Can Dogs Detect the Smell of Human Emotions?
A few years ago, I wrote about our neighbor Joe, his new dog, and Joe’s (somewhat ubiquitous) theory that dogs can “smell fear.” At that time, a team of researchers, led by Dr. Daniel Anielo, had just published a study of dogs’ ability to detect human emotions from chemosignals present in our sweat (1). They found that when presented with the sweat of a person who was anxious or afraid, dogs demonstrated stress-related behaviors, including seeking out their owner for support. Conversely, when presented with the sweat of a person who was relaxed and happy, the dogs tended to show more exploratory behaviors, were less dependent on their owner, and were more willing to interact with an unfamiliar person.
Puppies versus Adult Dogs
The same researchers recently studied this phenomenon in greater detail (2). Specifically, they asked the question, “Do puppies and adult dogs differ in their abilities to detect human emotions via scent alone?”
The researchers used the same methodology that they employed in the first paper. They collected the underarm perspiration of people who were experiencing either fear/anxiety or happiness (see “Joe” for details). The reactions of two sets of dogs were tested: (1) puppies less than six months of age and (2) adult dogs more than 1 year of age. All of the dogs lived in homes and participated in the study with their owner. A group of 61 puppies and 80 adult dogs completed the study. As in the earlier work, both the owner and the person acting as the unfamiliar human were blinded to the dog/puppy’s group assignment (fear, happiness, or control).
The results corroborated the earlier study’s findings with adult dogs, but showed some interesting differences for puppies.
- The Scent of Fear: Both puppies and adult dogs demonstrated signs of stress in response to being exposed to the odor of human fear. A common behavior in all of the dogs was to seek out the proximity of their owner. This response has been described in other studies and provides additional evidence for owners acting as a “secure base” for their dogs (and puppies) during stressful situations.
- The Scent of Happiness: The behaviors of the adult dogs when exposed to “happy sweat” were similar to those reported in the earlier study. Adult dogs were more likely to approach a stranger and somewhat less likely to move towards the door when compared with the control group and the fear group. Conversely, the behaviors of puppies when they were exposed to “happy sweat” did not differ from their behavior when in the control group. These results suggest that adult dogs, but not puppies, are sensitive to odors associated with human happiness and relaxation.
- Inability to Detect or Lack of Behavioral Response? The lack of a distinction between puppies’ behaviors during the control (no scent emotion) and the happiness scent condition suggests that either puppies do not possess an ability to detect the odor of happiness OR that they detect it, but have not yet developed a behavioral response to it. The authors make the point that the study design did not allow them to distinguish between these two possibilities.
- Fear Response – Innate vs. Biologically Prepared: The fact that puppies reacted to fear but not to happiness suggests that either puppies are born with an ability to detect and respond to the smell of fear (i.e. it is innate) or they are born biologically prepared for this response. Preparedness refers to puppies possessing the ability to rapidly learn a response shortly after birth.
The researchers found that responses to fear odors were pronounced and relatively consistent in both adults and puppies. The major difference between the two groups was that adult dogs showed moderate (but not highly consistent) positive responses to the happiness odors, while puppies’ responses to the scent of happiness did not differ significantly from their responses to no scent present (i.e. the control condition). These results suggest that young dogs must learn this association during development.
Take Away for Dog Folks
These results have important implications for our puppies and the experiences that we provide during their early months of life. If, as these results suggest, puppies come “pre-wired” to be sensitive to scents associated with human fear, it follows that having repeated (even if unintentional) exposure to stress-inducing odors is not desirable. For most trainers and owners, this is self-evident and well established. We know that proper socialization of young dogs not only includes exposing them to positive and pleasant experiences, but also avoiding situations that cause fear. Of additional importance is that our puppies learn that we always have their backs – we are and will always be, their secure base.
The added information that this study provides regards a pup’s apparent lack of a response to happy/relaxed odors. In explaining these results, the authors suggest that these responses, which are evident in adult dogs, naturally develop as puppies experience positive and enjoyable experiences with their owner. All of the cuddling, playing and training that goes into raising a puppy is certainly enjoyable for the owner, leading to production of happy sweat, if you will. The pairing of enjoyable experiences for the puppy with these odors may be a simple, classically-conditioned response. (i.e. “mom is happy, she smells good, I am having fun! This smell predicts safety and happiness!”). If this is true and our puppies must learn this association, this tells us that we must be careful with both our pups experiences as well as our own reactions to those experiences.
Bottom Line? If you are happy with your puppy – he will learn to understand and react positively to your happy scent. We can do our puppies a great service by paying attention to our own attitudes when we spend time with them – not only avoiding stressful situations, but providing plenty of opportunities for our pups to learn the scent of our own happiness.
- D’Aniello B, Semin GR, Alterisio A, Aria M, Scandurra A. Interspecies transmission of emotional information via chemosignals: From humans to dogs (Canis lupus familiaris), Animal Cognition 2017; DOI 10.1007/s10071-017-1139.
- D’Aniello B, Pinelli C, Scandurra A, et al. When are puppies receptive to emotion-induced human chemosignals? The cases of fear and happiness. Animal Cognition 2013, 1-10.
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One thought on “The Scent of Happiness”
I wonder if there are other emotions that have a scent? In particular, disappointment or unhappiness. For dog sports people, you do something with your dog and are disappointed by the result–an agility run, for example. But you do not “show” that instead telling the dog how wonderful they are. Does your scent override the verbals?