15/12/2025
Facial asymmetry in dogs the uneven use of one side of the face more than the other. It can offer insight into how dogs process emotions, perceive their environment, and communicate with humans and other animals. Like in humans, asymmetrical facial expressions in dogs are often linked to brain lateralisation (the idea that the left and right hemispheres of the brain are specialised for different types of processing).
Left hemisphere of the brain controls the right side of the face and body, and is typically associated with approach, positive emotions, and goal-directed behaviour.
Right hemisphere controls the left side, and is associated with withdrawal, negative emotions, fear, and threat detection.
What the Research Shows
1. A 2013 study showed when dogs wag more to the right, it's linked with more positive feelings (e.g., seeing their owner). Wagging more to the left is associated with negative or uncertain emotions. Similar asymmetries have been found in their facial muscles, particularly around the mouth and eyes.
2. Dogs tend to look at the left side of a human face first, which is the side controlled by the right hemisphere (sensitive to emotional cues). This means they may instinctively scan for emotional information when reading us and possibly expect us to do the same.
3. When dogs are feeling stressed or conflicted, they may show more tension or movement on the left side of their face (right-brain activation). A classic example is lip lifting on one side during social conflict or half-ear pinning when unsure (Siniscalchi et al, 2022)
Facial asymmetry in dogs isn’t random, it’s often tied to what the dog is feeling and how they’re processing their environment. When assessing a dog’s emotional state or response to a situation, pay attention to which side of the face shows more movement or tension. Combine this with other signals (tail wagging direction, posture, gaze, vocalisation) to build a clearer picture of the dog’s experience.
Recognising and interpreting asymmetry helps with early identification of stress or conflict, which is crucial for humane, effective behaviour support.
