Scientists Gave Dogs MRIs and Learned That They're Surprisingly Good at Distinguishing Between Human Emotions, Even Some Negative Ones

When interacting with dogs, you might have thought that the canines seem to respond to your emotions. Appear angry, and a dog may retreat. Cry, and it might try to comfort you.

Now, a new study has uncovered evidence to support what many dog lovers and scientists have understood for years: Dogs have the ability to distinguish between human emotions. Past research had already shown that dogs can recognize human emotions, but these studies usually tested two human facial expressions—one positive and one negative—at a time. It was therefore unclear whether dogs only perceive a difference between a “happy” mood and a “bad” mood or whether they can distinguish between emotions within one of these categories.

To fill this knowledge gap, researchers used machine learning to analyze the brain scans of pet dogs as they were shown images of human facial expressions. The study, published in the journal iScience this month, found that the animals process happy, scared and angry emotions differently. And, for the first time, they revealed that dogs can interpret a difference between negative emotions, such as fear and sadness or fear and anger.

Cuaya and her colleagues trained 14 pet dogs to stay still and awake during ten-minute MRI scans without any restraints—no small feat. Once the dogs were ready, the researchers conducted two sets of experiments. In the first test, eight dogs were shown happy or neutral human faces that were unfamiliar to them, while the MRI scanned their brains.

The happy faces lit up their temporal cortex and caudate nucleus, which are parts of the brain associated with higher cognitive and reward processing. In the second test, 12 dogs were once again shown happy faces, as well as sad, frightened and angry ones. Their brains did not react the same way to the negative emotions as they did to positive ones—the temporal cortex and caudate nucleus responded uniquely to happiness.

A different part of the brain activated while dogs were interpreting between sadness and fear, and yet another brain area was activated when distinguishing between anger and fear. There did not seem to be a difference in how the dogs distinguished between sadness and anger. This suggests, per the paper, that dogs might need more information beyond facial cues, such as body language, to differentiate between these emotions.