The Influence of Human Emotional Odors on Canine Cognition.
- Jeeva Nanthan
- Jan 14
- 5 min read
Dogs have long been cherished as our companions, and they are known for their remarkable ability to understand human emotions and behaviors. Yet, recent research has gone even deeper, exploring how dogs perceive and react to human emotional states, specifically through their sense of smell. A groundbreaking study published in Scientific Reports investigates how the scent of a stressed or relaxed person can significantly influence a dog's cognitive responses.
A team of researchers from the University of Bristol and Cardiff University conducted this study to explore whether human stress and relaxation odors affect dogs' cognitive bias—a measure of their emotional state. Cognitive bias in animals is assessed by observing their reactions to ambiguous stimuli, where a more negative (or pessimistic) response suggests a negative emotional state.
In the initial phase, 11 human volunteers, aged between 18 and 26, participated in sessions designed to induce stress and relaxation. During the stress sessions, participants underwent a Trier Social Stress Test (TSST), which involved preparing and delivering a speech and performing mental arithmetic in front of researchers. For the relaxation sessions, participants watched calming videos in a comfortable setting. Odor samples were collected from the participants' armpits and breath during these sessions.
Figure 1: Flowchart depicting the two main phases of the study: Phase 1 shows the process of
collecting human odor samples during stress and relaxation sessions, and Phase 2 illustrates the
cognitive bias testing in dogs exposed to these odors.
To examine the effect of these odors, 18 dogs were exposed to the collected human scents in a controlled environment. The dogs were trained to associate certain locations with rewards (positive) or no rewards (negative). They were then tested on their likelihood to approach ambiguous locations under three conditions: no odor, stress odor, and relaxed odor. The order of odor exposure was counterbalanced to ensure unbiased results.
The study found that when dogs were exposed to stress odors, they showed significant changes in their behavior. They were less likely to approach a food bowl placed at a near-negative location, indicating risk-avoidance behavior. This suggests that dogs can detect human stress through olfactory cues alone and that this detection influences their decision-making processes. The study revealed that dogs showed improved learning of the trained positive and negative locations when exposed to stress odors during the third session. This implies that the presence of stress odors may heighten dogs' awareness and influence their learning patterns.
This research underscores the profound impact human emotional states can have on dogs. The ability of dogs to perceive and react to human stress through smell has significant implications for their welfare, particularly for working dogs in high-stress environments. It suggests that managing the emotional environment around dogs is crucial for their well-being and performance.
This study is the first to demonstrate that human stress odors can affect dogs' cognition and learning without any visual or auditory cues. It opens up new avenues for understanding the emotional connection between humans and dogs and emphasizes the importance of considering olfactory cues in the management and training of dogs. As we continue to explore the depth of the human-animal bond, such insights are invaluable in enhancing the welfare and performance of our canine companions.
Dogs have long been cherished as our companions, and they are known for their remarkable ability to understand human emotions and behaviors. Yet, recent research has gone even deeper, exploring how dogs perceive and react to human emotional states, specifically through their sense of smell. A groundbreaking study published in Scientific Reports investigates how the scent of a stressed or relaxed person can significantly influence a dog's cognitive responses.
bulb, vomeronasal organ, and the process by which dogs detect and process emotional odors
from humans.
A team of researchers from the University of Bristol and Cardiff University conducted
this study to explore whether human stress and relaxation odors affect dogs' cognitive bias—a
measure of their emotional state. Cognitive bias in animals is assessed by observing their
reactions to ambiguous stimuli, where a more negative (or pessimistic) response suggests a
negative emotional state.
In the initial phase, 11 human volunteers, aged between 18 and 26, participated in sessions designed to induce stress and relaxation. During the stress sessions, participants underwent a Trier Social Stress Test (TSST), which involved preparing and delivering a speech and performing mental arithmetic in front of researchers. For the relaxation sessions, participants watched calming videos in a comfortable setting. Odor samples were collected from the participants' armpits and breath during these sessions.
To examine the effect of these odors, 18 dogs were exposed to the collected human scents in a controlled environment. The dogs were trained to associate certain locations with rewards (positive) or no rewards (negative). They were then tested on their likelihood to approach ambiguous locations under three conditions: no odor, stress odor, and relaxed odor. The order of odor exposure was counterbalanced to ensure unbiased results.
The study found that when dogs were exposed to stress odors, they showed significant changes in their behavior. They were less likely to approach a food bowl placed at a near-negative location, indicating risk-avoidance behavior. This suggests that dogs can detect human stress through olfactory cues alone and that this detection influences their decision-making processes. The study revealed that dogs showed improved learning of the trained positive and negative locations when exposed to stress odors during the third session. This implies that the presence of stress odors may heighten dogs' awareness and influence their learning patterns.
This research underscores the profound impact human emotional states can have on dogs. The ability of dogs to perceive and react to human stress through smell has significant implications for their welfare, particularly for working dogs in high-stress environments. It suggests that managing the emotional environment around dogs is crucial for their well-being and performance.
This study is the first to demonstrate that human stress odors can affect dogs' cognition and learning without any visual or auditory cues. It opens up new avenues for understanding the emotional connection between humans and dogs and emphasizes the importance of considering olfactory cues in the management and training of dogs. As we continue to explore the depth of the human-animal bond, such insights are invaluable in enhancing the welfare and performance of our canine companions.
Jeevananthan M
B. Tech Biotechnology
Undergraduate Student
References:
1) Parr‐Cortes, Z., Müller, C. T., Talas, L., Mendl, M., Guest, C., & Rooney, N. J. (2024).
The odour of an unfamiliar stressed or relaxed person affects dogs’ responses to a
cognitive bias test. Scientific Reports, 14, 15843
2) Hatfield, E., Cacioppo, J. T., & Rapson, R. L. Primitive emotional contagion. In Emotion
and Social Behavior Vol. 14 (ed. Clark, M. S.) 151–177 (Sage Publications Inc, 1992).
3) de Groot, J. H., Semin, G. R., & Smeets, M. A. I can see, hear, and smell your fear:
Comparing olfactory and audiovisual media in fear communication. J. Exp. Psychol. Gen.
143, 825–834.’
4) Prehn, A., Ohrt, A., Sojka, B., Ferstl, R., & Pause, B. M. Chemosensory anxiety signals
augment the startle reflex in humans. Neurosci. Lett. 394, 127–130.
Image credits:
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