When you have dogs, it’s easy to see that human faces are important to them. Surely, you’ve probably noticed the countless times in a day that your dog looks at your face: in the park, on the couch, when you are playing together. It’s very likely that dogs are the ultimate “human-stalker”, as they can pick up a lot of information with just a glance. In a simple image, dogs can discriminate between two familiar people1, and pick up subtle differences between a happy face and an angry face2. They can also recognize whether or not a face is paying attention.3
Thanks to many great behavioral experiments4 done in the past, we know that dogs can extract useful information by looking at a human face. For my PhD project, I decided to investigate the cerebral correlates of human face perception in dogs: what happens in a dog’s brain when it sees a human face.
My team and I chose to study this because the relationship between humans and dogs is remarkable in many aspects, and it’s mainly represented in the attachment between humans and dogs5. Processing human faces could be necessary for dogs to establish this attachment with humans6. Thanks to fMRI scanning, we were able to study this processing in a respectful, non-invasive way.
I believe that knowing about the cerebral correlates is useful to have an integrative knowledge about dog cognition, but this knowledge is never more important than the welfare of the dogs. In this sense, the fMRI resonator is a wonderful tool because it allowed us to harmlessly look at the cerebral activity related to different cognitive processes. The main problem is that, in order to do so, we needed to train dogs to remain still inside the resonator.
The first step in the process was to contact the dogs’ families. This was a crucial moment because we needed the families to trust us enough to let us bring their dog to the lab. Can you imagine the level of trust necessary to do this? And not only that, at the same time we needed to establish rapport with the dogs so that they would feel comfortable working with us. When the families agreed, the dogs came to the lab and we taught them to stay in the “sphinx” position inside a resonator replica for 5 minutes. During this step, the dogs wore protection against the resonator noise (Figure 1).
After this training, seven dogs were taken inside a real resonator, where they were shown images of human faces and objects. But the truth is that the first session didn’t go perfectly! Just see Figure 2. The resonator is an open tunnel. Despite all their training, in the first real session they all walked out of the resonator. At this point, it’s important to mention that at any moment the dogs were allowed stop the session and leave. And before every scanning session, we always took the dogs to the park, so that they could start in a positive mood.
Once the dogs were comfortable enough to sit calmly through the scanning sessions, we were able to collect the data we were looking for. Our results showed that, when processing human faces in comparison to objects, dogs have activity in the caudate, as well as the temporal and frontal cortices (see the video below). The activity in the temporal cortex is interesting because in other species (humans7, non-human primates8 and sheep9) it’s also related to face processing. At the behavioral level, face recognition is present in all major vertebrate taxa10. At the cerebral level, it’s possible that the specialized mechanism emerged early in evolution, although we need to test more species to have a complete picture.
The activity in the caudate and the frontal cortex is the most intriguing. Our work is the first to relate this cerebral activity to the perception of human faces in dogs. We think that the frontal cortex activity is related to higher processes, such as the processing of human faces, possibly attention (triggered by something more salient than regular objects), or categorization. And the caudate activity is probably related to a reward process. This was unexpected, as the stimuli we used were unfamiliar faces with neutral expressions. However, in this moment, we cannot discard that the caudate and the frontal activity are related to general face-like processing and not specifically to human faces.
In the future, we hope to uncover more evidence regarding how dogs process human faces. We think that the perception of human faces could be one of the foundations of social cognition in dogs. Adding the cerebral correlates of this process to the already existing behavioral data could improve our knowledge about dog cognition. I personally think that investigations in comparative psychology can also help us to reduce the cognitive distance between mental abilities across species.
This is a guest post written by Laura V. Cuaya. She is a researcher at the Institute of Neurobiology, National Autonomous University of Mexico. You can connect with her on Facebook.
Cuaya LV, Hernández-Pérez R, Concha L (2016)
Our Faces in the Dog’s Brain: Functional Imaging Reveals Temporal Cortex Activation during Perception of Human Faces.
PLoS ONE 11(3): e0149431
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