically give their opinions or methods any weight in my eyes. There are big name police dog trainers who also push cocktailing for imprinting, because it lets them claim a dog is done training faster so they can sell them sooner which means more profit made from a time invested point of view. They have mixed reputation for doing this because their dogs generally have very poor results when they are blind tested at alerting to target odors, and that was in fact one of the main points that my head trainer used to argue that most police dogs are actually trained to look for handler cues and not to alert on target odor (something we specifically accounted for in our experiments, and our detection training in general). I don't respect the opinions of those kinds of people in the police detection industry anymore than I do the AKC/CKC nosework sport trainers who push cocktailing, because them being able to sell overpriced dogs with poor success rates to ignorant cops looking to blow some big government provided money is not an indicator that they understand the science or that their method is better.
Okay, let's finally actually get on to why cocktailing is a worse choice for imprinting target odors than single odor imprinting. The majority of this argument of mine will focus on just one of the bullets I listed above - dogs' ability to perceive, learn, and recognize odors elementally and not just configurally. (This is not unique among mammals in general btw, we just uniquely suck at it as humans because we are specialized for sight, not smell.) There are lots of studies proving this in other lab-favored more scent-specialized mammals like mice and rabbits, fewer in dogs, but they do still exist.
Now if you're the kind of person who mostly reads article titles and then jumps to assumptions you might read the title of that study I just linked above ('Odor mixture training enhances dogs' olfactory detection of Home-Made Explosive precursors') and think "oh, so cocktail training is good then". Then, if you're a trainer trying to push a narrative to sell classes using a specific training method or sell dogs trained with that method you might decide to incorrectly cite that assumptive "conclusion" to back up cocktail methods of imprinting the way that screenshot I included earlier did, by saying that training on mixtures is better for real life scenarios where scents are generally contaminated so cocktailing scents for imprinting is good. However, if you actually read the study and take time to understand it then you will quickly see this is a incorrect conclusion that the study does not in any way support. It is not even something this study is looking at. All of the dogs in this study were imprinted on target odors as single odors/elements first to a required level of successful alerting to those single odors (which is actually surprisingly low to me ngl, only 50 successes out of 80 trials, we always went for minimum 80% in my training school) before any mixture training was added in.
What this study was actually looking at was how dogs' ability to learn odors elementally (meaning by learning individual compounds) should be used with later mixture training to make dogs more effective at alerting to target odors in mixtures they may come across in real life, and especially mixtures with novel compounds (meaning compounds that are new to the dogs), by teaching dogs to recognize elements within a mixture instead of just identifying mixtures configurally.
For example, a dog that is only ever trained to alert to pure potassium chlorate (PC) being present by itself will fail to alert to PC in an explosive mixture where other compounds are present most of the time. This is because of the PC after successful imprinting only being trained to be recognized as an individual element, but complex mixtures with the PC in them generally being recognized by dogs configurally. The dog must be taught after imprinting on any element to still discriminate (referred to as "figure-background segregation" in the study) for that element in a mixture, instead of only looking at complex odors and mixtures configurally as they are predisposed to do. Teaching dogs to recognize specific elements in a mixture requires mixture training after the elemental imprinting, but the elemental imprinting must still come first since the more complex an odor/mixture is the more likely a dog is to learn to identify it configurally, meaning that the same elements of that odor in different odor configurations/mixtures or presented separately as individuals will be unrecognizable to them.
This problem of elemental vs configural identification also works in the reverse of the above PC scenario when it comes to imprinting, which is why this training and experiment in the study I linked would not be possible with cocktail imprinting of target odors and therefore the conclusion does not support cocktail imprinting. Bundling together target odors - which are generally already made up of multiple elements/compounds themselves (and this is the case for those nosework essential oil target odors) - would greatly encourage configural learning of the mixed up odors (learning to recognize them together as a whole) over elemental learning (learning to recognize the individual component target odors making up the whole) because of the complexity of the mixture being presented to the dog. In order for specific odors being individually targeted in odor mixtures to be reliably recognizable to a dog as individual elements, dogs must first learn them elementally. As I said above, the more complex a target odor is the more likely a dog will learn to identify it configurally, as a whole, so any deviation from that specific configuration is likely to not be recognized - meaning if you imprint the cocktail and then split up the target odors from that cocktail for actual training and trials, the dog is very unlikely to recognize the individual target odors successfully.
