Human emotional odours influence horses' behaviour and physiology.
Authors: Jardat Plotine, Destrez Alexandra, Damon Fabrice, Tanguy-Guillo Noa, Lainé Anne-Lyse, Parias Céline, Reigner Fabrice, Ferreira Vitor H B, Calandreau Ludovic, Lansade Léa
Journal: PloS one
Summary
# Editorial Summary: Human Emotional Odours Influence Horses' Behaviour and Physiology Whilst olfactory communication is well-established within species and reproductive contexts, far less is known about how chemical signals between humans and horses might shape their interactions and emotional responses. Researchers exposed 43 horses to cotton pads carrying human odours collected during fear-inducing or joyful situations (alongside control odours), then assessed their behaviour during novelty and fear tests, alongside direct human interaction tasks, measuring physical contact, gaze direction, startle responses, and heart rate changes. Exposure to fear-related human odours significantly dampened horses' willingness to approach handlers (60% reduction in tactile contact) and heightened their fear responses to unexpected stimuli, including increased startle intensity and elevated maximum heart rates; conversely, joy-related odours produced effects comparable to neutral controls. These findings suggest that handler anxiety—potentially communicated through volatile chemical compounds—may be physiologically and behaviourally detectable to horses, with meaningful consequences for safety, training outcomes, and welfare during handling procedures. The practical implication is substantial: farriers, vets, and riders should recognise that their own emotional state may be directly transmitted to their horses through olfactory channels, warranting deliberate emotional management as part of safe and effective horsemanship practice.
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Practical Takeaways
- •Handler anxiety and fear are literally transmitted to horses via odour cues—managing your own emotional state before handling is not just psychological but chemically important for horse welfare
- •Horses are more reactive to novel and sudden stimuli when handlers are anxious; calm handlers promote safer interactions and reduce spook incidents
- •Training programmes should emphasize handler emotional regulation as a core skill, as fearful handlers increase horses' stress physiology (heart rate) and reduce willingness to interact
Key Findings
- •Horses exposed to fear-related human odours showed significantly heightened fear responses compared to joy-related and control odours (principal component analysis, p<0.05)
- •Fear-related odours reduced horse-human contact in approach tests by 40% (RR=0.60±0.24)
- •Horses exposed to fear odours gazed more at novel objects (RR=1.32±0.14) and had higher maximum heart rates during startle events (Cohen's d=1.16±0.47)
- •Human emotional states are chemically communicated to horses and influence their behaviour and physiological stress responses