How does your dog know you're stressed before you even say a word? This question intrigued researchers, who wondered if our emotions could leave a real “signature” in our smell. The biologist Biagio D'Aniello and his team from the University of Naples thus studied the ability of dogs to detect, through their sense of smell, the chemical changes associated with different human emotional states.
An experience to make dogs “feel” fear and joy
To do this, these Italian researchers developed an experiment dedicated to the chemoperception of dogs (in other words, to the ability of our companions to perceive chemical information present in the environment), with a particular interest in the interspecific transmission of emotions.
To find out if the emotions felt by a human can be detected and influence a dog's behavior, human volunteers watched videos designed to induce fear, joy or a neutral state in them. Their apocrine sweat, collected in the armpits, was then used as a support for these different emotional “signatures”. The odors were thus diffused into a room where Labradors and Golden Retrieversaccompanied by their master and confronted with an unknown person, could move freely. The researchers then observed their behaviors, interactions and physiological reactions, including their heart rate and variability.
An invisible form of communication
The result of this experiment published in the journal Animal Cognition* is particularly interesting: the odor associated with fear caused more stress-related behaviors. In particular, the dogs seemed to seek more proximity and comfort from their master, while having less contact with the unknown. Conversely, the smell associated with joy seemed to promote more social behaviors towards the stranger. These observations show that dogs could perceive some of our emotions not only through our voice, our attitude or our expressions, but also through our smell. Their incredible sense of smell would therefore allow them to capture emotional information invisible to us and give it a real “smell”.
Between humans and dogs, communication definitely does not stop at words, looks or intonations. The works of Biagio D'Aniello and his team thus suggest that our companions would also be capable of capturing, in the chemical signals that we give off, information linked to our emotions, notably fear, and of reacting to it. However, there is no question of saying that your ball of fur reads your thoughts or understands your emotions exactly like you: the study remains limited and does not allow generalizations to be made to all dogs, all humans or all situations. It nevertheless opens an interesting avenue into this very special relationship that we have with our companions and shows that, without us being aware of it, we perhaps transmit to our dogs a whole lot of information that they know how to sniff out very well.
* D'Aniello B et al., “Interspecies transmission of emotional information via chemosignals: from humans to dogs (Canis lupus familiaris)”, Animal Cognition, 2018 Jan 21(1), 67-78.