Even keeping which elements are in a mixture the same but changing the amount of them present from the original configuration is likely to end up with the slightly changed odor mixture not being recognized for this reason. This concept (preference for configural learning) is briefly touched on in the introduction of the study I linked and backed up by referenced studies in the introduction on mice, rabbits, and explosives detection dogs.
What this means is that when you are imprinting a dog to a cocktail of scents they are learning to recognize that cocktail as a whole, in the configuration of that specific cocktail. You are likely to see a lot of mistakes once you start working more on the dog identifying the individual odors, and that's because the dog is not actually imprinted on those target odors as individuals. Throughout your training your dog is now going to have to imprint on the individual target odors separately from the configuration of the cocktail on the fly. Instead of that imprinting taking place on its own before continuing to other parts of training to make learning easier for your dog, this imprinting is likely now taking place alongside you shaping your desired alert behavior and/or practicing searching for target odor in hides. This will most likely make the process much more confusing for the dog, leading to more mistakes and slowing down the entire learning process.
In this scenario the cocktailing for imprinting did not actually save you time by imprinting everything individually all at once. It just made you feel false confidence in moving past imprinting on to other parts of scent work training sooner than you should have, which meant your dog was forced to learn multiple things at once by having to catch up on imprinting to the correct odors while learning other stuff. Your dog was likely significantly more frustrated and prone to mistakes than they would have been otherwise because of this, which means you were also probably more frustrated training them. This is why I am totally unsurprised whenever I see tons of people complaining about how hard and unenjoyable they find nosework, despite nosework actually being a fairly easy thing when it is done correctly and proper time is set aside for imprinting.
Now, if you're curious about a likely reason why dogs that are cocktail imprinted are still successful enough to earn nosework titles, this is actually kind of touched on in a way in the description of the control tests described in the study I linked.
What these screenshots (mostly the second one) are saying in more simple terms is that the presence of odors period is itself a factor in the dogs' ability to successfully alert to the presence of target odors. Without any odors present in the control trials the dogs performances dropped significantly. Since there were no odors released in these control tests at all, the only way to fail would be for the dogs to give a false positive, so this means dogs began giving false positive alerts (and a lot of them too!) without the presence of any odor to affect their performance.
We saw presence of odor vs no odor as a factor for success in the experiment I participated in as well, though in a bit of a different way. This experiment was also a lot less controlled than the lab experiment in this study and a very different setup, though our sample size was the same. We put three dogs through our typical single odor imprint training on narcotic odors. (These individual odors were not single elements btw. They were synthetic odor mixtures made up of the most basic compounds found to always be present across hundreds of real material samples of the narcotics they represented, so essentially they were simplified odor mixtures that dogs were taught to recognize as an element of the even more complex odor mixtures of real materials full of contaminating elements.) A group of three other dogs were imprinted on the narcotic odors all bundled together as a cocktail. All of these dogs started with no detection training, and all of their training other than the imprinting method was kept the same as far as shaping the alert, teaching them to ignore reward distractions and handler cues, and adding in distraction odors and odor mixtures (most often in the form of intentional contamination replicating real world scenarios/materials). After training was complete for all six dogs we did two blind trials with them.
Around 20 identical hides were set up in a field for these trials, mimicking the setup of container searches in AKC scent work trials, and the handlers for the dogs during the trials had no idea where target odors were or if they were even present to avoid them accidentally cueing dogs. In one trial hides contained either individual target odor, cocktail target odor, distractor odors like tennis balls, kongs, or treats (all distractors with no target odor), or were left empty. Dogs who were initially imprinted on single odors were massively successful at correctly alerting to individual odors and cocktails. There was a dog who stubbornly alerted to a hide full of tennis balls though (most of the dogs' preferred reward during training, and this was a particularly ball obsessed shepherd). The cocktail trained dogs alerted almost equally randomly to individual target odors, cocktail odors, distractors, and empty hides, with more alerts on distractor and cocktail hides and less alerts on individual target odors and completely empty hides. Essentially, they seemed to be guessing, with preference in their guesses for more complex odors or known reward odors being present in a hide.
