The Scent Picture and Training the Dog

There have been many studies and continued research about how and what scents or odors dogs detect. Most of the research has been during the years after World War II. Consider that during World War II mine detection dogs were taught to look for disturbed soil. Trainers at that time did not believe a dog could detect the scent of explosives. Of course, this meant that the dogs had a very high failure rate because disturbed soil did not last long. 

In the United States William “Bill” Kohler used harsh methods, such as having a dog get caught in a leg hold trap, to teach the dog to identify mines. His success rate was very low. The British used reward-based training and their mine detection dogs had a higher success rate. 

​Today we have a much better understanding of how specialized a dog’s olfactory sense is. It has been proven that a dog can detect 1 – 2 parts per trillion of scent. How long the scent is available for the dog to detect depends on two main aspects of the scent. First is the makeup of the scent. A chemical compound is more likely to last longer than skin cells. Second is the weather and location of the scent source. Scent that is protected indoors or in a container might last longer than scent that is exposed to the weather. It is up to the handler to be knowledgeable enough to make a determination about the likelihood that the scent is still available to the dog.  

​Recently it was discovered that dogs have a unique connection between scent and sight. They cannot separate the two due to a neurological link between the dog’s sense of smell and their vision. So far it seems that dogs are the only animal that have this capability. Scientists know that dogs have connections in their brain that process memory and emotion that are similar to people but the ability to link scent and sight is due to connections between the spinal cord and the occipital lobe which people do not have. 

​This discovery presents new challenges when training a dog, not just for scent work, but in all aspects of SAR. This finding illustrates why it is critical to change the training conditions, location, people, and exercises as often as possible so that the dog learns to be eclectic. Since people cannot make the same link as dogs, we cannot imagine how this works. The closest example is when a scent that you remember from childhood brings a picture to mind. In some cases, the link between vision and scent can be used to advantage when training a dog. 

​Trainers have been successfully training dogs to detect scent for years, however, we still do not know and will never know exactly what the dog detects. It is important that the dog trainer and handler understand that there is no such thing as an uncontaminated scent article. There is nothing in the world that is pure scent. Consider the dog that is taught to follow the scent of a particular person using an object of clothing. Even if the clothing was not taken from the laundry basket but from that person’s dresser or bedroom, what scents are on the object? 

The list is quite extensive: 

1. The material that the clothing is made of contributes to the scent picture. Think of all the different types of fabrics and fabric blends that clothing is made from including the hair of animals. Each type of fabric has been treated with an array of chemicals, handled by numerous people during its composition, and run through machinery that has lubricants, such as oil, on it. The thread that was used to sew the clothing has its own set of scents. Both the fabric and thread have been dyed and treated with chemicals. When most clothing is new, it may have sizing in it. How long do those scents stay in the clothing even after being washed?

2. The container that the clothing was shipped and stored in has its own chemical makeup.

3. The dresser or closet has another set of scents that permeate the clothing. Most furniture is either solid wood, and each species has its own scent, or it is made of a composite which is another set of chemicals and wood. Of course, the finish that soaks into the wood has its set of chemical scents too. In the case of a closet, you can have cedar, sheetrock, paint and spackle.

4. The scent of the laundry detergent and possibly fabric softener adds another level of scent to the object.

5. As the clothing is taken from the dresser, the house scents cling to it. This includes all of the items in the house, cooking scents that cling to walls and fabrics, and scents of other household residents, both human and animal.

6. The scent of the person transporting the clothing is part of the scent picture. No matter how hard we try, our scent falls on the object, whether we touch it or not. 

7. Once the clothing is taken outside of the house, the general environmental scent will also cling to it as well as the vehicle that transports it to the command center.

8. The main scent, of course, is that of the target person. 

While not all of the scents listed above will last on the clothing or scent object, the ones that do last form the scent picture that the dog gets when he is given the scent article. 

The handler must take into consideration that the scent trail will have odors that change as well. Considering the complexity of the scent picture, it is amazing how well dogs can either find or follow the scent that we want them to. 

Keeping in mind what makes up the scent picture, let’s talk about training and working the scent specific dog. Most people who handle and train dogs know how to teach the dog to target on a specific scent. However, human nature, being what it is, and a person’s natural desire to communicate verbally, are often the undoing or the hindering of the dog’s ability to do his job. 

​Specifically, handlers talk to their dog too much. One command tells the dog what to do. In this case, the command is to find and/or follow a certain scent picture. 

Many handlers make the mistake of re-commanding their dog as the dog is following a scent. They feel that re-commanding is a form of encouragement to the dog. But re-commanding a dog can be detrimental to a young dog who is not solid in his training. It can also be distracting to the seasoned dog. Keep in mind that the handler has no idea what scent picture is on the trail or where it is. Even a scent trail that has been laid for training can have changes in it as the trail ages. Other people or animals may have crossed it. In some areas, a chemical scent may have blown onto the scent trail. Areas where there is farming often have strong fertilizer and/or chemical scents. Areas near industry may also produce scent that is carried on the air currents.

​If the scent picture has changed or been altered to some degree, and a handler re-commands his dog, the dog would be correct in following a new scent picture that may be stronger than the original scent picture. If the new odors dissipate, the dog could stop because the scent picture that he was re-commanded to follow no longer exists. A novice handler would assume that the dog has lost the scent. 

We know that when a hound follows a scent, he tends to block out all other distractions which is why hounds are typically worked on leash. They will ignore their handler in their quest to follow the scent. However, we do not know to what extent other breeds block out distractions. Those breeds and individual dogs who have been trained to be robotically obedient can easily be re-commanded off of the original scent picture. This is one reason why a working dog should be taught to make decisions and perform intelligent disobedience. But that is a topic for another article. 

To help clarify why you should not talk to your dog while he is working, consider this. Picture yourself or someone else deeply engrossed in a problem or project. Then imagine people making noise near-by or even talking to you, repeating themselves over and over telling you what a good job you are doing and to keep it up. After a while you will become annoyed or tune that chatter out, but no matter how hard you try, you cannot stop the noise. Talking to your dog while he is working as commanded is the same situation. 

But what if the dog does seem to lose the scent? The prepared handler will have the scent article on hand to re-scent the dog if necessary. If the dog still indicates that the scent no longer exists, then the experienced handler should (through much practice) be able to determine if the scent has indeed disappeared and trust his dog. 

Sometimes it is hard to remember that handlers cannot see or smell the scent picture that the dog must follow. Therefore, they should not try to tell their dog what and where the scent is or is not.

Handlers must never lose sight of the fact that humans have no way of knowing exactly what or where the scent picture is. Through training and experience, they must learn to read and trust their dog.

Journal Reference:

1. Erica F. Andrews, Raluca Pascalau, Alexandra Horowitz, Gillian M. Lawrence, Philippa J. Johnson. Extensive Connections of the Canine Olfactory Pathway Revealed by Tractography and Dissection. The Journal of Neuroscience, 2022; JN-RM-2355-21 DOI: 10.1523/JNEUROSCI.2355-21.2022

Cornell University. “New links found between dogs’ smell and vision.” ScienceDaily. ScienceDaily, 18 July 2022. <www.sciencedaily.com/releases/2022/07/220718181030.htm>.