We wanted to investigate the common belief that dogs can sense when a person is afraid of them.
Dogs possess a much better sense of smell than humans because they have approximately 200 million olfactory receptors in their nose, compared to our mere 6 million. This heightened sensitivity allows dogs to be widely used in search and rescue missions, bomb detection, and potentially even early cancer detection in humans. Additionally, dogs have a specialized olfactory organ called the Jacobson’s organ, which is responsible for “chemical communication.” The nerve cells in this organ transmit signals directly to the brain and can detect a range of substances that are almost impossible to identify with ordinary olfaction. Although the Jacobson’s organ is mainly used for intraspecific communication, there is reason to believe that it could help dogs detect human emotions. So, can dogs truly smell our fear?
Recently, the belief that there was no evidence to support dogs’ ability to sense fear in humans has been challenged. In 2017, a group of researchers conducted an experiment to investigate this idea. They took samples of sweat from the armpits of random male donors who were not involved in further testing while in different emotional states, including fear and happiness. During the main study, scientists sprayed the sweat in a room where dogs, including golden retrievers and Labradors, their owners, and strangers were present. Dogs placed in the “happy” scent room behaved more amiably by approaching strangers more frequently, and their heart rate was relaxed. Conversely, dogs placed in the “room of fear” experienced elevated stress levels and a significant increase in heart rate. This reaction could lead to aggression as the natural response to danger necessary for animal survival is “fight, freeze, or flee.”
In 2022, another group of scientists conducted a recent study to test the conclusions of their colleagues who had investigated dogs’ ability to sense fear in humans. The researchers took sweat and breath samples from 36 study participants who were asked to perform complex mental arithmetic. Subsequently, they took samples again. The participants’ stress levels were confirmed through their own reports and physiological measures. The researchers then tasked four dogs with identifying “stressful” samples. In the first stage, the dogs were presented with three samples: one “stressful” and two blank samples. In the second stage, they were presented with the “stressful” sample, the original sample taken before the mathematical exercises, and a blank sample. As a result, the dogs accurately identified human breath and sweat samples in a state of stress with 93.75% accuracy.
Our sweat appears to change its scent when we experience intense stress, as confirmed by scientific studies. Despite having a weaker sense of smell than dogs, humans can detect the “smell of fear” and respond to it. However, it is not yet clear how this detection occurs, as humans lack an organ that is responsible for detecting pheromones. This is unlike many animals who possess such an organ, rendering pheromone perfumes ineffective for humans, as previously mentioned.
Similar to animals, humans also exhibit the “fight or flight” response when faced with perceived danger, sometimes accompanied by a “fawn” response. When this happens, our muscles reflexively contract, which a dog may detect through unconscious movements. It is important to note that dogs may not necessarily interpret the scent or movements they detect as fear. Rather, they may perceive them as a threat and experience stress, subsequently choosing how to respond. In cases where the dog perceives a threat and responds with the “fight” option, they may resort to attacking.
Actually, dogs excel at sensing human emotions and can even synchronize with them. For instance, when a dog’s owner experiences extended periods of intense stress, the dog’s cortisol levels can increase significantly.
Recent studies have confirmed that dogs can distinguish the scent of a person in a stressful situation, irrespective of whether the stress is caused by encountering a dog or other factors. Though dogs may not comprehend the specific emotion of fear, they can still sense the stress and become aggressive as a result.
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