A favorite activity of the Case dogs is the “Find It” game. We play this out in the training building and begin by asking the dogs “What’s Hiding Today?”. We all visit the giant toy bin and select a toy for the day’s game. I show the toy to everyone, making sure that each dog gets a good long sniff. The dogs then run to the storage room where they wait as I hide the toy. The door is opened, dogs burst forth into the room and the competition begins! Everyone races around, air scenting, searching every nook and cranny of the room. The first dog to find the toy is the winner, grabbing the toy and running with it to home base to get their prize, a yummy treat.
Mike and I have played this game with our dogs for more than 30 years. While we have seen a range of talent and search strategies among them, all of our dogs adore this game, turn cartwheels to play it and always ask for “one more round” no matter how often we play. In addition to being convinced of the pleasure that dogs take in searching, it has always been obvious that our dogs not only search for the toy using primarily scent (olfaction), but also that they are able to discriminate between toys and will select only that toy that is chosen for the day’s game. For example, if another toy, one that was not chosen, has been left out somewhere in the building, it is summarily ignored, even if that toy has been hidden for the game on a previous day. It has always seemed that our dogs not only have been searching using their noses (not a big surprise of course), but that they are keenly aware of the smell of the blue ball versus that of the red tug toy.
Picture a Blue Ball: The mental representations of objects is something that most of us take for granted. For example, think of your dog’s favorite toy; for my dogs, this is a blue Planet Dog ball. What mental representation do you conjure? I bet it is a visual representation, correct? (I see the blue ball in my inner brain right now). We may naturally assume that other animals represent their worlds similarly. However, for species such as dogs, whose strongest sense is olfaction, it is quite possible, expected really, that their mental representations of objects may be more strongly olfactory than visual – in other words, the smell of the blue ball.
A recent study examines just this question – Do dogs represent objects as odors?
The Study: Researchers at the Max Planck Institute in Germany used a study paradigm called the “violation of expectation” test. There are various ways to design this test, and in this particular set-up, dogs were asked to track the odor trail of a selected toy. At the end of the odor trail, they found either the expected toy or, big surprise, a different toy! The researchers predicted that if the dogs had an internal olfactory representation of the selected toy, then finding a different toy at the end of its scent trail would be unexpected and discounted – meaning that they would hesitate or continue to search for the selected toy – just like my dogs do in the find it game. Conversely, if the dog simply grabbed the unexpected toy, this would suggest that although dogs are highly capable of following a scent trail (something that is already well supported and known), they do not have a strong internal scent representation of the scent of a specific object. Given what we know about the dog’s extraordinary sense of smell, the researchers hypothesized that dogs do indeed have very specific and distinct odor representations of objects and that the first scenario would predominate in their test.
The Dogs: They tested a group of 48 adult dogs of varying breeds and with different training backgrounds. Half of the dogs were trained either in search and rescue or police work. The other half were dogs living in family pets who had received no formal training. For each dog, two “high interest” toys of similar size were selected for use in the search tests. Each dog was tested in four randomized conditions in which one toy was dragged along the floor to leave a scent trail and then hidden in a cupboard. The routes and the hiding places were varied and dogs found either the expected toy (i.e. the toy that left the scent trail) or the unexpected toy in two trials each. Each dog’s searching and sniffing behaviors, time to find the hidden toy, and response when finding the expected or unexpected toy were recorded.
Results: All of the dogs searched for and found the toy successfully within 2 minutes and the majority retrieved the toy after finding it. Sniffing behavior was used to search in the majority of searches (75 %), and most dogs used both air scenting and ground sniffing to find the hidden toy. Dogs found the hidden toy significantly faster when they sniffed versus the smaller number of trials that they attempted to find it visually, without sniffing. Here are other interesting results:
- Surprise! On the first trial, there was no difference in the amount of time that it took to find the expected versus the unexpected toy, but significantly more dogs hesitated to retrieve the unexpected toy compared to the expected toy. This suggests that the dogs experienced a “violation of expectation”, supporting the hypothesis that they had an internal scent representation of the specific toy.
- Working dogs vs. pet dogs: On the very first trial, the working dogs searched at higher speeds and were considerably faster at finding the hidden toy than the pet dogs. However, after the first trial (when it is assumed that the dogs “learned the game”), there was no difference in search speed or success between the trained working dogs and the pet dogs.
- Not just the sniff: Dogs used a combination of both sniffing and visual searching in most trials. Interestingly, they tended to use vision immediately and when the toy was not obvious, such as when it was hidden in peripheral spots, they relied more heavily upon sniffing.
Take Away for Dog Folks: This study provides confirming evidence for something that many of us witness daily with our dogs – that they identify and discriminate among different objects using their sense of smell. But, there is also a bit more here. This study targets cognitive questions about internal representation and how human perceptions, which are primarily visual, may differ dramatically from a dog’s perceptions and representations. When Ally and Cooper compete to find the hidden blue ball, they may know what that blue ball looks like, but the internal image that they have of it is probably not an image at all…..but rather is a smell. The smell of the blue ball.
Can we, as a primate species, even know what that is like? Probably not, but it sure is cool to attempt to understand it.
Cited Study: Brauer J and Belger J. A ball is not a kong: Representation and search behavior in domestic dogs (Canis familiaris) of different education. Journal of Comparative Psychology 2018; https://doi.org/10.1037/com0000115.