How a Cat Person Helped Reveal Dogs' Ability to Distinguish Human Emotions

Laura Cuaya, a cat enthusiast, found herself sharing her life with two dogs, Odín and Kun-kun, during her Ph.D. studies. These dogs traveled with her from Mexico to Budapest and subsequently Austria. A subsequent dog brain study took place in Hungary, building on findings about how dogs' brains respond to human smiles and expanding to include negative expressions.

The study, published in iScience, utilized functional magnetic resonance imaging (fMRI) to scan the brains of pet dogs while they viewed photographs of human faces. When dogs encountered smiles, their brains showed stronger activity in a network that extended into a reward-related region. However, when the faces displayed fear, the dogs' brains exhibited whole-brain activity patterns that differed from those associated with anger and sadness.

This provided the first neural evidence that dogs can distinguish at least some negative human expressions.

Cuaya noted that the findings were surprising, especially given her focus on happiness throughout the research. She expressed excitement over the robustness of the results, which now allowed her to study the brain processing of negative facial expressions.

In the dog brain study, eight trained family dogs participated in an initial experiment. The dogs viewed unfamiliar people with happy or neutral expressions while awake and unrestrained in an fMRI scanner. Smiles triggered stronger activity in a network from the temporal cortex to the caudate nucleus, a brain structure involved in reward processing.

A second experiment involved 12 dogs, including six from the first experiment. The dogs viewed faces expressing happiness, anger, fear, and sadness. The researchers could determine when a dog was looking at a happy face versus a negative one based on the activity in the reward-related network. However, this network could not differentiate between the three negative expressions.

When the researchers examined the whole brain, fear was distinguishable from both anger and sadness. Yet, anger and sadness remained unreliably separated.

Cuaya highlighted the importance of these findings, emphasizing that dogs can perceive emotions expressed in human faces, but previous studies had only compared one positive and one negative expression. She found it exciting to discover that the dog brain can distinguish between some negative expressions within the same valence.

The study also involved Odín and Kun-kun, who were living with Cuaya and her partner Raúl Hernández-Pérez. This close proximity during the research allowed Cuaya to reflect on the extent to which dogs watch people and whether humans reciprocate that attention. She acknowledged that humans often struggle to understand dogs' emotions and suggested that studies like this could motivate people to pay closer attention to how dogs communicate their own emotions.