There is a widely held belief, mostly among people with a fear of dogs, that a dog can smell when someone is afraid. Indeed, scientists have found, dogs do “smell” people’s fear, and get stressed when they do. Their research did not, however, find any violent behaviour as a result of that stress.
Another team of scientists, meanwhile, looked at a different aspect of dogs’ interaction with humans: their facial expressions. Every dog lover is familiar with “puppy dog eyes”, the mournful look with which the animal faces them, its inner eyebrows raised. The new research has indicated that dogs wear that face on purpose, to communicate with the person looking at them.
The smell of fear
Biagio D’Aniello, a neurobiologist studying human-dog communication at the University of Naples Federico II, is also interested in the olfactory system, which is behind the sense of smell. The study he led, published in Animal Cognition, combines the two interests. “Since there are folkloristic beliefs that if a person is afraid of dogs, the dog can smell that fear, I decided to verify this popular assumption,” D’Aniello told The Indian Express by email.
The study began with human “odour donors” in Lisbon, away from the 40 Labradors and Golden Retrievers whose behaviour would be studied in Naples. Each of these persons was shown a 25-minute video that induced either fear or happiness, and their sweat samples were collected.
In Naples, each dog was placed in a room with its owner and a stranger — who was not from among the odour donors. The owner and the stranger did not interact with each other, or with the dog. An experimenter then placed an odour sample, and left.
Once the dog had sniffed at the sample, a “happiness” chemosignal led to more interest towards the stranger than a “fear” signal did. The latter odour led to more stressful behaviour, including a higher heart rate. The fear signal did not, however, trigger a threatening attitude towards the stranger.
“Thus our data, while supporting the dog’s ability to perceive human emotional chemo-messages, do not prove that they trigger attack,” said D’Aniello, while not ruling out different behaviour in breeds less sociable than retrievers. “Just a final consideration,” he said. “When people are afraid of dogs, they also assume unusual postures and look the dog in the eyes. This behaviour can be interpreted by the dog as a threat… Finally, I’m asking myself: are people attacked when they are afraid of dogs? Or were people who were attacked, afraid of dogs?”
Face to face
In the study on facial expressions, published in Scientific Reports, University of Portsmouth researchers observed 24 dogs between ages 1 and 12, from Kenny the Labrador to Luna the German Shepherd, from Paul the Golden Retriever to Wilma the mongrel.
An experimenter presented herself before each dog, separately, in four different ways in a room: facing it with food; facing it without food; back turned to the dog but showing it food behind her back; back turned and without food. The researchers then analysed the frequency of the dogs’ facial expressions using a technique called DogFACS. They found that the dogs made more expressions when the experimenter was facing them. The effect was strongest with “inner brow raiser”, or puppy dog eyes, besides “tongue show”. The study interpreted this as a sign that a dog makes those expressions in order to communicate.
What they are trying to communicate, however, was not part of the study. “We are not really saying anything about specific expressions; our finding is simply that dogs are more expressive when being attended to than when not,” said Paul Morris, co-author of the study led by dog cognition expert Juliane Kaminski.
It was not for the food that they made those expressions; their behaviour was not affected by whether or not the experimenter was showing them food. This, when previous research has indicated that food arouses a dog more than social contact does.
But shouldn’t that arousal have influenced the dog in the expressions it made? “We were not looking at arousal; we were looking at how expressive the dog was… you can be highly aroused and not very expressive,” Morris told The Indian Express in an email interview. “What is really interesting to us as comparative psychologists,” he added, “is that we have shown for the first time that a non-primate species is sensitive to the attention of the audience.”