We also did a trial with just target odor or empty hides. Single odor imprinted dogs had no trouble with this at all, cocktail imprinted dogs had an accuracy rate of around 70% IIRC (I know it was a good bit less than 80%, which is what our head trainer's assumption had been beforehand, but I have ADHD memory and this was over half a decade ago, sue me). The increase in success rate for cocktail imprint dogs from the trial with many odor options to the trial that was only target odors or nothing can likely be at least partially explained by the dogs having preference for the presence of some odor over a hide with no presence of odor at all as a factor for success. This performance controlling factor - the presence of odor vs no odor presence - is likely one of the explanations for dogs who are cocktail imprinted still being able to successfully alert at a high enough success rate in nosework trials to earn titles, especially at lower levels that use only one or two target odors and have few to no distractions. The other main factor I suspect is that most dogs are still eventually imprinting on the individual target odors over time with continued training using those individual odors separately from each other in hides after the imprinting phase, despite this being a more confusing and less efficient way for that imprinting to be done.
Now, all that being said, I do think dogs need to be trained on scent mixtures to make them more reliable in real world scenarios or trials mimicking real world scenarios. I just think that should be done AFTER individual target odor/element imprinting, not as a part of imprinting! People who are doing cocktail imprinting are assuming that dogs' ability to learn odors elementally is ALWAYS being applied, which is not what science has found to be true, as shown by the study I linked earlier and the studies on explosive detection dogs it references! If that were the case then dogs would not consistently be found to have high rates of failure at identifying mixtures containing target elements when they are imprinted on individual elements and then solely trained on alerting to those individual elements alone (like the earlier PC example). That failure to identify their target element within a mixture shows that dogs approach learning more elementally complex odors/element mixtures configurally, NOT elementally as cocktail lovers assume, so the presence of an individual element they are imprinted on is not registering to them as an element within a mixture unless they receive special training teaching them to segregate and recognize elements within mixtures like the dogs in the study I linked did.
You may get lucky and have a smart dog who relatively quickly figures out what your individual target odors are on their own during training despite your cocktail imprinting method, but that is NOT a benefit of cocktail imprinting, it is in spite of it. I see SO MANY complaints from people struggling with scent work sports online about dogs only recognizing one or two of the individual odors they need to know, seemingly having "preferences" for alerting only to certain target odors (usually the ones that get isolated for individual training first so receive the most individual training time), of dogs going significantly backward for a long while in success rates when switching from cocktail to individual odors or isolating a new individual odor for a higher sport level, or of owners/trainers getting frustrated at the seemingly random rate of success they have at scent work with their dog. Every time I see these things I just want to grab people by the shoulders and cry "STOP COCKTAILING TO IMPRINT! Go back and do individual target odor imprints! What's the harm in just trying it if you're already struggling so much?!?" but alas, I know all that would get me in most cases is "well my trainer said to do it this way" or "well I know someone who cocktails who has a high level title so clearly that's not the problem" or "well my dog still managed *insert lower level scent work trial* despite it so clearly he learned the individual target odors anyway and is just being a butt/having a bad day/*insert other excuse that blames the dog*"
Sigh. If you made it this far, give yourself a treat. That was a long ass ramble. You don't have to listen to me if you don't want to, cocktail your target odors for imprinting if that's what your heart and soul (or social anxiety) demands, but if you're curious and have had mixed or frustrating results with cocktailing in the past... idk what's the harm in imprinting odors one at a time just to see if it works better? It's not like you're going to be rapidly jumping from novice straight to advanced, expert, and master level and will need all those other target odors to be immediately imprinted all at once anyway. Slow down and enjoy the process instead of rushing for a desired destination, maybe? Scent work should be FUN and relatively easy, since the hardest part should just be learning to trust your dog once they know what target odor to look for! They're the ones doing most of the work, just teach them the correct individual targets!
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