Trained pet dogs remained awake during scans as researchers measured their brain activity.

Brain scans provide first evidence that dogs can tell fear from sadness. 

New research has shown, for the first time, that dogs can distinguish among negative facial expressions, including anger and sadness.

The study, published in the journal iScience, used brain scans to investigate how dogs’ brains react to different human expressions.

Focusing on happiness, the team showed eight pet dogs photographs of strangers displaying neutral or happy faces. They found that the happy expression activated brain regions associated with high cognitive and reward processing - specifically, the temporal cortex and caudate nucleus.

Next, the researchers assessed whether these same brain regions responded to other emotions. They showed 12 dogs images of happy, angry, fearful and sad faces, analysing their brain activity using machine learning.

In this second experiment, the dogs did not react in the same way to negative emotions. The network linking the temporal cortex and caudate nucleus responded uniquely to happiness, enabling the team to easily distinguish brain reactions to smiles from negative expressions.

Furthermore, a whole-brain analysis revealed distinct patterns of activity that separated fear from anger and sadness, providing the first evidence that dogs can distinguish between specific negative emotions.

First author Raúl Hernández-Pérez from the University of Vienna said: “Humans are really good at picking up small details on the face, and so are dogs. This makes dogs very interesting. By studying their brains, we can understand what adaptations have developed to support their remarkable social and emotional understanding of humans.” 

Laura Cuaya, also of the University of Vienna, added: “The activity in the caudate nucleus is particularly interesting. It suggests that happy human faces may have emotional significance for dogs.”

Looking ahead, the team plans to adopt a more dog-centric perspective to understand how dogs interpret these signals to make sense of their interactions with humans.

“I would like people to see dogs as emotional beings,” Cuaya said. “They have evolved with us to understand our expressions and cooperate with us, and recognising that can change how we communicate with and care for them.”

Image (C) Laura V. Cuaya