What Dogs' Noses Can Tell Them About Human Stress
Key Vocabulary
| Word / Phrase | Meaning | Example |
|---|---|---|
| baseline | a normal starting condition used for comparison | Researchers collected a baseline sample before the stressful task. |
| detect | to notice or discover something that is difficult to see or hear | The trained dogs could detect a change in human odor. |
| accuracy | how often a result or answer is correct | The dogs showed high accuracy during the test. |
| controlled conditions | a research setting where important factors are carefully managed | The experiment took place under controlled conditions. |
| emotional state | the way a person or animal is feeling at a particular time | Researchers studied whether smell changed the dogs' emotional state. |
Article
People often say that dogs know when we are nervous or upset. Research from the United Kingdom suggests that smell may be one reason. In a 2022 study led by Queen's University Belfast, trained dogs learned to tell the difference between human samples taken before and after a stressful task. [1]
Researchers collected breath and sweat from people at a normal baseline and again after a difficult mental-arithmetic task. They checked that the task had increased stress using people's reports and physical measurements.
Four trained dogs were then given choices between stress samples, normal samples and blanks. Across 720 test trials, the dogs chose correctly about 93.75 percent of the time. [1] They did not need to see or hear the person who produced the sample.
The result suggests that short-term psychological stress changes chemicals in our breath or sweat in a way dogs can detect. It does not mean that every pet dog automatically understands exactly why a person feels stressed. The study used specially trained dogs in controlled conditions. [2]
A 2024 University of Bristol study explored a different question: can human stress smell affect dogs themselves? Researchers tested 18 dog-owner pairs and found that an unfamiliar person's stress odor influenced some of the dogs' choices in a food-bowl task, suggesting a possible effect on emotional state or risk-taking. [3]
Both studies were relatively small, so the findings should be treated carefully. They are useful because they show possible ways that humans and dogs communicate without words, facial expressions or direct contact.
For service-dog trainers and ordinary owners, the research raises an interesting idea. A dog's world is built around smell far more than ours is. We may think we are hiding our stress, while our dog may be receiving information that we do not even know we are sending.
Discussion Questions
- How can you tell when an animal notices a change in a person's mood?
- What practical uses could come from understanding how dogs detect human stress?
- Why is it important to distinguish trained laboratory dogs from ordinary pets?
- How much do you think humans underestimate animals' sense of smell?
- What other forms of communication may exist between people and animals without words?
References
- Wilson et al., "Dogs can discriminate between human baseline and psychological stress condition odours," PLOS ONE.
- Queen's University Belfast, "Stress has an odour and dogs can smell it - new research."
- University of Bristol, "Smell of human stress affects dogs' emotions leading them to make more pessimistic choices."
- Parr-Cortes et al., "The odour of an unfamiliar stressed or relaxed person affects dogs' responses to a cognitive bias test," Scientific Reports.