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Dogs Search With Expectations

They form mental representations based on scent
By Karen B. London PhD, March 2018, Updated June 2021

It’s hardly news that dogs have an excellent sense of smell and can track scents in ways that astonish us olfactory-impaired-by-comparison humans. Despite the large number of studies and anecdotes related to how well dogs’ noses work, there is not much work on what dogs understand about what their noses detect. A recent study explored this question.

In “A ball is not a Kong: Odor representation and search behavior in domestic dogs (Canis familiaris) of different education”, the researchers conclude that when dogs are tracking familiar scents, they form a mental representation of what they are looking for. That is, they have expectations of the future because they anticipate finding something in particular based on the scent they are tracking.

To explore what’s going on in the minds of dogs while they track a scent, researchers set dogs up to have their expectations violated. The set-up is actually called a violation-of-expectations paradigm, which basically means that dogs expected to find one object at the end of an odor trail, but found a different one instead.

There were 48 dogs in the study—25 who had experience in searching with either the police or with a search-and-rescue team and 23 who were family dogs with no such experience. Researchers identified two toys that each dog cared enough about to retrieve. Dogs were tested four times, twice with each toy. In each trial, a scent trail was made with a toy. Half the time, the toy used to make the trail was at the end of the trail, but the other half of the time, the other toy was there instead.


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There were several interesting results in this experiment. One result was that the first time that dogs found the “wrong” toy at the end of the tail, many showed signs of surprise. They tended to hesitate and to keep on searching, perhaps still seeking what they expected to find. In subsequent trials, dogs did not exhibit this behavior. Perhaps they had learned that in this set-up, the toy used to put down the trail may not be at the end of it, or perhaps there was some odor contamination (despite cleaning attempts) after multiple trials. It could also be that the dogs were content to find any toy, since they were rewarded with a play session no matter what toy they found.

The second result was that the difference in the success of working dogs versus family dogs in the first trials had faded by the last trials. As expected, in the first trial, working dogs were faster at finding the toys than dogs without formal searching experience. However, by the fourth trial, the dogs in the two groups were equally quick to find the toys.

Evidence that dogs form a mental representation of an object from its scent may not be surprising given how much we’ve learned about the complexity of canine cognition in recent years, but it’s still newsworthy that dogs have future expectations when following a familiar scent. Another exciting thing about this study is the use of non-invasive methodology to reveal something about the inner workings of the canine mind.

Does this study give you the urge to surprise your dog with an unexpected item at the end of an odor trail just to see the reaction?

Photo: Bianca Ackermann / Unsplash

Karen B. London, Ph.D. is a Certified Applied Animal Behaviorist and Certified Professional Dog Trainer who specializes in working with dogs with serious behavioral issues, including aggression. Karen writes the animal column for the Arizona Daily Sun and is an Adjunct Professor in the Department of Biological Sciences at Northern Arizona University. She is the author of six books about canine training and behavior, including her most recent, Treat Everyone Like a Dog: How a Dog Trainer’s World View Can Improve Your Life