20/01/2026
Do Human Emotional Odours Shape Equine Reactions?
A recent study published in PLOS One by Plotine Jardat and her colleagues reveals that human sweat produced during fear makes horses more apprehensive and distant, whereas odours associated with joy do not significantly alter their behaviour.
To investigate this, researchers collected sweat samples on cotton pads from 30 adults (predominantly female) following twenty-minute sessions designed to induce specific emotions.
Fear was elicited through watching sinister horror clips, while joy was prompted by watching comedies & musical performances.
To ensure the purity of the samples, participants followed strict protocols prohibiting the consumption of spicy foods and alcohol, as well as the use of deodorant.
The research team selected pads from the 14 most intense responders. These pads were then fitted into Lycra muzzles at the nostrils of 43 young Welsh horses that were randomly assigned to fear, joy, or control groups, the latter of which used unexposed pads.
The experiments took place in a zoned arena, where a calm companion horse was present to minimise separation distress.
The horses underwent various tasks, including grooming sessions, voluntary free approach tests, a startle test involving a sudden umbrella, and interactions with a novel object.
Researchers measured heart rates using Polar monitors and tracked changes in salivary cortisol.
Blinded coders then analysed the data using Generalised Linear Mixed Models (GLMMs), Principal Component Analysis (PCA), and Tukey post-hoc tests to identify behavioural patterns.
Horses exposed to fear odours interacted with humans significantly less, touching them 40% less frequently than those in the other groups.
This group also displayed heightened vigilance toward novel objects, higher startle scores, and elevated peak heart rates during unexpected events.
While grooming interactions and physical contact with novel objects decreased slightly, the joy group performed similarly to the control group.
📑 Human emotional odours influence horses’ behaviour and physiology. Plotine Jardat, plotine.jardat@ifce.fr; Léa Lansade, lea.lansade@inrae.fr
