An international research team analyzed dog brain activity using fMRI and found that dogs process happy human faces and negative expressions (anger, fear, sadness) differently. In particular, happy faces showed strong activity in the reward-related areas of the dog's brain. Fear and sadness, as well as fear and anger expressions, showed different activity patterns in different brain regions, but there was no significant difference between sadness and anger expressions. This study shows that dogs do not simply categorize human facial expressions as positive/negative, but recognize different types of negative emotional expressions.
