For most people, dogs are a member of the family. Although we do not speak the same language, living together allows us to overcome that distance and facilitates communication with our furry friends. They don’t need to speak to make us understand what they want or how they feel, and it seems that dogs can also understand us quite well without using words.
The deep connection between dogs and their human family
Researchers at Queens University Belfast have found that dogs can indeed detect stress in humans. In fact, stress is not merely an emotional response, but also triggers multiple changes at the physiological level.
It can increase your heart rate and blood pressure, cause dizziness and shortness of breath due to the release of hormones like epinephrine and cortisol into your bloodstream. These changes also cause us to produce different types of volatile organic compounds through our breath and skin, generating what has been called the “anxiety smell”.
Therefore, if we emit a characteristic odor when we are stressed or anxious, it would not be unreasonable to think that dogs can smell it. In fact, owners of dogs trained to give medical alarm have reported that stress is the condition that most often alerts their pets.
Dogs are also known to be able to perceive human feelings and emotions through sound and sight. Researchers at the Karolinska Institute even found that they suffer from emotional contagion, reflecting the mood of their owners, and that their blood cortisol levels can be similar to those of the owners.
These are not extraordinary findings if we take into account that the relationship between a dog and its owner is functionally similar to that between parents and children, presenting similarities of a behavioral and neuroendocrine nature.
Dogs detect stress through smell
Since the sense of smell is essential for dogs and helps them understand the environment around them, the researchers wondered if they would be able to detect and respond to changes in human physiology associated with a psychological state, such as stress, simply by identifying changes in human body odor.
This study asked if dogs could discriminate between different levels of these volatile organic compounds. Therefore, the researchers took breath and sweat samples from 30 participants, both from the owners of the dogs participating in the research and strangers, while they were in a neutral mood or felt stressed due to an experimentally induced psychological threat.
Each dog participated in 20 discrimination trials, in which they consistently made consistent and accurate choices. Precisely, they detected the stress sample 94.44% of the time, almost always at the first exposure.
It should be noted that dogs have 220 million olfactory receptors, compared to 50 million in humans, so they are particularly effective at differentiating and identifying odors that go unnoticed for us. Therefore, it is not surprising that they are able to identify the volatile organic compounds that we release when we are stressed and respond accordingly. So now you know, when you get stressed, your pet notices it and chances are that he or she will get stressed too.
Sources:
Wilson, C. et. Al. (2022) Dogs can discriminate between human baseline and psychological stress condition odours. PlosOne; 10.1371.
Petersson, M. et. Al. (2017) Oxytocin and Cortisol Levels in Dog Owners and Their Dogs Are Associated with Behavioral Patterns: An Exploratory Study. Frontiers in Psychology; 10.3389.
