Dogs really can smell your emotional state

Dog owners are probably already keenly aware of how much their pets are tuned in to their emotions, and now science has proven it. A new study out of the University of Naples in Italy shows not only that dogs can interpret visual and auditory cues that tell them what humans are feeling; it shows they can actually smell human emotions, and then adopt those same emotions as their own, reports New Scientist.

"The role of the olfactory system has been largely underestimated, maybe because our own species is more focused on the visual system," said Biagio D'Aniello, a researcher on the study.

It might be common knowledge that dogs have a superior sense of smell, but the idea that they can smell the emotional states of others means they have access to a whole other world of social information. This heightened sense might be what makes our pets seem so intuitive.

For the study, D'Aniello and colleagues had human volunteers watch videos that elicited strong emotional responses, and then collected samples of their sweat. The sweat samples (and odors that accompany them) were then presented to a group of dogs, while researchers monitored the animals' behaviors and heart rates. Incredibly, the dogs adopted behaviors and stress responses consistent with the emotions that were experienced by the human volunteers.

The pets' reaction was perhaps most acute when they smelled sweat samples associated with human fear responses. Dogs acted fearful themselves, seeking out more reassurance from their owners while making less contact with strangers. These animals also displayed higher heart rates.

"This kind of research is needed to fully understand the bidirectional nature of the human-dog relationship," said Monique Udell of Oregon State University in Corvallis.

The research adds to a rich set of data demonstrating that dogs have a high level of emotional intelligence, especially when it comes to understanding their human companions. It's likely that the domestication of dogs over the course of thousands of years has bred striking intuitions into them about human emotion and human sociality, although more research will be needed before any clear conclusions can be drawn.

The research was published in the journal Animal Cognition.