Dogs’ Brains Distinguish Human Smiles and Specific Negative Expressions

Researchers from the University of Vienna, the National Autonomous University of Mexico, and Eötvös Loránd University used functional MRI to scan pet dogs while they viewed photographs of unfamiliar humans displaying five facial expressions. The first experiment, involving eight dogs, compared happy and neutral faces; the second experiment added sadness, fear and anger and included 12 dogs. All dogs were trained to lie still, awake and unrestrained inside the scanner. The study was published in *iScience* on August 7.

Dogs can distinguish between human fear and sadness The Guardian

• Happy faces triggered increased activity in the temporal cortex and the caudate nucleus, regions linked to visual, social and reward processing.

Dogs can distinguish between human fear and sadness

• Machine-learning analysis showed that the same brain network could reliably separate happy faces from each negative expression, but could not differentiate among the negative expressions when examined only in that network.

The Guardian

• Whole-brain analysis revealed distinct patterns that separated fear from both anger and sadness, and anger from sadness, providing the first neural evidence that dogs can discriminate specific negative emotions.

Dogs can distinguish between human fear and sadness

The authors suggest that the caudate response indicates emotional significance for human smiles, and that recognizing such cues may aid training. Evolutionary biologist Bridget Waller (Nottingham Trent University) described the work as “fascinating,” noting that domestication likely shaped dogs’ ability to read the most socially common human expression—smiling—while the capacity to parse less frequent negative expressions appears more limited. The researchers plan future work comparing human and dog brain responses to the same emotional signals and adopting a more dog-centric perspective on how these neural patterns guide behavior.

The Guardian

The sample was small and dominated by healthy border collies without behavioral problems. The authors acknowledge that real-world interactions involve body language, vocal tone and scent, which static photographs cannot capture, and that dogs may need additional cues to distinguish emotions of the same valence.

The Guardian

• “The activity in the caudate nucleus is particularly interesting,” — Laura Cuaya, says senior author

Dogs can distinguish between human fear and sadness

• “I would like people to see dogs as emotional beings,” — Laura Cuaya, says senior author

Dogs can distinguish between human fear and sadness